Effects of natural and field-simulated blooms of the dinoflagellate Prorocentrum minimum upon hemocytes of eastern oysters, Crassostrea virginica, from two different populations

Oysters, Crassostrea virginica, from two populations, one from a coastal pond experiencing repeated dinoflagellate blooms (native), and the other from another site where blooms have not been observed (non-native), were analyzed for cellular immune system profiles before and during natural and simulated (by adding cultured algae to natural plankton) blooms of the dinoflagellate Prorocentrum minimum. Significant differences in hemocytes between the two oyster populations, before and after the blooms, were found with ANOVA, principal components analysis (PCA) and ANOVA applied to PCA components. Stress associated with blooms of P. minimum included an increase in hemocyte number, especially granulocytes and small granulocytes, and an increase in phagocytosis associated with a decrease in aggregation and mortality of the hemocytes, as compared with oysters in pre-bloom analyses. Non-native oysters constitutively had a hemocyte profile more similar to that induced by P. minimum than that of native oysters, but this profile did not impart increased resistance. The effect of P. minimum on respiratory burst was different according to the origin of the oysters, with the dinoflagellate causing a 35% increase in the respiratory burst of the native oysters but having no effect on that of the non-native oysters. Increased respiratory burst in hemocytes of native oysters exposed to P. minimum in both simulated and natural blooms may represent an adaptation to annual blooms whereby surviving native oysters protect themselves against tissue damage from ingested P. minimum.     

Abundance,distribution, and secondary production of the apple snail Pomacea flagellata (Say, 1829) in Bacalar Lake,a tropical karstic system in southern Mexico

Pomacea flagellata is a gastropod conspicuous in freshwater environments, and represents a fishing resource. To assess their abundance, distribution, and secondary production, monthly samplings were carried out in Bacalar Lake from June 2012 to May 2013 at 12 sampling sites. In each site, three random transects were marked parallel to the shore. All snails on transect were collected and shell length and wet weight measured. The highest density occurred in September (1.27 ind.m^?2), lowest in October (0.47 ind.m^?2). Shell lengths ranged from 2 to 56 mm, with recruitment in January–March. Growth parameters were L_∞ 59.50 mm, K 0.65.year^?1; the lifetime span was 3 years. Average biomass reached 5.57 wet g.m^?2 and secondary production was 6.025 wet g.m^?2.year^-1; annual renewal rate P/B 1.08. Highest abundance and secondary production was contributed by individuals between 31 and 41 mm in length. A potential biomass of 25.06 tons of snails was estimated in the lake. Snail densities, secondary production, and turnover were very low during the year, indicating that it is not viable to consider a commercial catch without affecting the population. A ban of 10 years is proposed, and aquaculture practices of snails are recommended to recover the resource.     

Odor‐evoked responses in the olfactory center neurons in the terrestrial slug

The procerebrum (PC) of the terrestrial mollusk Limax is a highly developed second‐order olfactory center consisting of two electrophysiologically distinct populations of neurons: nonbursting (NB) and bursting (B). NB neurons are by far the more numerous of the two cell types. They receive direct synaptic inputs from afferent fibers from the tentacle ganglion, the primary olfactory center, and also receive periodic inhibitory postsynaptic potentials (IPSPs) from B neurons. Odor‐evoked activity in the NB neurons was examined using perforated patch recordings. Stimulation of the superior tentacle with odorants resulted in inhibitory responses in 45% of NB neurons, while 11% of NB neurons showed an excitatory response. The specific response was reproducible in each neuron to the same odorant, suggesting the possibility that activity of NB neurons may encode odor identity. Analysis of the cycle‐averaged membrane potential of NB neurons revealed a correlation between the firing rate and the membrane potential at the plateau phase between IPSPs. Also, the firing rate of NB neurons was affected by the frequency of the IPSPs. These results indicate the existence of two distinct mechanisms for the regulation of NB neuron activity. © 2003 Wiley Periodicals, Inc. J Neurobiol 58: 369–378, 2004     

Dynamic response in the larval geoduck (Panopea generosa) proteome to elevated pCO2

