The sea anemone Anthopleura elegantissima is a common member of intertidal communities along the west coast of North America, and can experience extended periods of increased temperature during summertime low tides. Internal body temperatures of emersed individuals of A. elegantissima were monitored in a laboratory wind tunnel and in the field, and factors influencing the anemones' thermal experience were examined. Larger body size and aggregation with conspecifics slowed body temperature increases in controlled wind tunnel conditions. In the field, anemones in the interior of an aggregation stayed cooler than those on the edges, and microhabitat features related to light exposure and surface orientation overshadowed any direct effects of body size. In the warmest month only (July), aggregations of A. elegantissima were significantly larger at the upper limit of their distribution than they were at the mid and lower limits, suggesting aggregation in high intertidal zones may be a behavioral response to desiccation and temperature stress. As this sea anemone can host multiple species of symbiotic algae with different thermal tolerances, the ability to slow body heating may affect the type of algae hosted and thus the potential contribution of this abundant anemone to primary production in the intertidal zone.

Rhogocytes are morphologically distinct cells distributed throughout connective tissues of crustaceans and molluscs. Using light microscopy, rhogocytes of the vetigastropod Megathura crenulata were identified by their ovoid shape, and their cytoplasm filled with spherical inclusions which contained lysosomal enzymes, based on uptake of neutral red and staining with LysoTracker dye. Rhogocytes were most abundant in the digestive gland (2,824 rhogocytes/mm²), followed by the connective tissue layer surrounding the middle and posterior esophagus and intestine (1,431 rhogocytes/mm², 872 rhogocytes/mm², and 1,190 rhogocytes/mm², respectively), and were lowest in abundance in the foot (154 rhogocytes/mm²). At the transmission electron microscopy level, characteristic features of rhogocytes were inclusions showing a variety of electron densities, abundant vesicles, and rough endoplasmic reticulum in the cytoplasm, and regions of plasma membrane folded to produce slits connected by thin diaphragms. Although several functions have been proposed for gastropod rhogocytes, much attention has been focused on their possible role in the synthesis of the respiratory pigment hemocyanin. In M. crenulata, this molecule exists in several isoforms called keyhole limpet hemocyanin (KLH). One isoform, KLH1, is a large didecamer and has been used extensively in studies on vertebrate immunology and cancer therapy. We present four lines of evidence indicating rhogocytes in M. crenulata synthesize KLH1. First, at the transmission electron microscopy (TEM) level, dilated cisternae of RER containing material similar in size and shape to KLH were observed in rhogocytes examined throughout the year. Second, KLH1 mRNA was identified exclusively in tissue samples that contained rhogocytes; no mRNA for KLH1 was identified in samples containing only hemocytes. Third, immunoperoxidase staining with antibodies specific to KLH was localized only to rhogocytes. Fourth, in situ hybridization with a probe specific for M. crenulata KLH1 demonstrated KLH1-specific mRNA was present only in rhogocytes. Identification of the cells responsible for the synthesis of KLH is important because of the clinical significance of this molecule.

Adults of the nudibranch mollusc Tritonia diomedea crawl using mucociliary locomotion. Crawling is controlled in part by the large Pedal 5 (Pd5) and Pedal 6 (Pd6) neurons that produce Tritonia Pedal peptides (TPeps). TPeps elicit an increase in ciliary beat frequency, thereby increasing crawling speed. In adults of T. diomedea, an extensive network of TPep-containing neurites adjacent to the basement membrane of the pedal epithelium delivers TPeps to the ciliated cells. In this study, we show that diverse nudibranchs all have a pattern of TPep-like immunoreactivity similar to that of T. diomedea, with thin tracts of TPep-like immunoreactive (TPep-LIR) neurites projecting to the epithelial layer. We also show that members of two non-nudibranch gastropod species have a pattern of TPep-innervation similar to that of the nudibranchs. In addition, we characterized two pairs of motor neurons in adults of the nudibranch Armina californica that are possible homologues of the Pd5 and Pd6 cells in T. diomedea. Activity in one of these pairs, the Pedal Peptidergic Dorsal 1 (PPD1) cells, was correlated with mucociliary locomotion. The second pair, the Pedal Peptidergic Ventral 1 cells, shared synchronous synaptic input with the PPD1 cells, a pattern consistent with the shared synaptic input of the T. diomedea Pd5 and Pd6 cells. These findings suggest that the roles of the Pd5 and Pd6 cells as mucociliary motor neurons in nudibranchs are conserved evolutionarily. Additionally, the extensive network of TPep-LIR neurites seen in the foot of T. diomedea appears likely to be a common feature among gastropods.

The purposeful introduction of the land snail Euglandina rosea, which feeds exclusively on snails and slugs, has been implicated as a major factor in the decline of diverse Pacific island land snail faunas. We report on the distribution, movement patterns, and microhabitat preferences of E. rosea in a gulch in the Waianae Mountains, Oahu, Hawaii, because such data will help focus management actions at a local scale to protect native snail populations in areas where E. rosea is established. The Waianae Mountains harbor many endangered or threatened snails, most currently found in isolated habitat patches near the ridges. Conversely, most living individuals (28/29) and shells (46/56) of E. rosea were collected within the gulch, which supported higher densities of other native and non-native snails, and was cooler and more moist than the ridges. Thirteen individuals of E. rosea were tracked (eight directly using a bobbin and thread method, and five indirectly by mark–recapture); most (10/13) moved on average <2.5 m per week (range 0.1–25.21 m), and all stayed within the gulch. Members of E. rosea preferred leaf litter over open, fern/shrub, or wood microhabitats. There were large differences in the population density of E. rosea over small spatial scales, indicating that there may be places where native snail populations could persist even in areas where populations of E. rosea are established. Identifying areas with differing population densities of E. rosea is critical for not only understanding why some native snail species may be more vulnerable to extinction, but also to locate areas where predation pressure is low and conservation efforts will be most likely to succeed.

