Billfish Bills - What Are They Good For?

In the prior article, I discussed long-beaked "dolphins" (Eurhinodelphidae) and noted that I couldn't find hypotheses on the function of their uneven jaws in the literature... aside from a weird proposal involving Skimmers. The Theatrical Tanystropheus mentioned a couple ("digging for small, sand-dwelling organisms or as a bat with which to stun fish") which are plausible, but I don't know where they are from or what lines of reasoning are behind them. There are extant species with a superficially similar condition - billfishes - and it could be relevant to review what they do with their bills.

Atlantic White Marlin (Tetrapturus albidus) from Wikipedia Commons.

Swordfish (Xiphiidae) and Marlins/Sailfishes/Spearfishes (Istiophoridae) are living sister taxa¹ in the clade Xiphioidea; while traditionally included in Scombroidei, billfishes are presently regarded as phylogenetically distinct (Orrell et al. 2006) and possibly close relatives of jacks and... flatfishes (Little et al. 2010). Fish phylogenetics is scary business, and I suspect billfish relations will undergo further revisions as the monstrosity known as "Perciformes" is reasoned into pieces. Anyways, while xiphiids² and istiophorids look superficially similar, they actually have rather distinctive morphology. Swordfish have a bill which is flat in cross-section, toothless, blunt-tipped, and with central chambers (compared to rounded, denticulated, pointed, and chamber-less for istiophorids), a weak mandible much shorter than the rostrum, no scales, and no pelvic fins (Collette et al. 2006; Fierstine 2006; Fierstine and Voight 1996 citing Nakamura 1983). Strangely, most extinct billfishes have jaws of equal length, and if the proposed (Istiophoridae + Hemingwayidae) and (Xiphias + Xiphiorhynchus) clades (Fierstine 2006) are correct (see note 1), this would mean the unequal jaws of extant billfishes evolved twice. 

¹ A detailed cladistic analysis with the fossil members of the group has yet to be undertaken (Fierstine 2006).
² As for what the deal with them and ziphiids is, I have no idea.

Swordfish (Xiphias gladius) from Wikipedia Commons.

One infamous use of the billfish bill is impaling unexpected objects. One Blue Marlin was found with rostrum fragments from two other, different billfish species (Fierstine 1997). Other unfortunates include large fish, whales, bales of rubber, boats, ships, deep-diving vessels, people, and turtles (Frazier et al. 1994 - citing various). The billfish-on-billfish impaling has been interpreted as defense against predators (Fierstine 1997) and in the case of the turtles, it was hypothesized that the billfish accidentally impaled them when aiming for fish aggregated nearby (Frazier et al. 1994). Istiophorids can survive with a foreshortened rostrum (Fierstine 2006) so apparently these accidents are survivable. But this raises another question - do they need an elongated rostrum at all?

One study of 227 Blue Marlins (Makaira nigricans) stomach contents found that 38% of prey items showed evidence of damage from the bill, 11% of which were speared and 81% of which were slashed, and the rest of which were in multiple pieces (Shimose et al. 2007). Bizarrely, another study with 226 Blue Marlins found no evidence of prey being struck or speared (Vaske et al. 2011). Vaske et al. (2011) offered no explanation for this anomaly, and I can't see an obvious one either. Both populations (from Japan and Brazil, respectively) even primarily preyed on Skipjack Tuna (Katsuwonus pelamis), which were normally killed with the bill in the former population. I'm stumped.

Fierstine (2006) hypothesized that unequal jaw length in billfishes may have evolved to avoid suffocation when impaling large objects (predator or prey) and to avoid damage to the mandible. I don't buy the mandibular reasoning since extant billfishes get by just fine with them naturally foreshortened. The available evidence suggests impaling is a rather rare event and thus unlikely to be the main factor in the evolution of the characteristic billfish bill. An alternate hypothesis could be that the mandible was shortened so the rostrum could be "weaponized" (sword-like flattening in xiphiids and denticles in istiophorids³) to slash at prey. However, the population which apparently doesn't use bills to feed and healthy individuals with damaged rostra are problematic for both of these hypotheses. Perhaps future studies will show that the bill is generally important for feeding in the group and that the counterexamples are just freaks, but either way, it seems premature to make any conclusions about why billfish have their striking morphology.


³ The ichthyosaur Eurhinosaurus has teeth on the upper jaw which could be a similar instance of "weaponization". 

I really have no idea how eurhinodelphids fit into this framework since Fierstine's hypothetical suffocation would not be an issue (if they could impale at all) and the rostrum does not seem particularly dangerous (no teeth, denticles, or flattening). I wonder if this morphology evolved for different reasons, or if it evolved for reasons that have yet to be hypothesized.

References:

Collette, B. B., McDowell, J. R., and Graves, J. E. (2006). Phylogeny of Recent Billfishes. Bulletin of Marine Science 79(3), 455-468. Available.

Fierstine, H. L. (2006). Fossil history of Billfishes (Xiphioidea). Bulletin of Marine Science 79(3), 433-453. Available.

Fierstine, H. L. (1997). An Atlantic Blue Marlin (Makaira nigricans), impaled by two species of billfishes (Teleostei: Istiophoridae). Bulletin of Marine Science 61(2), 495-499. Available.

Fierstine, H. L., and Voight, N. L. (1996). Use of Rostral Characters for Identifying Adult Billfishes (Teleostei: Perciformes: Istiophoridae and Xiphiidae). Copeia 1996(1), 148-161. Available.

Frazier, J. G., Fierstine, H. L., Beavers, S. C., Achaval, F., Suganuma, H., Pitman, R. L., Yamaguchi, Y., and Prigioni, C. M. (1994). Impalement of marine turtles (Reptilia, Chelonia: Cheloniidae and Dermochelyidae) by billfishes (Osteichthyes, Perciformes: Istiophoridae and Xiphiidae). Fisheries Science 39(1), 85-96. Available.

