Persistence of atrazine impact on aneuploidy in Pacific oysters,<Emphasis Type="Italic"> Crassostrea gigas</Emphasis>

Widespread use of the herbicide atrazine has incited much research on its toxicity in aquatic systems, where it is routinely detected due to runoff from cultivated fields. Moreover, the determination of the genotoxic effect of such pollutants in the marine environment has become a major requirement for ecosystem protection. In the Pacific oyster, Crassostrea gigas, hypodiploid aneuploid cells have regularly been reported. There is a negative correlation between this phenomenon and growth, as well as evidence for a genetic basis. A positive relationship between atrazine and aneuploidy has previously been demonstrated in C. gigas adults and juveniles. To evaluate the persistence of this impact, our study examined the offspring of the same adult population previously treated with different atrazine doses (10 µg l^–1, representing a peak value found in a polluted environment and 100 µg l^–1), and a seawater control. We observed that these offspring exhibited significantly higher aneuploidy levels when their parents had been exposed to atrazine (14.9–16.9% in comparison with the control where the levels ranged from 11.4% to 12.8%). In addition, the present study examined the aneuploidy level of a sample of juveniles, previously exposed for 3.5 months to the same doses of atrazine, then transferred to non-polluted conditions for an additional period of 2.5 months; this aneuploidy level remained significantly different between the treatments applied. These results demonstrate the persistence of an atrazine impact on Pacific oyster aneuploidy in time, within and between generations, indicating that this widely used compound may represent an important factor causing at least medium-term damage to genetic material.Communicated by S.A. Poulet, Roscoff     

Comparative life-history study on sympatric hyperiid amphipods (<Emphasis Type="Italic">Themisto pacifica</Emphasis> and <Emphasis Type="Italic">T</Emphasis>. <Emphasis Type="Italic">japonica</Emphasis>) in the Oyashio region,western North Pacific

Life-history features of the sympatric amphipods Themisto pacifica and T. japonica in the western North Pacific were analyzed based on seasonal field samples collected from July 1996 through July 1998, and data from laboratory rearing experiments. T. pacfica occurred throughout the year, with populations peaking from spring to summer. In contrast, T. japonica were rare from autumn to early winter, but became abundant in late winter to spring. Mature T. pacifica females and juveniles occurred together throughout the year, indicating year-round reproduction. Mature T. japonica females were observed only in spring, and juveniles occurred irregularly in small numbers, suggesting limited, early-spring reproduction in this study area. Size composition analysis of T. pacifica identified a total of eight cohorts over the 2 years of the study. Due to the smaller sample size and rarity of mature females (>9.6 mm) and males (>7.1 mm), cohort analyses of T. japonica were not comparable. Laboratory rearing of specimens at 2°C, 5°C, 8°C and 12°C revealed that a linear equation best expressed body length growth by T. pacifica, while a logistic equation best expressed body length growth by T. japoncia. Combining these laboratory-derived growth patterns with maturity sizes of wild specimens, the minimum and maximum generation times of females at a temperature range of 2–12°C were computed as 32 days (12°C) and 224 days (2°C), respectively, for T. pacifica, and 66 days (12°C) and 358 days (2°C), respectively, for T. japonica. The numbers of eggs or juveniles in females marsupia increased with female body length and ranged from 23 to 64 for T. pacifica and from 152 to 601 for T. japonica. Taking into account the number of mature female instars, lifetime fecundities were estimated as 342 eggs for T. pacifica and 1195 eggs for T. japonica. Possible mechanisms for the coexistence of these two amphipods in the Oyashio region are also discussed.Communicated by O. Kinne, Oldendorf/Luhe     

Time-course uptake and elimination of benzo(a)pyrene and its damage to reproduction and ensuing reproductive outputs of Pacific oyster, <Emphasis Type="Italic">Crassostrea gigas</Emphasis>

