The anatomies of two species of Neoleptonidae are described. Clearly heterodont with cardinal and lateral hinge teeth, the shell also has an internal, parivincular ligament. Shell form suggests a shallow burrowing mode of life in coarse gravels in coastal waters. The labial palps are small and the intestine short further suggesting deposit feeding in well-sorted gravels. A pronounced prodissoconch (II) with a marginal ridge argues for lecithotrophic development further facilitating re-colonization of a narrow niche. In most anatomical respects, the two species are simplified with conjoined inhalant and pedal apertures and few posterior sensory mantle papillae. The ctenidia comprise subequal demibranchs with the outer reduced and the inner modified for internally fertilized embryo brooding. The attachment of each embryo chord to the demibranch filaments is probably from secretions produced by basal glands developed on their abrofrontal surfaces. There may also be secondary external pallial brooding, accounting for the ridged prodissoconch II with attachment achieved via secretions from oil glands in the mantle margin.

Comparisons are made with representatives of the earliest-considered affiliates of the Cyamioidea, that is, the Arcticoidea [now rejected], the confamilial Gaimardiidae and Cyamiidae, and the recently suggested Ungulinidae. It is considered that although neoteny has been proposed for the Turtoniidae, Sportellidae, and Neleptonidae to explain cyamioidean small size, anatomical features of the studied species of the latter family herein investigated suggest, rather, that they are simply ‘small’ there being, contrary to the conclusions of others, little evidence of paedomorphosis. In this scenario, smallness is not a reflection of neoteny. It is the evolutionary selection of a life history trait and opted recipe for success.

Notwithstanding, earlier suggestions of an affiliation with the Veneroidea are considered plausible, although no reason is seen for not retaining the superfamily Cyamioidea nor its, as contemporaneously recognized, families, including the Neoleptonidae.

The anomalodesmatan family Laternulidae represents a group of bivalves with a very few well-known taxa and many more poorly known taxa. Laternula rostrata (G. B. Sowerby, 1839) and L. anatina (Linnaeus, 1758) occur in close proximity to each other in and along the margins of mangroves of Kungkrabaen Bay, Thailand. Laternula rostrata resides in soft to sandy sediments often within the interstices of mangrove roots located in more open portions of the mangrove mud flat. Laternula anatina lives deeper in the mangrove in more protected environs. Laternula anatina is a smaller bivalve that has a variable shell outline, sometimes a wrinkled shell appearance, thicker periostracum, and frequently extensive umbonal erosion. Both species have high concentrations of external shell spinules anteriorly and closer to the umbos (i.e., in juvenile shell) reflecting functionality in retaining an infaunal position. The larger L. rostrata is thinner shelled and more fragile; has more distinct and longer shell spinules composed of flattened lathes; a glossy external appearance; a longer umbonal slit; and a deeper pallial sinus. Additionally, L. rostrata has a saddle-shaped lithodesma; a lithodesma is absent in L. anatina as is typical of most laternulids. Shell microstructure of both is prismatonacreous, typical of the group, but the prismatic layer is thin and appears truncated into small blocky and/or granular columns in transitional zones. The bulk of the shell is tightly packed sheet nacre. The growth lines in L. rostrata, more pronounced but fewer in number than in L. anatina, appear as shallow rolling “hills” in both the shell and chondrophore. The differences in shell microstructure in these two species are specific to the taxa but based on different habitats and burrowing depths, albeit within the confines of a tropical mangal, could represent biomineralization events that reflect environmental adaptations. Variations in the thickness of the microstructural shell layers of four species of laternulids is compared and we speculate on possible functional and/or environmental relevance of these differences.

The distribution of Pyganodon grandis (Say, 1829) and the entire community of unionid freshwater mussels within the Laurentian Great Lakes became greatly reduced following invasion of dreissenid mussels. While some populations remain, how much gene flow still occurs is not known, nor has the level of population structure been examined within a large lake subsequent to dreissenid infestation. Pyganodon grandis is a common and relatively abundant lacustrine species that utilizes diverse host fish, and, therefore, it may disperse as much as or more than any other unionid species in the region. To test for population structure, we examined a fragment of the maternal mtDNA COI gene from 300 individuals encompassing shallow areas from Lake Erie's western and central basins, Sandusky Bay, Lake St. Clair, and the upper Niagara River. Another 94 individuals from the upper Great Lakes and upper Mississippi River watersheds were added to the analysis. A total of 34 different haplotypes were found for P. grandis in the Lake Erie watershed, but just one was common and composed > 80% of all individuals. No other haplotype exceeded a frequency of 2% and most were found only once. Just thirteen haplotypes were found west of Lake Erie, and only the common haplotype and one other were shared with the Lake Erie watershed. However, structure in haplotype frequencies and the presence of one very different clade were limited to samples abutting the Red River of the North. Thus recent population declines in Lake Erie appear not to have significantly impacted levels of genetic variation.

