The Caribbean sponge Mycale laevis is often found growing in close proximity to living scleractinian corals. This commonly observed sponge–coral association has been considered a mutualism, with the coral providing substratum for the sponge, and the sponge protecting the coral skeleton from boring organisms. We examined the specificity of sponge recruitment to live corals, expecting a positive and specific settlement response if a mutualism exists. Benthic surveys conducted off Key Largo, Florida, and Bocas del Toro, Panama, revealed that individuals of M. laevis grew on substrata that included dead coral and other species of sponges. Selectivity analysis indicated that at three of the four survey sites, M. laevis was not randomly distributed, but associated with live corals more frequently than expected from proportional coral cover. However, settlement assays demonstrated that larvae of M. laevis did not preferentially respond to the presence of live coral. We have previously demonstrated that adults of M. laevis are chemically undefended and readily eaten by spongivorous fishes unless protected by adjacent substrata such as live corals. In overfished areas, where spongivore density is low, the sponge is not selectively distributed near corals. Initial results of settlement experiments with different substrata suggested that larvae of M. laevis responded positively to the presence of the chemically defended sponge Amphimedon compressa, perhaps indicating an associational defense. Further experiments revealed that larvae were reacting to artificially high concentrations of exudates from cut surfaces of Am. compressa; settlement was not enhanced in response to healed pieces of Am. compressa. In addition, the larvae of M. laevis did not selectively respond to live coral or to chemically defended heterospecifics. These results indicate that the commonly observed proximity of M. laevis to live corals is not driven by larval settlement behavior, but instead by post-settlement mortality due to predation.

Mollusc shells are composed of two or three layers. The main layers are well-studied, but the structural and chemical changes at their boundaries are usually neglected. A microstructural, mineralogical, and biochemical study of the boundary between the inner crossed lamellar and outer prismatic layers of the shell of Concholepas concholepas showed that this boundary is not an abrupt transition. Localized structural and chemical analyses showed that patches of the inner aragonitic crossed lamellar layer persist within the outer calcitic prismatic layer. Moreover, a thin aragonitic layer with a fibrous structure is visible between the two main layers. A three-step biomineralization process is proposed that involves changes in the chemical and biochemical composition of the last growth increments of the calcite prisms. The changes in the secretory process in the mantle cells responsible for the shell layer succession are irregular and discontinuous.

Previous studies on the reproductive biology of littorinid snails have focused on rocky shore species, investigating how these gastropods can achieve maximal reproductive success, as well as on processes of sexual selection. This study documented differences in the reproductive traits of two mangrove-dwelling littorinids, Littoraria ardouiniana and L. melanostoma, in Hong Kong. Reproductive activity of both species was most intense during the summer months. Mating pairs of the two species generally occurred in the tree canopies. Few false mating pairs (same sex or heterospecific pairs: <10%) were recorded, and members of both species showed size-assortative mating. Littoraria ardouiniana had a shorter reproductive season but a higher intensity of mating and higher seasonal fecundity, than did L. melanostoma. Members of both species showed bi-lunar periodicities of egg or larval release, synchronized with spring tides. Fecundity showed a strong positive relationship with body size in L. ardouiniana, but not in L. melanostoma. Females of L. ardouiniana released entire broods of larvae in a single brief event, whereas females of L. melanostoma released fewer eggs over 1–8 d. Release of larvae in L. ardouiniana involved a series of short bursts and was much faster than the trickle release of eggs in L. melanostoma. The contrasting reproductive traits in these two species represent different strategies to optimize reproductive success in mangrove habitats.