The time-course of uptake and elimination of benzo(a)pyrene (BaP) for the Pacific oyster, Crassostrea gigas and reproduction damage and reproductive outputs were studied. Sexually immature C. gigas broodstock were fed for 28 days with live algae grown in four BaP solutions of 0, 50, 500, and 5,000 μg L⁻¹ (hereafter, control, 50, 500, and 5,000 oysters) and were subsequently conditioned to maturation by a feeding with BaP-free live algae under temperature manipulation for another 28 days. The 5,000 μg L⁻¹ oysters gained a steady state concentration, around 30,000 ng g⁻¹ d.w. for digestive gland, a week earlier compared to the 500 μg L⁻¹ oysters. The earlier gain or longer persistence of the steady state concentration influenced elimination of BaP, with an eliminating trend for 500 μg L⁻¹ oysters, while no elimination for 5,000 μg L⁻¹ oysters. The maternal persistence of the steady state concentration resulted in significant damages in the reproductive success and their reproductive outputs in terms of the hatching rate and larval growth, survival, and settlement. The 50 μg L⁻¹ oysters remained far below the steady state concentration, and showed a manifest eliminating behavior during the subsequent BaP-free 28 day maturation period. The reproductive success and initial larval events of 50 μg L⁻¹ oysters were comparable to those of control. However, the damage potential of the 50 μg L⁻¹ oysters might be more significant if their maternal exposure continued beyond 28 days, since the accumulation profile at this dose was linear.     

Isolation and characterization of two actins of the Pacific white shrimp, <Emphasis Type="Italic">Litopenaeus vannamei</Emphasis>

Two actin genes named actinT1 and actinT2 were isolated and sequenced from the Pacific white shrimp, Litopenaeus vannamei, by screening from a shrimp eyestalk cDNA library. L. vannamei actinT1 cDNA has a 1,128-bp open reading frame encoding for 376 amino acids while L. vannamei actinT2 cDNA has a 1,131-bp open reading frame coding for 377 amino acids. Alignment of the actinT1 and actinT2 cDNA sequences showed that these two actin genes share a sequence identity of 86% at amino acid residues. When compared with actins of several other invertebrate and vertebrate species, the nucleotide sequence of actinT1 is highly homologous (97–100%) with beta-actins, while actinT2 shares 86–95% identity with alpha-actins on the nucleotide level. Phylogenetic analysis and BLAST searches indicated that the ActinT1 protein is identical to crustacean beta-actins, while the ActinT2 protein is highly homologous to crustacean alpha-actins. Constitutive expression of the actinT1 and actinT2 genes were detected by RT-PCR in all adult shrimp organs, including brain, eye-stalk, gill, heart, hemolymph, hepatopancreas, muscle, swimming legs, and stomach, as well as in the shrimp zygote, nauplius, and mysis life stages. These data will facilitate attempts to clone and identify more shrimp genes and constitutive shrimp promoters.     

Ontogeny of space use and diet of two temperate damselfish species, <Emphasis Type="Italic">Parma microlepis</Emphasis> and <Emphasis Type="Italic">Parma unifasciata</Emphasis>

Studies of reef fish herbivory have mainly focused on the impacts and behaviour of adults of tropical species. In this study, the ontogenetic shifts in home range, aggression, feeding rate, diet and gut morphology in juveniles and adults of two temperate territorial damselfishes, Parma microlepis and Parma unifasciata, were determined. Both P. microlepis and P. unifasciata juveniles under 80 mm TL exhibited no aggressive chases towards conspecifics or other species, while above 80 mm TL aggressive chase frequency increased in conjunction with an increase in home range, defended as a territory. Ontogenetic diet shifts, characterised by an increase in herbivory (P. unifasciata: juveniles: 64% plant material, adults: 95% plant material; P. microlepis: juveniles: 43% plant material, adults: 67% plant material) were observed for both species. The ratio of digestive tract length to body length, which often accompanies a switch to herbivory, increased significantly with ontogeny for both species. Compared to tropical confamilial grazers, these temperate damselfish species feeding rates were lower, and they had larger territories which were not as strongly defended (fewer aggressive chases).     

