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.
Highlights
The unusual lifestyles of galeommatoidean bivalve mollusks have been extensively studied for over 185 years (Turton 1825)
Specimens of the heart urchin Brisaster latifrons were dredged in Barkley Sound, British Columbia, Canada by invertebrate biology classes held at the Bamfield Marine Sciences Centre on two occasions: in June 1989 from off Sandford Island at 80 m depth (48°51.47'N, 125°08.95'W), and in August 2011 from subtidal depths in the Imperial Eagle Channel (48°55.052'N, 125°13.657'W)
Live specimens of Waldo were observed attached to the ventral surface of the urchins
Summary
The unusual lifestyles of galeommatoidean bivalve mollusks have been extensively studied for over 185 years (Turton 1825). Two additional new South Atlantic Waldo species have recently been discovered (Zelaya and Ituarte 2013) and specimens were kindly forwarded to us for genotyping and morphologic examination. Specimens of the heart urchin Brisaster latifrons were dredged in Barkley Sound, British Columbia, Canada by invertebrate biology classes held at the Bamfield Marine Sciences Centre on two occasions: in June 1989 from off Sandford Island at 80 m depth (48°51.47'N, 125°08.95'W), and in August 2011 from subtidal depths in the Imperial Eagle Channel (48°55.052'N, 125°13.657'W) On both occasions, live specimens of Waldo were observed attached to the ventral surface of the urchins. For all species except Waldo paucitentaculatus, the 16S gene fragment was amplified using the Lasaea spp. primer set 16SLasF (5’-TAGATTAAGGGTTGGGCCTG-3’)/16SLasR (5’-GCCTAAATGGTAAGACTGTTCG-3’) (Li et al unpublished data) following a touchdown PCR protocol. Shell small (length less than 5 mm), ovate to trapezoidal, extremely thin, fragile, translucent to opaque, gaping ventrally and on anterior and posterior ends; sculpture of commarginal striae, weak radial ribs in some; periostracum thin to thick, translucent to white; hinge plate narrow, adults edentate; ligament internal; mantle papillate, reflected, covering most of outer shell surface; long, slender mantle tentacles extend well past shell margin; foot elongate, thin, triangular to cylindrical, heel strong to absent; with one demibranch on each side
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