Type specimens: Will the real slim [insert species name here] please stand up?

I've spent the past month or so re-curating our type collection of fishes and I just finished! This was great fun given the importance of type specimens in biology. A type specimen is the "name bearer" for a given species. That is, when a biologist discovers and describes a new species, he or she designates a single specimen to be the official representative of that species. As alluded to in the title of this post, I always think about the Eminem song The Real Slim Shady when I think about type specimens: if anyone ever wanted the "real" entity for any species to figuratively stand up, a biologist would go fetch you the type specimen. We designate type specimens this way so that if future researchers, for example, find an individual or a population that is similar to a known species but they suspect might be a new species, there is no question about which specimen of the known species they should compare it to. Type specimens are always the reference point when making any species updates and revisions.

Species updates and revisions actually happen more often than one might think! Systematic biologists (those who study life's diversity) are constantly acquiring new data that can lead them to discover that one species is really multiple species (this is called splitting), or to discover that groups that were thought to be different species are really only one (this is called synonymization, or lumping). Then of course there are always the discoveries of entirely new forms previously unknown to us humans, which are perhaps the most exciting type of update...

The changing nature of species boundaries (like that of scientific knowledge in general!) actually made cataloging and labeling our type collection an interesting job. Some species designations have stood the test of time. For example, we have the type specimen for the vermiculate electric ray, Narcine vermiculatus. It was originally described as Narcine vermiculatus in 1928 by Charles Breder, and today the species represented by this type specimen is still known as Narcine vermiculatus. Here's our type specimen:

On the other hand, some species names have not stood the test of time. For example, we have the type specimens for a dragonfish that was described as Flagellostomias tyrannus by Albert Parr in 1927. Here is one of them:

This species was synonymized with (shown to be the same species as) Flagellostomias boureei, in 1964 however, so any specimens that were once considered Flagellostomias tyrannus are now considered to be Flagellostomias boureei.

Our usual practice for labeling specimens in the collection is to label specimens with their current valid name. But these type specimens are well, special. No matter how the species is reclassified, the type specimen for a particular name will always be the type specimen tied to that name. And with new data, a  species name that has become invalid could be come valid again. So it's essential to preserve the linkage between the type specimen and its original name.

So here's the label template we made to solve this little dilemma -- that is, whether to label our types with the current name, or the original name. We labeled them with the original name in bold, and the current name designated underneath:

This works especially well because we keep our type specimens in their own section of the collection, not interspersed with the rest of the specimens.

It turns out that here at Peabody Vertebrate Zoology we have one of the largest ichthyological type collections in the United States and Canada (Poss & Collette 1995). Pretty cool, huh? For the next few posts I'll be featuring some of my favorites.


References:

Poss, S.G. and B.B. Collette. Second Survey of Fish Collections in the United States and Canada. Copeia 1995: 48-70.

Not-so-flabby flabby whalefishes

So this specimen first caught my eye because it belongs to a family of deep sea fishes known as the "flabby whalefishes" (Cetomimidae). But .... this little fish, caught off the coast of Portugal in 1959, was neither flabby, nor was it whale-y. To my eye at least. I found this pretty amusing in and of itself.

YPM ICH 4899

But THEN... I discovered that when alive, it is PINK! It so happens that I'm not really even much of a pink fan myself, but this species, Cetostoma regani, is bright pink as bright pink gets. (And its common name is the pink flabby whalefish. Fancy that.)

Photo from the MCZ

And THEN... upon further googling, I learned that in 2009, this species played a big part in an amazing story of scientific discovery. The story goes like this:

Once upon a time, there were three fish groups, the tapetails (Mirapinnidae), the bignoses (Megalomycterydae), and the whalefishes (Cetomimidae). They were all very funny-looking and lived in the deep sea. But they all looked wildly different, so --as one would expect--they were considered to be three families.

But in 1989, ichthyologist John Paxton noticed that, strangely, all of the known specimens of whalefishes were females. Similarly, biologists soon noticed that all of the known specimens of bignoses were males. And all of the known specimens of tapetails were sexually immature...

Following these clues, a team of biologists, headed by David Johnson of the Smithsonian, recently sequenced the DNA of specimens from these three families and found that the DNA from each was essentially identical.  These were not three families--they were only one! Consistent with the clues, they are simply different life stages of the same fish. The tapetails are the larvae, the bignoses are the males, and the whalefishes are the females. Pretty amazing. Here's a picture of all of the families:

Image taken from here.