Trace-metal detoxification and tolerance of the estuarine worm<Emphasis Type="Italic"> Hediste diversicolor</Emphasis> chronically exposed in their environment

Polychaete worms (Hediste diversicolor) originating from a strongly metal-contaminated area (Restronguet Creek) and a relatively clean site (Blackwater estuary) were exposed to a range of experimental doses of Ag, Cd, Cu and Zn. Specimens from both populations were compared to assess their relative sensitivity to metal stress and the physiological mechanisms involved in their respective adaptive strategies for coping with increased metal exposures. Taking into account the LC₅₀ values, increased tolerance to Cd, Cu and Zn of the Restronguet Creek worms over that of the Blackwater was demonstrated, whereas the opposite was shown for Ag. An abundant secretion of mucus in response to toxicants was observed, possibly reducing metal availability for uptake, at least under laboratory conditions. This mechanism was particularly active in specimens from Restronguet Creek exposed to Ag and Cu. Unexpectedly, of the two worm populations, Blackwater worms contained significantly higher concentrations of cytosolic heat-stable compounds (CHSTC), a category of cytosolic components that includes metallothioneins, the detoxificatory role of which is well documented, and other compounds binding trace metals via sulphur bonds. However, the concentration of such compounds is not totally representative in itself of their involvement in metal detoxification, because a high rate of their turnover in metal-exposed worms might be responsible for (at least) the Cu storage associated with S in lysosomes as a consequence of the breakdown of Cu-thionein. Cu-containing lysosomes were abundant in epidermal cells of Restronguet Creek worms, but were lacking in Blackwater worms. Extracellular granules present in the epicuticle also contained S and Cu, their number and size being much more important in Restronguet Creek worms, and they appear to be a major detoxificatory store for accumulated Cu. Spherocrystals in cells of the gut wall seem to be the major detoxified store of Zn in Restronguet Creek worms, whereas in specimens from the Blackwater they were also present but contained only S and Ca at detectable levels. Evidence was also found for the presence of detoxificatory intracellular structures containing other metals and metalloids in the tegument and gut epithelium of Restronguet Creek worms.Communicated by S.A. Poulet, Roscoff     

Population genetic and phylogeographic structure of wahoo,<Emphasis Type="Italic"> Acanthocybium solandri</Emphasis>, from the western central Atlantic and central Pacific Oceans

The wahoo, Acanthocybium solandri (Cuvier, 1832), is a pelagic, highly migratory, scombroid fish, distributed worldwide throughout tropical and warm temperate seas. To evaluate population genetic and phylogeographic structure against a null hypothesis of panmixia, the entire mitochondrial DNA control-region (~890 base pairs) was sequenced for 231 wahoo. Samples were collected from 1997 to 2001 from seven sites: North Carolina (NC; n=23), east central Florida (CF; n=30), Bimini, Bahamas (BB; n=40), southern tip of Florida (SF; n=21), Cayman Islands (CI; n=23), northern Gulf of Mexico (NG; n=54), and Hawaii (HI; n=40). Inter-annual samples were obtained from four of these locations (NC, BB, SF, NG). Seventeen haplotypes were shared by individuals within and among samples; 187 singleton haplotypes were observed. Within-sample haplotype diversities ranged from 0.995 to 1.000 (overall h=0.999) and within-sample nucleotide diversities ranged from 0.049 to 0.055 (overall =0.053). A neighbor-joining tree based on inter-haplotypic distances revealed two monophyletic lineages differing by 13.6% nucleotide divergence. Nested within each major lineage were several, well-supported subclades. There was no evidence of temporal heterogeneity in haplotype distributions. Partitioning mtDNA variation, 99.75% of the variance was within samples and 0.25% (P=0.307) between samples; the fixation index (_ST=0.0025) was not significant. Likewise, pairwise _ST values were low or negative, and none were significant on a table-wide basis. Exact tests for sample differentiation in haplotypes were also non-significant. All population analyses were consistent with the null hypothesis of panmixia. However, analytical power was limited by sample size. Mismatch distributions were inconsistent with expected distributions based on sudden-expansion and static-growth models. Wahoo exhibit concurrently high haplotype and nucleotide diversities, presumably a consequence of secondary contact between historical subpopulations rather than a long, stable evolutionary history. Given the level of geographic and individual sampling, wahoo thus far represent the sole example of a scombroid or xiphioid fish exhibiting coarse-grain genetic homogeneity across a broad, inter-oceanic range despite a deeply coalescing genealogical structure. Accordingly, cooperative fishery management on a broad, inter-ocean scale may be warranted.Communicated by J.P. Grassle, New Brunswick     

