Sequences of specimens of the xylophagaid genus Xyloredo revealed minimal molecular divergence among ten specimens from the North and South Atlantic and the northeast and southwest Pacific Oceans. Although genetically identical, the valves of two New Zealand specimens differ dramatically, likely due to their three-fold size difference. Comparable size differences among the type series of X. nooi, X. naceli and X. ingolfia and their disjunct distributions may have contributed to their recognition as distinct species; the species are synonymized here as Xyloredo nooi. The flattened umbonal-ventral ridge, the fold inside the posterior shell, the two elongate calcified strips of the mesoplax embedded in a periostracal anterior adductor cover and a two-parted siphon with the simple, separate openings are unique to members of Xyloredo. Molecular sequencing of the Japanese X. teramachii is needed to test if it is distinct.

Cephalopods have upper and lower chitinous beaks, and their shape can be used to identify species. However, the morphological attributes of beaks are commonly obtained from sources that contain little information on shape, compromising the determination of taxa. Thus, in this study, we used geometric morphometrics to analyze inter-specific differences in beak shape of six octopus species from the northeastern Pacific. We found evidence of species-level discrimination according to upper and lower beak shape. In addition, we provided a detailed description of these chitinous structures for each species, and we developed a key to identify the species based on upper and lower beak shape. The inter-specific morphological variation of beaks of the octopuses evaluated in our study could be the result of adaptive processes related to habitat and feeding habits. The information generated in our study can be used for identification of six octopus species from the northeastern Pacific based on upper and lower beak shape.

Darina solenoides (P. P. King, 1832) is an abundant clam of sandy shores of southern South America. It has an essential ecologic role as a main food source for marine predators, including migratory seabirds, and is an intermediate host in parasitic life cycles. We describe the reproductive cycle and recruitment of D. solenoides in relation to environmental factors in central Patagonia, Argentina. Histological analysis of gonadal stages and quantitative indicators such as the condition index (CI), oocyte density and relative oocyte area (ROA) were examined monthly for two years (2016–2017; n = 1,315) from clams collected from two sandy shores of the San Jorge Gulf (SJG). Recruitment pattern was followed at a single site. The shell lengths ranged between 25.2 and 42.8 mm and the sex ratio did not differ significantly from 1:1. The proportion of clams showing total or partial castration by digenean trematodes was low (< 5%). A clear annual reproductive cycle was found and was characterized by high synchrony between sexes, years and sites. Proliferation of gonia extended throughout the colder months and vitellogenesis occurred mainly during the spring increase of seawater temperature and shortly after the major phytoplankton bloom. Maximum development of oocytes (mean diameter, 32.1 ± 12.9 µm) and presumed spawning by both males and females occurred during the austral summer. Settlement was also highest (mean = 162.8 ± 47.1 ind.m^-2) during summer and was coincident with a second phytoplankton bloom that might favour larval development and subsequent early recruitment. This is the first reproductive study of a mactrid bivalve from the southwest Atlantic Ocean and provides useful information on the population dynamics of this key species from Patagonian sandy shores.

Populations of many native freshwater mussels such as the California floater, Anodonta californiensis, are declining in the Columbia River Basin in the western United States. There are many possible reasons for this decline, including increased presence of nonnative fishes, especially piscivores that displace and reduce the abundance of native fishes. These nonnative fishes can negatively influence the early life history of A. californiensis, because this mussel uses native fishes to complete its life cycle. While Anodonta spp. can use nonnative fishes as hosts with limited success, the extent of this for A. californiensis is not well understood. We determined if the glochidia (larvae) of A. californiensis can successfully metamorphose using certain nonnative fishes, and we quantified differences in host effectiveness (number of juveniles produced) between native and nonnative fishes based on available fin area for attachment.

Overall, native fishes hosted an average of 107.4 ± 39.9 (mean ± SE) juvenile mussels per fish while nonnative fishes hosted an average of 5.5 ± 4.9 juveniles per fish. This conclusion was unchanged when standardized for fish attachment area. Encystment of glochidia on native fishes yielded an average of 1.0 ± 0.1 juveniles/mm² of attachable surface (total area of fins) area while nonnative fishes yielded an average of 0.16 ± 0.1 juveniles/mm². The nonnative channel catfish, Ictalurus punctatus, did not yield any juvenile mussels and was identified as a nonhost species for A. californiensis. All other nonnative fishes tested were determined to be poor or marginal hosts. All native fishes were determined to be primary or secondary hosts for A. californiensis. The native fishes that yielded the highest number of juvenile mussels were sculpins, Cottus spp., and the redside shiner, Richardsonius balteatus, with an average of 196 and 151 juveniles per individual of each species, respectively. Our findings show that nonnative fishes are poor hosts for A. californiensis. However, nonnative fishes may contribute to the decline of native mussels in the Columbia River Basin by directly preying on and reducing the abundance of native host fishes and mussels. Future conservation plans for A. californiensis should consider the potential negative influence of nonnative fishes.