The dynamics and consequences of the varied reproductive modes of marine invertebrates is a rich and vibrant field of inquiry for ecological and evolutionary studies. One mode of reproduction that is not as well-studied as others is “spermcasting” or “spermcast mating,” when males broadcast sperm and females retain eggs and brood developing embryonic stages. This type of reproduction occurs in two small (maximum adult shell length ∼5–6 mm) venerid bivalves, Nutricola confusa and N. tantilla, that live in protected bays of the temperate eastern Pacific. Females of these species brood developing embryos in chambers formed by the inner demibranchs, and release fully formed juveniles. We discovered that upon exposing clams to fluvoxamine, a selective serotonin reuptake inhibitor, males release spermatozeugmata, clusters of sperm cells attached by their heads to a central core. Spermatozoa of Nutricola have unusually long, needle-shaped heads that are approximately one quarter of the total length of the cell. These heads are curled and “packaged” into the hemispherical-shaped cores of spermatozeugmata. The cores are about one-third as long as the heads, and the tails protrude out of the opposite side of the cap of the core. The spermatozeugmata display two different swimming patterns, one where the tails beat in synchrony, and the other where they do not. The size of the cores is not significantly different in the two species, but spermatozeugmata of N. tantilla have significantly longer and wider tails than those of N. confusa. Advantages to spermcasting spermatozeugmata instead of individual spermatozoa may include enhanced dispersal and increased probabilities of fertilization. One consequence of spermatozeugmata (rather than individual spermatozoa) entering female brood chambers might be lowering of the effective population size. For species like these, which lack pelagic larvae, spermatozeugmata could increase dispersal and gene flow.

The genome of the non-blood-feeding glossiphoniid leech Helobdella robusta was screened for leech antiplatelet protein (LAPP), an anticoagulant that specifically inhibits collagen-stimulated platelet aggregation. Previously identified LAPP sequences from Haementeria officinalis were used as queries against the predicted genes in the genome, employing a variety of BLAST protocols. Matches were reciprocally BLASTed against GenBank databases as a cross-validation of the predicted annotations of the genes. A total of eight loci, positioned as a tandem array, were recovered with significantly low e-values; these showed high sequence similarity (32.49% average sequence similarity of shared amino acid positions) to the known anticoagulants. Moreover, six of these possessed a predicted signal-peptide toward the N-terminus, indicating their secretion by the leech. All eight loci, together with known LAPP sequences from Ha. officinalis, as well as several sequences from publicly available expressed sequence tag libraries of Ha. depressa and He. robusta, were aligned and subjected to phylogenetic analysis. The resulting tree showed a monophyletic clade consisting of the He. robusta loci, which was sister to a clade comprised of Haementeriaderived sequences. To corroborate the evolution of the anticoagulants with the evolution of leeches more generally, the topology of the LAPP-tree was compared to that of a previously published leech phylogeny; these showed compatible topologies with respect to the included genera. These results corroborate recent phylogenetic work, which suggests that this non-blood-feeding leech has a hematophagous ancestry.

Symbiotic crustaceans are expected to live solitarily with their hosts when members of their host species are small (relative to symbiont body size) and structurally simple. We tested the hypothesis of a solitary lifestyle in Ascidonia flavomaculata, a symbiotic shrimp that inhabits the branchial chamber of the relatively small and structurally simple tunicate Ascidia mentula in the subtidal zone of the Islas Baleares, Spain. We found that members of A. flavomaculata dwell as solitary individuals in the branchial chamber of ascidians at a higher frequency than expected by chance alone. Given this host use pattern of A. flavomaculata, we hypothesized that males actively move among host individuals in search of receptive females. We provide several lines of evidence consistent with that hypothesis. First, a positive correlation between shrimp and host body size was detected for females, but not for males, during one of the sampling seasons. If males as well as females spend long periods of time within their host individuals, a positive correlation between shrimp and host body size should have been found for both males and females. Second, the body sizes of individuals in the few male-female pairs observed during this study were poorly correlated. If males of A. flavomaculata shared their host individuals with females for long periods of time, a positive correlation between the sizes of males and females in a pair should have been found. Lastly, the body sizes of paired males were larger than those of solitary males during summer, when reproduction was more intense. This difference in body size between paired and solitary males additionally suggests competition among putatively roaming males for receptive females. Manipulative experiments and behavioral observations are necessary to reveal the details of the mating system of A. flavomaculata and other symbiotic crustaceans with a solitary lifestyle.

Factors controlling sperm production in members of the Orthoptera have not been fully elucidated. In this study, the influence of intermating interval and ad libidum mating on sperm number was investigated in black field crickets (Teleogryllus commodus). Remating at a variety of time intervals was not characterized by a significant change in sperm number compared with the first mating. Ad libitum mating (i.e., continuous availability of unmated females) had two main effects on spermatophore production and sperm number: first, there was a trend toward increased time between copulations with each successive remating, and second, the number of spermatozoa encapsulated in the transferred spermatophore declined after most rematings, with 61.8% of the initial sperm number being produced for the second spermatophore and 51.3% of the initial sperm number being produced for the third. The decrease in mean sperm number was accompanied by increased variance in sperm number in later rematings. This study suggests that males are willing to suffer a decrease in sperm number if a mating opportunity occurs before the completion of sperm production.