Behavior of bigeye (<Emphasis Type="Italic">Thunnus obesus</Emphasis>) and skipjack (<Emphasis Type="Italic">Katsuwonus pelamis</Emphasis>) tunas within aggregations associated with floating objects in the equatorial eastern Pacific

The horizontal and vertical movements of bigeye (Thunnus obesus Lowe, 1839) and skipjack (Katsuwonus pelamis Linnaeus, 1758) tunas within large multi-species aggregations associated with moored buoys or a drifting vessel were investigated, using ultrasonic telemetry and archival tags, along with sonar imaging, in the equatorial eastern Pacific Ocean (at 2°S–95°W and 2°N–95°W). Four sets of observations, each consisting of the concurrent monitoring of pairs of skipjack and/or bigeye with implanted acoustic or archival tags, were conducted in May 2002 and 2003. Ultrasonic telemetry data were not collected until 24 h or more after the fish were tagged and released, to avoid any abnormal behavior as a consequence of tagging. The pairs of acoustically tagged bigeye and skipjack, and also the entire aggregations, were primarily upcurrent of the moored buoy and downcurrent of the drifting vessel during the day. At night the aggregations were observed to be more diffuse, and the fish were feeding on organisms of the deep scattering layer. The aggregations returned to positions upcurrent of the buoy or downcurrent of the drifting vessel at dawn, commonly breezing at the surface within cohesive monospecific schools. The bigeye and skipjack had concurrent changes in depth records, occupying significantly greater mean depths at night than during the day, in most cases. When associated with a moored buoy, bigeye depth distributions were deeper during the day and night than those of skipjack, but bigeye depth distributions were shallower during the day and night than those of skipjack when associated with the drifting vessel. Simultaneous depth records of a large and a small bigeye with archival tags associated with a moored buoy also indicated diel changes in depth. The mean depth at night was significantly less than during the day for the larger bigeye, but the mean depth during the day was significantly less than during the night for the smaller bigeye. The mean depths during the day and night were significantly greater for the larger bigeye than the smaller.Electronic Supplementary Material  Supplementary material is available in the online version of this article at http://dx.doi.org/10.1007/s00227-004-1480-xCommunicated by J.P. Grassle, New Brunswick     

Detrimental effects of the isopod, <Emphasis Type="Italic">Edotia doellojuradoi,</Emphasis> on gill morphology and host condition of the mussel, <Emphasis Type="Italic">Mytilus edulis platensis</Emphasis>

There are many reported associations between mussels and other invertebrates, such as pea crabs, polychaetes, turbellarians and copepods, which live in their mantle cavities. The boundary between commensalism and parasitism is often indistinguishable because of insufficient knowledge or because the interaction is variable. Preliminary evidence led to a closer examination of the relationship between the mussel, Mytilus edulis platensis, and an isopod, Edotia doellojuradoi, previously described as commensalism. Monthly intertidal samples of mussels were taken from September 2004 to August 2005 at Caleta Cordova Norte (45°43′S, 67°22′W) in southern Argentina and assessed for the prevalence and abundance levels of isopods. Mussels with and without isopods were measured, examined for evidence of gill damage and their condition (soft tissue dry weight) was determined. The overall isopod prevalence in mussels was 57.9% and infestation varied with mussel length, with maximum occurence at 30.2 mm (medium-sized mussels). Experimental evidence indicated that the position of the isopod inside the mussel depended on the feeding activity of the mussel. Female isopods were observed grasping the ventral food groove of the gill demibranchs and feeding on the mucous food strand produced by the mussel. Juveniles and males were observed clustered together on the dorsal side of the single female in each occupied mussel, suggesting extended maternal care. Gill damage was observed in 58.2% of mussels at the Argentine site and was significantly associated with isopod occurrence. Categorical regression analysis showed that the most important factor associated with the degree of gill lesions was the number of male and juvenile isopods per mussel, followed by the length of female isopods and the developmental stage of juveniles. Conversely, the degree of gill damage decreased with increasing mussel length. Overall, E. doellojuradoi had a significant effect on mussel condition throughout the year, with low flesh weight in mussels with isopods, except during the austral summer and early autumn. In contrast to previous studies, which concluded that the isopod was a commensal, the present study clearly demonstrates that E. doellojuradoi is a parasite of M. edulis platensis. Other symbiotic interactions formerly classified as commensal might not be innocuous on further investigation, especially if samples are taken at multiple sites and at different times of the year.     

