Danio year 2009: Rakhine Yoma

In the last few hours of the first decade of the 2000s, realising that my friends in the western Pacific time zones are already into the new decade, and writing this is not likely to come to an end this year. Snow and cold (-10 to -15C) outside demonstrate why tropical fish won't do in the garden. It was night outside already at 1600h, but inside electricity glows in every corner and it is a comfortable +23C, so the fish inside are just fine.

Stockholm area, Sweden, late December 2009

In 1998, Ralf Britz and I travelled westward from Yangon in a battered but still comfortable Toyota minibus, with driver and guide. We did not have permission to fly to Kalaymyo to look for Badis ferrarisi (this was a Badis trip, and a considerable contribution to the Badis revision of 2002). Our substitute goal was the western slope of the Rakhine Yoma (aka Arakan Mountain Range), separated from the Ayeyarwaddy drainage and ichthyologically quite unknown. Of course Day had been there, up to Akyab (Sittwe), and Hora had reported fish from Sandoway (Thandwe), but nothing substantial was known. It took a whole day to travel the dirt roads and hitting Gwa on the Andaman Sea coast, arriving late in the evening. Of course we made a few stops on the way, but very brief.

Sampling sites in Rakhine Yoma in 1998.

 

The soft hills of Rakhine Yoma in a top view.

We then travelled north along the coast to Taunggok and returned to the Ayeyarwaddy at Pyay, making excursions up and down logging roads to find small streams with freshwater. The coastal stretch along the main road was either brackish water or no suitable water at all. Unfortunately, in the remaining four days, no badid came into the seine, so badids are probably absent from the area we sampled, betwen Gwa and Taunggok. That may be significant, or just due to poor sampling. We did get quite some interesting Garra, already described by me and Fang (2004), and quite some danios and other cyprinids endemic to the region. The Rakhine Yoma forests are actually a biodiversity hotspot with numerous endemic species of animals and plants, so no surprise endemic species of fish are also abundant. Endemic fish species that come to mind are Danio feegradei, Garra vittatula, G. rakhinica, G. flavatra, G. propulvinus, G. nigricollis, Puntius binduchitra, Batasio elongatus, Hara spinulus, Akysis vespertinus, and Channa pulchra.

Danio feegradei has already been described from Thandwe (then Sandoway) by Hora, who also reported Danio choprae from the same locality. The latter was first described from near Myitkyina in the upper Ayeyarwaddy drainage. The danionins we encountered, of course included D. feegradei, but also Hora's choprae. The latter turned out to have very little in common with D. choprae and in fact to represent a new species. Along with it we were impressed by a huge danio that had two dark blotches on the side and inhabited small streams in the deep forest. This one nobody seems to have seen before, and the colour pattern was certainly not reported before.

Eventually these two new danios got their names. In 2009, 11 years and a bit more after we collected them. Why it takes so long time from discovery to description?

Danio aesculapii, preserved holotype.

The choprae-like fish was named Danio aesculapii, and with its 29 mm max SL in the wild is one tiny fish. The name was inspired by the popular name of snakeskin danio. In the living fish, not much of snake pattern shows, the most impressive in this highly agile being is a golden shine along the middle of the dorsum. In the preserved fish, however, there is a series of dark vertical bars anteriorly on the side and two rows of dark spots from above the anal-fin origin to the caudal-fin base. Unlike most Danio, D. aesculapii does not possess stripes on the caudal fin. The caudal peduncle is relatively deep, and has more scales, 12 around the middle, than most other Danio, which have 10 only. Asklepios or Aesculapius was the Ancient Greek god of medicine, typically equipped with a staff with a snake or two wrapped around it.

Devario xyrops. A male, just collected. 

The large double-blotched species got named Devario xyrops with reference to the sharp ridges rising along the anterior part of the orbit (xyrops means razor-eye), and is also diagnosed by the colour pattern with a diffuse blotch formed by irregular vertical bars anteriorly on the side, and separated from a well-defined dark stripe on the posterior part of the body. It was getting dark, and we were exhausted after chasing fish up and down the stream all afternoon, but realising that this was an exceptional species, we made an effort to take a live colour photo as per above. The pink sheen ventrally probably derives from the red lid of the container on which the photo tank was placed, however. Devario xyrops is large for a danio, with the largest specimen 77 mm SL. Comparing with other Devario we found that the colour pattern is not fully unique. Also Devario browni has a separation of the lateral marking into an anterior blotch and a posterior band, but not as conspicuous as in D. xyrops. A similar species, D. anomalus, was described by Conway et al. (2009) from Bangladesh, and differs in being much more slender.

