Flávio Dias Passos

A New Species of Cyamiocardium Soot-Ryen, 1951 from Shallow Waters off Brazil, with a Discussion on the Anatomical Characters of the Cyamiidae (Bivalvia: Cyamioidea)

Abstract. Cyamiocardium domaneschii n. sp. is described from shallow waters off the Southeastern coast of Brazil. An anatomical study provides comparisons with other Cyamioidea. It has a small shell (up to 3.1 mm in length), valves with a rounded contour, external radial sculpture, a distinct large prodissoconch, and hinge structure characteristics of the genus Cyamiocardium Soot-Ryen, 1951. Three well-defined pallial openings are present; tentacles border the anteriormost part of the pedal opening and the inhalant and exhalant apertures. The inner demibranchs are larger than the outers, do not have interlamellar junctions, and form a spacious brooding chamber. It is dioecious and developing oocytes are covered by a thin follicular tissue, which persists as a covering of each brooded young. Offspring are retained up to the juvenile stage, and are attached to the gill filaments by a long stalk. The foot has a narrow, grooved ventral sole; no byssus threads were observed. An active burrowing or crawling behavior is suggested for C. domaneschii n. sp., as there are well developed statocysts. This finding of a cyamiid from Brazil represents the extension of the geographical distribution of this family further north in the southwestern Atlantic Ocean. This study also reveals that some anatomical characters are variable in the genus Cyamiocardium: in C. denticulatum (Smith, 1907), there are only two pallial openings and its foot does not have a ventral sole. The attachment of young to the gills are not related to nourishment, and here for C. domaneschii n. sp. it is suggested that the stalk is only used as a “safety belt”, preventing embryos and juveniles to be released before the end of their development. More studies remain to be done on the anatomy of cyamioideans, particularly on living specimens; we paid attention to common characters used for discussions on the taxonomy and biology of these bivalves.

Falcidens targatus and F. acutargatus: two species of Caudofoveata (Mollusca, Aplacophora) new for Brazil

Two species of Falcidens Salvini-Plawen, 1968 (Chaetodermatidae) are recorded for the first time from Campos Basin, off south-eastern Brazil. Seventeen samples with 176 specimens of Falcidens targatus Salvini-Plawen, 1992 were collected from the continental shelf, and 141 individuals of Falcidens acutargatus Salvini-Plawen, 1992 were obtained in 53 samples from the slope. They are recognized by their external morphology and by the details of their sclerites, radula and oral shield; further, new morphometrical data are added. Type material was also examined. As for both these species the former subgenus name Lepoderma Salvini-Plawen, 1992 is a pre-occupied name by Lepoderma Looss, 1899 (Trematoda), the new subgenus name Chiastofalcidens is proposed to replace it. The finding of F. (Ch.) acutargatus from off Rio de Janeiro suggests that this species has a continuous distribution in the slope through all the Western Atlantic. In contrast, F. (Ch.) targatus appears to be more restricted in its distribution. http://zoobank.org/urn:lsid:zoobank.org:pub:7E79F655-8468-4113-AA2D-95FDCF0CF5EA

Spheniopsidae Gardner, 1928 (Bivalvia): Conchological Characters of Two New Species from off Brazil, Southwestern Atlantic

Abstract: The Spheniopsidae Gardner, 1928 comprises four living species of Spheniopsis Sandberger, 1861 and eight of Grippina Dall, 1912, the latter restricted to the Pacific Ocean, the former also occurring in the Atlantic. Spheniopsis brasiliensis new species and Grippina coronata new species are described from the Brazilian southeastern coast, based on a detailed study of their shells. They are distinguished from already described species mainly by differences in the outline of the valves, external sculpture and right hinge dentition. Shallow micro-pits present all over the outer surface of the dissoconch are viewed as similar to those already described for cuspidariids. They may, thus, represent further evidence for the relatedness of spheniopsids and cuspidarioideans. The new species from Brazil represent the first finding of these rare minute bivalves of this family from the southwestern Atlantic.

