Bittium

Abstract: Structured sampling designs are important in the assessment of environmental impacts of variable ecological systems. Recent developments have provided a useful framework extending existing univariate techniques into a multivariate context. Measures of taxonomic relatedness have also been introduced, which complement existing measures of diversity of assemblages. In this study, the potential effects of sewage discharge on spatial patterns of highly diverse molluscan assemblages in a Mediterranean rocky subtidal habitat were investigated. Nine 20 cm×20 cm quadrats were taken from each of three sites (80 m–100 m apart) within a putatively impacted location near a sewage outfall (I) and at each of two control locations (Cs) by destructive sampling by SCUBA divers at a depth of 3 m–4 m. A total of 5507 specimens of 151 species were collected. The average and the variance in total abundance of molluscs were greater, on average, at I than at Cs. Higher abundances at the sewage outfall were largely driven by greater numbers of juvenile molluscs. The Shannon diversity of molluscs (H′) was significantly lower at I, but no difference among locations was detected for the total number of species (S). In addition, the taxonomic distinctness (Δ*) of molluscs was greater at Cs, although it was more variable at I. Multivariate analyses showed that there was a significant difference in the structure of assemblages at I compared with Cs. The location near the outfall was characterized by greater abundances of several species, including especially the gastropods Pusillina philippi, Bittium latreilli, and Bittium reticulatum. There was also greater variability in the structure of assemblages among sites and among quadrats at control locations compared to those near the outfall. Using a suite of univariate and multivariate measures, including diversity indices, detailed information on taxonomic structure and analyses of variability at different spatial scales, provided useful insights into the effects of sewage impacts on these diverse assemblages. These results also highlighted the importance of analysing measures of variance, as well as mean in considering effects of stress in natural communities.

Abstract: The diet of the spider crab, Maja squinado, was studied in the rocky subtidal areas of the R|¤a de Arousa (Galicia, north-west Spain), by analysing the gut contents of crabs caught in the summer and winter of 1992. The highly diverse diet was made up primarily of macroalgae and benthic invertebrates that were either sessile or had little mobility.The most important prey were the seaweeds Laminariaceae (43% of the frequency of occurrence and15% of the food dry weight), Corallina spp. (38% and 3%), molluscs [the chiton Acanthochitona crinitus (15% and1%), the gastropods Bittium sp. (30% and 2%),Trochiidae and others andthe bivalve Mytilus sp. (32% and12%)], echinoderms [the holothurian Aslialefevrei (32% and18%) andthe echinoid Paracentrotus lividus (16% and 7%)] and solitary ascidians (18% and 6%). The variability in diet composition was determined by the season (Laminariaceae, Corallina spp., P. lividus, Mytilus sp., gastropods and chitons appeared in greater frequency in winter, while the solitary ascidians and A. lefevrei were consumedto a greaterextent in summer) inadditionto sexual maturity (prey such as Bittium sp. orTrochiidae were more common in juveniles). Moreover, the changes in the food consumption rate were linked primarily to the moult stage. Feeding activity plummeted during the phases immediately preceding and following ecdysis (stages D0^D3^4 and A), andthe diet was less diverse during these phases. No feeding diierences were found that could be linked to sex.The composition of the diet of Maja squinado appears to be determined by the seasonal abundance of the diierent prey in subtidal rocky areas and by their availability (depending on their behavioural and anatomical characteristics, mainly mobility and the presence of hard external structures). Moreover, life history factors have little importance in the variability of the diet composition and only the moultcyclehas a considerable eiecton feeding rate.

Abstract: The early Miocene mollusc faunas from the Proto-Mediterranean Sea are still poorly-known. Herein, Aquitanian gastropod assemblages from the Felli section in NW Greece are described. Two assemblages were recovered, a low-diversity coastal mudflat assemblage dominated by Granulolabium plicatum (Bruguiere, 1792) and Mesohalina margaritacea (Brocchi, 1814), and a high-diversity marine assemblage dominated by Bittium larrieyense (Vignal, 1911). The marine assemblage yielded 44 species, of which three species are described as new and 23 are left in open nomenclature. A new combination is proposed for Finella perpusilla (Grateloup, 1827). The family Pyramidellidae is exceptionally represented by 15 species. 17 new occurences are reported for the Proto-Mediterranean Sea. Alvania amphitrite n. sp., Homalopoma acaste n. sp. and Pyramistomia aliakmoni n. sp. are introduced as new species.

Abstract: The anatomy of seven members of the Bittium group is described, clarifying the status of the genus-level taxa comprising it. Bittium reticulatum, the type species of Bittium Gray, is described in depth, thereby establishing criteria for comparisons with other taxa of Bittiinae. The type species of Stylidium Dall and Lirobittium Bartsch, and representatives of Bittiolum Cossmann and Cacozeliana Strand are examined and compared with Bittium, s.s. Results of anatomical studies and a phylogenetic analysis using the Hennig86 and CLADOS programs, with Cerithium as an outgroup, establish monophyly for Bittiinae Cossmann and reveal six different genus-level taxa. A new genus, Ittibittium, from the Indo-Pacific, is proposed. Synonymies of each genus-level taxon and representative species examined are presented