Thomas J. Trott

Chemical stimulants of cheliped flexion behavior by the Western Atlantic ghost crab Ocypode quadrata (Fabricius)

Cheliped flexion behavior was used as a bioassay to measure the responses of the Western Atlantic ghost crab Ocypode quadrata (Fabricius) to pure and natural stimuli. Responses to mantle fluid of Geukensia demissa Dillwyn are based on heat stable components of < 1000 mol. wt. In each class of pure compounds the following were most stimulatory: butanoic acid, carboxylic acids; trehalose, carbohydrates; homarine, amines; asparagine, amino acids. The response to butanoic acid was the largest of any stimulus tested. Disaccharides were more stimulatory than their common monosaccharide component, glucose, and were significantly more potent than amines, except for homarine. Disaccharides, carboxylic acids, and most of the amines were significantly more stimulatory than any of the amino acids. Proteins were the least stimulatory in contrast to the tripeptide glutathione that elicited responses similar to amino acids. These chemical stimuli are components of both live and decomposing foods in the diet of this species. The wide response spectrum of this species may reflect its “plasticity” of foraging behavior

Large-scale spatial distribution patterns of echinoderms in nearshore rocky habitats

This study examined echinoderm assemblages from nearshore rocky habitats for large-scale distribution patterns with specific emphasis on identifying latitudinal trends and large regional hotspots. Echinoderms were sampled from 76 globally-distributed sites within 12 ecoregions, following the standardized sampling protocol of the Census of Marine Life NaGISA project (www.nagisa.coml.org). Sample-based species richness was overall low (<1–5 species per site), with a total of 32 asteroid, 18 echinoid, 21 ophiuroid, and 15 holothuroid species. Abundance and species richness in intertidal assemblages sampled with visual methods (organisms >2 cm in 1 m2 quadrats) was highest in the Caribbean ecoregions and echinoids dominated these assemblages with an average of 5 ind m−2. In contrast, intertidal echinoderm assemblages collected from clearings of 0.0625 m2 quadrats had the highest abundance and richness in the Northeast Pacific ecoregions where asteroids and holothurians dominated with an average of 14 ind 0.0625 m−2. Distinct latitudinal trends existed for abundance and richness in intertidal assemblages with declines from peaks at high northern latitudes. No latitudinal trends were found for subtidal echinoderm assemblages with either sampling technique. Latitudinal gradients appear to be superseded by regional diversity hotspots. In these hotspots echinoderm assemblages may be driven by local and regional processes, such as overall productivity and evolutionary history. We also tested a set of 14 environmental variables (six natural and eight anthropogenic) as potential drivers of echinoderm assemblages by ecoregions. The natural variables of salinity, sea-surface temperature, chlorophyll a, and primary productivity were strongly correlated with echinoderm assemblages; the anthropogenic variables of inorganic pollution and nutrient contamination also contributed to correlations. Our results indicate that nearshore echinoderm assemblages appear to be shaped by a network of environmental and ecological processes, and by the differing responses of various echinoderm taxa, making generalizations about the patterns of nearshore rocky habitat echinoderm assemblages difficult.

Spatial relationships between polychaete assemblages and environmental variables over broad geographical scales

This study examined spatial relationships between rocky shore polychaete assemblages and environmental variables over broad geographical scales, using a database compiled within the Census of Marine Life NaGISA (Natural Geography In Shore Areas) research program. The database consisted of abundance measures of polychaetes classified at the genus and family levels for 74 and 93 sites, respectively, from nine geographic regions. We tested the general hypothesis that the set of environmental variables emerging as potentially important drivers of variation in polychaete assemblages depend on the spatial scale considered. Through Morans eigenvector maps we indentified three submodels reflecting spatial relationships among sampling sites at intercontinental (>10000 km), continental (1000–5000 km) and regional (20–500 km) scales. Using redundancy analysis we found that most environmental variables contributed to explain a large and significant proportion of variation of the intercontinental submodel both for genera and families (54% and 53%, respectively). A subset of these variables, organic pollution, inorganic pollution, primary productivity and nutrient contamination was also significantly related to spatial variation at the continental scale, explaining 25% and 32% of the variance at the genus and family levels, respectively. These variables should therefore be preferably considered when forecasting large-scale spatial patterns of polychaete assemblages in relation to ongoing or predicted changes in environmental conditions. None of the variables considered in this study were significantly related to the regional submodel.