Pacific geoducks (Panopea generosa) are clams found along the northeast Pacific coast where they are important components of coastal and estuarine ecosystems and a major aquaculture product. The Pacific coastline, however, is also experiencing rapidly changing ocean habitat, including significant reductions in pH. To better understand the physiological impact of ocean acidification on geoduck clams, we characterized for the first time the proteomic profile of this bivalve during larval development and compared it to that of larvae exposed to low pH conditions. Geoduck larvae were reared at pH 7.5 (ambient) or pH 7.1 in a commercial shellfish hatchery from day 6 to day 19 postfertilization and sampled at six time points for an in‐depth proteomics analysis using high‐resolution data‐dependent analysis. Larvae reared at low pH were smaller than those reared at ambient pH, especially in the prodissoconch II phase of development, and displayed a delay in their competency for settlement. Proteomic profiles revealed that metabolic, cell cycle, and protein turnover pathways differed between the two pH and suggested that differing phenotypic outcomes between pH 7.5 and 7.1 are likely due to environmental disruptions to the timing of physiological events. In summary, ocean acidification results in elevated energetic demand on geoduck larvae, resulting in delayed development and disruptions to normal molecular developmental pathways, such as carbohydrate metabolism, cell growth, and protein synthesis.     

Continuous culture of Perkinsus mediterraneus, a parasite of the European flat oyster Ostrea edulis, and characterization of its morphology, propagation, and extracellular proteins in vitro

Continuous in vitro cultures of Perkinsus mediterraneus were established from tissues of infected European flat oysters, Ostrea edulis. The parasite proliferated in protein-free medium and divided by schizogony in vitro. Cell morphology was similar to that observed for P. mediterraneus in tissues of naturally infected O. edulis and for other Perkinsus spp. cultured in vitro. Parasite cells enlarged approximately 8-fold when placed in alternative Ray's fluid thioglycollate medium, and stained black with Lugol's iodine solution, a response characteristic of Perkinsus spp. DNA sequences matched those determined previously for P. mediterraneus, and phylogenetic analyses on three different data sets indicated that this was a Perkinsus species with a close relationship to another recently described species, Perkinsus honshuensis. Parasite viability was high (>90%) in vitro, but the proliferation rate was low, with densities generally increasing 2-to-6-fold between subcultures at 6-wk intervals. Enzyme analysis of cell-free culture supernatants revealed protease-, esterase-, glycosidase-, lipase-, and phosphatase-like activities. Incubation with class-specific protease inhibitors showed that P. mediterraneus produced serine proteases, and eight proteolytic bands with molecular weights ranging from 34 to 79 kDa were detected in the supernatants by gelatin sodium dodecylsulfate-polyacrylamide gel electrophoresis.     

Magnetic anisotropy of the radula of chiton Acanthochiton rubrolinestus LISCHKE

The magnetic anisotropy of the whole radula, the major lateral radula teeth, and magnetic material in the major lateral radula teeth of the chiton Acanthochiton rubrolinestus LISCHKE have been studied by a magnetic torque meter and superconducting quantum interference device (SQUID) magnetometer. The length and width axes of the teeth are the easily magnetized axes, while the thickness axis is difficult to magnetize. The width and thickness axes of the radula are the easily magnetized axes, and the length axis is difficult to magnetize. The measurement results of the whole radula and the major lateral radula teeth agree well with each other. The magnetic anisotropy of the magnetic material is given as well as a possible distribution of the magnetic material in the major lateral radula teeth.     

The presence of immunoreactive vertebrate bioactive peptide substances in hemocytes of the freshwater snailViviparus ater (gastropoda,prosobranchia)

1. Using an immunocytochemical procedure a wide range of immunoreactive vertebrate bioactive peptides (BAPs) has been found in hemocytes of Viviparus ater: bombesin, calcitonin, CCK-8, CCK-39, GH, glucagon, insulin, oxytocin, neurotensin, secretin, serotonin, somatostatin, substance P, vasopressin, and VIP. 2. No immunostaining was observed for antigastrin and antithyroglobulin antibodies. 3. The presence of BAP-like molecules in hemocytes suggests a correlation between hemocyte and APUD cells and is evidence of a relationship between the neuroendocrine and the immune systems.     