The degree of morphological difference between the larval and adult stages, and between the males and females, is truly remarkable. The authors of the study in 2009 note that although significant larval transformations occur in some other deep-sea fish families and extreme sexual dimorphism is common among vertebrates, "the extraordinary combination of both ... for the whalefishes is unparalleled within Vertebrata." And if there was any doubt about their findings, the team found morphological evidence to back up the DNA evidence. They were able to identify some transitional specimens-- that is, female "tapetails" transitioning to the "whalefish" stage, and male "tapetails" transitioning to the "bignose" stage.

Note that the whalefish at the bottom of the image above looks much more whale-y than the specimen I re-curated! Perhaps our specimen is in fact a transitional specimen ... 

For more details on the story, check out this interactive Smithsonian website about the discovery.


References:

Johnson, G.J. et al. 2009. Deep-sea mystery solved: astonishing larval transformations and extreme sexual dimorphism unite three fish families. Biology Letters 5: 235-239.

Shiny-buttoned Midshipman Fishes

A few months ago, I re-curated these specimens. They had funny dots lining their entire bodies, like so:

YPM ICH 8902

It turns out that these dots are photophores, which are little organs that produce light (often referred to as bioluminescence). The fish belong to a genus named Porichthys, and they're actually part of the same family, Batrachoididae, as the Oyster Toadfish from two posts back. The 15 species that make up the genus Porichthys are commonly known as Midshipman Fishes, because the 700+ photophores that adorn their epidermis are said to resemble the gleaming buttons of a naval uniform.

Here is a photo of a very fine human midshipman* specimen, Jack Vine, a childhood friend of mine, pictured here in full naval uniform with his proud mom:

And here is a photo of a bioluminescent midshipman fish specimen:

Photo taken from this website

I wonder if the person who first noticed the fishes' midshipman likeness was looking at the two rows of pores lining the anal fin (starting at the middle of the fish and continuing to the tail). To me, those two rows really jump out as resembling the naval uniform buttons:

YPM ICH 8902

I think that the clean, tapered lines of the midshipman fishes, as shown well by this sketch, also contribute to their overall resemblance to the naval uniform:

Image from NOAA

Why do the midshipman fishes have these photophores? That... is a good question. A number of functions have been hypothesized. One hypothesis is that they function to aid in prey capture. The idea here is that the Porichthys pattern of luminescence mimics the light of a small swarm of krill (Tsuji et al 1971). This might allow the midshipman fishes to approach such a swarm undetected and then easily feed on them. Or perhaps this sort of mimicry could even lure the krill swarms to the fish. As far as I could find though, this hypothesis hasn't really been tested.

Another hypothesis is that the photophores function in something known as "counterillumination." This is a form of bioluminescent defense against predators that is used in many types of organisms, including crustaceans and various fishes. Essentially what happens is that an organism using this "counterillumination" will use photophores on its underside to match any dim light coming from the surface of the water. In so doing, they can make a potential shadow disappear and thus camouflage themselves. This hypothesis has actually been tested and supported! It's been showed in laboratory experiments that midshipman fishes can match the intensity and color (among other things) of downwelling light (Harper and Case 1999). This hypothesis also makes intuitive sense because most of the photophores are concentrated on the bottom of the fishes-- where they would need to be for counterillumination.

One last hypothesis is that the glowing photophores function in courtship (Crane 1965). Various authors have expressed skepticism about this hypothesis, however, because there is a population of midshipman fish in Puget Sound, Washington, that has no luminescence capability, yet they still live and reproduce successfully. If the photophores were necessary for courtship, the Puget Sound population shouldn't exist (Warner and Case 1980).

How do midshipman fish get their ability to glow? By eating tiny bioluminescent crustaceans called ostracods. Without ostracods, the midshipman fishes' photophores are useless. This is where midshipman fishes get luciferin, which is a compound that bioluminescent organisms need to emit light. Many organisms produce luciferin on their own, but others, like the midshipman fishes, have to acquire it through their diet. It was actually the Puget Sound population of midshipman fishes that clued scientists in to the fact that midshipman fishes get their luciferin from ostracods. It turns out that the Puget Sound population has no luminescence capability because the there are no bioluminescent ostracods for them to eat there (Warner and Case 1980)! They can easily luminesce, however, if they are fed the proper ostracods.

