The American conchologist Isaac Lea had a long and productive career during which he introduced more than 1,800 names of molluscan species between 1827 and 1874, the majority North American land and freshwater species. His idiosyncratic way of publishing, by describing new taxa multiple times in duplicated and variously modified journal papers as well as in retitled collections of extracts, has led to considerable difficulties in determining accurate dates of his original descriptions. He considered the reading and presentation of a manuscript before a “learned society” as the date of its original publication and therefore his own recorded dates must be approached with caution. The problem of interpreting Lea's names was compounded by the fact that Lea frequently modified his own new taxonomic names in his subsequent publications, and often without providing justification for the change. The various name versions were inconsistently applied by subsequent authors. The current paper analyses Lea's substitutions and other modifications of his own names of molluscan species and discusses 131 of his publications in this context, for which attempts at precise dating were made. The status of these “replacements” of Lea's taxonomic names were evaluated under the current ICZN Code (). A few additional cases of changes of Lea's names by other authors are included; these are instances in which Lea had missed a primary homonym or a secondary homonym was discovered later. While some of the names here discussed are currently resting in synonymy, others are of greater current relevance as they are in use as valid names for taxa of conservation/management concern, including IUCN and U.S.-federally listed species.

The following 98 discussions of often-complex name changes involve 348 species-group names and their subsequent spellings, 231 of which were introduced by Lea. Based on their current taxonomic status, the names belong to 4 bivalve and 11 gastropod families, with the vast majority concentrated in Unionidae and Pleuroceridae. Under the current ICZN Code, the investigated changes fall into many different categories, which impacts their nomenclatural availability: 35 names changed by Lea (plus 6 by other authors) are interpreted as substitute names for junior primary homonyms, 7 of which were unnecessary; 1 name (plus 6 by others) as substitute names for junior secondary homonyms, 1 of which was unnecessary; 13 names as justified emendations; 10 names (plus 1 by another) as unjustified emendations that have not entered prevailing usage; 1 name determined by his first reviser action; 37 names (plus many by others) as incorrect subsequent spellings that are not in prevailing usage; and 1 incorrect subsequent spelling that is shown to be in prevailing usage and thus considered a correct original spelling. The concept of “prevailing usage,” ill-defined under the current (1999) ICZN Code, is addressed in this context. The following names in current use are corrected as follows: Helix balasteriana I. Lea, 1840 (taxon inquirendum, ?Dyakiidae), Lioplax cyclostomatiformis (I. Lea, 1844), Diplodon demararaensis (I. Lea, 1859), Iheringella isocardiodes I. Lea, 1856, Dilatata brongniartiana (I. Lea, 1843), Elliptio nasutidus (I. Lea, 1863), Elliptio pullata (I. Lea, 1857), Pleurocera picta (I. Lea, 1841) [instead of P. curta (Haldeman, 1841), which is preoccupied] and Beringiana youconensis (I. Lea, 1847); many others are confirmed in their recently applied spellings. This work serves as an example that the basic endeavor of summarizing available and valid names from the published literature is not always a straightforward task.

This is the first study to document the seasonal dynamics of oxidative and antioxidative parameters in Sadleriana fluminensis (Küster, 1853). Sadleriana fluminensis mostly inhabits spring biotopes, which are threatened by anthropogenic activities. We reported changes in the malondialdehyde (MDA) content, activities of superoxide dismutase (SOD) and catalase (CAT), total antioxidative capacity (TAC), and the qualitative and quantitative composition of the soluble proteins in S. fluminensis. We collected samples from four sites along the longitudinal profile of the Krupa River in three seasons (autumn, winter, and spring). The amount of total soluble proteins and the qualitative protein composition varied seasonally at all sites. Detected protein bands were in the range of 103.8–5.7 kDa in all three seasons, whereas protein bands in the range of 105–60 kDa and 5–10 kDa were not detected in autumn or in spring. In all three seasons, the highest level of MDA was observed upstream at site 1. The values of TAC varied with site and season and were positively correlated to the soluble protein content. SOD activities were highest in winter, followed by autumn and spring; CAT activities were highest in spring, followed by winter and autumn. Principal component analysis based on oxidative and antioxidative parameters revealed marked differences between seasons. The results of this study enhance our understanding of the seasonal dynamics in protein composition and cell redox status within S. fluminensis and will aid future studies. The approach used in this study could also be applied more generally in other ecosystems for the monitoring of bioindicators.

Over the last ten years, the interpretation of the presence of vertebrate sex steroids in molluscs has changed dramatically. Evidence has been accumulating that CYP11A and CYP19A genes (encoding cholesterol side-chain cleavage enzyme and aromatase), that are crucial for the biosynthesis of sex steroids in vertebrates, as well as key functional sex steroid receptors, are missing in molluscan genomes. To provide further evidence, we sequenced the whole transcriptome of the central nervous system of the great pond snail (Lymnaea stagnalis) and screened it for sequences homologous to those used in the generally accepted vertebrate sex steroidogenesis pathway as well as the known sex steroid receptor-related genes (such as CYP11A, CYP19A, 3β-HSD, nPR, and nAR). Our screening confirmed the absence of several key sequences that are essential to accomplish a full sex steroid biosynthesis pathway similar to that of vertebrates. There was also no evidence for nuclear sex steroid receptors. Our findings support the contention that molluscan endocrinology differs from the well-characterized vertebrate endocrine system.

