#lancelet

conseil's piece

so actually my affection extends to all stem chordates not just lancelets. to understand the lancelet first we must understand stem chordates

i think tunicates are cute too but they are too complicated to cover here. less basal, less conservative. nevertheless we can quickly make fun of one tunicate before continuing. people often make fun of non-larvacean (acopan) tunicates for losing all of their body plan and internal structure but the pancake batter tunicate is here to remind us that it could always be worse

the pancake batter tunicate is its own punchline. how can you take a creature that's this sticky and stringy seriously

well except when it invasively smothers your reefs but besides that

most of the following figures are from mussini et al, 2024. a new interpretation of pikaia reveals the origins of the chordate body plan. current biology, volume 34, issue 13, pages 2980–2989. full text available at https://doi.org/10.1016/j.cub.2024.05.026 which is to say here

the story of early chordate evolution is best told by the adorable lancelet-like wet slinky creature pikaia

the black bars are half a centimetre, so it's comparable in size to a lancelet. don't you think the whiskers are so cute though. it's actually morphologically more similar to cyclostomes in some ways than lancelets themselves; the whiskers are probably chemosensory like hagfish whiskers, and it had a little circular mouth for sucking up food

what captivates palaeontologists about pikaia is that it is the earliest stem chordate to have myomeres, which is to say segmented muscles. it may have had a notochord; notochords are incredibly poorly preserved even in the most conservative of lagerstätte. it did definitely have a nerve cord, at least. myomeres are somewhat functionally interdependent with notochords, so it is conjectured that it did. nevertheless, that is impossible to say for sure

there is, for some reason, an anime in which a magic pikaia helps kids restore the ecosystem of a ruined earth to the environment of the early cambrian, when the pikaia lived

i respect the concept but that is not really a pikaia so i am indifferent to it

anyway phylogenies of early chordates are centered on trying to position pikaia correctly relative to other stuff like tunicates (myomeres and notochords but they digest them?), vertebrates (hagfish-like creatures), lancelets (myomeres and notochords and tails but no head?), yunnanozoon (nerve cord but no myomeres?), and vetulicolians (what the fuck even are these things). the paper i cited above has the take that, since they discovered a digestive tract in pikaia like what lancelets and vertebrates and tunicates have, the phylogeny should go like this:

here are some pictures of various specimens and drawings of yunnanozoon (a through e), pikaia (f through i), and a strange vetulicolian with a corkscrew tail, banffia constricta (j and k)

besides alleging that everyone has been looking at pikaias upside down until now, the paper and its phylogeny also make the bold claim that the the atria (which is to say empty spaces for filter-feeding) in lancelets and tunicates were evolved separately. this is significant because the real implication is that filter-feeding itself evolved separately. usually, lancelets and tunicates are considered to form a clade of their own of filter-feeding chordates. the oldest version of this claim, actually, is that the adult stage of tunicates itself is a plesiomorphy, and the filter feeding is a symplesiomorphy between tunicates and lancelets; therefore, lack of filter feeding is a synapomorphy between pikaia and vertebrates; therefore, vertebrates are more closely related to pikaia than to lancelets.

leaving aside that this is a dearly cruel ostracism of my wonderful, innocent, and very closely held family member the lancelet, this popular claim is rather a stretch of the imagination to me either way. pikaia was indeed likely a hunter or scavenger, although it is hard to say what its gills were used for; perhaps respiration, as is commonly assumed, or perhaps filter-feeding, as lancelets use them for. they're very small compared to gills in every other kind of stem chordate, and they're located near the head, where the tentacles also are.

since the tentacles are presumed chemosensory alongside pikaia's presumed niche, i would suggest that the primary function of the gills is also chemosensory. hence why i suggested the connection to the niche of hagfish; how many soft slinky chemosensory specialists are there in the crown of chordata, really? of course, a hagfish also has a lot more brain cells, no offence to the pikaia, so presumably the hagfish can make better use of the information.

lancelets respire directly through their skin, and lack blood. food is delivered directly to cells in its digested form. one might call it ‘primitive,’ but it clearly works very well for them. (i mentally call this digested food ‘ichor;’ the ancient greeks believed that blood is just dissolved food, and therefore, since the gods ate golden ambrosia and drank yellow nectar, their blood would be yellow. medically speaking, what ichor actually refers to is bile, but let me pretend.)

