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Colossendeis

Colossendeis is a genus of sea spider (class Pycnogonida) belonging to the family Colossendeidae. These sea spiders are typically found in the deep sea. This genus includes the largest pycnogonids, with leg spans frequently ranging from 40 to 50 cm (16-20 in). The largest sea spider, Colossendeis colossea, can reach a leg span of 70 cm (28 in). This genus also includes some bioluminescent sea spiders.

Description

Sea spiders in this genus feature an unsegmented trunk, a low ocular tubercle, and a well-developed abdomen. Chelifores are absent in adults. The palps and ovigers touch at their bases, and the strigilis is tightly curved with a strong terminal claw. Species in this genus have only four pairs of legs. The ventral surface of the second most proximal article (second coxa) of some or all of these legs features tiny genital pores.

Feeding

Sea spiders in this genus feed on cnidarians, sponges, bryozoans, small mollusks, and small polychaetes.

Phylogeny

Although all species in this genus are eight-legged, phylogenetic analysis based on molecular data indicates that this genus is paraphyletic with respect to the ten-legged genus Decolopoda and the twelve-legged genus Dodecolopoda; these two polymerous (extra-legged) genera are nested within the genus Colossendeis in a phylogenetic tree. This paraphyly would normally make both Dodecolopoda and Colossendeis junior synonyms of Decolopoda, the oldest name, and require all three genera to merge under the name Decolopoda. To avoid this disruption, authorities keep these genera under different names and retain Colossendeis as a paraphyletic genus.

The molecular evidence also indicates that both Decolopoda and Dodecolopoda are nested within a monophyletic group containing the "longitarsal" species in the genus Colossendeis. The sea spiders in this "longitarsal" clade feature legs in which the three most distal articles (claw, propodus, and tarsus) taken together are at least three-quarters the length of the fourth most distal article (second tibia). This clade includes not only Antarctic species of Colossendeis such as C. australis and C. glacialis but also widespread taxa such as C. megalonyx and C. robusta. In "brevitarsal" species, such as C. macerrima, the three most distal articles are instead much shorter relative to the second tibia.

Species

There are 72 species:

References

Further reading

  • Manfred Moritz: Ordnung Colossendeomorpha in: Urania Tierreich. Wirbellose Tiere 2. Urania-Verlag, Berlin 2000; Seite 327. .
  • Tomás Munilla, Anna Soler Membrives: Check-list of the pycnogonids from Antarctic and sub-Antarctic waters: zoogeographic implications. Antarctic Science (2008) 1-13