In many taxa, initial differences in offspring size play an important role in mediating subsequent performance; however, the consequences of interspecific variation in size for the performance of co-occurring taxa have been rarely examined. We used the whelks Cominella virgata and C. maculosa, which co-occur on rocky shores throughout their life cycles, to examine the vulnerability of early life-stages to native predators under controlled laboratory conditions. Among all the predators evaluated (the cushion sea star Patiriella spp., the olive rockfish Acanthoclinus fuscus, the oyster borer snail Haustrum scobina, the smooth shore crab Cyclograpsus lavauxi, and the pebble crab Heterozius rotundifrons), hatchlings of both species (C. virgata: ∼3 mm shell length [SL] and C. maculosa: ∼1.5 mm SL) were especially vulnerable to the smooth shore crab Cy. lavauxi, the only potential predator in which mortality was greater than in the control treatment. Small shore crabs (∼8 mm carapace width [CW]) were unable to eat hatchlings of either whelk species, whereas medium and large shore crabs (∼12 and ∼18 mm CW, respectively) consumed hatchlings of both prey species. Hatchlings of C. virgata were less vulnerable to predation by medium crabs than large ones, and those of C. maculosa were equally vulnerable to both sizes of crabs. In hatchlings of both prey species, shell length and shell thickness increased over time. Two months after hatching, only individuals of C. virgata had reached a size refuge from predation. Our results show that interspecific vulnerability to predators can be mitigated by larger sizes and thicker shells at hatching; nonetheless, our results also suggest that other species-specific factors, such as juvenile growth rate, may also play key roles in determining the vulnerability of hatchling and juvenile snails to shell-crushing predators.

Speciation by host shift is one of the explicit models of ecological speciation. A prerequisite of this model is the formation of host races (sympatric populations that show host-specific genetic structuring and phenotypes). Many members of the diverse marine bivalve superfamily Galeommatoidea have obligate commensal relationships with invertebrate hosts. Some species have the ability to occupy multiple host species, thereby providing potential opportunities to test for the formation of host races. The Northeast Pacific galeommatoidean Neaeromya rugifera attaches to two strikingly different hosts: the blue mud shrimp Upogebia pugettensis and the polychaete sea mouse Aphrodita spp. We tested if this host difference has resulted in the formation of host races using shell morphologies and genetic markers. We found that populations from different hosts differ significantly in shell morphology. However, based on mitochondrial makers, N. rugifera showed no distinct host-specific genetic structuring, indicating the existence of a panmictic population. We conclude that the host-specific morphologies these clams exhibit may reflect ecophenotypic plasticity rather than the existence of host races, but this needs to be corroborated with additional genetic data and larger sample sizes. The pronounced conchological variation within N. rugifera calls for further investigation of its taxonomic relationship with its poorly studied, but morphologically similar, sympatric congener Neaeromya compressa.

Specimens of the deep-sea sipunculan Phascolosoma turnerae were retrieved over a 5-year period from fibrous collectors placed for various time intervals at a depth of 520 m in the Tongue of the Ocean, Bahamas. Sipunculans removed from the collectors were counted, weighed, and maintained in the laboratory at 14°C, where they were monitored for gametogenic activity, spawning, development, and growth. In a 2-year study of seasonality, worms were most abundant in collectors retrieved in the spring and summer, and least abundant in the fall. Small animals (<0.01 g) were present in all seasons and represented ≥ 70% of the animals in winter collections. Large specimens (>0.16 g) were found from May through August, but in markedly lower frequencies than small animals. Over the entire study, spawning was observed in the laboratory from April through August. We inferred from analyses of size frequencies, growth, and spawning seasonality that settlement of the larvae occurs primarily from November through April and that oceanic larval life could be as short as 7 months and as long as 12–14 months. Cleavage of fertilized eggs, as observed from laboratory spawnings, was spiral and holoblastic, resulting in a trochophore that transformed into a typical planktotrophic pelagosphera larva at 21 d. A few larvae survived as long as 2 months in the laboratory. This is the first study of biological processes in living sipunculans from the deep sea, and one of the first studies of living deep-sea wood dwellers.