Pathophysiologic alterations in Biomphalaria glabrata infected with Angiostrongylus costaricensis

Hemolymph glucose, alkaline phosphatase, lactic dehydrogenase, and creatine phosphokinase in Biomphalaria glabrata infected with Angiostrongylus costaricensis were significantly higher on day 27 postinfection (PI) than in uninfected snails. Hemolymph total calcium from infected snails was less on days 6, 12, and 27 PI than that from controls. Total hemolymph protein was similar for controls and infected animals during the entire study. Throughout the study the mean number of amoebocytes/mm³ hemolymph from infected snails was significantly less than that for controls. Mean total wet weights of digestive gland and foot muscle from infected and uninfected snails was similar throughout the study. Mean μg glycogen/mg wet weight of digestive gland from infected snails was significantly greater on days 24, 27, and 28 PI than that from controls. Mean μg glycogen/mg wet weight of foot muscle from infected snails was significantly reduced between days 12 and 28 PI from that of uninfected snails. It is suggested that hemolymph glucose and digestive gland glycogen in infected snails are augmented by glycogen breakdown in the foot muscle of parasitized animals. Elevations in hemolymph enzymes are due to tissue destruction by larvae emerging from the foot muscle of infected snails. Parasite-induced derangements in shell metabolism underlie observed changes in hemolymph calcium in infected snails.     

Systemic serotonin sulfate in opisthobranch mollusks

Serotonin (5-hydroxytryptamine, 5-HT) is a ubiquitous modulatory neurotransmitter with roles as a neurohormone and neurotransmitter. However, few studies have been performed characterizing this molecule and its related metabolites in circulating fluids. Here, we demonstrate native 5-HT sulfate, but much lower levels of 5-HT, in hemolymph of the marine mollusk Pleurobranchaea californica. The metabolite 5-HT sulfate forms from 5-HT uptake and metabolism in central ganglia of Aplysia californica and in the visceral nerve and eye of Pleurobranchaea, but not in hemolymph itself. In addition, 5-hydroxyindole acetic acid (5-HIAA), while not detected in hemolymph, forms in higher quantities than does 5-HT sulfate in the eye and visceral nerve, and gamma-glu-5-HT is also observed in this area but never in hemolymph. As systemic 5-HT sulfate appears not to originate from the optic region or from systemic 5-HT, 5-HT sulfate likely derives from the nervous system. Circulating 5-HT sulfate is at least 10-fold higher during the light portion of a 12 : 12-h light/dark cycle than during the dark portion (p < 0.0007), but there is no obvious trend for free systemic tryptophan (Trp) (p > 0.3) in Pleurobranchaea. 5-HT in mollusks is associated with general arousal state; thus, diurnal systemic changes in a 5-HT catabolite may reflect a regulatory role for indole catabolism in behavioral rhythms.     

No correlation between inbreeding depression and delayed selfing in the freshwater snail Physa acuta

Inbreeding depression, one of the main factors driving mating system evolution, can itself evolve as a function of the mating system (the genetic purging hypothesis). Classical models of coevolution between mating system and inbreeding depression predict negative associations between inbreeding depression and selfing rate, but more recent approaches suggest that negative correlations should usually be too weak or transient to be detected within populations. Empirical results remain unclear and restricted to plants. Here, we evaluate, for the first time, the within-population genetic correlation between inbreeding depression and a trait that controls the amount of self-fertilization (the waiting time) in a self-fertile hermaphroditic animal, the freshwater snail Physa acuta. Using a large quantitative-genetic design (36 grand-families and 348 families), we observe abundant within-population family-level genetic variation for both inbreeding depression (estimated for survival, fecundity, and size) and the degree of behavioral selfing avoidance. However, we detected no correlation between waiting time and inbreeding depression across families. In agreement with recent models, this result shows that mutational variance rather than differential purging accounts for most of the genetic variance in inbreeding depression within a population.