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Where''s Waldo? A new commensal species, Waldo arthuri (Mollusca, Bivalvia, Galeommatidae), from the Northeastern Pacific Ocean.
Valentich-Scott P
,
O Foighil D
,
Li J
.
Abstract
A galeommatid bivalve mollusk, representing a new species, is described from off the coasts of California and Vancouver Island, British Columbia. The new bivalve has a commensal relationship with the heart urchin, Brisaster latifrons. It has been observed crawling between the oral spines of this urchin, frequently near the peristome. The bivalve has been recorded from 80 (Vancouver Island) to 444 (southern California) meters depth, in muddy sediments. In common with other galeommatoideans, the new species broods its young; however it differs from the large majority of commensal members in lacking planktotrophic larval development. Waldo arthuri, new species, has multiple morphological, ecological and developmental similarities to other members of the genus Waldo Nicol, 1966, from the southern Atlantic and Antarctic Oceans. This is most pronounced for the Argentine species, Waldo paucitentaculatus Zelaya & Ituarte, 2013, Waldo arthuri''s sister speciesin nuclear and mitochondrial gene trees. Despite this close relationship, Waldo arthuri is phylogentically distinct and possesses several hinge, shell sculpture, foot, and mantle tentacle characteristics that merit its description as new.
Figure 1. A–H
Waldo arthuri new species A–E paratypes, SBMNH 149934 A–C Exterior of left valve D Prodissoconch E Close up of hinge of both valves F Close up of hinge of right valve G Live animal with extended mantle and mantle tentacles; posterior mantle tentacle (pt); siphon (s), foot (f), lateral mantle tentacle (lt), anterior mantle tentacle (at) H Detail of mantle papillae. A–C, G scale bar = 1 mm; D–F, H scale bar = 100 µm.
Figure 2. Photographs of live Waldo arthuri material sampled in Barkeley Sound in 1989. A Brooding adult attached to its host. Note the papillated mantle (m) that is partially retracted and the presence of ~ 200 µm diameter white yolky early embryos (e) in its ctenidia, visible through the transparent shell B Micrograph of mid-late development embryo (equivalent to the pediveliger stage in pelagic developing bivalves) that was dissected from its brooding parent’s ctenidia. Labels indicate protruding foot (f), modified non-ciliated velum (v) with partially consumed yolk reserves (white areas) and mantle papillae (mp) in addition to a dense mass of yolk (y) sequestered in the anterior shelled half of the embryo C Micrograph of smallest/youngest (20 µm of dissoconch growth) specimen observed attached to an urchin host. Note the protruding foot (f) and the apparent presence of persistent yolk reserves (y) dispersed throughout much of the juvenile’s visceral mass.
Figure 3. 16S and 28S phylogenies of three Waldo species. Numbers at branch tips represent specimen ID numbers. Support values along branches are reported as Bayesian posterior probabilities and ML bootstrap values respectively. An asterisk indicates a support value of 100. The scale bars represent numbers of substitutions per site.
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