Sex-change (protandry or protogyny) has gone unnoticed in many bivalves due to the rapid occurrence of this process. In this paper, histological evidence and analyses of the size structure of three geographically separated populations on the northwestern coast of México together with theoretical considerations strongly suggest that Atrina maura (Sowerby I, 1835) is a protandric species. The gonads of a total of 931 A. maura specimens collected in the three study sites were analyzed: Ojo de Liebre lagoon (27°55′N, 114°20′W from March 2002 through February 2003), Ensenada de La Paz (24°11′N, 110°26′W, from May 2004 through June 2005 and during 2007), and Bahía Magdalena (24°30′N, 111°48′W, from March through October 2008). Microscopic analysis of gonads of hermaphrodite specimens enabled the reconstruction of a detailed histological sequence during the male-to-female transition. Analysis of the sex ratio by size class revealed that males occur primarily in the smaller classes, females in the larger classes and hermaphrodites in intermediate size classes. All the evidence substantiate the hypothesis that this species is not gonochoric.

Assessing genetic variation in species of conservation concern is critical for developing sound recovery strategies. In this study, we compared sympatric populations of two related species, the endangered Quadrula fragosa (Conrad, 1836) and its common relative Amphinaias pustulosa (Lea, 1831), using standard genetic parameters such as allelic richness, heterozygosity, and effective population size. Our primary aim was to determine if a small population size and isolation from conspecifics had negatively affected the genetic diversity of this population of Q. fragosa. By comparing the endangered species to a related and sympatric, common species we can assess the rare species for genetic effects associated with reduced population size, and in addition, develop management targets for what a recovered Q. fragosa population looks like genetically. Examination of eight microsatellite loci indicated that Quadrula fragosa exhibited reduced genetic variation when compared to A. pustulosa at all measures, however, no evidence of a genetic bottleneck or inbreeding was discovered for either species. A comparison of known fish hosts and reproductive period for these two species point to competition for fish hosts as one possible explanation for the smaller population size of Q. fragosa. We discuss the implications of our findings for the conservation and management of freshwater mussels.

Freshwater gastropods are important components of aquatic ecosystems yet little is known of their distribution and abundance in most states. To clarify historical species presence in Nebraska, I created a database from literature and museum records to catalog each species of freshwater gastropod. Records provided a list of more than 80 provisional species of freshwater snails in the state. I then evaluated each species for possible misidentification and/or synonyms based on known geographic ranges and systematic studies thereby reducing the number of species expected to be present in Nebraska to 31, including one non-indigenous species. I suspect eight species are rare based on the number of records.

The taxonomy of Okenia zoobotryon (Smallwood, 1910) has been extremely problematic, affected by vague original description, complementary descriptions with confusing information, and re-descriptions of species using material collected across a wide geographic range without reference to type material. A recent study based on morphological and molecular data showed that specimens initially identified as O. zoobotryon from Australia belonged to a recently described species, Okenia harastii Pola, Roldán and Padilla, 2014. The collection of several specimens from the type locality, Bermuda, facilitated a complete re-description of O. zoobotryon, with color photographs of the living animal and scanning electron microscopy pictures. In order to preserve the current use of the name Okenia zoobotryon (Smallwood, 1910), a neotype is proposed for this species.

This report provides information on 28 specimens of the giant squid, Architeuthis dux (Steenstrup 1857), discovered in the western North Atlantic Ocean between Newfoundland and the Gulf of Mexico. Some specimens have been reported in the press or popular literature, but others are recorded herein for the first time. Nominal architeuthid species are provided as well as tables listing repositories of types of nominal species, and repositories of non-type specimens from the study area. An extensive list of references of pertinent regional literature is provided, and recommendations for fixation and preservation are described.

Aspects of the reproductive biology of Octopus hubbsorum Berry, 1953 from the Coast of Oaxaca, Mexico, were analyzed. A total of 998 specimens of mantle length (ML) ranging from 40–220 mm were obtained from catches of artisanal fisheries from January 2011 to December 2012. The reproductive activity was assessed using gonad histology, oocyte development, maximum oocyte size, maturity, and gonadosomatic index. A good correspondence between main macroscopic characteristics and histological structure was observed, as emphasized in females where oviductal gland morphology correlates very well in the macroscopic evaluation of maturity. The fecundity range was estimated between 22,447–545,444 oocytes. Maturing oocyte size—frequency distribution was polymodal, and the spawning season is extended with two reproductive peaks. These results indicate that O. hubbsorum has asynchronic ovulation and, is an intermittent terminal spawner. The estimated size at sexual maturity (L₅₀) for females was 90.5 mm ML and for males 74.5 mm ML. The presence of mature population may be related to generally warm water conditions during most of the year. The results have identified the coast of Oaxaca as an important area for O. hubbsorum spawning in the Eastern Tropical Pacific.