Small pool close to Thandwe, habitat of Danio aesculapii.

 

Habitat of Devario xyrops and Danio aesculapii north of Thandwe.  

And with that pass the last day of 2009 and the first of 2010. It is still cold out there, and very dark. Not a very inspiring setting, but not all days are like this so I do dare wish you a productive 2010 full of excitement and happiness!

References

To learn more you can download the original descriptions of both Danio aesculapii and Devario xyrops which are available online as Open Access from the publisher's website:

Kullander, S.O. & F. Fang. 2009. Danio aesculapii, a new species of danio from south-western Myanmar (Teleostei: Cyprinidae). Zootaxa, 2164: 41-48. [Errata: p. 46 line 3 from bottom: vittatula should be vittatula, add G. nigricollis]

Fang, F. & S.O. Kullander. 2009. Devario xyrops, a new species of danionine fish from south-western Myanmar (Teleostei: Cyprinidae). Zootaxa, 2164: 33-40. 

And here are other papers mentioned (none of them Open Access):

Conway, K.W., R.L. Mayden & K.L. Tang. 2009. Devario anomalus, a new species of freshwater fish from Bangladesh (Ostariophysi: Cyprinidae). Zootaxa, 2136: 49-58.

Hora, S.L. 1937. Notes on fishes in the Indian Museum. XXXI. On a small collection of fish from Sandoway, Lower  Burma.  Records of the Indian Museum, 39: 323-331.

Kullander, S.O. & R. Britz. 2002. Revision of the family Badidae (Teleostei: Perciformes), with description of a new genus and ten new species. Ichthyological Exploration of Freshwaters, 13: 295-372.

Kullander, S.O. & F. Fang. 2004. Seven new species of Garra (Cyprinidae: Cyprininae) from the Rakhine Yoma, southern Myanmar. Ichthyological Exploration of Freshwaters, 15: 257-278.

Image credits:

Map from the NRM Ichthyology Collection online database, using Google Maps

All other images: Sven O Kullander, CC-BY-NC 

At last: calendar boy

Being a well-known figure in fish circles can lead to occasional highlights. Last year I delivered my first fan autograph, quite unexpectedly, and I know I didn't manage it with the speed of a movie celebrity. And now, the next step in an ichthyological career: calendar boy. Chatting with Christer Fredriksson in his shop Akvarielagret, Christer came up with the idea to include me and my goldfish pot in the annual calendar of the Nordic Cichlid Society. And that did not work out, so the outcome is actually a shot in front of the two aquariums in our lab corridor (African lungfish in one, some other fish in the other), holding a jar of Cichla, wearing a T-shirt from the Sydney Aquarium, and a FishBase vest.

Christer is a highly motivated aquarist and innovative entrepreneur with the largest aquarium shop in Stockholm, and probably the most interesting shop in terms of fishes because he is not only focussed on selling, but also displaying and breeding quite a number of less common species. The business was recently expanded to include the Butterfly House at the northern outskirts of Stockholm (actually in Solna, the siamese twin city of Stockholm) which is now being converted to have more aquatic components. The most interesting recent move, however, was to convert supplier pricelists into a searchable online database. Customers can seach for the fish they are interested in, see the approximate retail price, and order online for pickup at shipment arrival. This saves time and money for both parties. Christer does not have to guess what customers may like, and customers can make more directed decisions.

Christer is also a persistent supporter of the Nordic Cichlid Society (Nordiska Ciklidsällskapet), which has one of the finest cichlid journals in the world, presently edited by Ola Svensson who recently graduated from Stockholm University.

You may indeed wish to join the Nordic Cichlid Society, not least for the 2010 calendar with me in it (and a number of more worthy celebrities), but also for the many well-written articles and so many beautiful photos of cichlids in the Society journal. The only bad thing is that they insist on using Metriaclima instead of the senior synonym Maylandia, and that something that really needs a blog later on.