based on this new investigation of its digestion, pikaia appears to have a similar system, but it also has a relatively thick cuticle surrounding its exterior, unknown among modern chordates. therefore, it would likely have trouble respirating through its skin, especially since there was less than half as much oxygen available to begin with in the environment as there is today (although this is a somewhat meaningless statement without knowing how deep it lived). nevertheless, it is unlikely it had blood. it is dubious whether blood had been invented yet

so it is ultimately hard to conclude things about its gills and respiration. respiring through a cuticle isn't actually a terribly difficult thing to ask, but it is surely a complicating factor

one beautiful thing that lancelets have that pikaia doesn't is the tail. pikaias are… tail-shaped, maybe, but their vent is at the very back, and don't have a tailfin. whereas lancelets have proper tail, with a cute little fin at the end. the paper imagines that a lancelet's tail is synapomorphic with vertebrates and tunicates, which is just adorable to me. imagine a lineage of tailed animals going all the way back to a wiggly little cambrian filter-feeder… it is cruel that birds and apes have been denied this birthright, but what can you do, really. (and various other vertebrates too, of course, but those are the two clades relevant to me.)

around the same time that paper was published, another really cute stem chordate was discovered, described in lerosey-aubril and ortega-hernández, 2024. a long-headed cambrian soft-bodied vertebrate from the american great basin region. royal society open science, volume 11, issue 7, page 240350. full text available at https://doi.org/10.1098/rsos.240350, which is to say here. careful there's a fuckin disqus widget on there for some goddamn reason. i mean if that's what keeps journals free i'll take it but wow

they got an artist to draw a nice picture of it for them:

this creature is nuucichthys and as you can see it is very creature. possibly among the most of creatures even. it's like if you combined lancelets and yunnanozoon somehow into something beautiful in its uniqueness

despite the drawing the paper says they don't imagine it a very good swimmer. but the paper is mean to stem chordates in general and i bet they'd also call lancelets bad swimmers. i think lancelets are very good at swimming and wouldn't deserve to be insulted like that, how could you possibly hurt their precious feelings like that even. hence i believe this applies to nuucichthys as well and they deserve just as much praise

as you can see their phylogeny is completely different from the other paper's. the thing is they barely put any effort into creating or defending it so i will barely put any effort into dunking on it. the other paper is about phylogeny, and goes to great lengths to investigate and substantiate specific claims of plesiomorphy and apomorphy. whereas this paper takes a matrix of morphological traits and plugs them into mrbayes and runs metropolis-coupled markov chain monte carlo on it. (mcmcmc, if you will. if i remember correctly, when i used mrbayes in 2013, the command to invoke it was just mcmc, which was devastating to my self-image and confidence.) clearly only one of the two papers is taking this seriously so let's move on

so in my recent lanceletpost i described a case where, based on molecular clocks of nuclear dna and mtdna, two lancelet species ostensibly separated by at least 120 million years of time depth for their last common ancestor could produce viable hybrids. ‘hardcoded animal left over from testing the universe.’ true, but combined with the lesson of the sturddlefish, this has a deep implication for the genetics of ‘living fossils’: they are not just morphologically living fossils, but even biochemically and epigenetically, preserving so much that two living fossils separated by a great time depth can hybridise as though the time depth were much smaller. hence we should be looking at the term somewhat more literally, perhaps: seeing lancelets as having directly arrived to us from the distant past. and what might that tell us about phylogeny, then…? well, whatever, it is easy to make claims, much harder to prove them. i only permit myself idle speculation, not serious conclusions, unless i'm already part of the academic dialogue

(that post also contains a very endearing video of lancelets swimming around. at one point one of them swims into the ground and bumps into it and i just go. me too! me too, little lancelet, i have swum into the ground and bumped into it for lack of sight so many times, too…)

in conclusion lancelets are perfect creatures and deserve everyone's affection constantly

ned land's piece

this is going to be much shorter because nobody actually eats lancelets. both wikipedia and baidu baike insist that people do, but i cannot find any evidence of it happening as a regular cultural or culinary staple. and i have a good explanation for why, but first may i remark on where the impression even comes from

the impression comes from a very enthusiastic 2001 paper, which explained how they have omega-3 fatty acids and proteins and whatever. and vanadium, apparently? if you eat piure (a chilean tunicate dish), you will get your recommended dose of selenium; if you eat lancelets, you will get your recommended dose of vanadium. point of fact, tunicates have plenty of vanadium too, so you don't need the lancelets for that, really. my understanding is that vanadium is only really an important nutrient for sea creatures, and it is of no particular use to land creatures such as humans, but it is an interesting fact, i guess

the paper insists on comparing them to anchovies and i don't know if that's an advertising tactic or if that's how the authors (jennifer frick and edward ruppert) got the idea for the paper in the first place. did they look at them and go ‘hm you know what this would be good in any dish that uses anchovies’

there was apparently an early english king, henry i (1100–1135), who loved lamprey pie so much he died from overeating it, which is a pretty strong recommendation of stem chordate-based cuisine to me, so i imagine both cyclostomes and lancelets to be very tasty, in addition to being conveniently boneless. but i have eaten neither myself. i would like to at least try lamprey pie at one point to see if it's worth the hype. the recipe is more or less aligned with my sensibilities for eating fish:

To make a Lamprey Pie Take your Lamprey and gut him, and take away the black string in the back, wash him very well, and dry him, and season him with Nutmeg, Pepper and Salt, then lay him into your Pie in pieces with Butter in the bottom, and some Shelots and Bay Leaves and more Butter, so close it and bake it, and fill it up with melted Butter, and keep it cold, and serve it in with some Mustard and Sugar

there's no good sources for this recipe. it's not on gutenberg so i have a suspicion it's fake. nevertheless it seems like a good idea, at least if i titrate in some of my own habits (such as a quick blanch in salt and ginger). i expect the recipe adapts straightforwardly to hagfish and lancelets as well, if i ever get ahold of one, although for hagfish i'd sooner try a taiwanese recipe probably.

so why don't people eat lancelets already? this is perhaps a sinocentric perspective of mine, but the cuisine that has been handed down to me, south chinese cuisine, is famous (in china, at least) for cooking basically anything that moves. ragworms, stick bugs, jellyfish; my favourite salad, possibly moreso than cucumber salad even, is a jellyfish salad.* there are some more normalised chinese staples that may be shocking to international onlookers, such as river snails and beef intestines and beef arteries and blood cakes. (i have asked butchers in some five countries across three continents if they'd prepare intestines, and they all shook their heads. how do these people make sausage, then?)

*jellyfish are nutritionally worthless, and are only there for texture. they can be substituted with equally nutritionally worthless wood ear fungi, and indeed that is what i tend to use, if jellyfish are unavailable. though just like the fungi, you can buy jellyfish dried. but most of china's jellyfish is fished in georgia the us state, so it is not a very economically tenable relationship. the past year and a half have been bad for my ability to buy jellyfish.

in any case, if something is eaten ‘in parts of the world,’ and it exists in south china, it is probably eaten in south china. and south china has lancelets, branchiostoma belcheri. so i thought, perhaps that would be it? but the baidu wiki politely points out that they are a protected species in the prc, and killing and eating them is punishable by law. now, this also applies to stick bugs, and people eat those anyway; and i doubt the baidu wiki would report that. nevertheless, i do not care to look into it much further, and indeed lancelets seem to be much more numerous in the north sea of europe than in the south china sea, so perhaps it is truly ecologically untenable to eat them.

so then why don't europeans eat them? i conjecture that europeans are stupid. qed

no but i don't know. i have no sense of the traditions or politics of fishing in the north sea. i can name many things adjacent to the north sea, such as how bottom trawling bycatch has inspired people to try to eat the greenland sleeper shark the way that it has inspired the portuguese to try to eat the black scabbardfish (to resounding success i must say, although the way filete de espada is seasoned, i feel it would make any fish taste impeccable), and how much of the world's salmon (such as is eaten in japan) is fished in the fjords of norway, but i don't know what fishing in the north sea itself is like. i guess it is not very easy to fish for lancelets? they are too small to be bycatch, i suppose… but, i don't know

and well lancelet husbandry is sort of a bust. that 2015 paper the previous lanceletpost is based on (holland et al 2015, researchgate, sci-hub) was the first time anyone managed to breed lancelets across multiple generations at all in captivity, apparently. there was this lancelet husbandry paper published two years later (carvalho et al 2017) that… exists. and that's about it. like most sea creatures, it is vastly more profitable to fish them than to breed them

so how would i eat lancelets, then. well i could do the south chinese thing and just stir fry them (cut them into rings? blanch in ginger saltwater to toughen and normalise taste somewhat beforehand?), or maybe mince them and make fish balls out of them. but i bet they'd also be good in that lamprey pie recipe. i'd use different seasonings but surely you can just eat it cooked until soft and placed on bread. bone marrow is one of my favourite things to put on bread and i imagine them being similarly fatty and gelatinous to bone marrow when cooked right. (it has been a long time since i've had adequate bone marrow. the last few times it's been hypothetically available, people conflated it with brain when i tried to buy it. not only do i think brain tastes worse, but i also don't want a prion disease, so i was disappointed.) such recipes are equally so about the bread however, and good bread is hard to come by, so it is perhaps not a realistic ask

perhaps it is horrifying to talk about eating my blorbos, i don't know. the cuter something is, the more pleasure i get in its suffering, and the more appetising it is to me to eat it, although the latter is altogether not a very strong compulsion. (i prefer things that could remain alive inside me if i swallowed them, for that purpose. in the past this has mostly just been various sorts of small worms.) whether i actually choose to eat something has ultimately little relationship with how cute i find it, however. it is just more fun to talk about eating small, cute, pathetic, helpless things. in real life, my relationship with my food is dictated by a completely different fucked up dynamic (the feeling that i'm constantly starving and will run out of food). the real reason i have not yet eaten lancelets or a cyclostome is that it has never been a logical way to fulfill my nutritional needs. i don't do food tourism or whatever. i don't even do tourism at all. everywhere i've lived is accidental