Octopus insularis (Leite and Haimovici, 2008) occurs in a wide region of the tropical Atlantic, inhabiting shallow waters along the coast and oceanic islands of northeastern Brazil, where it is considered the primary target of octopus fisheries. This species was only recently described, and detailed information about its spawning, eggs, and paralarvae is unknown. The objective of this study was to estimate the fecundity, describe the eggs and paralarvae and the duration of embryonic development of O. insularis under culture conditions. Broodstock were captured and transported to the laboratory, where they were acclimated in a closed recirculation water system at 26 °C and 32 salinity. Eggs were obtained from two spawning females and were monitored throughout development; samples of 30 eggs were obtained 1 day after spawning and 1 day prior to the first hatching day, and their length, diameter and weights measured. The duration of embryonic development lasted from 30–38 days and fecundity was estimated as 85,000 eggs per female. The length and width of the eggs on the first day after spawning were 2.13 ± 0.06 mm and 0.82 ± 0.04 mm, respectively, and were 2.29 ± 0.06 mm and 0.92 ± 0.03 mm, respectively, one day before hatching. The newly hatched paralarvae exhibit 3 suckers per arm and a mean mantle length of 1.68 ± 0.13 mm. The chromatophore pattern of paralarvae is conspicuous, with ~ 90–111 chromatophores. A total of 32–40 and 56–69 chromatophores were found on the dorsal and ventral view, respectively. These results are of essential importance for identifying the eggs and paralarvae of O. insularis and in broadening our knowledge of this species.

Eubranchus amazighi sp. nov. (Gastropoda, Heterobranchia) is described based on two specimens collected at the harbour of Agadir (Morocco, Atlantic). The translucent white ground colour with opaque white and red-orange speckles over the dorsum and cerata, smooth rhinophores and morphology of the lateral teeth of the radula characterize this species, which is compared with all the Atlantic and Mediterranean red/orange-spotted species of the genus.

Here I present notes on two new species recently found in the upper freshwater portion of the Hudson River, Floridobia winkleyi (Pilsbry, 1912) and Valvata lewisi (Currier, 1868) collected during a study in 2008 (Coote and Strayer 2009, Strayer et al. in prep). Floridobia winkleyi is not only a new record for the river but its presence represents a significant expansion of its limited range from Connecticut to Maine (Smith 1994) and brings into question previously identified specimens attributed to Marstonia lustrica (Pilsbry, 1890) in the river. The other new record is the New York state listed species Valvata lewisi. All species found during the 2008 survey are reported here as well.

Clione limacina (Phipps, 1774) was attained from a broad bipolar distribution in latitudes of 40°N and 40°S. So far southern populations have been described as a subspecies and even a separate species based on morphological and physiological characters. In this study we found a 23.17% (± 0.59%) difference in cytochrome c oxidase subunit I (COI) gene sequences between C. limacina collected from the Arctic and Antarctic oceans. Our work indicates that Clione limacina from the Southern and Northern Hemisphere are not genetically similar enough to represent a single bipolar species and confirms their separate taxonomic status on molecular level.

The green-lipped mussel (Perna canaliculus Gmelin, 1791) is an economically and ecologically important marine species within New Zealand, yet the ability of adult mussels to cope with acute temperature change remains unknown. To address this, we sought to characterize the thermotolerance capacity of P. canaliculus adults and, using metabolomics, identify any metabolic biomarkers of thermal stress in this species. To achieve this, mussels were exposed to a 3 h acute temperature challenge using temperatures of 20 °C (Ambient), 25 °C, 29 °C, 31 °C, 33 °C, and 35 °C. No mortality was observed in mussels exposed to 31 °C or less, even after 30 days recovery. However, mussels exposed to 33 and 35 °C exhibited 100% mortality within 48 h of the challenge. Gill tissues were harvested from mussels for metabolomic analysis of thermal stress biomarkers via Gas Chromatography-Mass Spectrometry (GC-MS). Discriminant Function Analysis (DFA) of 52 metabolites identified eight key biomarkers indicative of thermal stress in this species (i.e., cis-11-Eicosenoic acid, Palmitic acid, Proline, GABA, Aspartic acid, Fumaric acid, beta-Alanine and Asparagine). These metabolites were entirely consistent in their ability to classify the exposure temperature that mussels experienced, indicating that the discriminatory capacity of these biomarkers was strong. Therefore, our results reveal that mortality in thermally-stressed adult P. canaliculus seems assured once temperatures reach 33 °C. Additionally, metabolite biomarkers can discriminate those mussels exhibiting varying levels of thermal stress; thus, metabolomics offers a new tool for physiologists seeking to gain greater mechanistic understanding of the effects of acute thermal stresses on invertebrate species.