Links
Akvarielagret
Nordiska ciklidsällskapet

Danio year 2009: Danio quagga

In March last year, our PhD student Te Yu Liao and I were able to collect along the Myanmar border with India, in tributaries to the Chindwin River. Our intended stops were Kalaymyo and Tamu, but we also tried stopping at streams along the road. It was very dry at the time, and even large rivers reduced to small streams.

Stopping by one of these streams, in the heart of a large village, we seined a pool with some vegetation. And in there was a zebrafish! Zebrafish in Myanmar, in the Ayeyarwaddy drainage. No way. It had to be something new, and as we have learned from Meinken, all danios are striped anyway. The fish went into formalin, and the chase for the next specimen commenced.

The stream

After one more hour, still not one more specimen of this schooling species, but hundreds of Danio albolineatus, and we were called to inspection by the local authorities, so we had to move on. Indeed, we were in a hurry between Kalaymyo and Tamu to arrive at our destination before dark, not only because of likely shortage of accommodation in Tamu, but also because we were given only one day of permanence in Tamu and would need to spend time with local authorities to explain our presence. But hand on heart, you can't leave a new species like that? Well, we moved on convinced we would find more specimens in some other place. Unfortunately it did not turn out so. We left Tamu with four more specimens from the market, where they hid in heaps of plenty of other little fish, dead to the bone, and with the total of five we eventually left Myanmar. Myanmar markets have large fish, but also large quantities of very small ones, used to prepare a special fish paste, ngapi. In the early morning there is thus plenty of fresh fish in the market and saves on collecting in the wild, with the caveat that fresh fish from the stream preserve better.

So, we were back with only formalin preserved specimens, and in the present times that is bad, because DNA sequencing is in the vogue, and generally a useful tool to check on phylogenetic relationships, and because formalin denatures DNA. Some of us can still do systematics without DNA, however, and that we did. The striped danio turned out not very similar to zebrafish at all, except in the general colour pattern. It is rather related to the spotted species, Danio kyathit from the neighbouring upper Ayeyarwaddy drainage and with one specimen recorded from the uppermost Chindwin.

The mammal: Equus quagga.

We named our striped danio Danio quagga. Quagga is the species or subspecies epithet of one of the zebras, so that within the genus of the zebrafish there should be at least one species with a name associating to zebras. We didn't call it Danio zebra just not to confuse things for the zebrafish people (and perhaps, in the end, ourselves). (But wouldn't it have been fun?)

The fish: Danio quagga, holotype.

See above what it looks like, now that the holotype has been dead for a while. Exciting as it was to encounter another zebrafish in the wild, I am not convinced that this will become an ornamental fish hit. Our comparisons suggest that it is most close to Danio kyathit, which hasn't outcompeted the leopard danio in the hobby. It is also somewhat larger than a normal Danio rerio, requiring more swimming space (the holotype was the only one in 50 m of stream ...). And, of course, why would we need another striped danio in our tanks. Seems we have exhausted danios as ornamental fish? But there is of course more to a fish than populating an aquarium. We are gradually building a phylogenetic history of danios, and then it is just great to find a sister-species pair, a split branch on the tree, rather than having single branches of uniques. Now we will move on to connect D. quagga and D. kyathit to the rest of the tree.

If you want to read the original description, you can download an Open Access copy, which you can share with families and friends as much as you like. Just click on the reference below. It's magic!

Reference
Kullander, S.O., T.Y. Liao & F. Fang. 2009. Danio quagga, a new species of striped danio from western Myanmar (Teleostei: Cyprinidae). Ichthyological Exploration of Freshwaters, 20: 193-199. Open Access PDF

Image credits:
Map from the NRM Ichthyology Collection online database, using Google Maps
Danio quagga and stream: Sven O kullander, CC-BY-NC

Equus quagga: Muhammad Mahdi Karim, from Wikimedia Commons, GNU FDL 1.2

Danio year 2009: Danio tinwini

The year is isn't over, and the snow did not fall over Stockholm yet, so it may be a bit early to summarise the year. But it might be better to start early, not to end up in december 2010 summarizing 2009, and then it has to be piece by piece. Writing this, I am reminded of one of the most famous aquarium books, Aquarienfische in Wort und Bild, which was issued over a period of 30 years in instalments of a smaller number of sheets, and the authors were indeed writing continuously on it between 1932 and 1962. In the 1950s there were similar initiatives elsewhere in Europe, e.g., the Belgian Vissentlas, but I have not kept track of them. Also TFH publications tried, much later, to publish a loose-leaf edition of Exotic Tropical Fishes, and the German cichlid society sent out species descriptions with their journal supposed to be collected by the subscribers. Of course, this is in most cases an awkward way of publishing where the customer is the big loser. The following scenarios are possible:

• Publication terminates after a smaller number of pages. You end up with a quarter or half of a book.
• Publication goes on indefinitely, with or without revisions of outdated pages. You end up with a book containing almost duplicate pages, and a span of many years between the earliest and the latest information (could be blurred b/w photos mixed with excellent digital colour photos. Half the book will be outdated.
  
• You stop subscription and end up with a half book
• Everything completes but in the meantime you already had to buy some complete books, just not to stay ignorant about everything from H to Z.

Die Aquarienfische in Wort und Bild (there is also the corresponding Aquarienpflanzen) is an exception among the bad examples because it (1) terminated a long time ago, so all you can buy now is the complete book (€70-150 on eBay), and (2) it was actually quite complete in coverage, and especially the species descriptions were more detailed than anything in other contemporary aquarium books. I am actually not quite sure when it was published, but it seems it started in 1932, and went on till 1962, with Hermann Meinken (1896-1976) as the sole author after co-authors Maximilian Holly (*-*) and Arthur Rachow (1884-1960) long before had retired from writing. Die Aquarienfische in Wort und Bild was a highly influential work, the mother of all other European aquarium books.

That it wasn't published after 1962 seems likely because the description of Brachydanio frankei, described by Meinken in 1963, is missing. Every other fish imported to Germany up till the late 1950s/early 1960s are there, and Meinken had a particular interest in danios.

Now we are getting to the point: Brachydanio frankei was, at that time, known only from aquarium specimens. It is still not known from the wild, as already pointed out in an earlier post about fish from nowhere. Meinken lists the following species of danios:

Danio devario
Danio malabaricus
Brachydanio kerri
Brachydanio albolineatus
Brachydanio nigrofasciatus
Brachydanio  rerio

That is a very short list. (And by the way, Brachydanio is presently considered a junior synonym of Danio, and Meinken's Danio are now in Devario; but they are all danios.) A much larger number of species of Rasbora are described in the same book. At present it looks to me that there are more danios than rasboras in the shops, but I may may be biased.

  

Danio rerio, aquarel by Curt Bessiger, used in Die Aquarienfische in Wort und Bild.

The most characteristic about Danio frankei is the colour pattern, which is golden with small brown or black spots. At the time that was quite remarkable because all known danios (listed above) were striped (except that the stripe in Devario devario is not so prominent, and Danio nigrofasciatus has spots on the abdomen. Over the time, no wild specimens of D. frankei appeared, and it has turned out rather certain that it is a colour mutation of the zebrafish, Danio rerio.

In the original description of Danio frankei, Meinken wrote (my translation from the German):

Shortly before the end of the year 1962, through my old friend Heinrich Grauel from "Vivarium-Bremerhaven", my friend Diplom-Biologe Hanns-Joachim Franke in Gera/Thüringen, gave me  six captive bred specimens of a very handsome Brachydanio novelty with the request that I study the specimens, if possible identify them and give them a name. According to the information from Mr Grauel, at that time Mr Franke already had bred several hundred specimens of this species in his breeding tanks. Unfortunately the novelty was lacking a name.

Upon my immediate checkback concerning details about the importation and my notice that -- in case the animals would represent a scientifically still unknown and undescribed novelty -- a determination based on captive bred specimens would be unreliable because that could lead to mistakes, Mr Franke then most friendly told me that he had obtained the import specimens from the familiar and active Diplom-Biologe Stanislav Frank in Prague. Unfortunately, the place of capture was unknown also to Mr Frank. That the animals came from India was only a very weak consolation, because first all Danio and Brachydanio species come from India and the Indo-Malayan area, and second India is large, about several times larger than the previously undivided Germany. Mr. Franke, however, made the great sacrifice in the interest of science and nomenclature, killing four of his import specimens and sent them to me for examination.

Meinken then went on with a very detailed description, a lamentation of the lack of locality data, and finally, a long discussion about relationships. According to Meinken, D. frankei would be most closely related to B. tweediei (from Malaysia), a nominal species currently synonymized with D. albolineatus.

