The assassin snail genus Anentome is widespread in Southeast Asia, and is distributed all over the world via the aquarium trade. One species of genus Anentome, Anentome helena, is known to act as intermediate host of parasitic trematodes. This study investigates the taxonomic diversity of larval trematodes infecting A. helena and Anentome wykoffi in Thailand. Larval trematodes were identified by combining morphological and DNA sequence data (cytochrome c oxidase I and internal transcribed spacer 2). Species delimitation methods were used to explore larval trematode species boundaries. A total of 1107 specimens of Anentome sp. were collected from 25 localities in Thailand. Sixty-two specimens of A. helena (n = 33) and A. wykoffi (n = 29) were infected by zoogonid cercariae, heterophyid metacercariae and echinostome metacercariae, with an overall prevalence of 5.6% (62/1107) and population-level prevalences in the range of 0.0–22.3%. DNA sequence data confirmed that the larval trematodes belong to the families Echinostomatidae, Heterophyidae and Zoogonidae. As such, this is the first report of zoogonid cercariae and heterophyid metacercariae in A. helena, and echinostome metacercariae in A. wykoffi. Moreover, this study provides evidence of tentative species-level differentiation between Thai Echinostoma sp. and Cambodian Echinostoma mekongi, as well as within Echinostoma caproni, Echinostoma trivolvis and Echinostoma revolutum.

The superfamily Pronocephaloidea Looss, 1899 comprises digeneans occurring in the gut and respiratory organs of fishes, turtles, marine iguanas, birds and mammals. Although many life cycles are known for species of the Notocotylidae Lühe, 1909 maturing in birds and mammals, relatively few are known for the remaining pronocephaloid lineages. We report the cercariae of five pronocephaloid species from marine gastropods of the Queensland coast, Australia. From Lizard Island, northern Great Barrier Reef, we report three cercariae, two from Rhinoclavis vertagus (Cerithiidae) and one from Nassarius coronatus (Nassariidae). From Moreton Bay, southern Queensland, an additional two cercariae are reported from two genotypes of the gastropod worm shell Thylacodes sp. (Vermetidae). Phylogenetic analysis using 28S rRNA gene sequences shows all five species are nested within the Pronocephaloidea, but not matching or particularly close to any previously sequenced taxon. In combination, phylogenetic and ecological evidence suggests that most of these species will prove to be pronocephalids parasitic in marine turtles. The Vermetidae is a new host family for the Pronocephaloidea.

Among gastropods, dimorphism is reported in shell size, radular characteristic, and to a lesser extent in shell shape. The relationship of dimorphic characters of the shell with spawning is scarcely studied in literature. Buccinanops globulosus is an interesting model to study sexual dimorphism in shell shape, because the adults attach their egg capsules to the females’ own shells (callus zone). Our hypothesis is that the shell dimorphism is evidenced in the form (size and shape) of callus zones of the females' shells, compared with the males'. In order to test this hypothesis we use a 3D geometric morphometrics (GM) method with several advantages over 2D GM. The relationship between callus shape and size was allometric. During growth, the main callus shape changes are related to the mean size increment, which is more evident in larger females. These callus zones are characteristically slender in males and small females, and more inflated in large females. Our analyses revealed that female shells are different from male ones and those differences are significant on the callus zone where the egg capsules are attached by the female. This finding suggests a relationship of the shell form with spawning. Our findings are not only relevant in terms of the shell dimorphism of the particular spawning substrate area (callus zones) and its reproductive implications, but also provide insights into the evaluation of shell shape variation on areas without type I or II anatomical landmarks in 3D GM.

The gastropod Buccinanops globulosus is commonly used as a bioindicator of tributyltin (TBT) contamination due to its high imposex incidence in maritime traffic areas. The aim of this study was to evaluate both oxidative stress in B. globulosus at three sites with different maritime activity, and imposex incidence in Nuevo Gulf, Argentina. Oxidative stress parameters in digestive glands, like superoxide dismutase (SOD) and glutathione-S-transferase (GST) activities, reduced glutathione levels (GSH), and oxidative damage to lipids, estimated as thiobarbituric acid reactive substances (TBARs) as well as imposex parameters (% imposex and female penis length (FPL)) were measured in females. Gastropods from the harbour area showed 100% imposex, the highest FPL and TBARs content, as well as GSH levels and SOD activity.

The different oxidative stress responses and high imposex incidence at the harbour site may indicate a negative effect on the organism's physiological state due to environmental pollution.