The phenomenon of the uptake, intracellular sequestration, and subsequent usage of algal chloroplasts by the digestive cells of many species of sacoglossan sea slugs, currently called kleptoplasty, has been of considerable interest since its discovery in the 1960s. While a large body of literature reported that captured chloroplasts were photosynthetically active inside slug cells and that plastid longevity in some species might be the result of the horizontal transfer of functional algal nuclear genes into the slug genome, a few recent studies have called the older results into question. Here, we have reviewed the literature and showed that while kleptoplasty occurs in many slug species and almost all derive benefit from kleptoplast photosynthesis, the slug adaptations to maintain the chloroplasts differ from species to species. These adaptations range from behavioral to molecular, including gene transfer, in a variety of combinations.

The giant Caribbean sea anemone, Condylactis gigantea, is an ecologically important member of the benthic community. It provides habitat for many species, including symbiotic cleaner shrimps, and is recognized by reef fishes as a cleaning station cue. Numbers of C. gigantea in Florida have recently declined, possibly due to deteriorating environmental conditions and increasing harvest pressure. A previous research finding indicating that C. gigantea spawns in the late spring has been questioned by fishers for the aquarium trade industry. We therefore examined specimens of C. gigantea collected monthly from October 2011 to September 2012 in the Florida Keys to characterize the reproductive cycle, also measuring several physical and chemical parameters of concurrently collected water samples. We ascertained that the anemone is gonochoric and has a 1:1 sex ratio. Within and between individuals, at the same time and place, spermatogenesis was synchronous, whereas oocyte development was asynchronous. Low-level spawning occurred between October and April with a peak in May, in good agreement with earlier research. Water quality at both sites showed no discernible change over the study period. Conservation efforts directed at population management could benefit this anemone.

Freshwater mussels of the order Unionoida have life cycles that include larval attachment to and later metamorphosis on suitable host fishes. Information on the trophic relationship between unionoid larvae and their host fishes is scarce. We investigated the trophic interaction between fish hosts and encysted larvae of two species of freshwater mussels, Margaritifera margaritifera and Unio crassus, using stable isotope analyses of larvae and juvenile mussels as well as of host fish gill and muscle tissues before and after infestation. Due to different life histories and durations of host-encystment, mass and size increase in M. margaritifera during the host-dependent phase were greater than those of U. crassus. δ¹³C and δ¹⁵N signatures of juvenile mussels approached isotopic signatures of fish tissues, indicating a parasitic relationship between mussels and their hosts. Shifts were more pronounced for M. margaritifera, which had a five-fold longer host-dependent phase than U. crassus. The results of this study suggest that stable isotope analyses are a valuable tool for characterizing trophic relationships and life history strategies in host–parasite systems. In the case of unionoid mussels, stable isotopic shifts of the larvae are indicative of the nutritional versus phoretic importance of the host.

Sperm ultrastructural features of the honeycomb (foam) oysters Hyotissa hyotis, H. sinensis, and H. mcgintyi (Gryphaeidae) are described and compared with other Ostreoidea and more generally with other pteriomorphian Bivalvia. Spermatozoa of H. sinensis and H. mcgintyi (the type species of Parahyotissa Harry 1985) exhibit (1) a broad, low-conical acrosomal vesicle; (2) subacrosomal material (very electron-dense granular material and an almost electron-lucent axial rod); (3) a spheroidal nucleus with a wide anterior invagination (filled with subacrosomal components); (4) a midpiece composed of four spherical mitochondria surrounding a pair of centrioles (rootlet associated with proximal centriole); and (5) a flagellum. Sperm of Hyotissa hyotis (type species of Hyotissa Stenzel 1971) differ markedly from those of H. sinensis and H. mcgintyi, in having (1) a conical acrosomal vesicle showing coarse granular texture anteriorly; (2) a very electron-dense axial rod; (3) a barrel-shaped nucleus with a long, narrow anterior invagination (filled with both subacrosomal components) and a basal invagination partly housing the proximal centriole; and (4) five midpiece mitochondria and no proximal centriolar rootlet. Results indicate that H. sinensis should be relocated to another genus, possibly a revised genus Parahyotissa, and also show that the sperm of H. sinensis and H. mcgintyi show many similarities to those of the Ostreidae, with the exception that the ‘axial rod’ component of the subacrosomal material is less electron-dense than the surrounding substance (more dense in Ostreidae, as in H. hyotis). No family defining sperm features of the Gryphaeidae can be identified.

