Caecidae

Abstract: Caecidae is a species-rich family of microsnails with a worldwide distribution. Typical for many groups of gastropods, caecid taxonomy is largely based on overt shell characters. However, identification of species using shell characteristics is problematic due to their rather uniform, tubular shells, the presence of different growth stages, and a high degree of intraspecific variability. In the present study, a first integrative approach to caecid taxonomy is provided using light-microscopic investigation with microsculptural analyses and multi-marker barcoding, in conjunction with molecular species delineation analyses (ABGD, haplotype networks, GMYC, and bPTP). In total 132 specimens of Caecum and Meioceras collected during several sampling trips to Central America were analyzed and delineated into a minimum of 19 species to discuss putative synonyms, and supplement the original descriptions. Molecular phylogenetic analyses suggest Meioceras nitidum and M. cubitatum should be reclassified as Caecum , and the genus Meioceras might present a junior synonym of Caecum . Meiofaunal caecids morphologically resembling C. glabrum from the Northeast Atlantic are a complex of cryptic species with independent evolutionary origins, likely associated with multiple habitat shifts to the mesopsammic environment. Caecum invisibile Egger & Jorger, sp. nov. is formally described based on molecular diagnostic characters. This first integrative approach towards the taxonomy of Caecidae increases the known diversity, reveals the need for a reclassification of the genus Caecum and serves as a starting point for a barcoding library of the family, thereby enabling further reliable identifications of these taxonomically challenging microsnails in future studies.

Abstract: EnglishThis regional revision of the family Caecidae from the South-West Pacific, is based on material collected during oceanographic expeditions made by the Museum national d�Histoire naturelle (Paris) from 1976 to 2006. The material consists of about 8250 specimens from 208 stations. In addition, material from the Australian Museum (Sydney) (94 lots) and the Western Australian Museum (Perth) (42 lots), and other specimens from private collections, were used. In the present work, 43 species are dealt with, belonging to the genera Caecum (31), Meioceras (4), Parastrophia (6) and Strebloceras (2). Two genera, Gladioceras and Ctiloceras, were not dealt with because of the absence of related material. These are the sole genera considered valid on the basis of their distinct type of development. Of these species, 18 are described as new. An extensive usage of type material was done for comparisons, either on directly or by means of photographs. Lectotypes were selected for Strebloceras cornuoides Carpenter, 1859�, C. chinense Folin, 1868, C. modestum Folin, 1868, C. sepimentum Folin, 1868, C. succineum Folin, 1879, C. bimarginatum Carpenter, 1858, C. inflatum Folin, 1869, C. attenuatum Folin, 1879, M. legumen Hedley, 1899, Parastrophia cornucopiae (Folin, 1869) and Strebloceras subannulatum Folin, 1879. italiano[La famiglia Caecidae nel Pacifico sud-occidentale (Gastropoda: Rissooidea)]. Questa revisione regionale della famiglia Caecidae nel Pacifico sud-occidentale, e basata sul materiale raccolto durante le spedizioni oceanografiche effettuate dal Museum national d�Histoire naturelle (Parigi) dal 1976 al 2006. A questo materiale, proveniente dai dragaggi effettuati in 208 stazioni (circa 8250 esemplari raccolti), e stato aggiunto quello fornito dall�Australian Museum (Sydney) (94 lotti) e dal Western Australian Museum (Perth) (42 lotti), oltre a materiale delle collezioni private degli Autori. Lo studio di questo copioso materiale ci ha permesso di ampliare la conoscenza della famiglia Caecidae nel sud-ovest del Pacifico e di fare confronti con la fauna a Caecidae di altri settori, sia del Pacifico, sia dell�Oceano Indiano. In questo lavoro, sono trattate 43 specie, appartenenti ai generi Caecum (31), Meioceras (4), Parastrophia (6) e Strebloceras (2). Questi sono gli unici generi ritenuti validi sulla base dei loro distinti modi di sviluppo. I generi Gladioceras e Ctiloceras non sono stati considerati a causa dell�assenza di materiale relativo. Su 43 specie, 18 sono descritte come nuove. In questo studio sono stati ampiamente fatti confronti con materiale tipo, sia direttamente, sia su documentazione fotografica. Per le seguenti specie, sono stati selezionati i rispettivi lectotipi: Strebloceras cornuoides Carpenter, 1859�, C. chinense Folin, 1868, C. modestum Folin, 1868, C. sepimentum Folin, 1868, C. succineum Folin, 1879, C. bimarginatum Carpenter, 1858, C. inflatum Folin, 1869, C. attenuatum Folin, 1879, M. legumen Hedley, 1899, Parastrophia cornucopiae Folin, 1869 e Strebloceras subannulatum Folin, 1879.

Abstract: Six sediment samples weighing between 224-735 g were collected in June of 2016 from Cayo Nuevo reef, located at the Campeche Bank, southern Gulf of Mexico. Samples were collected by SCUBA diving, from were two stations at depths of 7.6 and 18.2 m. Sediment was sieved and molluscs (adults and micromolluscs ≤ 10 mm) were sorted, examined, and identified to the lowest taxonomic level. A total of 1,347 specimens was found, of which 224 shells were dead and 1,123 were alive. Thirty-four families, 53 genera, and 67 species were identified. The most abundant families were Chamidae and Arcidae for the Bivalvia class, and Caecidae and Tornidae for the Gastropoda class. The vertical range of Bentharca sp. was extended.