Detection of oxidative stress and DNA damage in freshwater snail <Emphasis Type="Italic">Lymnea leuteola</Emphasis> exposed to profenofos

Extensive production and use of organophosphate pesticide in agriculture, has risen concerned about its ecotoxicity and risk assessment of insecticides, which are more important. Therefore, the present investigation was aimed to study the induction of oxidative stress and DNA damage by organophosphate insecticide profenofos (PFF) in freshwater snail Lymnea luteola (L. luteola). The median lethal value (96 h LC₅₀) of PFF was estimated as 1.26 mg/L for L. luteola in a semi-static system and on the basis of LC₅₀ value three concentrations viz., 0.126 (1/10 of LC₅₀, Sublethal I), 0.63 (1/2 of LC₅₀, Sublethal II) and 0.84 mg/L (2/3 of LC₅₀, Sublethal III) were determined. Snails were exposed to above-mentioned concentrations of PFF along with solvent control (acetone) and negative control for 96 h. The haemolymph was collected at 24 and 96 h of after treatment. In heamolymph of PFF exposed snail, lipid peroxide, glutathione reduced glutathione S transferase and superoxide dismutase activities at the tested concentrations significantly differ from those in the control. The genotoxicity induced in hemocytes of treated snails was measured by alkaline single cell gel electrophoresis assay. The data of this experiment demonstrated significantly enhancement of oxidative stress and DNA damage in the treated snails as compared to controls. Also, we observed statistically significant correlations of ROS with DNA damage (% tail DNA) (R² = 0.9708) for 24 h and DNA damage (R2 = 0.9665) for 96 h.

Results of the current experiment can be useful in risk evaluation of PFF among aquatic organisms. The study confirmed the use of comet assay for in vivo laboratory experiments using freshwater snail for selecting the toxic potential of industrial chemicals and environmental contaminants.

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Worms without borders: genetic diversity patterns in four Brazilian <Emphasis Type="Italic">Ototyphlonemertes</Emphasis> species (Nemertea,Hoplonemertea)

Understanding the evolutionary processes from recent demographic history is especially difficult for interstitial organisms due to their poorly known natural history. In this study, the genetic variation and population history of the four Ototyphlonemertes (Diesing in Sitz ber Math Nat Kl Akad Wiss Wien 46:413–416, 1863) species were evaluated from samples collected along the Brazilian coast (between 27°31′S and 13°00′W) in 2006. The mitochondrial region cytochrome c oxidase subunit 3 (COX3) is analyzed to assess the genetic variation of these dioecious species. Although these species have a sympatric distribution along the coast, our data suggest that their levels of differentiation and their demographic histories differ sharply. There is strong evidence of gene flow among demes in O. erneba and O. evelinae, and their level of structuring is much lower than for the other two species. Indeed, the COX3 fragment reveals cryptic lineages in O. lactea and O. parmula. The results seem to contradict the high genetic structuring and low intrapopulational variability expected with the ecological constriction and habitat discontinuity faced by these organisms, meaning that there might be gene flow among populations or their dispersal capability has been underestimated.     

The oral cavity and bioluminescent organs of the cardinal fish species<Emphasis Type="Italic"> Siphamia permutata</Emphasis> and<Emphasis Type="Italic"> S. cephalotes</Emphasis> (Perciformes,Apogonidae)