Patterns of Spatial Variation of Assemblages Associated with Intertidal Rocky Shores: A Global Perspective

Assemblages associated with intertidal rocky shores were examined for large scale distribution patterns with specific emphasis on identifying latitudinal trends of species richness and taxonomic distinctiveness. Seventy-two sites distributed around the globe were evaluated following the standardized sampling protocol of the Census of Marine Life NaGISA project (www.nagisa.coml.org). There were no clear patterns of standardized estimators of species richness along latitudinal gradients or among Large Marine Ecosystems (LMEs); however, a strong latitudinal gradient in taxonomic composition (i.e., proportion of different taxonomic groups in a given sample) was observed. Environmental variables related to natural influences were strongly related to the distribution patterns of the assemblages on the LME scale, particularly photoperiod, sea surface temperature (SST) and rainfall. In contrast, no environmental variables directly associated with human influences (with the exception of the inorganic pollution index) were related to assemblage patterns among LMEs. Correlations of the natural assemblages with either latitudinal gradients or environmental variables were equally strong suggesting that neither neutral models nor models based solely on environmental variables sufficiently explain spatial variation of these assemblages at a global scale. Despite the data shortcomings in this study (e.g., unbalanced sample distribution), we show the importance of generating biological global databases for the use in large-scale diversity comparisons of rocky intertidal assemblages to stimulate continued sampling and analyses.

Current Patterns of Macroalgal Diversity and Biomass in Northern Hemisphere Rocky Shores

Latitudinal gradients in species abundance and diversity have been postulated for nearshore taxa but few analyses have been done over sufficiently broad geographic scales incorporating various nearshore depth strata to empirically test these gradients. Typically, gradients are based on literature reviews and species lists and have focused on alpha diversity across the entire nearshore zone. No studies have used a standardized protocol in the field to examine species density among sites across a large spatial scale while also focusing on particular depth strata. The present research used field collected samples in the northern hemisphere to explore the relationships between macroalgal species density and biomass along intertidal heights and subtidal depths and latitude. Results indicated no overall correlations between either estimates of species density or biomass with latitude, although the highest numbers of both were found at mid-latitudes. However, when strata were examined separately, significant positive correlations were found for both species numbers and biomass at particular strata, namely the intertidal ones. While the data presented in this paper have some limitations, we show that latitudinal macroalgal trends in species density and biomass do exist for some strata in the northern hemisphere with more taxa and biomass at higher latitudes.

On the Sex Ratio of the Painted Ghost Crab Ocypode Gaudichaudii H. Milne Edwards & Lucas, 1843 (Brachyura, Ocypodidae)

The sex ratio of the painted ghost crab Ocypode gaudichaudii is 1 : 1. When sampled in different areas of the intertidal zone, the number of males and females varied according to differences in their spatial patterns of behaviour. Male crabs that remained in the burrow area, i.e., the upper third of the beach, at low tide outnumbered females 2 : 1. Large sexually mature males were more abundant in the upper third of the beach in the burrow area than near the low-tide mark. Equal numbers of males and females foraged away from the burrow area at the waters edge. Twice as many females were captured away from the burrow area than in it. Previous reports of skewed sex ratios may have resulted from sampling bias introduced by the different behaviours of each sex.

Aspects of Benthic Decapod Diversity and Distribution from Rocky Nearshore Habitat at Geographically Widely Dispersed Sites

Relationships of diversity, distribution and abundance of benthic decapods in intertidal and shallow subtidal waters to 10 m depth are explored based on data obtained using a standardized protocol of globally-distributed samples. Results indicate that decapod species richness overall is low within the nearshore, typically ranging from one to six taxa per site (mean = 4.5). Regionally the Gulf of Alaska decapod crustacean community structure was distinguishable by depth, multivariate analysis indicating increasing change with depth, where assemblages of the high and mid tide, low tide and 1 m, and 5 and 10 m strata formed three distinct groups. Univariate analysis showed species richness increasing from the high intertidal zone to 1 m subtidally, with distinct depth preferences among the 23 species. A similar depth trend but with peak richness at 5 m was observed when all global data were combined. Analysis of latitudinal trends, confined by data limitations, was equivocal on a global scale. While significant latitudinal differences existed in community structure among ecoregions, a semi-linear trend in changing community structure from the Arctic to lower latitudes did not hold when including tropical results. Among boreal regions the Canadian Atlantic was relatively species poor compared to the Gulf of Alaska, whereas the Caribbean and Sea of Japan appeared to be species hot spots. While species poor, samples from the Canadian Atlantic were the most diverse at the higher infraordinal level. Linking 11 environmental variables available for all sites to the best fit family-based biotic pattern showed a significant relationship, with the single best explanatory variable being the level of organic pollution and the best combination overall being organic pollution and primary productivity. While data limitations restrict conclusions in a global context, results are seen as a first-cut contribution useful in generating discussion and more in-depth work in the still poorly understood field of biodiversity distribution.