Little, A. G., Lougheed, S. C., and Moyes, C. D. (2010). Evolutionary affinity of billfishes (Xiphiidae and Istiophoridae) and flatfishes (Plueronectiformes): Independent and trans-subordinal origins of endothermy in teleost fishes. Molecular Phylogenetics and Evolution 56(3), 897-904. doi:10.1016/j.ympev.2010.04.022

Nakamura, I. (1983). Systematics of billfishes (Xip­hiidae and Istiophoridae). Publications of the Seto Marine Biological Laboratory 28, 255-396.

Orrell, T. M., Collette B. B., and Johnson, G. J. (2006). Molecular data supports separate scombroid and xiphioid clades. Bulletin of Marine Science 79(3), 505-519. Available.

Shimose, T., Yokawa, K., Saito, H., and Tachihara, K. (2007). Evidence for use of the bill by blue marlin, Makaira nigricans, during feeding. Ichthyological Research 54(4), 420-422. DOI: 10.1007/s10228-007-0419-x

Vaske, T., Travassos, P. E., Pinheiro, P. B., Hazin, F. H. V., Tolotti, M. T., and Barbosa, T. M. (2011). Diet of the Blue Marlin (Makaira nigricans, Lacepède 1802) (Perciformes: Istiophoridae) of the southwestern equatorial Atlantic Ocean. Brazilian Journal of Aquatic Science and Technology 15(1), 65-70. Available.

Derichthys: The Neck Eel

From Wikipedia Commons.

Derichthys serpentinus* is yet another deep-sea fish with a strikingly odd appearance - it has what appears to be a neck! On the basis of maxilla and premaxilla morphology, early workers placed the fish in its own order, Carenchelyi (Jordan and Evermann 1896), or argued that it was a synbranchiform (Gill 1905). Relying on a couple characters is of course a terrible way to go about phylogenetics, and it was eventually realized that Derichthys was a true eel despite its neurocranial oddities (Castle 1970). Derichthys is now coupled with Nessorhamphus in the clade Derichthyidae, which itself has variably been placed as a relative of Heterocongrinae (Eagderi and Adriaens 2010) or sister clade of Serrivomeridae (Mehta et al. 2010), but either way is certainly nestled deep within Anguilliformes

* Derichthys roughly means 'fish with a neck', and serpentinus refers to its pronounced resemblance to snakes, even more so than other eels.


Gill (1884) claimed that Derichthys appeared to be the only fish with a "true neck", but is this really the case? The illustration at top unfortunately has forward-bending pectorals obfuscating the distance between the head and pectoral fin base, which is about 4/5th the head length (Jordan and Evermann 1896). The dorsal fin in this species is peculiar in that it begins midway between the snout and vent (Jordan and Evermann 1896), and coupled with the constricted appearance of the fish's anterior portion, makes Derichthys look even 'neckier'. Derichthys is not the only eel with pectoral fins set far back on their body, as members of Ophichthidae do as well, albeit with much thicker 'necks'. Both Derichthys and ophichthids demonstrate 'branchial displacement', a phenomenon where connections between the cranium and gill arches are lost (as well as interconnections of the gill arches), and the gill arches are pushed back, forming an extended branchial region* (Mehta et al. 2010). Derichthys has both considerable branchial displacement and a large gape, although it is no longer clear if the two are related to processing large food items (Mehta et al. 2010). Interestingly Derichthys avoids competition with its close relative Nessorhamphus - which it overlaps in distribution and habitat - by utilizing its large gape to feed on sergestid shrimp rather than the smaller euphausiids (Hoar et al. 1997).

* I really wish I could find a picture demonstrating this.



So Derichthys isn't a complete anomaly as Gill suggested, but it would still be interesting to learn why the anterior portion of the animal would be constricted if it feeds on large-ish organisms. After looking into ophichthids, I found some of them to be so monstrously bizarre they're my new blogging priority.

References:

Castle, P. H. J. (1970). Distribution, Larval Growth, and Metamorphosis of the Eel Derichthys serpentinus Gill, 1884 (Pisces: Derichthyidae). Copeia 1970 (3), 444-452.

Eagderi, S. and Adriaens, D. (2010). Head morphology of the duck bill eel, Hoplunnis punctata (Regan, 1915; Nettastomatidae: Anguilliformes) in relation to jaw elongation. Zoology 113, 148-157. Available.

Gill, T. (1905). A New Introduction to the Study of Fishes. Science 21 (539), 653-661. Available.

Gill, T. (1884). Three New Families Of Fishes Added To The Deep-Sea Fauna In A Year. The American Naturalist 18, 433. Available.

Hoar, W. S., Randall, D. J., Conte, F. P. (1997). Fish Physiology Volume 16: Deep-Sea Fishes. Academic Press: San Diego, California. Partially Available.

Jordan, D. S., and Evermann, B. W. (1896). The Fishes of North and Middle America. Bulletin of the United States National Museum 47. Available.

Mehta, R. S., Ward, A. B., Alfaro, M. E., and Wainwright, P. C. (2010). Elongation of the Body in Eels. Integrative and Comparative Biology. doi:10.1093/icb/icq075

Colossal Armored Suckermouth Catfishes!

I apologize to those who saw an accidentally published early draft of this post. Anyways:

Pseudacanthicus histrix reportedly measuring 0.91 m (total length?). Contra to the prior reference, this is not Acanthicus hystrix. Source unknown.

At some point in my childhood, I was awestruck by several very large loricariids at the Shedd Aquarium. I had a ~30 cm (TL) Hypostomus plecostomus at home, among the biggest I had seen up until then, but the largest individuals from those two species at least doubled that. Does anybody know if the fish are still there - and what species they are? The concept of colossal loricariids has been bumping around in my brain ever since...

As you probably noticed, in a couple recent posts I discussed how invasive armored suckermouth catfishes (Loricariidae) impact local ecologies. Several of the Pterygoplichthys species appear to be the cause of the most problematic "infestations"; their large body size is probably one of the traits responsible for their success, as it allows them to outcompete indigenous species and escape predation. Exactly how large these and other loricariids can grow is an interesting question, to me at least, hence this post.