The anatomical characters related to the brooding behavior of two Antarctic species of Mysella Angas, 1877 (Bivalvia, Galeommatoidea, Lasaeidae), with direct and indirect evidences of ovoviviparity

Brood protection is a common feature of marine bivalves from higher latitudes. In this study the pallial organs of the Antarctic bivalves, Mysella charcoti (Lamy, 1906) and M. narchii Passos & Domaneschi, 2006 were investigated with respect to anatomical characters related to brooding. Both species are simultaneous hermaphrodites and their eggs contain a large amount of yolk. The number of broods ranges from 16 to 30 in M. narchii and 7–27 in M. charcoti, and ovoviviparity was observed for both. Their ctenidia differ in structure, those of M. charcoti being simpler. In M. narchii there is a large elasticity of the tissue of the marginal food grooves of ctenidia, and cilia are much more abundant on the ctenidial abfrontal surface and on the visceral mass epithelium than in M. charcoti. Anatomical characters of M. charcoti can be considered derived when compared to those of M. narchii. In conclusion, detailed anatomical characters related to brooding may be useful in future systematic studies of Antarctic Bivalvia.

The organs of prey capture and digestion in the miniature predatory bivalve Spheniopsis brasiliensis (Anomalodesmata: Cuspidarioidea: Spheniopsidae) expose a novel life-history trait

ABSTRACT Spheniopsis brasiliensis, from depths of 17–148 m off the southern Atlantic coast of Brazil, is a predator of epipsammic micro-crustaceans which it sucks into the infra-septal chamber using a raptorial inhalant siphon and internally generated hydrostatic suction forces. Prey items, which include ostracods, are thought to be pushed into the funnel-shaped mouth using the foot. The stomach is capacious with a short style sac conjoined briefly with the mid gut and possessing a stubby crystalline style. Internal stomach architecture is simplified, with no identifiable sorting areas (unlike other cuspidarioids) and lined virtually completely by a gastric shield. The exoskeletal remains of digested prey are held in the posterior end of the stomach and not in a specialised waste storage pouch as in the con-familial Grippina coronata. The mid gut, hind gut and rectum are all extremely narrow and, thus, only the smallest of faeces can be accommodated and transmitted for anal discharge. Spheniopsis brasiliensis, like G. coronata is a self-fertilising simultaneous hermaphrodite with encapsulated lecithotrophic eggs brooded internally. Both taxa are thus ovovivaporous. It is also believed that both taxa are univoltine so that larvae and the exoskeletal prey remains are all released post mortem. Cuspidariids are generally regarded as dioecious but, recently, Cardiomya costellata has been shown to be a non-brooding simultaneous hermaphrodite. The distinguishing characters between cuspidariids and spheniopsids thus appear to be their differing reproductive strategies and life history traits.

Environmental Processes, Biodiversity and Changes in Admiralty Bay, King George Island, Antarctica

The isolation of Antarctica from South America during the Oligocene (~35 mya) formed the Southern Ocean, generated the northward flow of the Atlantic Antarctic Bottom Water, and numerous unique geological and oceanic processes (e.g. an active spreading centre in the Bransfield Strait, ridge trench collision, gas hydrates on modern sediments, and complex circulation) along the northern end of the Antarctic Peninsula in particular (Barker and Burrell 1982; Pearse et al. 2001; Barker and Thomas 2004; Thomson 2004; Turner et al. 2009).