Quantitative magnetic resonance (QMR) is a new technology for measuring the body composition (wet lean mass, fat mass, and total body water mass) of unrestrained and unanesthetized animals. We conducted a validation study using two species of crayfish (mass range 5.5–27 g), American lobsters (680–732 g), and Madagascar hissing cockroaches (6.5–14 g) to assess the utility of QMR for quantifying the body composition of crustaceans and other large arthropods. A comparison of crayfish, lobster, and cockroach wet lean, fat, and body water masses calculated by QMR with those obtained from the traditional chemical extraction method demonstrates that QMR is a valid technology for analysis of wet lean mass and body water. Fat mass could not be accurately predicted, although this might be improved with the use of a QMR analyzer designed specifically for animals of low fat content. QMR analysis allows rapid (<4 min) and non-destructive determination of body composition in field and lab environments, enabling researchers to conduct longitudinal studies and to increase the ethicality and practicality of studying rare or threatened species.

Five color morphs of Paracentrotus gaimardi can be distinguished along the coast of Rio de Janeiro, Brazil: black, brown, gray, green, and pink. All co-occur and are apparently exposed to similar environmental conditions. This study compares the morphology of these color morphs and investigates their gametic compatibility. All specimens of the five color morphs matched earlier descriptions of the species. The number of lateral spines on globiferous pedicellariae, the presence of small ophicephalous pedicellaria, and the pattern of distribution of pedicellaria on the test were reliable morphological characters for taxonomic purposes. The five color morphs were not clearly differentiable in terms of morphology. Fertilization success in crosses within color morphs was greater than in the majority of heteromorphic crosses. Only three heteromorphic crosses – ♀gray and ♂brown, ♀black and ♂gray, and ♀brown and ♂black – were as successful as control, within-color morph crosses. Therefore, some color morphs seem to be partially isolated by an incipient barrier to fertilization. Low fertilization rates among color morphs should result in genetic divergence among them. In fact, genetic divergence at bindin and ATPase genes has been reported among color morphs of P. gaimardi. Natural selection seems to favor fertilization within color morphs, but the mechanism for this differentiation in gametic compatibility is not known.

We present here the first documentation of the entire life cycle of a crinoid. A population of the diminutive feather star Aporometra wilsoni, which broods larvae, was sampled near Adelaide, in the Gulf St Vincent, South Australia, every fortnight between February 2004 and February 2005. Body size, sex, and reproductive status were recorded for 30–50 individuals collected on each occasion. The population showed a sex ratio of 1:1, with unequivocal male and female specimens found in 10 of 13 months. The average size (arm length) of individuals increased until June, when it stabilized and females began to brood larvae. Females were found brooding larvae until November, when adults began senescing. By January, the majority of the population consisted of small recruits. The entire life cycle of this small ovoviviparous crinoid occurs over a single year, a life cycle that is unique among echinoderms.

Enteropneusts in the family Torquaratoridae were imaged using still and video cameras in the deep North Atlantic and then collected by remotely operated vehicles. From this material, we describe Yoda purpurata n. gen, n. sp., Tergivelum cinnabarinum n. sp., and Allapasus isidis n. sp. Individuals of the first two species were browsing completely exposed on the sea floor, whereas the specimen of the last species was encountered floating ∼1 m above the sea floor. Living specimens of Y. purpurata were 12–19 cm long and had a dark reddish-purple proboscis, collar, and genital wings (folded dorsally over the anterior region of the trunk). Members of this species were hermaphrodites (the first ever discovered in the phylum Hemichordata), with numerous separate testes and ovaries in the genital wings. Living specimens of T. cinnabarinum were 12–26 cm long and had a cinnabar-colored proboscis, collar, and back veils (arising from the anterior region of the trunk); sexes were separate, and body shape and internal morphology closely resemble those of its brown congener, T. baldwinae, from the eastern Pacific. The only specimen of A. isidis collected was a male 13 cm long and pale yellow when alive. Its body shape was proportionally shorter and broader than that of its orange congener, A. aurantiacus, from the eastern Pacific, but the internal anatomy of the two species is virtually identical. [Correction made after online publication August 21, 2012 to correct species name in preceding sentence.]