Determining the sizes of loricariid species is a needlessly complicated affair - weight data is sparse, maximum lengths are given more frequently than averages, total length (TL - counting the caudal fin) is sometimes used instead of standard length (SL), confusion between cm and mm sometimes occurs, species are often confused, and there are wild rumors. The definition of a "colossal" loricariid should be something like 10+ kg on average, but given the current state of the data I'll consider any species which can exceed 50 cm SL "colossal".


The Colossi That Never Were

Attention researchers: If you see a loricariid listed at ~100 cm, please check to see if the original source is actually in mm!

Fishbase listed Peckoltia braueri at 88.6 cm maximum SL, which would make it larger than almost every other loricariid. A photograph from Fishbase gives the impression of a much smaller animal, and I subsequently noticed that while one other site gave a similar size, several others did not. I do not have access to the original description nor the paper that Fishbase cited, but I found that Armbruster and Werneke (2005) noted that the largest species of Peckoltia had a SL of 103 cm. My hunch turned out to be correct and the issue is currently being fixed.

Fishbase lists Lasiancistrus guacharote at an incredible 135 cm TL... and stated that it occurs in Puerto Rico. In the last post the notion that Puerto Rico had any native loricariids was discounted and consultation of the same source revealed that the L. guacharote was 119.5 mm SL (Armbruster 2005). It is possible that both records are in fact from the same specimen. Unfortunately, at least one source currently reports the erroneous locality and size.

While this erroneous information probably hasn't become too entrenched, I think it is still worth pointing out the errors and their likely cause.


Rumors of Mega-Colossi, Conflicting Math, and Pterygoplichthys

The blog NO FORM - NO SUBSTANCE reported a rather lively radio broadcast from the Philippines which claimed that invasive "janitor fish" (Pterygoplichthys disjunctivus) reached 2-3 meters and 30 kilograms! One telltale factor of a "fish story" is an implausible length-weight relationship, which was my first impression with the rumor.

The quickest way of roughly extrapolating mass (assuming isometric growth) is the square-cube law; if we use the 0.512 m/1.8 kg P. multiradiatus (?) from my last post as a template, this means that a 2 m P. disjunctivus would be 3.9 times longer and implies that it is (3.9³ =) 60 times more massive, which is over 100 kg. Liang et al. (2005) recorded the lengths and weights of over 500 invasive P. multiradiatus in Taiwan and extrapolating from their averages predicts about 2 kg for a 0.512 m specimen, suggesting that isometric growth is likely and that the 100+ kg prediction is not off the mark. But...

Growth is not necessarily isometric (i.e. proportions vary) so the equation W = aL^b is used, where L = total length (cm), W = weight (grams), b = exponent describing growth, a = a constant, for those interested, there's this. Using the equation from Liang et al. (2005) predicts 22-27 kg (depending on gender) for a 2 m (standard length) P. multiradiatus and Shukor et al. (2008) predicts 27.6 kg for a similarly sized P.  pardalis. Since laypeople generally use total length (including the caudal fin) when measuring fish and scientists use standard length (distance to caudal peduncle) this suggests that 30 kg is probably still too light for a 2 m Pterygoplichthys - but it is still probably close. To put that in perspective, a 2 m sturgeon weighs around 60 kg and a 1.8 m eel is over 20 kg - in other words the weight derived from W = aL^b is clearly off the mark. I'm assuming that while it is valuable as a tool for determining traits like condition, it has limited ability to predict length-weight relationships considerably outside the range of data used to calculate it. Or I could have screwed everything up somehow...

So how large can Pterygoplichthys species get? Fishbase lists the maximum size of P. pardalis at 42.3 cm SL; however Shukor et al. (2008) report that invasive individuals from the Malaysian peninsula are in their best condition between 30 and 40 cm and according to their Figure 1, 5 individuals out of 928 were ~50 cm in length. Invasive P. multiradiatus in Taiwan averaged about 30 cm for 537 specimens with a maximum length of 43.7 cm SL (Liang et al. 2005); Fishbase lists a cool 50 cm TL for the maximum, possibly equivalent to the SL. However, Bunkley-Williams et al. (1994) list a possible 51.2 cm specimen and cite Page and Burr 1991, which give 70 cm. Pterygoplichthys undecimalis reportedly gets up to 50 cm SL, but I cannot find (or read the language of) any corroborating sources. Quevedo and Reis (2002 - citing Schaefer 1986) state that Pterygoplichthys can reach one meter in length. Not knowing the species or any other details is certainly frustrating.


Other Colossal Loricariids

The same source states that Panaque and Acanthicus also can exceed 1 meter in length. According to Fishbase, P. nigrolineatus is the largest species at 43 cm TL - leaving me perplexed. The Acanthicus species are much more likely to reach 1 m; Fishbase and its source list A. hystrix at SL, this source from 1890 lists the length at 0.71 m, this aquarium atlas lists the length at 1.1 m, and this book lists the length at "over" 1.2 m. The Fishing World Records page also lists 1.2 m, although it does not lists sources and confuses Pseudacanthicus histrix for A. hystrix. That website and Planet Catfish also list A. adonis at 1 meter, strangely Fishbase puts it at a mere 20.6 cm SL.

As far as I can tell, Pseudacanthicus histrix is the largest loricariid for which there is reasonable evidence. The lack of peer-reviewed literature on the species, and the paucity of data on colossal loricariids in general, is a concern. It does not seem unreasonable to assume that some loricariids can reach about a meter and 20 kg in weight, although if the individuals belong to any of the species here or even some taxa yet to be described has yet to be seen.

References:

Armbruster, Jonathan W., and Werneke, David C. (2005) Peckoltia cavatica, a new loricariid catfish from Guyana and a redescription of P. braueri (Eigenmann 1912) (Siluriformes). Zootaxa 882, 1–14. Available.

Armbruster, Jonathan W. (2005). The loricariid catfish genus Lasiancistrus (Siluriformes) with descriptions of two new species. Neotropical Ichthyology 3(4), 549-569. Available.

Bunkley-Williams, Lucy, et al. (1994). The South American Sailfin Armored Catfish, Liposarcus multiradiatus (Hancock), a New Exotic Established in Puerto Rican Fresh Waters. Caribbean Journal of Science 30(1-2), 90-94. Available.