The mechanism of bacterial-derived bioluminescence in the apogonid species Siphamia permutata and S. cephalotes presents some special structures, particularly the existence of two sites harboring bioluminescent bacteria, and not only one as previously described. One site, is the familiar disc-like, bacteria-harboring gland and paired ventral bioluminescent reflectors, typical for this genus, that merge and end at the level of the hypobranchial region. The second and more anteriorly situated site of luminescence features two sacs that originate in the gular region and protrude into the oral cavity, via the free space left by the laterally notched tongue. The apical parts of these luminous sacs harbor the bacteria whose light diffuses within the oral cavity. The tongue surface in the studied species is unique in character among the cardinal fishes, being criss-crossed anteriorly by protruding dermal ridges, rich in taste buds and mucus-producing cells. It would appear that at night when feeding, the luminous mouth cavity of these fish acts as a lure to attract the small prey, while the ridged structure of the tongues surface facilitates their collection and aggregation before they are swallowed.Communicated by O. Kinne, Oldendorf/Luhe     

Genetic structure of camouflage grouper,<Emphasis Type="Italic"> Epinephelus polyphekadion</Emphasis> (Pisces: Serranidae), in the western central Pacific

The objective of the present study was to investigate the population genetic structure of the commercially important camouflage grouper, Epinephelus polyphekadion (Bleeker, 1849), in the western and central Pacific Ocean to improve existing management. Camouflage grouper are widely distributed in the Indo-Pacific and form brief, seasonal, spawning aggregations that are often heavily fished. The present study examined populations sampled in 1997-1998 at five sites in the western central Pacific spanning a geographic distance of ~5,000 km: New Caledonia, Great Barrier Reef, Palau, Marshall Islands, and Pohnpei (Micronesia). Primer pairs were developed to examine genetic variation at three polymorphic microsatellite loci. Cluster analysis, using genetic distance, revealed three regional groupings: (1) Palau, (2) Pohnpei and the Marshall Islands, and (3) the Great Barrier Reef and New Caledonia. Highly significant allele frequency differences were observed among sites. At Pohnpei, significant allele frequency differences in successive years were also apparent, possibly related to genetic variation among cohorts or between local spawning groups. The inter-annual differences at Pohnpei suggest that there may be further genetic structuring over relatively modest distances, a finding relative to determining management units for this commercially valuable species and suggests that future studies need to incorporate possible small-scale temporal or spatial components into study design.     

Population structure of <Emphasis Type="Italic">Symbiodinium</Emphasis> sp. associated with the common sea fan, <Emphasis Type="Italic">Gorgonia ventalina</Emphasis>, in the Florida Keys across distance,depth, and time

Numerous marine invertebrates form endosymbiotic relationships with dinoflagellates in the genus Symbiodinium. However, few studies have examined the fine-scale population structure of these symbionts. Here, we describe the genetic structure of Symbiodinium type “B1/B184” inhabiting the gorgonian Gorgonia ventalina along the Florida Keys. Six polymorphic microsatellite loci were utilized to examine 16 populations along the Upper, Middle, and Lower Keys spanning a range of ~200 km. Multiple statistical tests detected significant differentiation in 54–92% of the 120 possible pairwise comparisons between localities, suggesting low levels of gene flow in these dinoflagellates. In general, populations clustered by geographic region and/or reefs in close proximity. Some of the sharpest population differentiation was detected between Symbiodinium from deep and shallow sites on the same reef. In spite of the high degree of population structure, alleles and genotypes were shared among localities, indicating some connectivity between Symbiodinium populations associated with G. ventalina. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Distribution patterns of different age classes and sexes in a Tyrrhenian population of <Emphasis Type="Italic">Talitrus saltator</Emphasis> (Montagu)

Temporal and spatial distribution patterns of a population of Talitrus saltator living on the Tyrrhenian coast of Tuscany (Italy) were studied. Bimonthly surveys were performed from March 1991 to January 1992 along transects using a standard system of pitfall traps and sieves for surface-active and burrowed individuals, respectively. Captured individuals were subdivided into sex and age classes (on the basis of the number of articles of the flagellum of the second antenna). Abundances were calculated for each sampling period and sex ratios were determined. For each sampling period the mean hour of surface activity was calculated together with the mean zonation of both surface-active and burrowing sandhoppers belonging to the different sex and age classes. Shifts in mean zonation between the resting and active phase were also determined. For each category of sex, age, and reproductive phase, simple and multiple regression analyses were used to find relationships of the mean zonation of surface-active animals with climatic data, and of the number of burrowed individuals with surface sand parameters recorded in correspondence to the sieves. On the whole, the results show that this Tyrrhenian population of T. saltator exhibited a bivoltine reproductive cycle and that the sex ratios of active sandhoppers were male or female biased according to the season. The variations in the mean hour of surface activity and in the zonation patterns of sandhoppers depended more on the age than on the sex. Furthermore distribution patterns were generally related to seasonal changes in the local climatic and substrate parameters. The observed differences between burrowing and activity zonations were interpreted on the basis of the nocturnal migrations of the different categories.     