To understand how ecological communities may respond to climate change we have adopted the approach of determining the response of major ecosystem engineers that determine community composition and function. We utilize two approaches, correlative and mechanistic, to understand the current and future distributions of the marine mussels Mytilus edulis Linnaeus, 1758 and M. galloprovincialis Lamarck, 1819 in Europe. Both are dominant space-occupying species that control biodiversity in many coastal ecosystems and are the basis of the largest aquaculture production in Europe. A mechanistic analysis of physiological energetic response to temperature of the two species indicates that M. edulis cannot sustain a positive energy balance for sustained periods when sea surface temperature (SST) is greater than 23 °C, while M. galloprovincialis can maintain a positive energy balance at SST up to 30 °C. There is no difference in energetic response of the two species at cold temperatures (5–10 °C). The upper temperature threshold of positive energy balance in each species corresponds closely to the distribution of SST at their respective southern range limits in Europe. Alternatively, the northern range limit of M. galloprovincialis coincides with areas where winter SST is less than 9 °C, but there is no evidence of an energetic limit to this species at the cold end of its geographic range. Presently there is no mechanistic explanation for the difference between species in their northern range limits; however, as indicated by Random Forest modeling, M. galloprovincialis appears to be limited by cold temperatures during winter, suggesting the hypothesis of failure in reproductive development. These approaches allow for the ability to forecast changes in the distributions of these two species in Europe as SST continues to increase.

Climate change is already impacting marine ecosystems across a range of scales, from individual physiology, to changes in species interactions and community structure, and ultimately to patterns in geographic distribution. Predicting how marine ecosystems will respond to environmental change is a significant challenge because vulnerability to climatic and non-climatic stressors is highly variable, and depends on an organism's functional traits, tolerance to stressors, and the environment in which it lives. We present a mechanistic approach based on biophysical and dynamic energy budget models that integrates the cumulative effects of multiple environmental stressors (temperature and food) and stress associated with the presence of predators (the “fear of being eaten”), with the functional traits of an organism. We describe how multiple factors such as feeding time, food availability, and weather can be combined into a few simple metrics and explore how the physiological and behavioral impacts of predation risk can be included in this framework by altering prey feeding time and performance. Importantly, we highlight several critical gaps in our basic understanding of the fundamental mechanisms that drive responses to multiple stressors in natural systems. The framework presented here is, thus, intended to serve as a guide for the formulation of explicit, testable hypotheses and further controlled experimentation.

Dosidicus gigas (d'Orbigny, 1835) is a large, active squid that undergoes a diel vertical migration in the Eastern Tropical and Temperate Pacific. It is a voracious predator on zooplankton and micronekton and supports a large fishery. It is further preyed upon by large vertebrate predators, including whales. Its horizontal distribution is closely tied to productive upwelling regions that are characterized by strong oxygen minimum zones (OMZs). The apparent association with extreme hypoxia is surprising given its large size and high oxygen demand. As part of its daily vertical migration, D. gigas experiences daily temperature changes of 15–20°C, oxygen partial pressures ranging from near anoxia (< 0.8 kPa) to air-saturation (21 kPa) and pH changes from ∼8.1 to < 7.6 at depth. Oxygen minimum zones are believed to be expanding due to climate change, with minimum oxygen levels in the core of the OMZ declining and the low oxygen horizon shoaling. Simultaneously, surface waters are becoming more acidic and temperatures are rising. Here I review the extensive studies of this species that have been conducted over the past decade. D. gigas has a high affinity respiratory protein in the blood that supports a low critical oxygen partial pressure (3.8 kPa at 20 °C) and aerobic survival at night in the upper 200 meters of the water column. A pronounced pH- and temperature sensitivity of oxygen binding promotes oxygen transport across a depth range and in support of high rates of oxygen utilization but may impose constraints on high-temperature and CO₂ tolerance. At its deeper, colder daytime habitat depth, D. gigas undergoes a pronounced metabolic suppression. Reduced activity levels and an apparent suspension of transcription and translation contribute to a ∼80% reduction in oxygen demand under 1% oxygen (0.8 kPa at 10 °C). Anaerobic metabolic pathways contribute some energy under these conditions. This metabolic suppression likely limits feeding at depth. Sub-critical oxygen levels, rather than temperature, predator avoidance or prey availability, appear to set the daytime depth distribution. Thus, expanding oxygen minimum zones will alter the daytime depth of peak abundance for these squids while ocean acidification and warming may impose a shallow ceiling above which squid performance is limited. The role of climate change in setting the vertical and horizontal distribution of the species is discussed.