Bivalves of the São Sebastião Channel, north coast of the São Paulo state, Brazil

The north coast of the Sao Paulo State, Brazil, presents great bivalve diversity, but knowledge about these organisms, especially species living subtidally, remains scarce. Based on collections made between 2010 and 2012, the present work provides a species list of bivalves inhabiting the intertidal and subtidal zones of the Sao Sebastiao Channel. Altogether, 388 living specimens were collected, belonging to 52 species of 34 genera, grouped in 18 families. Tellinidae, Veneridae, Semelidae, Ungulinidae, Mactridae, Solecurtidae, Corbulidae, Cardiidae, Lucinidae, Cooperellidae, Nuculidae, Psammobiidae, Donacidae, Solenidae, Periplomatidae, Thraciidae and Arcidae were the most representative families in this collection. Among the identified species, Caryocorbula caribaea , Codakia pectinella and Diplodonta punctata were intertidally abundant, while Macoma uruguayensis and Pitar fulminata were subtidally abundant.

Functional morphology of Cardiomya cleryana (d'Orbigny, 1842) (Bivalvia: Anomalodesmata: Cuspidariidae) from Brazilian waters: new insights into the lifestyle of carnivorous bivalves

Of the more than 800 Recent species of Anomalodesmata only 16 have been studied alive. The Septibranchia, comprising a number of carnivorous bivalve superfamilies, are no exception to this generalization and, until recently, no living member of this group has been studied since the 1980s. Collected from the shallow, shelf seabed off Brazil, Cardiomya cleryana is one of only a few species to have its morphology described in recent years and the first ever anomalodesmatan to be filmed alive. Important anatomical features such as a greatly extensible foot to secure itself in the sediment with a single byssal thread, exhalant siphon inter-tentacular projections and micro-papillae on the surface of the siphonal tentacles are described. Observations on the species’ behaviour have revealed a lifestyle hitherto not recorded for any septibranch, indeed any anomalodesmatan. The anchoring mechanism of C. cleryana using an extraordinarily long byssal thread is described for the first time. The life position of C. cleryana is at 45° to the sediment-water interface whereas other cuspidariids have been considered to orient themselves vertically. An anatomical comparison between Cardiomya and Bathyneaera has revealed close affinities. This study thus provides new insights into the morphology and behaviour of the Cuspidariidae.

A new species of Falcidens (Mollusca, Aplacophora, Caudofoveata) from the southeastern Brazilian coast: external anatomy, distribution, and comparison with Falcidens caudatus (Heath, 1918) from the USA

Falcidens australocaudatus sp. nov. is described from the southeastern Brazilian coast, based on characters of external anatomy, including size, shape, and ornamentation of the sclerites, and on the structure of the radula. It bears a tail characteristically distinct from the trunk, a U-shaped oral shield, and the sclerites of the trunk and shank are slender, without an obvious separation between a blade and base; it differs from all other tailed species of Falcidens, which have sclerites that are flared at the base. Externally, it is very similar to F. caudatus, recorded from the northeastern coast of the USA; the sclerites of this species are illustrated here and are characterized as being larger, slightly flared, and with a different ornamentation as compared to those of the new Brazilian species. Based on the examination of a large collection, the new species can be characterized as very abundant at the southeastern Brazilian coast, with a wide bathymetric distribution, but mainly occurring in the upper continental slope.

The biology and functional morphology of Macoma biota (Bivalvia: Tellinidae: Macominae)

Macoma biota Arruda & Domaneschi, 2005, is a recently described species known only from the intertidal zone of Praia da Cidade, Caraguatatuba Bay, in the state of Sao Paulo, southeastern Brazil. The main purpose of the present paper is to describe the biology of M. biota, beginning with a detailed analysis of its anatomy and functional morphology and how these attributes are correlated with its habitat and life history. The morphology of the organs in the pallial cavity and their sorting devices indicate that this species has efficient mechanisms to process large amounts of particles that enter this cavity via the inhalant current. M. biota can rapidly select the material suitable for ingestion and direct the undesired excess to the rejection mantle tracts. These characteristics along with the siphons behavior and the digestive tract configuration reveal that this species can be classified primarily as a deposit feeder, like other species of the genus; however, it can also behave as a suspension feeder, depending on the environmental conditions.