Liang, Shih-Hsiung, et al. (2005). Size Structure, Reproductive Phenology, and Sex Ratio of an Exotic Armored Catfish (Liposarcus multiradiatus) in the Kaoping River of Southern Taiwan. Zoological Studies 44(2), 252-259. Available.

Quevedo, Rodrigo and Reis, Roberto E. (2002). Pogonopoma obscurum: A New Species of Loricariid Catfish (Siluriformes: Loricariidae) from Southern Brazil, with Comments on the Genus Pogonopoma. Copeia 2002, 402-410.

Shukor, Samat A., et al. (2008). Length-weight Relationship and Condition Factor of Pterygoplichthys pardalis (Pisces: Loricariidae) in Malaysia Peninsula. Research Journal of Fisheries and Hydrobiology, 3(2), 48-53. Available.

Invasion of the Armored Suckermouths!

Alternate title: Endangered pelicans try to swallow invasive catfish. Pelicans suffocate. Die.

Due to the probability of a cease-and-desist letter from England, I'll weave the hinted-at tale above into the tapestry of woe that the armored suckermouth catfishes have caused.

My highly derivative alternate title refers to a phenomenon that occurred in Oct. 1992* in the lower Loiza and Gurabo Rivers of Puerto Rico: at least twenty Brown Pelicans (Pelecanus occidentalis, a locally endangered species at the time) were found strangled to death with large armored suckermouth catfish (over 40 cm, 16" in length) lodged in their throats (Bunkley-Williams et al. 1994). It is worth pointing out that Brown Pelicans typically take prey under 25 cm in length (ref.), do not have bills over 16"/40 cm in length (according to this), and weigh 2-5 kg compared to the ~1 kg that the catfish weighed**. The possibility that Brown Pelicans can successfully swallow prey of that size cannot be precluded, so the extensive armor and unusual morphology*** of the catfish may have been the fatal factors. As to why the phenomenon was so widespread, the catfish became established in Puerto Rico only a few years before and their ease of capture may have prompted curiosity towards a new potential food source. No more reports have been published, so it is possible that the local Brown Pelican population has learned to avoid the catfish, which are probably now permanently established. And sorry to those seeking out morbid photos of the failed loricariid consumption, photographs do not seem to have been published, or even taken as far as I know.

* The table actually says "Ott 1992", I'm fairly certain it's a typo and not some hyper-obscure Latin abbreviation.

** The first recorded loricariid from Puerto Rico was a 1.8 kg, 51.2 cm "Hypostomus plecostomus" - this identification is dubious and the (lost) specimen was presumably the same species as the ones the pelicans swallowed (Bunkley-Williams et al. 1994). Anyways, extrapolating from that record gives 0.86 kg for a 40 cm specimen - I stated ~1 kg due to uncertainty and the implication that 40 cm was a minimum. 
*** Hoover et al. (2004) suggest that the dorsal and pectoral defensive spines were the cause of the mortalities.

Bunkley-Williams et al. (1994) identified the invasive loricariid catfish species as Liposarcus multiradiatus, which is now (again, actually) known as Pterygoplichthys multiradiatus. Puerto Rico has no native loricariids* and while a report occurred as early as 1983 (a likely accidental), P. multiradiatus became established in eight rivers and two reservoirs in the early 1990's, with numbers significant enough to support a local fishery in one area (Bunkley-Williams et al. 1994). While there are markets for the fish in the food and pet industries (at least one fish farm existed on the island for the latter purpose), Bunkley-Williams et al. (1994) suggested that the unexpectedly large size reached by the species led to amateur aquarists discarding them. The catfish appear to be incredibly tolerant of handling stress and can even reportedly survive out of the water for hours** (Bunkley-Williams et al. 1994).


* The type locality of Lasiancistrus guacharote (formerly Hypostomus) was Puerto Rico, but it turns out that this is in error, the species is actually from Venezuela and Columbia (Armbruster 2005). 
** Over 30 hours, in fact (Armbruster 1998 citing Val and De Almeida-Val 1995). They accomplish this by breathing air into an enlarged and highly vascularized stomach, which primarily functions to survive low-oxygen conditions in water (Armbruster 1998). Hoover et al. (2004) documented Pterygoplichthys specimens which apparently entered a period of estivation in burrows, from which they recovered as soon as they returned to water. The implication is that they can survive considerably longer than 30 hours out of the water. Oh, and they can also move on land during extreme environmental conditions.


If the trouble caused by Pterygoplichthys multiradiatus seems familiar, that's because a couple posts ago I discussed how P. disjunctivus (and/or hybrid descendants) specimens in Florida grazed on manatees to a likely deleterious effect. I didn't properly introduce the loricariid catfishes then, and I'm not sure how I passed on such a succulent tangent. So here's a scenic detour through the world of these bizarre armored suckermouth catfishes.

P. multiradiatus from the Wikipedia Commons.

Ideally, the common name "armored suckermouth catfishes" should be used for Loricariidae since they are not the only clade with extensive armor (Callichthyidae) nor are they the only ones with a sucker mouth (Astroblepidae). Loricariidae and Astroblepidae are sister clades (indicating the suckermouth is a shared derived character) and Callichthyidae is a more distant relative (indicating the extensive armor is convergent, unless lost numerous times) in the greater clade Loricarioidea, which includes everything from parasites to a monotypic oddity. Loricariidae itself has a staggering array of morphological variability: Panaque nigrolineatus (Ancistrinae) has an incredibly large head, Tim Burton-esque stripes, and the ability to digest wood with the aid of bacteria; some species (e.g. Farlowella amazonum - Loricariinae) have a body shape reminiscent of pipefish (likely for similar camouflage needs); the Sturisoma species and relatives (Loricariinae as well) look similar except with very exaggerated fins; dwarf suckermouths (Otocinclus et al. - Hypoptopomatinae) look more like generic tetra-like fishes than highly derived catfishes at first glance; one Ancistrus species is a blind cave-dweller, others have bizarre facial tentacles (Ancistrinae); Chaetostoma sovichthys (Ancistrinae) and relatives hardly look like fish at all in dorsal view - more like a revisitation of Cephalaspis or even the ichthyological answer to Triops. The point is, with 700+ species, Loricariidae is a very successful clade - considering they're mostly freshwater* and restricted to one continent. Adriaens et al. (2009) discussed the highly derived jaw morphology** which apparently allowed the loricariids to radiate into the algae-scraped niche; exactly how the numerous species differ niche-wise has not had much discussion.The species Adriaens et al. (2009) used as a model for their study of loricariid jaw mechanics? - Pterygoplichthys disjunctivus.