Continuing molecular and morphological investigations of a limpet recently reported as introduced to Sicily in the Mediterranean Sea have revealed it to be an undescribed species of Lottia Gray, 1833, a genus that is native to Sri Lanka and vicinity in the northern Indian Ocean. The genetic and morphological features of the limpets compared from Sicily and Sri Lanka correspond so closely that we do not hesitate to describe it collectively as Lottia iani n. sp., with type locality of Tangalle on the coast of Sri Lanka. Much is still unknown about its native range, when and how it arrived in Sicily, whether it is capable of impacting native species, and whether its introduction might be more widespread in the Mediterranean than just the particular eastern Sicilian localities where it has been observed. It is plausible that the introduction of L. iani to Sicily could have resulted from recent expansions to the Suez Canal, which is known to have led to other species introductions in recent years. Other possibilities include an introduction related to shipping or mariculture activities. However it managed to arrive, this limpet species has clearly been able to establish a self-recruiting local population at particular Sicilian localities with rocky volcanic shores.

Predatory strategies used by carnivorous gastropods may change during their ontogeny. In muricid gastropods attack mechanisms include an accessory boring organ (ABO), radula, labral tooth and/or pedal muscle. However, these mechanisms and their patterns of use in relation to the ontogeny of the carnivorous gastropod remain uncertain. We studied the occurrence of shifts in predatory strategies through the ontogeny of the gastropod Acanthina monodon preying on the mytilid Perumytilus purpuratus. Our results showed a direct relationship between predator and prey size. During attack, the small-sized snails (up to 18 mm shell length, SL) used exclusively the ABO, and medium-sized snails (18–20 mm SL) shifted to using the radula for rasping shells. Meanwhile, the largest-sized snails (> 20 mm SL) used the radula, but also occasionally the pedal muscle and labral tooth, to attack their prey. The site selectivity on the mytilid shell varied according to predatory mechanisms used. The small-sized gastropods used the ABO to drill the center of the prey valves, whereas mid-sized and large-sized snails used the radula and the labral tooth on the valve edges. Occasionally, large-sized snails also used ABO. Shifts in predatory strategies and attacked areas are influenced by the development and consolidation of structures involved in the attack as predator size increased. The incorporation of trace elements during rachidian teeth growth may enable major resistance to friction against carbonate prey valves, as well as the appearance and development of the labral tooth, play relevant roles in the predatory mechanism shifts, which allows the consumption of larger prey. These patterns described evidences the gastropod's predatory behaviour in terms of energetic gain while minimizing the risk of the predator itself being preyed on.

Heterobranch sea slugs exhibit a wide range of body shapes, sizes and color patterns. The genus Placida (Sacoglossa) includes cryptic species, and in 2019 four species were recovered through molecular studies. Specimens of Placida collected in the Argentinian Sea (San Matias Gulf, Patagonia) between 2016 and 2019 are shown to belong to an undescribed species using molecular and morphological evidence. Placida sudamericana n. sp. is described using external, radular, penial stylet and egg mass characters. The specimens were always found associated with the green algae Codium fragile. Placida sudamericana is the only Placida species in the South Atlantic waters of South America and was recorded in a molluscan biodiversity hotspot.

Phenotypic characters of the uncommon Dimya cf. japonica, based on a specimen from Niue Is. in the South Pacific, are reported to represent the enigmatic Dimyidae in a wide-ranging Bivalvia phylogenetic scenario. The main conclusion is that dimyids are placed between ostreoideans and pectinoideans. This is supported by five synapomorphies. Dimyids are closer to pectinoideans, in that they share four synapomorphies.

Intertidal animals experience reduced feeding times and differentiated respiratory capacity associated with aerial exposure, the duration of which depends on their location within the intertidal zone. Perumytilus purpuratus is a sessile mussel that forms dense mats in the rocky mid-intertidal in southern Chile. For this species, we documented the impact of different times of aerial exposure (3 and 6 h) on rates of oxygen consumption and feeding, according to their vertical location (upper and lower limits) within the intertidal zone. Mean oxygen consumption rates in air for individuals located in the upper intertidal zone were 52% higher than those of individuals located at the lower limits of their intertidal distribution. Additionally, individuals from the lower intertidal region always presented higher rates of oxygen consumption and particle clearance rates (58% higher and 18% higher, respectively) during immersion compared to individuals collected from the upper limit of their intertidal distribution, regardless of the duration of previous aerial exposure. Although we found no significant habitat-related differences in the relationship between shell length and gill surface area, individuals sampled from the lower intertidal zone were 8% heavier in dry tissue weight than individuals with the same shell lengths collected from of the upper limit of their intertidal distribution. Our results suggest that the individuals of this species near the upper limits of their intertidal distribution can probably compensate (e.g., higher absorption rate) for the reduced time that they have available for clearance, which might help them to avoid a major energetic disadvantage.