The phylogenetic relationships of inshore squid species in the family Loliginidae is still ambiguous owing to the lack of morphological and molecular data. In the present study, the taxonomic status of squid species Uroteuthis duvaucelii (Orbigny, 1848), Uroteuthis edulis (Hoyle, 1885), Uroteuthis singhalensis (Ortmann, 1891) and Loliolus hardwickei (Gray, 1849) from the Indian coast was elucidated by performing both morphological and genetic analyses. These Uroteuthis species showed marked differences in arm sucker teeth among species. Sharpness of tentacular sucker teeth was slightly increased in the order U. edulis < U. duvaucelii < U. singhalensis. Sexual dimorphism in tentacular teeth was observed in L. hardwickei. Uroteuthis singhalensis is morphologically very close to U. duvaucelii, as inferred by similar shape (broad, squared) and number (5–9) of arm teeth. Bayesian phylogenetic analysis using mitochondrial COI (650 bp), Cyt b (900bp) and COI-Cyt b combined gene sequences re-established the concept of monophyly of Loliolini with the additional number of species U. singhalensis and L. hardwickei. Our reconstructed phylogeny strongly supports Uroteuthis as a paraphyletic taxon as all organisms belonging to the genus Loliolus, including L. hardwickei (subgenus: Loliolus) explicitly grouped with one of the Uroteuthis clades. Distinct subclades within U. duvaucelii and U. edulis from the Indian Ocean may represent cryptic species.

The genus Rhinus Martens, 1860, is represented in Brazil by about twenty species, which are predominantly found in the Atlantic rainforest, an endangered ecosystem with extraordinary biodiversity and high endemism. There is a dearth of detailed morphological data for most species of the genus Rhinus, and the anatomy of only a few species has been described. Rhinus ciliatus, an endemic species from southwestern Brazil, is known by few conchological traits and scarce anatomical data from the reproductive system and pallial cavity. In this study, we redescribe the shell morphology and soft body anatomy of Rhinus ciliatus in detail and compare the new data with known traits of other closely related species. Rhinus ciliatus is diagnosed by the following features: (i) transition from protoconch to teleoconch well marked; (ii) shell ovate-conic, accuminate; (iii) aperture sub-ovate, lip simple; (iv) kidney with granulated lamellae; and (v) marginal teeth with blunt spatula-shaped mesocones. The record of spermatophores for the genus is provided here for the first time.

Understanding aspects of development in animals posessing certain “ancestral” traits can provide key insights into the evolution of various larval forms of invertebrates. Little is presently known concerning the neurodevelopment of Protobranchia, a group of bivalve mollusks. We are first to demonstrate that neurogenesis of the pericalymma larvae of the protobranch Acila insignis differs dramatically from that of the larval nervous system of autobranchia species as revealed by serotonin (5-HT) and FMRFamide antibodies and whole-mount confocal microscopy. Early in the development of pericalymma, two and then three flask-shaped cells immunopositive for 5-HT appear in the apical organ (AO). Later on, in mid-stage larvae, cells immunostained for FMRFamide appear in the dorsal portion of the larva, including a weak signal in the AO. Immediately prior to metamorphosis, the larval FMRFamide-ergic nervous system consists of a single cell in the AO together with several non-sensory cells in the posterior and dorsal regions. No neuronal connections between the larval neuronal cell groups were observed. However, despite the obvious differences in early neurogenesis, there are clear neuromorphological similarities of the studied protobranch species to (1) spiralians (by the presence of an AO), (2) certain trochozoans (by peripheral cells containing FMRFamide) and (3) bivalve mollusks (by AO including three flask-shaped cells revealed by immunostaining for 5-HT). Thus, the nervous system of A. insignis is similar to that of other mollusks and lophotrochozoans due to the presence of an AO, while differing from all the studied groups in other characters (location and composition of FMRFamide cells). Morphological and molecular development of key protobranch taxa need to be further studied in order to infer the evolution of mollusks.