Ostracod

Oh, one more thing before I sign off. Just like the toadfishes, the male midshipman fishes also make humming sounds with their swim bladders! (Like I mentioned earlier, the midshipman fishes are part of the same family as the toadfishes). Instead of people living on the east coast though, it's the people in San Fransisco Bay who are kept awake by their mating calls. You can listen to them hum on this little feature by NPR.

And here's one last picture of one of our specimens, species Porichthys porosissimus, collected in the Gulf of Mexico off Galveston, Texas, in 1932 by the vessel Mabel Taylor.

YPM ICH 8900

*I should note that Jack is no longer a midshipman, although I think he was when that photo was taken. He graduated from the Naval Academy in 2008 and is now a fully commissioned Navy pilot serving in the Middle East.


References:

Crane, J. M., 1965. Bioluminescent courtship display in the teleost Porichthys notatus. Copeia, 2 : 239-241.

Harper R.D., Case J.F. 1999. Disruptive counterillumination and its anti-predatory value in the plainfish midshipman Porichthys notatus. Mar. Biol. 134: 529–40.

Tsuji F.I., Haneda Y., Lynch III R.V., Sugiyama N. 1971. Luminescence cross-reactions of Porichthys luciferin and theories on the origin of luciferin in some shallow-water fishes. Comp Biochem Physiol 40A: 163-179.

Warner J.A., Case J.F. 1980. The zoogeography and dietary induction of bioluminescence in the midshipman fish, Porichthys notatus. Biol Bull mar biol Lab, Woods Hole 159: 231-246.

Happy Valentine's Day! Rock-paper-scissors, anyone?

Forget about love, flowers, chocolates, teddy bears, etc. etc. Common side-blotched lizards decide on their Valentines by playing rock-paper-scissors. True story.

Here are three specimens of this species, Uta stansburiana, from our collection, HERR 7589, 7594, and 7595, collected in Texas in 1971:


So the way this crazy love (or not... love...) game works is like this. Male common side-blotched lizards come in three different forms. There are orange-throated males, yellow-throated males, and blue-throated males. Here's a pic, taken from the website of Barry Sinervo, one of the biologists who first figured out the rules of this lizard's game.


Orange-throated males are largest and the most aggressive of them all and as such they're able to defend large territories with lots of females in them. They can easily overpower the blue-throated males, which are of a medium build.

Orange-throated males cannot defend against yellow-throated males, however. Yellow-throated males are the smallest of them all and look like females! Given this, they're able to sneak into the territories of orange-throated males unnoticed and mate with any of the females there who might be tired of bloated orange-throated machismo.

The stealth strategy of the yellow throats is powerless, however, against the medium-size blue-throats. The blue-throated males keep small territories and work together to guard their females. As a result, the yellow-throated males can't fool the watchful blue-throats like they can with the orange-throats.

So to sum up, orange beats blue, blue beats yellow, and yellow beats orange. Pretty cool if you ask me.

The success of these different mating strategies depends on the the rarity of each form in a given population. For example, if there are too many yellow-throated males, their "sneaker" strategy becomes ineffective, because well, it's not very sneaky anymore if everyone is doing it, too. So the prevalence of any given form will cycle every few years in a given population of common side-blotched lizards. In some years, there will be more blue-throated males, other years more orange-throated males, and in other years, more yellow throated males. When one form becomes too common, the others start to be more successful.

Sources:

Sinervo, B. and Lively, C.M. 1996. The rock-scissors-paper game and the evolution of alternative male strategies. Nature 340:240-246

Corl, A., Davis, A. R., Kuchta, S. R., Comendant, T. and Sinervo, B. 2010. Alternative mating strategies and the evolution of sexual size dimorphism in the side-blotched lizard, Uta stansburiana: a population-level comparative analysis. Evolution 64: 79–96.

Singing Toadfishes in Space

Like the Lizardfishes from a few posts back, here is another fish family named for a land-dwelling look alike. The toadfishes make up the family Batrachoididae and are benthic ambush predators that use their ugly appearance for camouflage as they lie in wait for their prey. They're quite hardy creatures, too! Some individuals have remained alive for more than 24 hours out of the water (Paxton and Eschmeyer 1994).