* Although sources like Fishbase state that they are strictly freshwater, Hoover et al. (2004) report that they occur in brackish water. 
** Catfish jaw morphology is normally conservative, but loricariid jaws have a uniquely mobile upper jaw (as in, it typically doesn't move at all in other catfishes) and the bones of the lower jaw are decoupled to allow for asymmetric scraping movement. 


Back to the invasive loricariids. As it appears that the most widespread and damaging taxa are a few related Pterygoplichthys species (e.g. within the genus), I'll be focusing on those sailfin catfishes - distinguishable by their large dorsal fins consisting of more than 10 rays. In addition to Puerto Rico and Florida, Hawaii has a particularly noteworthy population of Pterygoplichthys and several other genera of loricariids (Bunkley-Williams et al. 1994 - citing various). In the Philippines, P. disjunctivus and P. pardalis were present in the Laguna Lake region since the 1950's and in the early 2000's were found in the Agusan marsh, one of the largest in Asia (Hubilla et al. 2007). Members of Pterygoplichthys are also established in Taiwan, Singapore, Malaysia, Indonesia, and Mexico (Page and Robins 2006, Armando et al. 2007). While Pterygoplichthys spp. are reported from a few states in the mainland USA, there is a chance that like could go from localized to very widespread and wreak havoc (Hoover et al. 2004). So what makes these loricariids particularly damaging invasive species?

The Pterygoplichthys species are capable of far more severe impacts than choking pelicans and cleaning manatees. In fact, Hoover (2004) states that the variety and severity of the ecological impacts from the catfish are unprecedented. I can't emphasize that enough. Loricariids burrow into the banks of streams and lakes in order to spawn and take refuge from droughts and cold temperatures; this behavior can erode away 4 meters of bank annually and cause increased silt loads and turbidity (Hoover et al. 2004, Hubilla et al. 2007). The increased turbidity slows down photosynthesis and likely has negative effects on the food web and energy flow (Hubilla et al. 2007). The catfishes also plow into the substrate and uproot plants, which likely reduces the abundance of native plants and may even aid in the spread of invasive plants (Hoover 2004). Invasive Pterygoplichthys, being large and bewilderingly resilient species, likely outcompete the native algae consumers, aggressively drive them away, and consume the eggs of those species and others (Hoover 2004). The presence of a ravenous algae grazer may also reduce cover for aquatic insects and disrupt the food chain by prematurely diverting nutrients into feces Hoover 2004). Having owned Hypostomus plecostomus specimens in my life, I can't help but wonder if the prodigious amount of feces that loricariids produce has some sort of impact as well.

So what can be done to prevent the potential ravaging of aquatic freshwater ecosystems by invasive loricariids? Bunkley-Williams (1994) discussed the possibility of large predatory fish controlling Pterygoplichthys numbers (Peacock bass, Cichla ocellaris, and Largemouth bass, Micropterus salmoides), however they concluded that there was no known effective predator, disease, or parasite. The Philippines populations also do not appear to have any significant predation, even from native fishermen gillnets as they are damaged from the large fish (Hubilla et al. 2007). Hoover et al. (2004) and Hubilla (2007) suggest that fisheries, possibly with government incentive, could be a way of controlling populations (presumably with better equipment) as the fish are valued for their flesh and eggs. Hoover et al. (2004) also suggested protecting banks from burrowing and isolating the "infected" areas as method for preventing the problem from becoming very widespread. Hoover et al. (2004) and Bunkley-Williams et al. (1994) suggest public education to the prevent further release of loricariids and the latter publication proposed a program to return unwanted fish from amateur aquariums. Those two papers and Hubilla (2007) all suggest that environmental laws should be strengthened in order to prevent multiple Pterygoplichthys species or even multiple loricariid genera from being established. Bunkley-Williams (1994) doubt that the invasive species can ever be eradicated, but the chances of controlling the spread of the catfishes are still good if people recognize the problem before it gets completely out of control.

I'll admit that when I was a kid I released a large loricariid into a quarry before I moved. Even though it had no chances of becoming widespread, it was still a very dumb decision. So please, if you own these catfishes, whatever you do, don't release them into the wild!

References:

Adriaens, Dominique, et al. (2009). Extensive Jaw Mobility in Suckermouth Armored Catfishes (Loricariidae): A Morphological and Kinematic Analysis of Substrate Scraping Mode of Feeding. Journal of Experimental Biology 212, 116-125. Available.

Armando, T. et al. (2007). Amazon Sailfin Catfish Pterygoplichthys pardalis (Castelnau, 1855) (Loricariidae), another exotic species established in Southeastern Mexico. The Southwestern Naturalist 52(1), 141-144.

Armbruster, Jonathan W. (2005). The loricariid catfish genus Lasiancistrus (Siluriformes) with descriptions of two new species. Neotropical Ichthyology 3(4), 549-569. Available.

Armbruster, Jonathan W. (1998). Modifications of the Digestive Tract for Holding Air in Loricariid and Scoloplacid Catfishes. Copeia 1998(3), 663-675. Available.

Bunkley-Williams, Lucy, et al. (1994). The South American Sailfin Armored Catfish, Liposarcus multiradiatus (Hancock), a New Exotic Established in Puerto Rican Fresh Waters. Caribbean Journal of Science 30(1-2), 90-94. Available.

Hoover, Jan Jeffrey, et al. (2004). Suckermouth Catfishes: Threats to Aquatic Ecosystems of the United States? ANSRP Bulletin 04(1). Available.

