The rotifer integument is a well-described syncytium that contains an apical intracytoplasmic lamina (ICL) that functions for both skeletal support and muscle insertion. To date, there is limited information on the structure of the integument in species of Gnesiotrocha, a diverse subclade of Monogononta that consists of solitary, colonial, sessile, and planktonic species. In this study, we examined the ultrastructure of the integument in the colonial rotifer Sinantherina socialis to determine how it corresponds to that of other monogononts. The integument of S. socialis was broadly similar to that of other rotifers, consisting of a thickened glycocalyx, multilaminate ICL, and syncytial epidermis. However, it was different in several regards. The ICL consisted of three distinct layers from apical to basal: layer 1 consisted of at least two electron-dense laminae; layer 2 was a thickened matrix of amorphous, electron-dense material or was fibrous; and layer 3 was an electron-dense lamina of varying thickness that covered the underlying syncytium. Significantly, layers 1 and 2 formed a ridge-and-groove like system of finger-like projections across the trunk surface that has not been observed in other rotifers. A voluminous syncytial cytoplasm (up to 3 µm thick) was present beneath the ICL and was mostly electron lucent and with few organelles. Bundles of potential microtubules were scattered throughout the syncytium. We hypothesize that the voluminous cytoplasm with microtubules serves as skeletal support for the rotifer's sessile lifestyle, while the external ridges may function as a texture-based deterrent to predators, or serves to trap secretions from the species' defensive glands. Basally, the epidermis was highly folded and bordered by a thin basal lamina that separated the plasmalemma from the blastocoel. Membrane-bound vesicles were present throughout the integument's cytoplasm and are hypothesized to function in the secretion of extracellular matrix and in the maintenance of the ICL.

Sessile aquatic invertebrates are at great risk for temperature stress. Changes in ambient temperature affect metabolic demands, thus altering energy budgets, and often reducing performance or survival of these species. Zebra mussels are highly invasive, yet little is known about their physiology under biologically relevant conditions, especially with regard to cellular parameters. This study examined the effect of temperature on zebra mussel physiology and investigated whether the levels of two cellular markers, HSP70 and AMPK activity, could serve as indicators of chronic thermal stress. Mussels were collected from a site in central Illinois, slowly acclimated to either 10, 20, or 30°C, and held at these temperatures for four weeks. Size, mortality, and the cellular markers were measured. Size and mortality data indicate heat stress at 30°C. Elevation in HSP70 levels confirmed this temperature elicits a stress response. Elevation in AMPK activity was not detected at 30°C, most likely indicating this temperature is beyond the scope for this marker, and therefore at or near the lethal limit. These data suggest this zebra mussel population experiences reduced performance and potential mortality in the field during summer months. Interestingly, cold acclimation resulted in a temporary elevation in AMPK activity, a result that has not been reported previously in ectotherms and is likely attributable to the metabolic demands of thermal acclimation.

Energy investment in reproduction and somatic growth was investigated for summer spawners of the Argentinean shortfin squid Illex argentinus in the southwest Atlantic Ocean. Sampled squids were examined for morphometry and intensity of feeding behavior associated with reproductive maturation. Residuals generated from length-weight relationships were analyzed to determine patterns of energy allocation between somatic and reproductive growth. Both females and males showed similar rates of increase for eviscerated body mass and digestive gland mass relative to mantle length, but the rate of increase for total reproductive organ weight relative to mantle length in females was three times that of males. For females, condition of somatic tissues deteriorated until the mature stage, but somatic condition improved after the onset of maturity. In males, there was no correlation between somatic condition and phases of reproductive maturity. Reproductive investment decreased as sexual maturation progressed for both females and males, with the lowest investment occurring at the functionally mature stage. Residual analysis indicated that female reproductive development was at the expense of body muscle growth during the immature and maturing stages, but energy invested in reproduction after onset of maturity was probably met by food intake. However, in males both reproductive maturation and somatic growth proceeded concurrently so that energy allocated to reproduction was related to food intake throughout the process of maturation. For both males and females, there was little evidence of trade-offs between the digestive gland and reproductive growth, as no significant correlation was found between dorsal mantle length-digestive gland weight residuals. The role of the digestive gland as an energy reserve for gonadal growth should be reconsidered. Additionally, feeding intensity by both males and females decreased after the onset of sexual maturity, but feeding never stopped completely, even during spawning.

