Friday Cephalopod: Kawaii gallery

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Representatives of the Antarctic and deep-sea genera of
octopuses. (a) Pareledone charcoti, a shallow-water species from the
Antarctic Peninsula. (b) Thaumeledone gunteri, a deep-water species
endemic to South Georgia. (c) Megaleledone setebos, a shallow water
circum-Antarctic species endemic to the Southern Ocean. Specimen
shown is juvenile; adults reach a total length of nearly 1 m. (d)
Adelieledone polymorpha, a species endemic to the western Antarctic.
All specimens illustrated are adult unless specified and were collected
from the South Shetland Islands except T. gunteri from South Georgia.
Scale bars all represent 1 cm.

(from Strugnell, JM, Rogers AD, Prodo PA, Collins MA, Allcock AL (2008) The thermohaline expressway: the Southern Ocean as a centre of origin for deep-sea octopuses. Cladistics 24:1-8)

Odontochelys, a transitional turtle

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Now this is an interesting beast. It’s a 220 million year old fossil from China of an animal that is distinctly turtle-like. Here’s a look at its dorsal side:

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a, Skeleton in dorsal view. b, Skull in dorsal view. c, Skull in ventral view. d, Body in dorsal view. Teeth on the upper jaw and palatal elements were scratched out during excavation. Abbreviations: ar, articular; as, astragalus; ca, calcaneum; d, dentary; dep, dorsal process of epiplastron; dsc, dorsal process of scapula; ep, epiplastron; fe, femur; fi, fibula; gpep, gular projection of epiplastron; hu, humerus; hyo, hyoplastron; hyp, hypoplastron; il, ilium; ipt, interpterygoid vacuity; j, jugal; ldv, last dorsal vertebra; m, maxilla; n, nasal; na, naris; op, opisthotic; p, parietal; phyis, posterolateral process of hypoischium; pm, premaxilla; po, postorbital; prf, prefrontal; q, quadrate; sq, squamosal; st, supratemporal; sv1, 1st sacral vertebra; ti, tibia; ul, ulna; vot, vomerine teeth; I, V, 1st and 5th metatarsals.

Notice in the skull: it’s got teeth, not just a beak like modern turtles. The back is also odd, for a turtle. The ribs are flattened and broadened, but…no shell! It’s a turtle without a shell!

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Old friends, new tools

Once upon a time, way back when I entered graduate school, the first big project I was involved in was essentially a morphological mapping of the circuitry of the larval zebrafish. We did lots of backfills of neurons with horseradish peroxidase, and later the fluorescent dye DiI, and then with injected lineage tracers like rhodamine dextran. I guess technology has greatly advanced, because we never got anything as pretty as this set of fluorescently labeled neurons in the brain and spinal cord of a larval zebrafish.

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(click for larger image)

This image was made using brainbow fluorescent microscopy. Transgenic fish carry an assortment of fluorescent protein genes that are randomly flipped on in the cells to produce these multicolored views of a subset of the neurons. It’s like the good old Golgi silver stain, only in technicolor.

The heartbreaking beauty of development

This is a spectacular video of the development of Clypeaster subdepressus, also called a sand dollar or sea biscuit. These are stunningly beautiful creatures (as are we all, of course), and it is so cool to see them changing here. The video starts with a little echinoderm porn — these animals are profligate with their gametes — and then we see early divisions, gastrulation, the formation of the pluteus larva, metamorphosis into Aristotle’s lantern (one of the more charming names for a developmental stage), and into an ungainly spiky juvenile.

This is why some of us are developmental biologists: it’s all about the exotic weirdness and delicate loveliness of transformation.


A Sea Biscuit’s Life from Bruno Vellutini on Vimeo.

Charismatic cephalofauna

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Christine Huffard sent me a note alerting me to the publication of her latest paper, and she thought I might be interested because I “seem to like cephalopods”. Hah. Well. I’ve noticed that Dr Huffard seems to have some small affection for the tentacled beasties herself.

The paper follows on an old tradition and an old problem. While people have no problem distinguishing human individuals, we have a tough time telling one individual animal from another. This perceptual difficulty complicates problems of studying variations in behavior or physiology, or monitoring numbers and behavior, in natural populations. One solution is tagging or marking the animals in some way, but that always has the risk of changing or harming the disturbed animals — non-invasive procedures are much preferred. This is an especially difficult problem with small animals, like zebrafish or small octopus; I’ve struggled myself with trying to track individual fish in experiments.

I came up with one solution, and Huffard et al. have come up with something similar: humans can be trained to recognize distinctive individual variations, and learn to identify single animals. In this paper, they describe a pattern of white pigmented regions that are consistent within single animals of the species Wunderpus photogenicus…and as you might guess, that is a great excuse to put together a collection of photographs of these aptly named animals.

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