Leopard danio. Preserved aquarium specimen from Taiwan.

That did not stop other leopard danios from coming in. The first was Danio kyathit, described by Fang in 1998. The second was just described by me and Fang based on a large series collected by U Tin Win in the same region as D. kyathit, and we named it Danio tinwini. 

Danio tinwini, female paratype.

Danio tinwini is spotted and the spot pattern is quite similar to that of D. kyathit, but not so much to that of the leopard danio. It is a much smaller species than either D. kyathit or the leopard danio, however, and external morphological characters suggest that it is more related to D. nigrofasciatus or D. aesculapii. It is indeed a remarkably small species. The largest wild male examined was 21.7 mm in standard length, the largest female 25.6 mm. That is almost as small as the smallest Danio species (D. margaritatus, 21.3 mm).  What provokes most thought, however, is the fact that the only two spotted danios, D. kyathit and D. tinwini occur in the same general area (but not syntopic), and are not closely related. Would we be surprised if D. frankei were found in northern Myanmar one day as well?

Danio tinwini lives together with a much more famous fish, Danionella dracula, the Vampire or Dracula fish. Much more we do not know about the natural habitat och accompanying species. You can read all the technical details about Danio tinwini in the Open Access original description.

References
Holly, M., H. Meinken & A. Rachow. 1932-1962. Die Aquarienfische in Wort und Bild. Kernen, Stuttgart, Loose-leaf publication, 1328 pp.

Kullander, S.O. & F. Fang. 2009. Danio tinwini, a new species of spotted danio from northern Myanmar (Teleostei: Cyprinidae). Ichthyological Exploration of Freshwaters, 20: 223-228. [errata:  p. 227, col 2, para 2, line 10: "1" should be "4"; p. 228, col. 1, line 3: "19.3" should be "21.2"]

Meinken, H. 1963. Mitteilungen der Fischbestimmungsstelle des VDA XLII: Brachydanio frankei spec. nov., der Leopard-Danio. Monatsschrift für Ornithologie und Vivarienkunde. Ausgabe B. Aquarien und Terrarien, 10:75-79.

Perplexion
*-* I cannot find any information about Maximilian Holly. I don't even know where to start...?

Photo credits:
Top image: living Danio tinwini,Sven O Kullander, CC-BY-NC
Leopard danio and Danio tinwini, Sven O Kullander, CC-BY-NC
Danio rerio aquarel, public domain.

Penis fish

My friend Ralf Britz (Dracula fish), just released the description of a species related to the Dracula fish (Danionella dracula), viz., the Penis fish (Danionella priapus), which is number four in the genus (D. mirifica, and D. translucida were described earlier). This was a bit of of concern to me. Is the evolution of Danionella Nature's idea of a freak show (or a Japanese game show...)? Or perhaps the fishy Fantastic Four (Bloodsucker, Flasher, Beauty, and Invisible). By the way, there is a Marvel character called Priapus.

Danionella priapus, the male holotype. Photo (c) Ralf Britz, reproduced with kind permission.

The penis, a worm-shaped intromittent reproductive organ characterizing mammals, some reptiles and very few birds, has fascinated male ichthyologists for a long time. The typical penis, in placental mammals, contains some spongy tissue and ducts for urine and sperm. Many species of fish with various elongate reproductive structures have been named with reference to the penis, or after the Greek minor deity commonly associated with an oversize penis (list below). The only group of fish that had escaped until 2008 were the Chondrichthyans, equipped with the most penis-like intromittent organ among fishes, known as mixipterygia and a synapomorphy of the group. Perhaps because in Chondrichthyans, the male reproductive organ, a modifiction of the pelvic fin, is paired. Yes, they have two. Theoretically a male shark could mate with two females simultaneously, but there seems to be no observation of such act and perhaps for reason that such pairing must be very complicated to coordinate, no other vertebrates invested in double external reproductive organ. But we all do maintain a paired internal set, except that in many fishes there is only one ovary. Marsupials, it must be added, are an exception here as in so many other respects. Males usually have a bifurcate penis unfit for peeing with and consequently used only for copulation. Females have two vaginas (with common opening), each with its own uterus, and a third for parutition.