The embryology of Scoloplos armiger (“intertidalis clade”) was described in detail using light microscopy in a landmark paper by DT Anderson in 1959. To expand these investigations, we used immunohistochemical staining techniques (phalloidin, anti-FMRF amide, anti-serotonin, and anti-α-tubulin) coupled with confocal laser scanning microscopy to describe the early development of musculature and nervous system of this species. Moreover, we applied the same methods (and Azan staining) to adults of the putatively paedomorphic orbiniid species Proscoloplos cygnochaetus. Our results showed comparable patterns for stainings of the nervous and muscle system for juveniles of Scoloplos and adults of Proscoloplos. Both show scarce transverse musculature and only a few dorsoventral muscle fibers in the anterior body region. For the nervous system, the observed immunoreactive pattern is nearly superimposable for juveniles of Scoloplos armiger and adults of Proscoloplos. Moreover, the intraepidermal and basiepithelial position of the ventral nervous system only found in juvenile Scoloplos is comparable with the conditions exhibited in adults of Proscoloplos. In summary, our data are in congruence with the hypothesis of a paedomorphic origin for Proscoloplos as derived from molecular phylogenetic analyses.

Exposure to wave action and other environmental factors can alter the morphology of intertidal barnacles. We tested several hypotheses on the causes of morphological variation in the cirri and penises of the barnacle Tetraclita stalactifera at sites differing in wave exposure, at different heights in the intertidal zone, and at different levels of population density. Unlike many other acorn barnacle species, cirrus and penis characteristics did not correspond to differences in wave exposure or crowding. However, barnacles from higher tidal elevations had thicker cirri and thicker penises than those from lower elevations. Because of reduced time submerged at higher elevations, increased thickness may be a means of compensating for reduced feeding and mating opportunity by allowing for continued feeding and mating attempts during periods of greater wave action. Our observations of differences in cirrus and penis morphology suggest that phenotypic plasticity in penis and cirrus characteristics are adaptations shared by the species T. stalactifera and other acorn barnacles, but that T. stalactifera responds differently to environmental stimuli than do other species.

Caves are not closed systems. Trophic dynamics in these habitats are driven by resource availability, and species that move between cave and outdoor environments may play a major role in resource availability. Spiders are among the most abundant invertebrates in caves; however, very few studies have tested factors hypothesized to affect the distribution of spiders among caves, and it is not known whether the trophic features of caves play a role in determining the occurrence, abundance, or breeding success of spiders. We assessed the distribution of the cave-dwelling orb-weaver spider Meta menardi in Italy, in a Mediterranean and in a Pre-alpine area during summer and winter. We analyzed the relationships between spider distribution and multiple cave features, describing both the abiotic and the biotic environment. Using visual encounter surveys, the detection probability of this species was high, indicating that this technique provides reliable information on spider distribution. In Mediterranean caves, spider presence was more likely in cold and wet caves with abundant dipterans. In Pre-alpine caves, spider presence was more likely in deep caves with abundant dipterans. Dipteran abundance was the variable best explaining spider distribution when pooling all sampled caves. This study shows that adults of M. menardi do not occur randomly among caves, but select caves with specific features. Prey availability and abiotic features are major determinants of habitat suitability for cave spiders. The strong relationship between spider distribution and prey availability suggests that the distribution of these spiders might be an indicator of the resources available in the twilight zones of caves.

Increasing demand and overfishing of high-value species has promoted interest in both conservation and aquaculture initiatives supporting stock restoration programs for tropical sea cucumbers. Accordingly, there is a need for baseline information on the genetic structures and relatedness of sea cucumber populations to support sustainable implementation of mariculture and conservation programs, which often involve coastal communities in developing countries. Identification of a non-destructive tissue sampling technique for sea cucumbers that allows extraction of high-quality genomic DNA in a sustainable and culturally appropriate way is thus required. Six sampling techniques were assessed for their suitability to collect tissue for DNA extraction from sandfish (Holothuria scabra): core needle biopsy, punch biopsy, shave biopsy, buccal swab, anal swab, and evisceration. The quantity, quality, and purity of extracted DNA were compared to assess the relative merit of each sampling method. The swab biopsy method produced the best quality DNA agarose band image, and evisceration resulted in the highest yields of DNA, at an average of 525.9 (±98.0) µg g^–1. However, when considering all criteria assessed, the swab biopsy methods (both buccal and anal) proved superior. Swabbing not only produced the best quality DNA agarose band image, it was also the only technique that produced DNA that amplified 100% of the time across both extraction protocols. We hope that the non-destructive sampling techniques evaluated in this study provide a foundation for the genetic analysis of sea cucumber stocks to support their conservation and management.