A new species of the genus Catillopecten (Bivalvia: Pectinoidea: Propeamussiidae): morphology, mitochondrial genome, and phylogenetic relationship

Abstract

Catillopecten is a small genus of deep-sea glass scallops, but its diversity is poorly known in many parts of the world ocean. We described C. margaritatus n. sp. (Pectinoidea: Propeamussiidae), and performed morphological analyses and DNA sequencing, and estimated the divergence time of scallops based on samples collected from Haima cold seep in the South China Sea. Morphologically, the new species can be distinguished from congeneric species by its large shell size, relatively small auricle length, absence of without monocrystal aerials, presence of longitudinal radial ridges on the left valve, and the alternated rounded striae and distal and proximal growth lines of prisms on the right valve. Anatomically, this new species can be distinguished from C. vulcani by its anteriorly located auriculate gills, compared to the centrally located lamellar gills of the latter, and the different locations of the pericardium. Sequence comparison and phylogenetic analysis based on the 18S rRNA fragments supported the placement of the new species in Catillopecten. We also report the mitogenome of C. margaritatus n. sp. as the only reported mitogenome of the family Propeamussiidae, which differs from those of other scallops substantially in gene order arrangement. Divergence time estimation revealed that Propeamussiidae and Pectinidae diverged in the early Carboniferous, while Catillopecten and Parvamussium diverged during the late Cretaceous to early Eocene. Finally, we presented a key to the species of Catillopecten.

Scallop-bacteria symbiosis from the deep sea reveals strong genomic coupling in the absence of cellular integration

“…Catillopecten margaritatus usually lives on the empty shells of vesicomid A. marissinica or the sediment around aggregations of the tubeworm S. annulatum [ 24 ]. Although they co-occur, the SOB symbionts of these three species showed huge phylogenetic divergences [ 5 , 22 , 24 ], which may reflect their distinct evolutionary histories and subtle physiological differences allowing them to exploit sulfur resources in the heterogeneous habitats.…”

“…Therefore, it is possible that the ectosymbionts of C. margaritatus disperse and colonize the scallop larvae in the water column within a short period of their release from the host. That the scallops usually live in aggregations could provide such opportunities for close contact [ 22 ].…”

“…Yet, the discoveries of simple homorhabdic gills bearing chemosymbionts in thysarids [ 20 ] and a heterotrophic alphaproteobacterial endosymbiont in a shallow-water scallop [ 21 ] supported further investigation of chemosymbiosis in vent and seep scallops. Catillopecten margaritatus —a deep-sea glass scallop that inhabits the Haima seep in the South China Sea— is commonly found on the empty shells of the vesicomyid Archivesica marissinica and around the tubeworm Sclerolinum annulatum aggregation [ 22-24 ]. Our previous analyses of the stable isotopes of C. margaritatus [ 23 ] revealed δ 13 C and δ 34 S values typical of the SOB symbiont-bearing bivalves that are known to rely solely or mainly on SOB for nutrition [ 12 , 23 , 25 ].…”

Same (sea) bed different dreams: Biological community structure of the Haima seep reveals distinct biogeographic affinities

“…22 The patellogastropod limpets mainly living on mussel shells at Haima were exclusively B. lactea; but at Site F the dominant species was Bathyacmaea nipponica which co-occurred with a few B. lactea. 41,42 Clusters of the vestimentiferan tubeworm Paraescarpia echinospica were found from at least three localities at Haima; 29 nevertheless, only one individual of this species was found at Site F. 20 Brittle stars were highly abundant at Haima, but they were scarce at Site F. 37 At least 35 of the species found at Haima (~54%) appear to be endemic to this site, but only seven of them have been named, including the vesicomyid clam Archivesica marissinica, 21 the glass scallop Catillopecten margaritatus, 43 the bathymodioline mussels Gigantidas haimaensis 22 and Nypamodiolus samadiae, 35 the limpet Paralepetopsis polita, 44 the chiton Thermochiton xui, 36 the brittle star Histampica haimaensis, 37 and the tubeworm Sclerolinum annulatum. 34 Many others are also almost certainly undescribed species.…”