Bivalves of superfamily Galeommatoidea (Mollusca, Bivalvia) from western South Africa, with observations on commensal relationships and habitats.

The Galeommatoidea are a diverse but little-studied group of small bivalves, well known for the symbiotic relationships many species have with a range of invertebrate taxa. Four species collected from the Western Cape region of South Africa were examined and illustrated, providing new details on their habitat preferences, and depicting the mantle structure of live specimens for the first time. Brachiomyaducentiunus sp. nov., is described herein, and an additional record of Montacutasubstriata (Montagu, 1808) is reported from South Africa. Brachiomyaducentiunus and Montacutasubstriata have obligate symbiotic relationships with different burrowing echinoids, while Kelliabecki (WH Turton, 1932) and Melliteryxmactroides (Hanley, 1857) are free-living. DNA data and phylogenetic analyses are provided for three of the species.

A fossil species found living off southern California, with notes on the genus Cymatioa (Mollusca, Bivalvia, Galeommatoidea).

A small bivalve mollusk previously only known from the Pleistocene of Los Angeles County has recently been found living intertidally near Santa Barbara, California. The bivalve has been determined to be Cymatioacooki (Willett, 1937), a member of the Galeommatoidea J.E. Gray, 1840. We document the habitat for the newly discovered C.cooki, and compare it to C.electilis (Berry, 1963), the other extant member of this genus recorded from the region. Cymatioacooki is rare, and while many galeommatoid species have been shown to be commensal with other invertebrates, we have been unable to determine any specific commensal relationships for it.

A new species of Malletia (Bivalvia, Malletiidae) and new records of deep-water bivalves from Pacific Southern Colombia.

In order to enhance the understanding of Pacific Colombia's deep-water marine fauna, a benthic research cruise (2012 TUM Offshore 6 and 7) was conducted off the coast of the Department of Nariño, in southern Colombia. Biological, oceanographic and sediment samples from the continental shelf and slope were collected at depths between 350 and 941 m. A new species of Malletia obtained on that cruise is described and compared with other species from the eastern Pacific. Sixteen species of bivalve mollusks (belonging to 12 families and 15 genera) were identified. Five of them were the first records for Pacific Colombia (Jupiterialobula, Limatulasaturna, Lucinomaheroica, Cuspidariapanamensis, and Dallicordiaalaskana). Four of them had geographic distributions that now extend to Tumaco at the southern end of Nariño.

Deep-water bivalve mollusks collected during the TALUD XV cruise off the west coast of the southern Baja California Peninsula, Mexico.

BACKGROUND: During the TALUD XV research cruise off the southern part of the Baja California Peninsula, Mexico, samples of macro-invertebrates obtained in the deep-sea (296-2136 m) revealed a rich fauna of bivalves (17 species belonging to 10 families). The number of species per station varied from one to five. The richest families were Nuculidae, Nuculanidae, Neilonellidae, Limidae, and Cuspidariidae. Solemyidae, Lucinidae, Poromyidae, Verticordiidae, and Pectinidae were each represented by a single species. Some species groups need a thorough revision and were tentatively identified (Nuculana cf. hamata, Limatula cf. saturna). NEW INFORMATION: Significant new distribution information is provided for two species, both recorded for the first time from off western Mexico: Ennucula panamina with an extension of its known distribution over 20° of latitude north and Jupiteria callimene with an extension of 16° 42' of latitude to the north. One species (Ennucula taeniolata) is reported in shallower depth and one in deeper water (Acesta sphoni). New records are provided for an additional nine species. Environmental and habitat conditions are given for the first time for many of the bivalve species.

Ecology of Endolithic Bivalve Mollusks from Ko Chang, Thailand.

Cheewarat Printrakoon, Thamasak Yeemin, and Paul Valentich-Scott (2016) The objective of this study was to examine the ecology of coral boring bivalves from four islands southeast of Ko Chang, Trat Province, Thailand. A total of 11 bivalve families containing 18 species were recorded in the survey, including six reported for this first time in the region. Members of the Mytilidae comprised the highest bivalve diversity with five species recorded. The five most abundant species were Leiosolenus lima (Jousseaume in Lamy), Lithophaga teres (Philippi), Botula cinnamomea (Gmelin), Coralliophaga coralliophaga (Gmelin), and Gastrochaena cuneiformis Spengler. Ecological analysis showed that Ko Bai Dung had the highest density of boring bivalves, with 196.29 ± 118.24 individual/ m2. Density of coral boring bivalves was variable; the highest density was recorded for Coralliophaga coralliophaga (85.18 ± 74.35 individual/m2) at Ko Bai Dung. The highest diversity of boring bivalves was found on Ko Phrao Nok, and in dead coral. Multivariate analyses did not reveal a clear differences in the boring bivalve community composition between sites, or with coral age, or with coral species, however dead coral was well-grouped at 50% similarity. The number of species and number of specimens of boring bivalves in this study was significantly positively correlated with coral age. The maximum number of boring bivalve specimens was found in the oldest coral (11 years old) and in dead Porites host corals. Following the same trend of all dominant boring bivalves, corals more than nine years old showed the highest frequency distribution and the largest shell length. The distribution of shell height frequency showed Leiosolenus lima and Lithophaga teres had more variation in shell height than the other five dominant boring bivalve species. Endolithic bivalves are one of the main bioeroders in the coral biome. The ecologic data presented in this study can be used as one indicator of coral reef status, including bioerosion and nutrient recycling in coral ecosystems.

A new genus and species of Thyasiridae (Mollusca, Bivalvia) from deep-water, Beaufort Sea, northern Alaska.

Bivalve mollusk shells were collected in 2350 m depth in the Beaufort Sea, Arctic Ocean off northern Alaska. Initial identification suggested the specimens were a member of the bivalve family Thyasiridae, but no known eastern Pacific or Arctic living or fossil thyasirid resembled these deep-water specimens. Comparisons were made with the type of the genera Maorithyas Fleming, 1950, Spinaxinus Oliver & Holmes, 2006, Axinus Sowerby, 1821, and Parathyasira Iredale, 1930. We determined the Beaufort Sea species represents a new genus, herein described as Wallerconcha. These specimens also represent a new species, herein named Wallerconchasarae. These new taxa are compared with known modern and fossil genera and species of thyasirds.

Where's Waldo? A new commensal species, Waldo arthuri (Mollusca, Bivalvia, Galeommatidae), from the Northeastern Pacific Ocean.

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.