Altered c-Fos expression demonstrates neuronal stress in mummichog, <Emphasis Type="Italic">Fundulus heteroclitus</Emphasis>, exposed to <Emphasis Type="Italic">Pfiesteria shumwayae</Emphasis> and <Emphasis Type="Italic">Chaetoceros concavicornis</Emphasis>

To better understand sublethal effects of harmful algal blooms (HABs) on fish, mummichog, Fundulus heteroclitus (L.), were exposed in the laboratory to varying, environmentally relevant densities of Pfiesteria shumwayae (Glasgow et Burkholder, CCMP 2089, dinoflagellate) and Chaetoceros concavicornis (Mangin, CCMP 169, diatom). Two experiments were conducted during the spring of 2003 and 2004 to quantitatively examine the effects of acute (2 h) P. shumwayae and C. concavicornis algal exposure on mummichog brain activity using c-Fos expression as a marker of altered neuronal activity. Brains from HAB-exposed fish were removed, sectioned, and stained using immunocytochemistry prior to quantifying neuronal c-Fos expression. Fish exposed to P. shumwayae and C. concavicornis showed increased c-Fos expression compared to unexposed control fish. A significant dose-response relationship was observed, with increased labeling in brains of fish exposed to higher cell densities for both HAB species tested (P ≤ 0.01). Increased labeling was found in the telencephalon, optic lobes, midbrain, and portions of the medulla. The greatest increases in expression were observed in the telencephalon of P. shumwayae-exposed fish, and in the telencephalon and optic lobes of C. concavicornis-exposed fish (P ≤ 0.01). These increases in c-Fos expression are consistent with other physical and chemical stress exposures observed in fish. Neuronal stress, evidenced by c-Fos expression, demonstrates a sublethal effect of exposure and changes in brain activity in fish exposed to HAB species.     

Sperm storage and use in laboratory-reared<Emphasis Type="Italic"> Aplysia californica</Emphasis>, a simultaneous hermaphrodite

Aplysia californica, an opisthobranch mollusc, possesses a complex reproductive system that includes a seminal receptacle for the storage of exogenous sperm received from mating. Based on this reproductive anatomy, A. californica should have the ability to maintain and use viable exogenous sperm stores to fertilize multiple eggmasses for extended periods of time. Using controlled matings and careful observation of the development of eggmasses over time, we attempted to quantify A. californicas ability to store and use exogenous sperm following a single mating. On average, A. californica (240.6±31.7 g; mean±SE, n=9) produced 8.8±0.6 eggmasses containing 16.9±2.2×10⁶ fertilized eggs over a period of 22.3±3.6 days following a single mating encounter. The maximum duration an individual A. californica produced fertilized eggs, following a single copulation, was 41 days. The primary factor determining the cumulative number of fertilized eggs produced from a single mating in A. californica was the mass of the sperm recipient (r=0.773, P<0.05, n=9). Our results demonstrated that A. californica are not sperm limited following a single mating as has been suggested for other opisthobranch molluscs by Leonard and Lukowiaks (1991) gamete-trading hypothesis.Communicated by P.W. Sammarco, Chauvin     

Gametogenic and reproductive cycles of the sea anemone, <Emphasis Type="Italic">Entacmaea quadricolor</Emphasis>

