Onchidiidae, one of the higher clades of pulmonates, have been understudied for the last 70 years; its systematics is in a state of confusion; and the internal anatomy of most species is still largely unknown. The anatomy of Semperoncis montana, a terrestrial species that lives in high-elevation rain forests of the Philippines Islands, is redescribed based on 91 specimens representing ten populations. New geographic records (Panay Island) and elevation records (up to 1,850 m) are provided. All type material available was re-examined. The intra-specific variation of anatomical characters is analyzed, with special attention to the radula and the male reproductive organs. Male organs (penial stalk and hooks, papillae and spines of accessory glands) are illustrated using scanning electron microscopy for the first time in onchidiids. Ontogenetic changes in the shape of male organs are described and illustrated in detail, indicating that S. montana was described based on immature specimens of the later named Platevindex apoikistes. Therefore, this latter name is regarded as a junior synonym of S. montana. The supra-specific relationships of S. montana are commented upon.

The involvement of associative learning in predator recognition has not been clear in aquatic invertebrates, including molluscs, due to confounding effects of sensitization. The freshwater apple snail, Pomacea canaliculata, displays an alarm response (crawling above the waterline) when exposed to crushed conspecifics or some predators. We conducted two series of experiments to investigate whether the apple snail learns to avoid predators. In the first experiment, hatchlings were conditioned simultaneously to crushed conspecifics and either a live carp, Cyprinus carpio, or a turtle, Chinemys reevesii, and subsequently exposed to the same predator without crushed conspecifics. Irrespective of the predator species used, the alarm response was significantly higher in conditioned snails than in unconditioned snails. Thus, the snail is able to avoid predators by learning, in a broad sense. In the second experiment, designed to distinguish associative learning from sensitization, we conditioned hatchlings to crushed conspecifics and either a carp or a turtle. The hatchlings were subsequently exposed to one or other of the predators. Hatchlings that were conditioned to a predator displayed significantly higher alarm response when later exposed to the same predator than another predator, suggesting that the snail can recognize predators by associative learning.

A common mactrid from the southwestern Atlantic Ocean has been largely misunderstood in the literature. Since the early 20^th century, this species has been referred to as Mactra patagonica d'Orbigny, 1846. However, the latter is recorded in Quaternary deposits of Northern Patagonia. Mactra guidoi n. sp. is described herein, including its shell ultrastructure, hinge features, and soft parts, and compared with the holotype of M. patagonica. To compare and to correctly identify both species, a morphometric analysis was carried out using conventional and geometric morphometric methods. Mactra guidoi n. sp. has an elongate shell that is more fragile than that of M. patagonica. In addition, its ventral posterior edge is usually sinuous. The ultrastructure of the shell reveals two layers with cross lamellar structure. The anatomical features agree with those of the congeneric M. isabelleana, although they differ in the morphology of the labial palps and foot. Morphometric analysis revealed significant differences between M. patagonica and the new species. The relative warp analysis allows us to understand the variation recognized by using CVA. Only M. patagonica revealed significant allometry between Relative Warp and Centroid size. Finally, the comparison of the types clearly points towards the existence of two different species.

Members of the cephalopod genus Idiosepius Steenstrup, 1881, are currently mainly identified based on the arrangement of suckers on the tentacular club (i.e., in two or four transverse rows) and the number of suckers on the male hectocotylized ventral arms, as stated by Nesis (1982). However, the discovery of a further species, I. thailandicus, raises questions about the validity of the present systematic characters. Alternative morphological features, such as the mantle length and peg arrangement on the tentacle suckers, were proposed by Chotiyaputta et al. (1991) to be suitable for species classification.

To determine whether these attributes are more reliable diagnostic characters valid for all Idiosepius species, we re-evaluate all the above taxonomic characters as well as others features, such as the number of suckers on the other extremities, the shape of the hectocotyli, radula morphology, and beak size.

Based on the present analysis, the systematic positions of I. macrocheir and I. thailandicus are uncertain, although they both correspond morphologically to I. biserialis.

The current evaluation supports a revision of the systematic key of Nesis (1982). The data presented here indicate that the species should be characterized by the shape of the hectocotylus and its appendages rather their sucker number. All other evaluated morphological attributes—sucker and its peg arrangement, mantle size, beak and number of suckers in the first three arm pairs — do not provide good characters to discriminate the species of Idiosepius.