Hubilla, Marianne, et al. (2007). Janitor Fishes Pterygoplichthys disjunctivus in the Agusan Marsh: a Thread to Freshwater Biodiversity. Journal of Environmental Science and Management 10(1), 10-21. Available.

Page, Lawrence W. and Robins, Robert H. (2006). Identification of Sailfin Catfishes (Teleostei: Loricariidae) in Southeastern Asia. The Raffles Bulletin of Zoology 54(2), 455-457. Available.

The Ateleopodids; or, Jellynose Fishes

I probably shouldn't admit this, but I was unaware of this order of fishes until National Geographic updated an AP story concerning a strange fish captured near Brazil with input from an ichthyologist. Few 'fish' clades* have an elongate body with a prominent first dorsal fin located almost directly behind the head, so I reasoned the the catch was some sort of aberrant macrourid... whoops.

* That is, 'fish' in the paraphyletic sense. Other actinopterygians with roughly similar morphology include (larval?) Stylephoriformes (no longer thought to be Lampridiformes, Miya et al. 2007) and several derived families within Lampriformes (see below). Captain Hanna's Mystery Fish (a probable lampridiform) had this morphology as well. The only non-actinopterygian example that comes to mind are members of Chimaeriformes, distant relatives of sharks and rays.

The 'jellynose fish' order is Ateleopodiformes; the former is a reference to the (sometimes - see below) bulbous snout and the order name, meaning 'imperfect feet', likely refers to the pelvic fins which are typically reduced to a single ray. Fishbase 'remarks' that other characters include a largely cartilaginous skeleton, a dorsal fin with 3-13 rays, a small caudal fin confluent with the long anal fin, and 7 branchiostegal rays. It is curious that National Geographic states that ateleopodids are "well-known" as the opposite appears to be the case; Prokofiev (2006) remarks that the clade is "very poorly studied" and Sasaki et al. (2006) note that there has yet to be a comprehensive morphological review.

Ateleopodids are paedomorphic and specialized, which has complicated analysis of their phylogeny (Sasaki et al. 2006). Early workers placed ateleopodids near (Sasaki et al. 2006 - citing Rosen and Patterson 1969) or within (Miya et al. 2001 - citing Nelson 1976, 1984) Lampridiformes, although one analysis placed them in an unresolved trichotomy with Stomiiformes and derived teleosts (Sasaki et al. 2006 - citing Olney et al. 1993). Sasaki et al. (2006) described the cranial morphology in detail and noted that ateleopodids and lampridiformes share the character complex of deep insertion of the rostral cartilage into an open space in the ethmoid region - albeit with differing methods of insertion. The two groups also share early life history characters such as large pelagic eggs and newly-hatched larvae with dorsal, pectoral, and pelvic fins (the latter positioned posterior to the yolk sac); at least one member of each group also possesses spotty educationalists muscles separated from the epaxial muscle mass (Sasaki et al. 2006 - citing various). Quite interestingly, mitogenomic evidence has placed Ateleopodiformes and Lampridiformes as sister groups (Miya et al. 2001). Since a long body with a prominent first dorsal fin appears in ateleopodids and derived lampridiformes (Miya et al. 2001), this indicates that the morphology is either due to parallel evolution or (less likely in my opinion) that opahs and velifers are secondarily shortened.

Evolutionary relationships aside, Sasaki et al. (2006) document the incredible phenotypic plasticity exhibited by ateleopodids. The 'jellynose' appearance does not occur in all ateleopodids, and in fact its presence is variable within species.

Ateleopus japonicus from Sasaki et al. (2006). These are young individuals, the top individual is pelagic and the bottom is benthopelagic.

Phenotypic plasticity can be explained as one genotype expressing multiple phenotypes due to differing environmental conditions. The Journal of Experimental Biology has a whole open-access issue devoted to the concept -this article in particular sums the concept up well. Anyways, pelagic individuals have a flat head and terminal mouth and benthopelagic individuals have the 'jellynose' condition with a rounded head and more subterminal mouth (Sasaki et al. 2006). The 'pelagic' condition is the default and at some point early in development the low jaw shortens and the upper jaw shifts posteriorly, 'folding' the head in the process (Sasaki et al. 2006). The authors unfortunately did not mention phenotypic plasticity by name, it was beyond the scope of the morphology-centric paper, which leaves an opening for a followup...

Guentherus katoi, Senou et al. (2008). 643.7 mm (25") SL. Photograph by H. Senou.

While the taxonomic status of the Brazil fish cannot be determined at the present time, one new species has been described quite recently. Three large specimens of Guentherus katoi were caught in a trawl off Japan in 2006; like the other member of its genus (the enormous G. altivela) there are three free pelvic fin rays followed by normal rays (as opposed to one) and the body shape is far from anguilliform (Senou et al. 2008). G. katoi differs from G. altivela in having a somewhat smaller head (25.6-26% SL vs. 26.4-35% SL), and larger orbits (5.2-6% SL vs. 2.4-3.5% SL); curiously, the G. katoi specimens had a small adipose fin behind the dorsal fin, and lacked scales, pores, and a lateral line (!) (Senou et al. 2008).

I think that about wraps it up for the ateleopodids, what started off as a commentary on a news item has blown up beyond recognition.

References:

Miya, Masakai, et al. (2001). Mitogenomic Exploration of Higher Teleostean Phylogenies: A Case Studyfor Moderate-Scale Evolutionary Genomics with 38 Newly Determined Complete Mitochondrial DNA Sequences. Mol. Biol. Evol. 18, 1993–2009.

Miya, Masakai, et al. (2007). Mitochondrial genome and a nuclear gene indicate a novelphylogenetic position of deep-sea tube-eye fish (Stylephoridae). Ichthyological Research 54, 323-332.

Prokofiev, A. M. (2006). New Finding of Ateleopus purpureus Tanaka, 1915 Ateleopodiformes: Ateleopodidae) in the Pacific Waters of Japan. Journal of Ichthyology. 46, 342-344.

Sasaki, Kunio, et al. (2006). Cranial morphology of Ateleopus japonicus (Ateleopodidae: Ateleopodiformes), with a discussion on metamorphic mouth migration and lampridiform affinities. Ichthyological Research 53, 254-263.