The freshwater pearl mussel (Margaritifera margaritifera) is one of the longest-lived invertebrate species in the world and one of the most threatened freshwater animals in Europe. Its southernmost populations, located in northwestern Spain, are in a critical conservation situation and are still understudied. Here we calibrate a non-invasive method for calculating the volume of the shell and use it to study the ontogenetic scaling of shell volume on shell length. We characterized ontogenetic growth and determined allometric relationships in 16 M. margaritifera northwestern Spain populations by using ordinary least squares regression, major axis and reduced major axis methods. We estimated topographic slopes of the sampling points using a GIS system, as a proxy of water speed. We measured 803 shells and found that the volume of the shell can precisely be estimated using three linear measurements. We found evidence for negative allometry of shell volume in the global sample and in 11 populations. We hypothesized that water speed would affect allometric patterns of local populations. Results suggest a negative relationship between the allometric slope and the topographic slope of the river section inhabited by M. margaritifera. We propose that when water speed is higher, larger mussels become proportionally flatter than in locations where water current is slower, allowing them to burrow more easily in the sediment. Our method will allow estimation of M. margaritifera biomass and ontogenetic growth without killing any specimens, which will contribute to conservation programs for this species.

South American land snails are relatively poorly known, but their taxonomic relationships can be illuminated with the help of detailed anatomical descriptions and comparisons. The genus Habeas Simone, 2013, species of which are associated with caves, was tentatively described in the prosobranch family Diplommatinidae. Recently collected samples that permitted anatomical investigation, revealed that Habeas actually belongs to the eupulmonate family Urocoptidae. The genus is thus reviewed, including the three so far known species: H. corpus, H. data and H. priscus, all Simone, 2013. Four new species collected in Brazil are described: Habeas lekolus (from Cônego Marinho, Minas Gerais), H. peruassus (from Januária, Minas Gerais), H. lapensis (from Bom Jesus da Lapa, Bahia) and H. claudus (from Cocos, Bahia). Anatomical description is based on H. lekolus, revealing in its most interesting features, the absence of the ureter, presence of a pallial gland, lack of anterior duct to digestive gland, small penis and epiphallus, and absence of bursa copulatrix. Species in this genus usually inhabit cave habitats and are only found in Bahia (BA) and Minas Gerais (MG) Brazilian states, in areas close to São Francisco River. A brief discussion of the family attribution to Habeas is also performed. The present seven species in a genus recently discovered in a relatively small area demonstrate how weak the knowledge on the Brazilian malacofauna is.

Cephalopods are a commercially important resource for the Indian coast. Species of Octopus alone account for around 10% of the global cephalopod fishery and roughly 3% of Indian fisheries. Proper identification of cephalopods in the field is difficult, and accurate identification of species is important for conservation as well as for sustainable fisheries management of octopus species. With a view to identify and genetically catalogue the octopus species from the southwest Indian coast, 28 specimens were collected from different landing centres in the region and identified morphologically. Molecular characterization was done with partial sequence information from the mitochondrial Cytochrome C Oxidase-I (COI) gene. All the specimens analysed in the study belong to the family Octopodidae. The specimens were identified as four species of Amphioctopus: Amphioctopus neglectus, A. marginatus, A. aegina and A. rex, and two Cistopus: Cistopus indicus and C. taiwanicus, as well as, Octopus vulgaris and Callistoctopus macropus. In the present study, Octopus vulgaris showed genetic similarity with Octopus vulgaris Type III but with 1% divergence from Octopus vulgaris Type II and 3% divergence from Octopus vulgaris Type IV.

Research on endangered species is important for species conservation. Some lines of conservation research require tissue or fluids so that molecular data can be obtained. Thus, there is an increasing demand for methods of DNA sampling in endangered species that minimize harm to live animals. This especially concerns such highly threatened and protected freshwater mussels as the thick-shelled river mussel Unio crassus. With two different field experiments in Germany under natural conditions, the short- and long-term survival of Unio crassus after hemolymph extraction from the foot tissue was evaluated. We detected no negative effects in individuals of over 40 mm shell length and older than five years. We also followed some individuals for up to three years after treatment and detected no harm to these individuals. DNA quality was high and proved fully suitable for single-gene sequencing (COI) and microsatellite analyses.