Cephalopyge trematoides explained

Cephalopyge trematoides is a pelagic species of nudibranch. A free-swimming marine gastropod in the family Phylliroidae.^[1] Cephalopyge trematoides is the only known species in its genus (i.e. the genus is monotypic).

Etymology

Cephalopyge is a contraction of cephalus (Greek: κεφαλή Greek, Ancient (to 1453);: kephale, "head") and (πūγή, "behind") referring to the position of the anus close to the head. The species epithet trematoides expresses a likeness to flukes.^[2]

Description

C. trematoides grows to 2.5 cm in length. It swims at approximately 12 cm/s, by passing several undulatory waves down its body each second.^[3] It is flattened and transparent; its internal organs are visible.^[4]

Pelagic nudibranchs

Of the approximately 3000 species of nudibranch, the vast majority are benthic, only a couple are neustonic, and C. trematoides is very unusual in that it is pelagic.^{[5] [6]} It is estimated to be one of only five planktonic nudibranch species (another epipelagic example is Phylliroe bucephala).^[7]

Further information (including photos):

• Nudibranch Encyclopedia Kousuke Chibi (in Japanese)
• Seaslugs of Hawai'i by Cory Pittman and Pauline Fiene

External links

• film of Cephalopyge swimming

Notes and References

1. http://www.marinespecies.org/aphia.php?p=taxdetails&id=140776 World Register of Marine Species
2. Book: Lalli. Carol M.. Gilmer. Ronald W.. 1989. Pelagic Snails: The Biology of Holoplanktonic Gastropod Mollusks. Stanford University Press. 9780804714907.
3. http://www.seaslugsofhawaii.com/species/Cephalopyge-trematoides-a.html Sea Slugs of Hawaii
4. Marine species identification portal: Cephalopyge and Cephalopyge trematoides.
5. J.E. Steinberg, The pelagic nudibranch, Cephalopyge trematoides (Chun, 1889), in New South Wales with a note on other species in this genus, Proceedings of the Linnean Society of New South Wales 81:184-192 (1956) http://biostor.org/reference/68603
6. G.M. Mapstone & M.N. Arai, Siphonophora (Cnidaria, Hydrozoa) of Canadian Pacific Waters, p.33. "The best documented predators of pelagic cnidarians from the phylum Mollusca are the neustonic nudibranchs and snails [...and] the pelagic nudibranch [...]"
7. Orso Angulo-Campillo, Gerardo Aceves-Medina and Raymundo Avedaño-Ibarra, Holoplanktonic mollusks (Mollusca: Gastropoda) from the Gulf of California, México http://www.checklist.org.br/getpdf?SL057-09