Posts Tagged ‘fish’

Mandalatory Reading

5 May 2010

Go read this. Seriously.  Now.  Live fish dumped from airplanes.

Harissa Grilled Trout:

Clean trout and remove head (optional)

Rinse trout and pat dry with paper towel

Make harissa (ask Jessica, but basically this just involves re-hydrating some dried chiles and pureeing them with some olive oil, garlic and spices, probably coriander, cumin, and maybe pepper, super easy and will keep in the fridge for a week or more)

Spread the harissa, liberally, all over the myomeres I don’t know what you call them in fish, subcostalis?

You can thin the harissa out with some water if you want first use your best judgement here

I don’t know, you can squirt some lemon on there too if you want

Let fish sit in a closed container in the fridge for a “while”

Start the grill, and allow to come to uniform high temperature

You can oil the grill to keep the fish from sticking

Or, Actually like to make a bed of rosemary on the grill and put the fish skin-side down on that, genius

It will be done eventually, you don’t even have to flip it, just cook skin side down for with the cover on the grill till the harissa is dark and delicious and the fish is cooked all the way through – maybe 6 minutes depending on the size of your fish.

enjoy

Endangered by Taxonomy

5 January 2010

Taxonomists really are a miserable lot.  Like mall cops and Canadians, they sport inferiority complexes the size of Wales.  Make the mistake of asking one about her work and expect a nauseatingly lengthy lecture on the “relevance” of systematics.

Sometimes though, they have a point.  Classification systems can have real world consequences.  Perhaps no where is this more striking than in cases of conservation efforts for endangered populations of organisms.  There is an implicit assumption that “species” are more worthy of protection than “subspecies.”

Occasionally, one endangered population that constitutes a putative species is sunk into synonymy with another more abundant species, alleviating or at least diminishing what had appeared to be a conservation crisis.  Such was the case Chelonia “agassizii,” the black turtle of the eastern Pacific now considered to be a distinctive (but not specifically distinct) sub-population of the green turtle Chelonia mydas. In some cases there are factions that resist such taxonomic revision on the grounds that it will jeopardize the population — taxa that are distinguished on the basis of conservation concerns have been termed “geopolitical species.”

More often it seems to go the other way though.  One species is split into two or more, often creating endangered species in the process whole cloth when a restricted regional endemic or rare variant is elevated to species status.  Today the BBC is reporting just such a case.  Biologists are beginning to suspect that one threatened species of Amazon fish, the pirarucu (Arapaimagigas“), may in fact be several critically endangered species.

Among the largest freshwater fish in the world pirarucu, belong to an ancient and impressive family of fish, the Osteoglossids.  Aptly named, the group is distinguished by a bony “tongue” covered with toothlike projections that function in feeding.  Like many fish that live in sluggish waters, all members of the family occasionally gulp air and absorb oxygen across a vascularized swim bladder.  Pirarucu are “obligate” air breathers frequently coming to the surface to breathe, one of the factors that makes them easily hunted by Amazonian fishermen.  Apparently they are also delicious.  For some reason they are also quite popular with video game designers. They also appear to like sticking anacondas in trees but that’s a whole other story.

Pirarucu seemingly take to captivity fairly well, and can be seen in many public aquaria including the California Academy of Sciences where I shot the time lapse sequence at top a few days ago.

Hat-tip: Knight Science Journalism Tracker

Something my body needs anyway…I like that.

16 September 2008
As you’ll note from the logo over there, this marks the first issue of “blogger half-assedly opining about peer-reviewed publications when, really no one asked in the first place anyway.”  I’ll use this logo whenever I…well you get the picture.  Feel free to borrow the logo for your own half, or even whole-assed efforts.

Invert-workers are always carping1 about vertocentrism, and of course they have a point: tardigrades are like a gajillion times radder than tyrannosaurs and it’s a shame that Discovery Channel programming doesn’t reflect this fact.  I guess they’re busy vetting questions for Cash Cab or whatever.  But it occurs to me: it’s actually unfair to resent vertebrates as a whole for this injustice because, let’s face it, aside from lamnids no one gives a swimming crap about fish.

I know, I know, cladistically speaking, tetrapods like Sue and me are just aberrant terrestrial fish. Aside from our freakish lineage however, the silent majority of “values” vertebrates (i.e fish) might as well be ostracods for all the press attention they get.  I mean, ostracodes. Whatever.  (Actually ostracods/es have a pretty good PR person these days).

A few cases in point2: Funisia, an ediacaran with all the charisma of a sodden mop head, got major press attention thanks to some good old fashion sexing up by the media.  Likewise, Martialis heureka, the recently discovered basal ant, is already generating major buzz3 well before the peer-reviewed paper announcing the discovery has even hit the presses.  And don’t get me started about Aptostichus stephencolberti.