Senou, H., et al. (2008). A New Species of the Genus Guentherus (Ateleopodiformes: Ateleopodidae) from Japan. Bull. Natl. Mus. Nat. Sci., Ser. A, Suppl. 2, 13–19

The Molids, part 4: The least of the Molids (but not the least interesting); Ranzania

Not to be confused with the plant genus of the same name.

Photograph from Wikipedia

Poor neglected Ranzania, how has it been over a month since I've last discussed molids? Now that I've hit a clear patch with projects and activities, I'll finally be able to complete that last, nagging chapter on molids.

Had I been aware from the outset, I would have made Ranzania the subject of the first chapter; this taxa lacks many of the traits which define (Mola + Masturus) and, I suppose, could be regarded as a 'transitional form' between other tetraodontiformes and derived molids. I use that term cautiously because Ranzania isn't some unmodified holdover from the last common ancestor of molids - nothing is a true 'living fossil' or 'missing link', but basal members of a clade can still be useful for inferring evolution.

It deserves a mention that Raven (1939) thought that Ranzania was the most specialized of the molids based on the extreme development of the erector and depressor muscles of the dorsal and anal fins (see below) - this seems strange because the author recognizes several 'primitive' characters present in Ranzania including inclinator muscles for the aforementioned fins and the vestige of the puffing apparatus (m. retractor postclavicularis). These days phylogeny is no longer determined from a single character; the character-taxon matrix from Gregorova et al. (2009) has 57 characters and includes the extant molids (Ranzania, Masturus, Mola), the extinct ones (Austromola) and non-molid tetraodontiformes (Triodon, Lagocephalus), the latter of which is the most basal member of the clade and the former of which is in the sister group to molids. Ranzania has one unique character* state (pseudocaudal fin rays branch >5 times) in this analysis and shares 32 characters exclusively with other molids (but not always all of them); on the flip side Ranzania has 19 characters states present in non-molid tetraodontiformes such as an elongate pectoral fin, a body depth two times longer than deep, an absent 'carapace' (thick layer of collagenous tissue under scales), gill rakers not concealed in thick layers of skin, no secondary post-metamorphosis, and densely ossified bone (as opposed to weakly ossified and spongy) (Gregorova et al. 2009). Oh yes, and molecular evidence agrees that Ranzania is the most basal molid (Bass et al. 2005).

* Ranzania also has a vertical mouth slit, an unique apomorphy as far as I can tell. Molids lack muscles capable of closing this structure (Raven 1939).

External, musculature, and skeletal morphology of Ranzania. Taken from Johnson and Britz (2005) - itself modified from Fraser-Brunner (1951) and Raven (1939). In 'B', note that the entire lateral muscular mass is composed of muscles controlling the dorsal and anal fins - this is a singularly extreme development, even amongst molids. Juveniles have a slimmer body and evenly-sized dorsal and anal lateralis muscles, adults (pictured) have a thicker body due to more developed anal lateralis muscles (Raven 1939). Fishbase mentions that there are two more anal fin rays than dorsal. These aren't traits we would expect from an underwater 'flier', however Robison (1975) mentions that Ranzania is negatively buoyant and sinks head-first - is this morphology due to stabilization needs?

Morphological oddities, and lack thereof, aside, Ranzania also appears to occupy an unusual niche for a molid. Juveniles eat planktonic crustaceans such as calanoid and cyclopoid copepods, ostracods, and amphipods (Robison 1975) and adults also reportedly consume small crustaceans in addition to lanternfish, hyperiid amphipods, crab larvae (megalops and zoae), and pteropods (OceanSunfish.org citing Fitch 1969). The other, larger molids (Ranzania reportedly only reaches 1 m in length) are famous for consuming jellyfish in bulk, although they will consume a variety of prey including bottom dwelling and deep water species (OceanSunfish again for the save). This abstract suggests that the range of Mola is influenced by temperature while the range of Ranzania is influenced by productivity of zooplankton and small fish, itself influenced by large-scale atmospheric conditions; Castro and Ramos (2002) found captures of Ranzania to coincide with a warming process of the sea surface although if I had access to the former study I'm sure they'd discuss this.

Although typically stated to be a tropical to subtropical species (e.g. Castro and Ramos 2002), Ranzania can occur up to 71 degrees north (Castro and Ramos 2002 mention its occurrence in Scandinavia, huh) and Fishbase accurately describes the species as cosmopolitan. The only extant recognized species is R. laevis, but considering the vast range it would not be surprising if a study of population genetics turned up distinct clades possibly worthy of species-status. Fossil Ranzania species have been reported from the Middle to Late Miocene (see Gregorova et al. 2009 for a review) but I am cautious of species assigned to the clade solely on the basis of polygonal scale plates. Molecular estimations of molid divergence suggest that the Ranzania lineage diverged between 17.6-52.1 mya (Early Miocene to Early Miocene), which supports the assignment of the aforementioned fossils to Ranzania.

I think that about does it for Ranzania and the other molids. But not for weird fish...

References:

Bass, Anna L., et al. (2005). Evolutionary divergence among lineages of the ocean sunfish family, Molidae (Tetraodontiformes). Marine Biology 148, 405-414.

Castro, J. J. and Ramos, A. G. (2002). The occurrence of Ranzania laevis off the Island of GranCanaria, the Canary Islands, related to sea warming. Journal of Fish Biology 60, 271-273.

Gregorova, Ruzena, et al. (2009). A Giant Early Miocene Sunfish from the North Alpine Foreland Basin (Austria) and its Implication for Molid Phylogeny. Journal of Vertebrate Paleontology 29, 359-371.

Johnson, G. David, and Britz, Ralf. (2005). Leis’ Conundrum: Homology of the Clavus of the Ocean Sunfishes. 2. Ontogeny of the Median Fins and Axial Skeleton of Ranzania laevis (Teleostei, Tetraodontiformes, Molidae).

Raven, Henry C. (1939). Notes on the Anatomy of Ranzania truncata. Am Mus Novitates 1038, 1-7.

