Genus of sea spiders
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:
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References.
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