Here are some pictures of YPM 8923, species Opsanus tau, collected on October 6, 1932, off of Long Island, NY:





The most interesting thing about toadfishes, I think, is that they are known for their singing. During mating season different toadfish species produce a variety of sounds using their swim bladders. Opsanus tau in particular produces a loud "boatwhistle" sound that is famous for keeping people living near the shores of North America's east coast awake (Paxton and Eschmeyer 1994). It's no wonder that they make such a loud noise, too-- the muscles in their swim bladder that contract to make this noise are the fastest contracting vertebrate muscles known (they contract at a rate of 200 Hz). The next fastest muscles known are those at the base of the tail in rattlesnakes, and they only contract at half the rate of Opsanus tau's (Rome et al. 1996).

And yet another interesting fact about species Opsanus tau-- NASA has sent a bunch of these guys to space! NASA scientists use them to perform experiments designed to better understand balance disorders that affect astronauts in space. Why toadfishes for this task? The structure of their inner ear--the place that helps control balance--is very similar to ours, making it a good model organism. Who would have thought...


References:

Paxton, John R., and W.N. Eschmeyer. 1994. Encyclopedia of Fishes. Academic Press, San Diego.

Rome L.C., D.A. Syme, S. Hollingsworth, S.L. Lindstedt, and S.M. Baylor. 1996. The whistle and the rattle: the design of sound producing muscles. Proc Natl Acad Sci USA 93:8095-8100.

YPM ICH 5971 & 22495: Sea devils at the Peabody

Happy Halloween! In Halloween spirit, here are some ghouls and goblins:



Sailors dating at least to the 16th century would find these horrors at sea and often brought them back to shore as evidence for their stories of sea monsters, sea devils, and the like. What are they exactly? Called "Jenny Hanivers," they're actually just dried-out specimens of skates, rays, and guitarfishes!

Skates, rays, and guitarfishes make up the superorder Batoidea, and what you see in the pictures are the undersides of the animals. The nostrils and mouths of these creatures are positioned perfectly, as you can see, such that they look like a demonic face. (The eyes are actually on the top sides of the animals.)

Here is YPM ICH 5971, a guitarfish of species Aptychotrema vincentiana, collected in 1968 off the coast of Adelaide, Australia. Here's the underside of the animal, where you can see the "Jenny Haniver" face:


Here is the top side of the animal, where you can see the true eyes:


Of course, this specimen isn't properly a Jenny Haniver in the full sense of the term. But it's halfway there! To make a Jenny Haniver, once you've caught a skate, or a ray, or a guitarfish, you should dry it out, not fix it with formalin and preserve it with ethanol as we did with this one. It's when they're dried out that they really take their ghoulish shape.

You should then carve it and shape it to make it look even more grotesque. Sailors in Antwerp, Belgium, were famous for the Jenny Hanivers that they carved on their docks and then sold to superstitious tourists. In fact, it's thought that the term "Jenny Haniver" might come from these sailors. The French phrase jeune d'Anvers means ('young [person] of Antwerp'). The thinking is that British sailors then turned this phrase into the personal name "Jenny Haniver."

Here is YPM ICH 22495, one more almost-Jenny Haniver from our collection. It's a skate of species Bathyraja maccaini that was collected on a 2009 Yale research voyage to Antarctica. Here's its underside:


And here's its top side:

YPM ICH 7720 & 12449: Lizardfishes!

I'm afraid the title of this post gives it all away: these fish look exactly like lizards! Here is YPM ICH 7720, a lizardfish of species Synodus variegatus, collected in the Indian Ocean's Seychelles Islands in 1957:


As you can see, the head of a lizardfish looks, well, like a lizard, but they were actually named for their posture, which is also eerily lizard-like. They like to sit at the bottom of shallow seas in sandy areas, with their head raised like a lizard, propped up by their fins. Here's a picture that shows this:


The above shot was taken this summer by Alex Dornburg, a Yale Ecology and Evolutionary Biology Phd candidate, who was in Curacao collecting specimens for his research on marine fish macroevolution.

Many of our museum specimens are actually still preserved in the lizard posture! Here's one, YPM ICH 12449, species Synodus foetens:


Man, I wish I had posture like that. Mom would be proud....

Here's a final picture, a headshot of YPM ICH 12449:



Source:

Paxton, John R., and W.N. Eschmeyer. 1994. Encyclopedia of Fishes. Academic Press, San Diego.