''Xyloplax turnerae'' is a sea daisy, a member of an unusual group of marine taxa belonging to the phylum Echinodermata. It has been found living on decaying timber in a deep oceanic trench in the Bahamas.

Discovery

An enigmatic new species of echinoderm, ''Xyloplax medusiformis'', was discovered in the

South Pacific The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...

near New Zealand and first described in 1986 by Baker, Rowe and Clark. Further deep sea exploration by the same team using a submersible vehicle led to the discovery of a new species of '' Xyloplax''. Pieces of timber were deposited at a depth of in an oceanic trench known as the Tongue of the Ocean between the Bahamian islands of Andros and

New Providence New Providence is the most populous island in the Bahamas, containing more than 70% of the total population. It is the location of the national capital city of Nassau, whose boundaries are coincident with the island; it had a population of 246 ...

. When recovered nearly two years later they yielded more than two hundred specimens of ''Xyloplax turnerae''. In 2004, another species in this genus was collected in a similar way from a depth of in the north east Pacific Ocean. It has since been named ''

Xyloplax janetae ''Xyloplax janetae'' is a ''Xyloplax'' of the family Xyloplacidae. It lives on the surface of wood sunken to abyssal depths. Morphology ''Xyloplax janetae'' is a flattened disk, from in diameter, and about thick. It has adambulacral spines wh ...

''.

Description

''Xyloplax turnerae'' is very much like ''Xyloplax medusiformis'' in appearance. It is shaped like a flattened disc and is fringed by a row of short spines which are all of approximately equal length in the range 300–400 μm. The aboral (upper) surface is clad in a series of concentric plates each bearing three spines. The tube feet have rounded bulbous tips. On the oral (lower) side the mouth leads to an eversible stomach but there is no gut or anus. There is a single row of tube feet circling the mouth and these number up to 110 while ''X. medusiformis'' has fewer than 65. The females grow to about in diameter and the males to . All the

embryo An embryo is an initial stage of development of a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male spe ...

s found in the females were small, less than 180 μm in diameter, and it seems unlikely that this species broods its young in the same way that ''X. medusiformis'' does. The marginal spines are mobile and are disproportionally longer in smaller individuals than they are in larger ones. It is thought that juveniles may use them to "parachute" and that this may aid in their dispersal.

References

{{Taxonbar, from=Q2089789 Peripodida Animals described in 1988