In actinopterygian fish, sperm-transmitting elongate structures, intromittent organs, are technically known as gonopodium (live bearing poeciliids), or andropodium (Hemiramphidae; Goodeidae) in livebearers and are formed by modifications of anal-fin rays. Egglaying fish are commonly equipped with a genital papilla through which sperm or eggs are released. The genital papilla of females is sometimes referred to as the egg-laying tube or ovipositor. It is very impressive in bitterlings in which it is used for depositing eggs deep inside bivalves. None of these terms were considered suitable for a fish name, however.

What about naming fish after mammal female external reproductive organs? There is the south Asian Trypauchen vagina Schneider, 1801, a goby, for which Schneider did not explicitly explain the etymology but gave the local name, obviously based on information from the collector/correspondent in Danish India (Tranquebar), Christoph Samuel John (1747-1813), "Sewwöli, i.e., vagina cultri rubra, Tamulice", what would mean: "Sewwöli, that is, red knife slide, of the Tamils", i.e., nothing to do with humans. It is a slender, caudally tapering fish with a predominantly red colour. Schneider gave the same name also, spelled Sewwöti, for Cepola coecula (junior synonym of another goby, Taenioides anguillaris), another slim, red fish. There are also Thai cyprinids Probarbus labeamajor and P. labeaminor, named by Tyson Roberts in 1992, but for the thick and thin lips, respectively, of the mouth.

Trypauchen vagina

Priapos was an ancient Greek god of fertility, usually depicted with an oversize, erect penis, and according to Lemprière a rather deformed figure, not worthy of residing in the Olympics, and on the whole more of a rapist and rascal than anything else, requiring sacrifice in the form of of asses (Equus africanus, that is). This sad figure seems eventually to have converted into a garden gnome in Western garden culture. In Rome, Mutunus was the approximate equivalent. There is no fish named for Mutunus.

Interestingly, a very large number of fish possess a well developed genital papilla. In cichlids, for instance, it is long and pointed in males, but short and swollen, with at least a transverse fold in females, although there is variation, and in some genera it is hard to tell males and females apart on the papilla alone. Cottids are also well known for the long male genital papilla, as exemplified by Phallocottus, and it is also prominent in gobioids, but I could not find any relevant name in that group. The group that have most of the penile names are the livebearing poeciliids, in which the anal fin is modified to an elongate intromittent organ.

Back to Fantastic Four. As Ralf points out, these miniature fishes, and other miniatures as well, are remarkable not only for their small size. They also have conspicuous novel characters which gain significance particularly in a small body. The elongate fangs of Danionella dracula are the only oral tooth structures known from cypriniforms, and may very well be the beginning of a radically different evolutionary lineage. Males of Paedocypris (another miniature), and D. priapus have developed accessory sexual organs not known from other cyprinids, and may be actively evolving in organs that larger, more long-lived fish with longer generation times cannot afford to invest in.

Small size apparently calls for radical solutions, and those radical solutions may be the matter of evolutionary leaps. We are accustomed to think, at least I am, of evolution among fishes being based on something mid-sized rather normal fusiform, which then strikes off in different feeding niches, becoming smaller or larger depending on energy householding. But, that does not seem to lead to much real diversity (after all, all cichlids and cyprinids look very much the same). Radical morphological change as within Danionella may be one of the clues to evolutionary stepping. Most striking about species of Danionella is that they are so radically different from each other. Had they been a few centimeters longer, they would probably have been placed in different genera, but now they are considered as specialized close relatives. So, there is something important to be learned from the penis fish and friends.

Not all small fish present novel characters or behaviour, but the phenomenon seems to be particularly evident in progenetic species. This is then seen clearly in the larvae of many marine fishes in particular. The amazing spinature of many pelagic acanthopterygians, and the strange leptocephali of eels, demonstrate this. In this case, the "normal" adult provides for a backup morphology, should juvenile experimentation fail, but if these fishes turn progenetic and skip the adult stage, they may blast off in a different morphological evolutionary trajectory.

Origin of a new phylum? Larva of an unidentified species of the family Gempylidae. Photo NOAA.

Can I then go so far as to postulate that larval specializations must precede progenesis? Or does necessarily specializations have to come along with or after progenesis? Or am I making it unnecessarily difficult?

As you can now see, this post is all about evolution. But, you are right: I am also fascinated by biological nomenclature as a graffitti wall...

