Corresponding author: Paul Valentich-Scott (
Academic editor: N. Yonow
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,
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.
The unusual lifestyles of galeommatoidean bivalve mollusks have been extensively studied for over 185 years (
An undescribed galeommatid species was discovered in the late 1980’s in two regions of the northeastern Pacific Ocean: Vancouver Island, British Columbia and Santa Barbara, California. The new species lives commensally with the heart urchin,
Specimens of the heart urchin
In 1986, independent sampling via box corer off Santa Barbara, California yielded additional specimens of the new species. It has subsequently been collected off Monterey Bay, Point San Luis, Los Angeles, and San Diego, California. None of the California
For the molecular phylogeny, specimens of
A small piece of mantle tissue from each specimen was isolated for genomic DNA extraction using the Omega Biotek E.Z.N.A. Mollusc DNA Kit (Omega. tech). Fragments of two ribosomal genes, the mitochondrial large subunit 16S and the nuclear large subunit 28S, were used to reconstruct the phylogenetic relationships of the North American and Argentine
The 16S and 28S sequences were aligned respectively using ClustalW (
Bayesian and maximum likelihood (ML) inferences were used to reconstruct the
Santa Barbara Museum of Natural History, Santa Barbara, California, USA University of Michigan, Museum of Zoology, Ann Arbor, Michigan, USA
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.
The reproduction is typical of galeommatoideans, in that the animal is hermaphroditic, and the young are brooded in the ctenidia. Two brooding individuals sampled in 1989 showed early and mid developmental stages respectively. Fecundity was low; the early developmental stage individual (3.8 mm length) had 160 yolky embryos all at the blastula stage (approximately 200 µm in diameter) (
Photographs of live
USA, California, San Luis Obispo County, off Pt. San Luis;
Holotype, SBMNH 235142, conjoined shell and anatomy, length 2.5 mm, height 1.5 mm. Holotype comprises two conjoined valves, with anatomy, preserved in 70% ethyl alcohol. Given its wet preservation and small size we were unable to capture high quality photographs of the holotype.
7 Paratypes, SBMNH 149934, same locality as holotype (
3 Paratypes, SBMNH 235142, same locality as holotype (preserved in 100% EtOH).
4 Paratypes, SBMNH 149933, Canada, British Columbia, Sanford Island, Barkley Sound;
34 Paratypes, UMMZ 303919, Canada, British Columbia, Imperial Eagle Channel;
Canada, British Columbia, Barkley Sound, Sanford Island, 80 meters, and Imperial Eagle Channel in soft sediments; and United States, California, from Monterey Bay to La Jolla, from 113 to 444 meters [SBMNH].
Ten juvenile specimens from the intertidal zone of Smeaton Bay, Alaska (
Crawling on the oral surface of the heart urchin
Independently discovered in the late 1980’s by Arthur Fontaine and Diarmaid Ó Foighil in British Columbia and Paul Valentich-Scott and Donald Cadien in southern California.
This species is named after Dr. Arthur Fontaine, Professor Emeritus of Biology at the University of Victoria, British Columbia, Canada.
Comparison of morphologic characteristics of members of the genus
|
|
|
|
|
|
|
|
1 pair | no |
|
|
|
5 pair | yes |
|
|
unfigured | 3 pair | no |
|
|
|
1-3 pair | yes |
|
|
|
5-15 pair | slightly |
A species from Japan and Hawaii,
In the eastern Atlantic Ocean,
Other similar North American species include those belonging to
Results from the phylogenetic analyses are shown in
16S and 28S phylogenies of three
Specimens of
The molecular phylogenetic and morphological data concur that the new species here described is a member of the genus
We are grateful to the many individuals who loaned specimens of the new species to us over the past two decades, and are too numerous to mention here. Cristián Ituarte forwarded us critical comparative material from Argentina. The 2011 Bamfield Marine Science Centre Marine Invertebrate Zoology Course (Instructed by Majorie Wonham and Tara Macdonald) made a special effort to get us fresh material of the new species. We are deeply appreciative of the patience and assistance from Kelley Bartlett, Donald B. Cadien, Tony Phillips, Ronald Velarde, and Linda Kuhnz. Diego Zelaya provided images of the Atlantic species of