Meanwhile, the discovery of a new and extraordinarily bizarre fossil fish, Hsianwenia wui, announced in last week’s issue of PNAS (Chang et al. 2008), sank with less of a splash than a 49 kg Chinese diver making a perfect entry4.  And that’s unfortunate, because if the public has an inordinate fondness for things with hydroxylapatite endoskeletons, well Hsianwenia is about as bony as they come.

Hsianwenia (which I’m pronouncing “shee-An-Wen-ya” until someone corrects me) was discovered in Pliocene lake sediments from the Qaidam basin on the north side of the Tibetan plateau.  Hsianwenia belongs to the largest family of freshwater fishes the Cyprinidae which also includes minnows, carp and goldfish among many others.  The uplift of the Tibetan plateau over the past several million years has created multiple small, isolated lakes and waterways.  This in turn has driven the evolutionary radiation of an endemic suite of Cyprinids.  These 100 or so species in 15 genera are grouped together the subfamily Schizothoracinae, known to the more poetically-minded as “snow trout” or “snow carp” (Qi et al. 2006).

While FishBase reports that the flesh of living schizothoracines is “much relished”, eating Hsianwenia would have been a chore.  That’s because unlike its relished relatives, Hsianwenia is characterized by a peculiar thickening of the skeleton.    This “pachyostosis” is so extreme that the authors state that the bones appear to leave little room for muscle.

Hsianwenia wui from Chang et al. (2008).

While no known living fish possess a similar super-skeleton, another extinct fish, Aphanius crassicaudus—from Miocene sediments on the northern margins of the Mediterranean—apparently independently evolved extremely thick bones.  Multiple specimens from both species demonstrate that the pachyostosis is not evidence of disease or disorder, but was a natural feature in each fish.  More over, this condition was amplified through the course of ontogeny with fish becoming progressively stouter as they aged.

What factors could have selected for this unusual evolutionary quirk not once but twice?  The sediments containing the two fish species—though separated by space and time—share some provocative mineralogical clues: gypsum and calcium carbonate.  Both of these minerals are calcium salts and their presence as inorganic precipitates suggests that the bodies of water these fish lived in had extraordinarily high concentrations of dissolved calcium and other minerals.

The authors of the recent paper suggest that the hypertrophied skeleton of Hsianwenia (and Aphanius) was a novel solution for ridding the body of excess calcium5.  By thickening their bones, these fish were able to sequester calcium before it built up to toxic levels within its tissues.  Chang et al. also speculate that the saline waters were toxic to other vertebrate species given the absence of other vertebrate fossils.  So, these strange fishes may have had no need to escape from predators and could afford to reduce muscle space and add bulky bone.  Pollen and, yes, ostracods/es provide circumstantial support for generally arid and saline conditions in and around the lake while the fish were thriving.

Hsianwenia’s solution to it’s hard-water environment worked pretty well for 200,000 years or so, allowing it to thrive in waters where no other fish could.  Of course, Mother Nature’s a vindictive bitch, and all evolutionary solutions are by definition, temporary.  A thick evaporite deposit capping the fish-bearing layers speaks to our tale’s tragic end: the aridification of the Qaidam basin continued, the lake dried up, the freaky thick-boned fish died, the end.

So there you have it: tectonics, climate, aqueous geochemistry, evolution, morphological novelty and million-year-old fossil fish bones scattered across the high desert.  A fish story worth telling.

And you thought fish were boring.

REFERENCES

Chang, M. et al. 2008.  “Extraordinarily thick-boned fish linked to the aridification of the Qaidam Basin (northern Tibetan Plateau).” PNAS 105: 13246-13251.

Porter, S. M. 2007.  “Seawater Chemistry and Early Carbonate Biomineralization.” Science 316: 1302.

Qi, D. et al. 2006. “Mitochondrial cytochrome-b sequence variation and phylogenetics of the highly specialized schizothoracine fishes (Teleosti: Cyprinidae) in the Qianghai-Tibet Plateau.” Biochemical Genetics 440: 270-285.

1 As we’ll soon see, this is a hilarious pun.
2 There is one, sort of.  Be patient.
3 I suppose I’m mixing hymenopteran metaphors here.
4 Credit where it’s due: a German science blogger has already written about Hsianwenia here (in German).
5 One hypothesis to explain the “explosive” evolution of organisms with hard parts in the Cambrian holds that changes in seawater chemistry (perhaps linked to tectonic activity) drove organisms to begin precipitating minerals to prevent toxic buildup inside their cells.  Subsequently these structures were exapted into shells and carapaces and bones and teeth ultimately triggering an adaptive arms race.  While this hypothesis is speculative and controversial recent research does support the importance of seawater chemistry in setting the patterns of biomineralization among various lineages (Porter 2007).