Anyway, here is the list of the penis fishes, based on active search in Catalog of Fishes. Many of them do not have a common name, so here is a goldmine for those constructing common names based on translations of the scientific ones ... Of course all names are masculine, and all the authors are male... And, by the way, penis means tail, but is never used in that meaning, and the word phallos wasn't intended for other than the drawings and sculptures, and again is not used in that meaning.

Phalloceros Eigenmann, 1907. Poeciliidae: Poeciliinae.

Allophallus Hubbs, 1936. Synonym of Carlhubbsia Whitley, 1951. Poeciliidae: Poeciliinae.

Arthrophallus Hubbs, 1926. Synonym of Gambusia Poey, 1854. Hubbs, 1926. Poeciliidae: Poeciliinae.

Aulophallus Hubbs, 1926. Synonym of Poeciliopsis Regan, 1913. Poeciliidae: Poeciliinae.

Curtipenis Rivas & Myers, 1950. Synonym of Poecilia Schneider, 1801. Poeciliidae: Poeciliinae.

Dicerophallus Alvárez, 1952. Synonym of Gambusia Poey, 1854. Poeciliidae: Poeciliinae.

Flexipenis Hubbs in Rivas, 1963. Synonym of Gambusia Poey, 1854. Poeciliidae: Poeciliinae.

Furcipenis Hubbs, 1931. Synonym of Alfaro Meek, 1912. Poeciliidae: Poeciliinae.

Heterophallina Hubbs, 1926. Synonym of Gambusia Poey, 1854. Poeciliidae: Poeciliinae.

Heterophallus Regan 1914. Synonym of Gambusia Poey, 1854. Poeciliidae: Poeciliinae.

Orthophallus Rivas 1963. Synonym of Gambusia Poey, 1854. Poeciliidae: Poeciliinae.

Phalloptychus Eigenmann, 1907. Poeciliidae: Poeciliinae.

Phallotorynus Henn, 1916. Poeciliidae: Poeciliinae.

Plectrophallus Fowler, 1932. Synonym of Brachyrhaphis Regan, 1913. Poeciliidae: Poeciliinae.

Priapella Regan, 1913. Poeciliidae: Poeciliinae.

Priapichthys Regan, 1913. Poeciliidae: Poeciliinae.

Trigonophallus Hubbs, 1926. Synonym of Brachyrhaphis Regan, 1913. Poeciliidae: Poeciliinae.

Ctenophallus Herre, 1939. Synonym of Neostethus Regan, 1916. Phallostethidae.

Gulaphallus Herre, 1925. Phallostethidae.

Mirophallus Herre, 1926. Synonym of Gulaphallus Herre, 1925. Phallostethidae.

Penicelinus Bolin, 1936. Synonym of Icelinus Jordan, 1885. Cottidae.

Phallichthys Hubbs, 1924. Poeciliidae: Poeciliinae.

Phallobrycon Menezes, Ferreira & Netto-Ferreira, 2009. Characidae.

Phalloceros Eigenmann, 1907. Poeciliidae: Poeciliinae.

Phallocottus Schultz, 1938. Cottidae.

Phalloptychus Eigenmann, 1907. Poeciliidae: Poeciliinae.

Phallostethus Regan, 1913. Phallostethidae.

Solenophallus Herre (ex Aurich), 1953. Synonym of Neostethus Regan, 1916. Phallostethidae.

Galeus priapus Séret & Last, 2008. Scyliorhinidae.

Online reference:
Britz, R. 2009. Danionella priapus, a new species of miniature cyprinid fish from West Bengal, India (Teleostei: Cypriniformes: Cyprinidae). Zootaxa 2277: 53-60. (Abstract only; not Open Access)

Book references:
Lemprière, J. 1984. Lempriere's classical dictionary. Bracken books, London, xv+734 pp. Original: A classical dictionary; containing a full account of all the proper names mentioned in Ancient authors. Reading, 1788. [Second edition, 1792] [11th edition, 1820]

Image credits:
Cover of Fantastic Four from Wikipedia, copyright, but used in fair sense, to illustrate that Nature and Fiction sometimes go hand in hand, you just need the imagination.
Trypauchen vagina from Wikimedia Commons
Gempylid larva from Wikimedia Commons.
Danionella priapus courtesy Ralf Britz