Davisassiminea, a new genus of the Assimineidae, is proposed for Rissoa (Cingula) capensis G. B. Sowerby III, 1892 from tidal flats of southeastern South Africa. The new genus is unique for the family in the morphology of the radula and reproductive system, and the absence of distinct omniphoric grooves. A congeneric species, Assiminea globulus Connolly, 1939, was also examined anatomically. Our molecular phylogenetic analysis using two mitochondrial genes and one nuclear gene confirms that these taxa are members of the subfamily Assimineinae. Based on molecular and radular evidence, Microsetia durbanensis Tomlin, 1916 is also a member of the new genus. Uniquely for assimineids, these species live on seagrass in marine habitats.

A review of valid species within genus Pygmaeconus Puillandre & Tenorio, 2017, is presented. Combined analysis of molecular [partial mitochondrial cytochrome c oxidase subunit I (cox1) gene sequences of several individuals, and a nearly-complete mitogenome for one individual] and morphological (shell and radular tooth) characters revealed that tiny cone snails collected with algae and shell grit by scuba at 12 m depth in the southeastern Philippines correspond to a new species, introduced here under the name Pygmaeconus atomus sp. nov. It attains a maximum adult size of < 5 mm, being arguably the smallest recorded member of the cone-snail fauna worldwide.

The study of diet and how a species obtains food is relevant to understand its role within natural environments. The apple snail Pomacea canaliculata (Lamarck, 1822) is a freshwater dweller that primarily consumes aquatic macrophytes and detritus but also incorporates resources of animal origin in its diet. Our aim was to investigate the ingestion of macroinvertebrates by P. canaliculata in four watercourses from its native range by analyzing its digestive contents. The frequency of occurrence of animal remains in the digestive contents of P. canaliculata snails was 68.50% across different seasons, with values of more than 50% in each of the watercourses studied. The spring-summer contents showed high frequencies of animal remains, whereas in autumn they were recorded only in 10% of the contents from one of the watercourses. The macroinvertebrates ingested belonged to six different insect orders, crustaceans, mites, bivalves, and gastropods. The frequencies of occurrence were higher for arthropods than for mollusks in two watercourses and similar in the other two. In two watercourses, the relative abundances of mollusks were higher than those of arthropods and the opposite was true in the other two. The number of individuals ingested by an average P. canaliculata was highest for the snail Heleobia parchappii, followed by arthropods, H. parchappii eggs, and the snails Physella acuta and Chilina parchappii. Most ingested macroinvertebrates were small, slow or with little or no mobility, such as snails and case-bearing insects. Arthropods able to swim or to swiftly escape, such as Amphipoda and nymphs of Odonata and Ephemeroptera, were not detected at all in the digestive contents. Ingestion of macroinvertebrates appears to be opportunistic and even accidental and probably depends more on their microhabitats or behavior than on preferences of P. canaliculata. Notwithstanding, the high frequency of ingestion observed on some species of snails could have a significant negative effect on the abundance of their populations.

Aneuploidy, or presence of an abnormal number of chromosomes, has been commonly observed in marine bivalves. This phenomenon has also been shown to be negatively correlated with growth and survival rates in several species of oysters and clams. The impact of pollutants on the aneuploidy level in bivalves has also been previously demonstrated. Over the past two decades, evidence of nonrandom chromosomal loss has been demonstrated, with the identification of the missing chromosomes in aneuploid karyotypes reported in several species. The results have shown that only a few pairs were preferentially affected by the loss of one homologue chromosome in different species of oysters and clams. Recently, during the genotoxicity assessment of the marine environment in Qatar using the pearl oyster Pinctada radiata (Leach, 1814) as model and surrogate species, we observed hypodiploid and hyperdiploid karyotypes. Hyperdiploidy was more frequent, which is highly uncommon in bivalves. The identification of the extra and missing chromosomes in aneuploid cells showed that pairs 4, 5, 12, and 13 were found to be more susceptible than others in having an extra individual chromosome. The same set of pairs showed a tendency to lose one homologue chromosome. Several hypotheses on the preferential chromosomal susceptibility in bivalves, in general, are discussed.

The poisonous eggs of Pomacea canaliculata hardly have any predators. This invasive snail, listed among 100 of the worst invasive species, is a serious crop pest and a vector of human parasitic diseases. Females lay eggs in pink-reddish masses, the colour presumably a warning of their chemical defenses. Egg ingestion alters rodent gastrointestinal tracts and is lethal if injected, but its effect on other taxa is unknown. Here we explored the toxic effects of Pomacea canaliculata eggs on the bullfrog Lithobathes catesbeianus (Anura, Ranidae).Juvenile bullfrogs were gavaged with egg extracts and their digestive tract analyzed after 24 h and 48 h using histological, immunohistochemical and lectin-histochemical techniques. Toxicity was also evaluated by intraperitoneal injection of egg extract.Egg extract ingestion adversely affected the small intestine of the bullfrogs. Short term (24 h) effects included large, reversible changes of the intestinal wall, villi morphology, and changes in the glycosylation patterns of enterocytes. The mucosal area increased and infiltration of inflammatory cells, mainly eosinophils and macrophages, were observed together with a weak hemorrhage. Most of these changes reversed after 48 h. In addition, intraperitoneal injection of egg extract was nontoxic to bullfrog juveniles and no lethality or behavioral changes were observed, a remarkable difference from the effect on rodents.Overall, these results indicate that toxins of apple snail eggs reversibly modify gut morphology, which may alter bullfrog physiology, limiting their ability to absorb egg nutrients. This study extends the known targets of the apple snail egg defenses against predation to amphibians.

The radula is the anatomical structure used for feeding in most Mollusca species and is one important autapomorphy. Previous studies were focused on the radular teeth and their functional morphology, but their anchorage in the radular membrane and its function have never been examined. Here, we analyse the micro-structure of connecting chitinous fibres and its implication on the radular function in 13 closely related paludomid gastropod species from the so called “ancient lake” Tanganyika. This species flock shows a stunning interspecific diversity in their radular tooth morphology and tooth embedding in the membrane as well. The species studied here feed on organics from different substrates, both soft and solid, and are substrate-specific. Here, the morphological composition of the membrane is described in detail for the first time, it consists of parallel fibres that extend also within the teeth. We also show that morphologies of the anchorage correlated with the specific preferred feeding substrate can hence be identified as functional adaptation.

ABSTRACT The hatching of an embryo from its egg is a crucial point in its development. This is the moment that decides whether the animal will be able to emerge and survive or whether it will remain trapped and die. Cephalopods usually produce enzymes in a system of glands known as the Hoyle organ, which weakens the chorion and enables hatching. In addition to this chemical approach, four cephalopod genera develop a terminal spine to further support the hatching process. The presence of such a spine has been mentioned for the well-known cephalopod species Euprymna scolopes. However, little is known about either its structure or its cellular details. Our present results indicate that the spine consists purely of musculature, and no intermediate connective tissue was observed. No nerves were detected within the spine, although nerve fibers are present within the surrounding epithelium and dermal muscle layer, indicating that the spine stretching is controlled by this dermal musculature. Our data show that t...