Agametic reproductive activity (via paratomy) of Aeolosoma viride was analyzed throughout the life cycle in individually reared specimens. Aeolosoma viride is organized in linear chains of 3–4 zooids; the main zooid is anterior, and the secondary zooids are positioned posterior to the main zooid in inverse order with respect to their degree of growth, the most advanced being at the posterior end, and those less advanced nearer the main zooid. On average, worms lived 66±10 d and produced 57±6 offspring. A budding area located in the sub-terminal part of the main zooid produced chaetigers that formed the origin of the secondary zooids. A growth zone was located in the posterior end of each secondary zooids. Fission occurred between the penultimate and the last zooid of the chain. Just before fission, the growth zone of each secondary zooid became a budding area. Agametic reproduction was via multiple paratomy with linear succession of the secondary zooid and terminal fission. The structure of the chain was therefore modulated by the interaction of the processes of budding, growth, cephalic differentiation, and fission, which occurred continuously and on different timescales. Values of parameters describing paratomic activity (interval between origin of the zooids, time to produce a chaetiger, growth time of the zooids, and interval between the fission of the filial chains) are low early in an individual's life, but increase during senescence. Due to its relatively rapid lifecycle and high reproductive activity, A. viride is a convenient experimental organism for the study of agametic reproduction.

Descriptions of the diversity of sexual systems in animal taxa such as the thoracican barnacles are needed to study the evolution of sexual systems. Androdioecious systems (coexistence of hermaphrodites and males) are particularly important due to their possible role as evolutionary intermediates in transitions between hermaphroditism and dioecy. In this study, we used histology to examine the sexual system of the crab-epizoic barnacle Octolasmis unguisiformis to determine if dwarf males were present or not; a previous study reported the existence of conspecific-attached individuals, but did not investigate their sexuality. All conspecific-attached individuals were dwarf males, irrespective of their attachment site. However, crab-attached individuals never acted as dwarf males even if they were small and lived together with large individuals. The result emphasizes the importance of attachment to conspecifics, but not to specific sites on conspecifics, in the evolution of dwarf males. Other individuals were hermaphroditic, indicating androdioecy in this species. However, their functional sexuality (that is, whether they actually do act as males) requires further study. The presence of dwarf males in this species supports theoretical predictions that small group size, short-lived habitats, or spatial limitation favor the evolution of dwarf males.

Brooding behavior and the brooded young of Ophioderma wahlbergii, a common, large, shallow-water brittle star from South Africa, are described for the first time. Monthly samples of 20 specimens were collected from June 2013 to May 2014 (n=240 in total). The species was shown to be gonochoric. Females reached maturity at 17 mm disc diameter (dd), and their ovaries contained 5±3 yolky eggs of mean diameter 0.25±0.1 mm. No seasonal trends in reproduction were found, and >50% of females examined in each month were brooding. Brooding individuals contained an average of 7±6 and up to 33 developing young. Small stages were more frequent than larger young, suggesting that juveniles either emerge at different sizes, or more likely suffer mortality during development. Young within individual adults were of different clutches, but those within individual bursae were all of the same stage. No signs of larval stages were found, indicating that development is direct. Given the large size of emerging juveniles, the species is likely to be matrotrophic and hence truly viviparous. Brooding is a recent discovery in Ophioderma and, so far, the only known brooder has about 1000 small embryos. This study shows quite a different reproductive strategy within the genus, with few, large eggs developing into the largest brooded young known from any species of ophiuroid.