There is growing concern about the impact of contemporaneous ocean acidification on marine ecosystems, but strong evidence for predicting the consequences is still scant. We have used the gastropod Trophon geversianus as a study model for exploring the importance of oceanographic variables (sea surface temperature, chlorophyll a, oxygen, calcite and pH) on large-scale latitudinal variation in mean shell length and relative shell weight. Data were collected from a survey carried out in 34 sites along ~1600 km. Neither shell length nor relative shell weight showed any monotonic latitudinal trend, and the patterns of spatial variability were rather complex. After correcting for spatial autocorrelation, only pH showed a significant correlation with mean shell length and relative shell weight, but contrary to expectations, the association was negative in both cases. We hypothesize that this could mirror the negative effect of acidification on growth rate, which may cause larger asymptotic size. Latitudinal trends of body size variation are not easy to generalize using ecogeographic rules, and may be the result of a complex interaction of environmental drivers and life-history responses.

The present study reports morphometric relationships and discusses the relative growth in the banded murex (Hexaplex trunculus) and the purple dye murex (Bolinus brandaris) from the Ria Formosa lagoon (southern Portugal). A total of 11 morphometric parameters (eight linear variables: shell length, shell width, total aperture length, aperture length, aperture width, spire length, spire width and siphonal canal length; three ponderal variables: total weight, soft parts weight and shell weight) were analysed in both species. The analyses comprised numerous individuals of both sexes and with broad size ranges (H. trunculus: 10.7–82.8 mm shell length; B. brandaris: 14.6–107.7 mm shell length), fairly representative of the populations from the Ria Formosa lagoon. In general, B. brandaris exhibited greater morphological plasticity and higher variability in shell shape compared with H. trunculus. In both species, the vast majority of morphometric relationships displayed positive allometries, distantly followed by negative allometries and by isometries. Although H. trunculus and B. brandaris are known to lack external sexual dimorphism, several morphometric relationships revealed significant differences in the type of growth between sexes, which should be further confirmed using more powerful techniques, such as geometric morphometric analyses of shell shape.

The ultrastructure of spermatogenesis, the euspermatozoa and paraspermatozoa, is investigated in Trophon geversianus. Spermatogenesis follows the general developmental pattern of caenogastropods. Paraspermatid development is characterized by elongation of the cell, concurrent with the appearance of a cytoplasmic elongation at the apex of the cell and the breakdown of the nucleus into small round fragments (caryomerites). Euspermatozoa consist of: a tall, conical acrosomal vesicle (with a invagination); a rod-shaped, highly electron-dense nucleus with an internal axoneme; an elongate midpiece consisting of the axoneme sheathed by helical mitochondrial elements; an elongate glycogen piece; and a short free-tail region. Paraspermatozoa of T. geversianus are vermiform. They contain approximately 12–16 axonemes arranged peripherally, numerous oblong dense vesicles, numerous less dense (round) vesicles, and scattered mitochondria. Most of the euspermatozoal features of T. geversianus are also observed in many neogastropods. However, the presence of the axoneme continuously located inside of the nucleus has not been reported before, and may prove to be a diagnostic feature of the Muricidae.

Ocinebrina nicolai Monterosato, 1884 a marine mollusc belonging to the Muricidae family is reported from Algarve, south coast of Portugal for the first time and is a new record for the biodiversity of the Portuguese malacological fauna and north-eastern Atlantic waters. This species with a medium-size shell for the genus (14–16 mm) was initially sampled during a baseline project that studied marine biotopes in the central Algarve region. This short note presents a brief diagnosis of the species, provides local information on geographical distribution, habitat, and compares it with other congeneric species found in Portugal: Ocinebrina aciculata (Lamarck, 1822) and Ocinebrina edwardsii (Payraudeau, 1826).

Edge drilling is a form of predation in which a predatory snail excavates a hole at a point along the margin of the closed valves of a bivalved animal. We tested the hypothesis that edge-drilling attacks by the predatory snail Chicoreus dilectus on its clam prey Chione elevata shorten the duration of the predation process relative to the alternative behaviour of drilling through the prey's shell wall away from its edges. The time required to complete an edge-drilling attack was on average about three times less than when prey were attacked through the shell wall. This improvement in predation speed was a function of the thickness of the prey's shell at the point of attack. We suggest that owing to the shorter length of time required to kill prey, the edge-drilling behaviour may be selectively advantageous in environments where enemies are abundant, especially competitors that might attempt to steal prey. Behaviours that speed up the predation process may create opportunities for more effective exploitation of available prey resources in highly competitive environments.

Among the gastropods, some muricid shells are composed of an inner aragonitic crossed lamellar layer and a calcitic prismatic outer layer. The analysis of the structure and composition of the two layers of Concholepas shows that the crossed lamellar layer is similar to those of other Mollusc taxa. Sr, Mg and S contents are low in both layers. According to infrared spectrometry, the organic content of the outer calcitic layer is higher than that of the aragonitic crossed lamellar layer. The study of the nanostructure allows for the proposal of a new 3D interpretation of the fine structure of the crossed lamellar layer. The calcitic prismatic layer is compared with the outer calcitic prismatic layer of an archaeogastropod genus: Haliotis.