Discontinuous wildlife reserves can lead to inbreeding depression for fragmented populations of threatened species. To offset such effects, conservation managers frequently turn to translocation strategies, such as the one-migrant-per-generation rule (OMPG), which relies on many unrealistic assumptions of Wright's (1931) island model. We therefore propose an alternate translocation approach based on the natural dispersal rates of focal species, using two endangered Hawaiian tree snails species, Achatinella sowerbyana and A. mustelina, as practical examples. The rate at which tree snails historically dispersed across reserve boundaries can be used to guide contemporary translocation across those dispersal barriers. Snail movements were monitored for three years using capture-mark-recapture (CMR) methods, and analyzed with a multi-strata model in program MARK to obtain survival and dispersal rates. We tested and ranked models, including age, time, weather, and location effects on survival, dispersal, and capture probabilities. Annual mortality ranged from over 50% to less than 20%, by site, mirroring expectations from anecdotal observations of predator abundances. Monthly dispersal rates between isolated tree clusters were recorded between 3% and 24% of a population, depending on the population's exposure to severe weather rather than its species designation. Simulations based on dispersal-distance distributions were then applied to estimate emigration rates beyond the finite study sites. Emigration rates ranged among sites from 0.7% to 6.7% of the population per month, translating to between 6 and > 100 emigrants per year, depending on the density of snails at each site and the site's dimensions. The site boundaries are directly analogous to current and future reserve designs, and we show how such emigration rates can be used to guide two-way translocation rates across such artificial barriers.

The land snail Solatopupa guidoni has an interesting disjunct distribution in the peri-Tyrrhenian area, with a few scattered populations in Sardinia, Corsica, and Elba Island. The species is strictly bound to limestone and has poor dispersal capacity. Here, we used sequences of two mitochondrial genes, cytochrome oxidase I (COI) and 16S rRNA (16S), to reconstruct the species phylogeography. The study is based on nine of the 13 populations reported in the literature. Phylogenetic methods and nested clade analysis failed to retrieve reciprocally monophyletic lineages on each island. Sardinian and Elba Island populations were found to be embedded within those of Corsica. These results contrast with previous phylogeographic studies of other organisms with similar distribution patterns, showing major phylogeographic breaks between islands. Molecular clock estimates suggest that species diversification occurred less than 2.5 Myr ago, in line with a previous study that dated the split of S. guidoni from its continental sister species at 3–5 Myr. Corsican populations can be tentatively sorted into two haplo-groups. A first group includes haplotypes found in central inland Corsica only, whereas haplotypes found in northern coastal locations cluster in a second haplo-group. The latter also includes Sardinian and Elba Island populations. Molecular data indicate that a combination of vicariance and dispersal events provide the best explanation of the distribution of this species.

Because of a serial arrangement of supposed pedal muscles and its high-conical shell, Hypseloconus from the Late Cambrian to Early Ordovician of North America is generally believed to be a monoplacophoran relative of cephalopods. The distinctive pattern of muscle attachments and shell form indicates its close relationship to roughly coeval Siberian Kirengella and several other genera classified in the order Kirengellida. Newly collected material from the Early Ordovician of Siberia shows that the bivalved Angarella, with its ventral valve cementing to a hard substratum, is closely similar to Kirengella and Hypseloconus in the arrangement of shell muscles. Permanently fixed to its substratum was also another probable member of the group, Pygmaeoconus. Musculature of Angarella in some aspects resembles that of the Early Cambrian mobergellans with phosphatic shells, but in the calcitic shell structure it is similar to the craniopsid brachiopods. Irrespective of whether the kirengellids are brachiopods or not, they should be removed from considerations on the ancestry of cephalopods. The alternative to Hypseloconus as a candidate for cephalopod ancestry is the Early Cambrian Turcutheca, an enigmatic mollusk with endogastrically curved and laterally compressed conch and relatively large subspherical embryonic conch, in both aspects resembling the earliest ellesmeroceratid nautiloids.

The anatomy of five poorly known endemic species of paludomids — Bathanalia straeleni, Chytra kirkii, Limnotrochus thomsoni, Mysorelloides multisulcata, Paramelania iridescens — from Lake Tanganyika is described. This assemblage, currently united in the Tiphobiini, is loosely characterized by a more or less trochiform shell shape and a mostly oviparous life mode. However, only scant information on the anatomy is available in the literature. Despite significant conchological variability, anatomical investigations reveal overriding similarity in features of the alimentary system (radula, midgut), kidney, and reproductive anatomy. Bathanalia and Mysorelloides are found to share features of the ovipositor, esophagus and spermatophore bursa; Chytra and Limnotrochus share features of the salivary glands and spermatophore bursa. Paramelania remains a clear outlier in shell morphology, but shares several likely plesiomorphic features of the operculum, midgut and nervous system with Tiphobia. Unlike other morphologically distinct clades of Lake Tanganyika paludomids, no unique anatomical character was found that unambiguously unites the Tiphobiini.