Mollusks are considered ideal systems for understanding combined defensive strategies as evolutionary or local phenotypical responses to numerous predators with distinct attack modes. Despite the growing knowledge of morphological and physiological defensive mechanisms, studies on behavioral adaptations among shelled mollusks, especially among terrestrial gastropods, are still astonishingly scarce. The present study records and describes mechanical and presumably defensive behavior in two species of Simpulopsidae, Leiostracus perlucidus and Simpulopsis cf. tryoni, in the Atlantic Rainforest biome in southeastern Brazil. These behaviors are similar between the two species but differ slightly probably because of differences in body and shell shape.
The complete mitochondrial genome of Voluta musica, the type species of the type genus of the family Volutidae, was determined using Illumina sequencing and found to be a double stranded circular molecule 15,306 base pairs in length with a GC content of 37.2%. It contains 13 protein-coding genes, 2 ribosomal RNA genes, and 22 tRNA genes with the same gene order and strand orientation as in most neogastropods, including all Volutidae, for which mitogenomes have been determined. The potential origin of replication is located in a 62-bp non-coding region between tRNA-Phe and the gene for COX3. Phylogenetic analyses using maximum likelihood and Bayesian inference with nucleotide sequences of all protein coding and ribosomal genes show Voluta musica to be most closely related to Fulgoraria rupestris, support the monophyly of Volutidae, and contradict the inclusion of Cancellariidae within Volutoidea.
An earlier molecular phylogeny of the rapanine muricid genus Acanthais Vermeij and Kool, 1994 indicated that this tropical American group contains two morphologically distinct taxa, one comprising the type species together with a fossil precursor, and the other comprising two Recent eastern Pacific and one Miocene Caribbean species. Despite the molecular results, I propose the new genus Penethais for this second group, with type species Purpura triangularis de Blainville, 1832. Penethais differs from Acanthais by having a lower spire, broader and rounder aperture, and the absence of a columellar fold, adapical notch in the outer lip, and labral tooth. Both groups are Paciphilic, surviving only in the eastern Pacific. I also refine an earlier account of the distribution of columellar folds in the Rapaninae and in its sister taxon, the subfamily Ergalataxinae.
Otostomus is a monotypic and poorly known genus Bulimulidae genus. Only parts of the reproductive system and hard parts are known for Otostomus signatus. The present study goals are, first, to redescribe O. signatus through a detailed investigation of shell features, including microornamentation and ultrastructure, radula and jaw, and detailed anatomical data of its pallial cavity and associated organs, digestive, reproductive, and nervous systems. We also compare the morphology of the species with closely related bulimulids to assess if the phylogenetic relationships recently proposed in a molecular study are supported by morphology. Otostomus signatus is characterized by a conical shell sculptured by thick growth lines, with a truncate-ovate aperture, expanded peristome with three teeth, odontophore retractor muscle ramifying two times, the first in two almost symmetrical muscles, and the second in 4-5 closely attached pack of fibers, intestinal loop absent, imbricated radula, radular formula (9-(31)-1-(31)-9), ovotestis with several thin, tightly squeezed, digitiform ramifications leading to a compact seamless irregular shape, almost symmetrical nervous ring, cerebral ganglia completely fused, without commissure, posterior ganglia completely fused, single large statocyst inside the posterior ganglia. Otostomus signatus shares more similarities in both hard and soft parts with Cochlorina than with Bulimulus, supporting recent molecular phylogenies.
Despite their species being fairly common throughout the world's oceans, the genus Diplodonta is one of the least under stood. Exact taxonomic placement has been problematic for more than a century and it does not appear that this will be resolved anytime soon. Diplodonta enenkionensis is a new spe cies described from the sublittoral zone, off the western coast line of Wake Atoll (Pacific Ocean). It is the first Ungulinidae to be recorded from this remote location, and the smallest known species of Diplodonta.