Host sea anemones are ecologically important as they provide habitat for obligate symbiotic anemonefish in many areas of the Indo-Pacific. Despite their importance, no information is available on their gametogenic cycles. This study aimed to address this lack of knowledge by determining the gametogenic cycles of Entacmaea quadricolor. Gonad samples were taken from January 2003 to February 2005 at North Solitary Island, Solitary Islands Marine Park, Australia using a specially developed non-lethal field biopsy sampling technique. Sampling was done 17 times during the study period, with 15–20 individuals being sampled on each occasion. Samples were examined prior to fixation, and then histologically sectioned to determine the reproductive activity of each individual. Female anemones were significantly more abundant than males, and had asynchronous oocyte development both within and among individuals. Male anemones showed a single annual cycle of spermary growth, development and spawning. Data from the 26-month study indicated that spawning occurred in the austral summer and autumn between January and April, which coincided with the observed spawning periods that have previously been documented for this species in outdoor flow-through seawater tanks at the study location. The biopsy sampling technique used during this study provides an opportunity to gain a more thorough understanding of the gametogenic cycles and sexual pattern of host sea anemones throughout their distribution.     

Pursuit deterrence,predation risk,and escape in the lizard <Emphasis Type="Italic">Callisaurus draconoides</Emphasis>

The frequency of pursuit-deterrent signaling should vary with predation risk for factors affecting decisions to flee and hide. Distance to refuge, temperature, and microhabitat types affect risk, and their effects may differ among defenses. Because risk is greater farther from refuge and at lower temperatures that impair escape ability in ectotherms, I predicted that when farther from refuge ectothermic prey flee sooner, enter refuge more frequently, and signal more frequently. At low temperatures, prey should flee sooner, enter refuge, and signal less frequently. Because signaling sometimes deters attack, lowered risk might allow prey to permit closer approach when signaling. In the zebra-tailed lizard Callisaurus draconoides, which signals by waving its tail, signaling and the other behaviors were affected by the same risk factors. Probability of signaling before fleeing increased with distance to refuge and temperature, but variation in temperature accounted for the effect of distance to refuge. Lizards signaled not at all at low temperatures, after starting to flee at intermediate temperatures, and before, during, and after fleeing at higher temperatures. This pattern is consistent with honest signaling of escape ability. Refuge entry was more frequent nearer refuge (lower risk) and at lower temperature (higher risk). Display was less frequent on rock than ground, possibly due to conspicuousness or delay in attaining high speed. Flight initiation distance was shorter after signaling. This novel finding suggests that signaling reduces risk and prey alter escape decisions based on lower risk as a consequence of their own signaling behavior.     

How size relates to oxygen consumption,ammonia excretion,and ingestion rates in cold (<Emphasis Type="Italic">Enteroctopus megalocyathus</Emphasis>) and tropical (<Emphasis Type="Italic">Octopus maya</Emphasis>) octopus species

The scaling of metabolic rates with body mass is one of the best known and most studied characteristics of aquatic animals. Herein, we studied how size is related to oxygen consumption, ammonia excretion, and ingestion rates in tropical (Octopus maya) and cold-water (Enteroctopus megalocyathus) cephalopod species in an attempt to understand how size affects their metabolism. We also looked at how cephalopod metabolisms are modulated by temperature by constructing the relationship between metabolism and temperature for some benthic octopod species. Finally, we estimated the energy balance for O. maya and E. megalocyathus in order to validate the use of this information for aquaculture or fisheries management. In both species, oxygen consumption and ammonia excretion increased allometrically with increasing body weight (BW) expressed as Y = aBW ^b . For oxygen consumption, b was 0.71 and 0.69 for E. megalocyathus and O. maya, respectively, and for ammonia excretion it was 0.37 and 0.43. Both species had low O/N ratios, indicating an apparent dependence on protein energy. The mean ingestion rates for E. megalocyathus (3.1 ± 0.2% its BW day⁻¹) and O. maya (2.9 ± 0.5% its BW day⁻¹) indicate that voracity, which is characteristic of cephalopods, could be independent of species. The scope for growth (P = I − (H + U + R) estimated for E. megalocyathus was 28% higher than that observed in O. maya (320 vs. 249 kJ day⁻¹ kg⁻¹). Thus, cold-water cephalopod species could be more efficient than tropical species. The protein and respiratory metabolisms of O. maya, E. megalocyathus, and other octopod species are directly dependent on temperature. Our results offer complementary evidence that, as Clarke (2004) stated, the metabolic response (R and U) cannot be determined mechanistically by temperature, as previously proposed (Gillooly et al. 2002).