Robison, Bruce H. (1975). Observations on Living Juvenile Specimens of the Slender Mola, Ranzania laevis (Pisces, Molidae). Pacific Science 29, 27-29. Available.

The Molids, part 3: Enough with Mola!

In the first two posts I've mostly discussed Mola, a clade of three genetically distinct species whose morphological and biogeographical differences have just begun to be investigated. While Mola mola was a "flagship" species which obfuscated [previously recognized] diversity, there are other molids which are effectively unknown to Western public consciousness.

The so-called sharp tail/fin mola Masturus, taken from here. The dorsal fin is of course heavily damaged and while the clavus also looks attenuated compared to those of other specimens, the rounded edge seems to suggest that it isn't damaged. Liu et al. (2009) recovered a linear relationship of total length and standard length (TL - SL = clavus length) and fairly similar proportions in males and females - the large sample of primarily immature fish may have masked differing clavus proportions in large individuals.

As the above photo illustrates, Masturus is very similar in appearance to the Mola species and can be easily differentiated by a projection of the clavus (hence the common name). Gregorova et al. (2009) found Masturus and Mola to be sister taxa with the only differences (4 characters of 57 total) relating to one less caudal vertebrae in Masturus and clavus rays terminating in bony plates exclusively in Mola. Bass et al. (2005) recovered the same topology with combined d-loop and cyt b data; d-loop data in the same study also revealed that the small sample (n = 5) of Masturus did not show clear differences across ocean basins. This seems curious since the same authors mention unpublished tracking data which showed no indication of ocean basin-scale movement or large-scale migrations in the species* (Bass et al. 2005). Also interesting was that the authors only discussed Ma. lanceolatus and didn't mention Ma. oxyuropterus; the small sample size leaves open the possibility of an additional species despite the wide geographic sampling (including the type locality for Ma. oxyuropterus). Who knows, there could be another Mola-like situation at hand here...

* Seitz et al. (2002) tagged a 1 m (TL) individual which travelled 9.7 km/day - although where it traveled was not mentioned. Contrary to prior suggestions, the fish was epi-pelagic (preferring waters <>2.7% of its time in the top 5 m of the water column and could apparently dive below 1000 m (Seitz et al. 2002). I'd assume that older individuals are more tolerant of of cold water, but due to the extreme rarity of surface behavior in Masturus it may be a while before this is confirmed.

Masturus has very recently become the target of a fishery off Eastern Taiwan and this gave Liu et al. (2009) an opportunity to examine the basic biology of the species. The population ranged in length from 42 to 192 cm (SL - the clavus was often damaged) with most individuals between 80 and 119 cm (Liu et al. 2009). All specimens over 158 cm SL were female although since only one gravid individual was recorded it appears likely that this locale is not a spawning ground for the species (Liu et al. 2009). The authors speculated that juveniles may frequent inshore nurseries (where the fisheries primarily operate) while the adults occur further offshore - they noted that specimens greatly exceeding the maxima in their study have been recorded (262.5 cm SL/313.8 cm TL - another 337 cm TL*) (Liu et al. 2009). Vertebra centra were examined for rings and working under the assumption that ring count correlated with age (it did correlate with size) this indicates that their largest female was 23 years old and longevities were estimated to be 105 and 82 years for females and males, respectively (Liu et al. 2009). The authors note that the lack of very young and old specimens can greatly affect growth estimates and of course it can't be emphasized enough that ring formation may be caused by events which do not occur annually. It seems unlikely that data pools as extensive as that of Liu et al. (2009) will be encountered elsewhere (fortunately, in a way) and it appears exceedingly unlikely that a mark-recapture study or study of captive specimens** can resolve the questions of growth and longevity in Masturus - presumably a model species can be used to answer the question that the authors brought up but couldn't answer: if the fishery will lead to a decline of stocks.

* Assuming this is a female, it would have a SL of 282 cm from the equation established in Liu et al. (2009) and 281 cm extrapolating from the largest fish with both TL/SL measurements - this seems to imply that the clavus length has the same proportion throughout life after all. A male, by the way, would have an estimated SL of 277 cm, implying that this is not a dimorphic trait.

What's especially confusing to me is that estimating the weight of the 282 cm SL individual from the equations set up by the authors yields weights of ~1000-1200 kg (the larger from a male) and scaling up from their largest individual (195 cm SL, 409) also yields ~1200 kg. This seems very strange since a 2.7 m Mola (TL?) weighs around 2.3 tonnes - how on earth can a Masturus of roughly the same linear dimensions weigh around half as much? More data on large Masturus individuals, with clearly differentiated total and standard lengths, is desirable to solve this puzzle!

** At least one Mola in an aquarium gained weight extremely quickly and possibly abnormally. If they can actually grow this quickly in the wild then perhaps the Masturus fishery won't totally wreck the population... in the near future.

It's amazing that a species for whom the discovery of a single specimen was notable several decades ago (e.g. Gudger 1935) is now being harvested by the ton - and hardly any more is known about it. While the cosmopolitan range of the species and lack of direct harvesting in most locales probably prevents it from being in any direct danger, exploiting an organism with little known about its basic biology is a dangerous game.

There's still one more molid left, the smallest, most basal, and arguably most neglected of them all!

References:

Bass, Anna L., et al. 2005. Evolutionary divergence among lineages of the ocean sunfish family, Molidae (Tetraodontiformes). Marine Biology 148, 404-415

Gregorova, Ruzena, et al. 2009. A giant early Miocene sunfish from the North Apline Foreland basin (Austria) and its implications for molid phylogeny. Journal of Vertebrate Paleontology 29, 359–371.

Gudger, E. W. 1935. A photograph and description of Masturus lanceolatus taken at Tahiti, May, 1930. American Museum Novitates 778, 1-7. Available

Liu, Kwang-Ming, et al. 2009. Age and growth estimates of the sharptail mola, Masturus lanceolatus, in waters of eastern Taiwan. Fisheries Research 95, 154-160

Seitz, A. C., et al. 2002. Behaviour of a sharptail mola in the Gulf of Mexico. Journal of Fish Biology 60, 1597–1602.