Gustatory responses of priapulus caudatus de lamarck, 1816 (priapulida, priapulidae): Feeding behavior and chemoreception by a living fossil

Feeding behavior and chemoreception by the living fossil Priapulus caudatus is described and characterized by behavioral methods. Worms respond to chemical stimulation of the anterior circumoral field with a Stereotypic feeding reflex. This response is not elicited by tactile stimuli alone. Chemoreceptors appear to be restricted to the circumoral field since the feeding response is not evoked when other regions of the body are chemically stimulated. Priapulus caudatus fed only on tissues of macrobenthic species common to its habitat. Ingestion of both live and dead tissues, in addition to algae, indicates that P. caudatus is omnivorous in the Bay of Fundy region. This feeding strategy is adaptive for survival in the extreme environmental conditions characteristic of the niche occupied by P. caudatus.

Large-scale spatial distribution patterns of gastropod assemblages in rocky shores.

Gastropod assemblages from nearshore rocky habitats were studied over large spatial scales to (1) describe broad-scale patterns in assemblage composition, including patterns by feeding modes, (2) identify latitudinal pattern of biodiversity, i.e., richness and abundance of gastropods and/or regional hotspots, and (3) identify potential environmental and anthropogenic drivers of these assemblages. Gastropods were sampled from 45 sites distributed within 12 Large Marine Ecosystem regions (LME) following the NaGISA (Natural Geography in Shore Areas) standard protocol (www.nagisa.coml.org). A total of 393 gastropod taxa from 87 families were collected. Eight of these families (9.2%) appeared in four or more different LMEs. Among these, the Littorinidae was the most widely distributed (8 LMEs) followed by the Trochidae and the Columbellidae (6 LMEs). In all regions, assemblages were dominated by few species, the most diverse and abundant of which were herbivores. No latitudinal gradients were evident in relation to species richness or densities among sampling sites. Highest diversity was found in the Mediterranean and in the Gulf of Alaska, while highest densities were found at different latitudes and represented by few species within one genus (e.g. Afrolittorina in the Agulhas Current, Littorina in the Scotian Shelf, and Lacuna in the Gulf of Alaska). No significant correlation was found between species composition and environmental variables (r≤0.355, p>0.05). Contributing variables to this low correlation included invasive species, inorganic pollution, SST anomalies, and chlorophyll-a anomalies. Despite data limitations in this study which restrict conclusions in a global context, this work represents the first effort to sample gastropod biodiversity on rocky shores using a standardized protocol across a wide scale. Our results will generate more work to build global databases allowing for large-scale diversity comparisons of rocky intertidal assemblages.

The Prevalence of Left-Handedness in the Painted Ghost Crab Ocypode Ga Udicha Udii H. Milne Edwards & Lucas (Decapoda Brachyura, Ocypodidae)

Handedness, or laterality, in crabs possessing dimorphic claws has been examined for several species of brachyuran decapods. These studies have revealed that the major (crusher) chela is located predominately on the right cheliped in species that depart from a 1 : distribution of rightand lefthandedness (Przibram, 1931; Hamilton et al., 1976; Vermeij, 1977; Barnwell, 1982; Jones & George, 1982; Ng & Tan, 1985). Haley (1969) reported that the major chela occurred on the right side on 50 % of the 500 Ocypode quadrata (Fabricius, 1787) he collected from the Texas coast. Similar information on other species of Ocypode is lacking, although this genus has been the subject of several morphometric studies (Cott, 1929; Huxley, 1931; Sandon, 1937; Crane, 1941; Haley, 1973). The painted ghost crab Ocypode gaudichaudii H. Milne Edwards & Lucas, 1843, ranges intertidally along the Pacific coast from the Gulf of Fonseca, San Salvador, to Chile, and the Galapagos Islands (Rathbun, 1918). This crimsonred species of ghost crab has dimorphic chelae with truncated tips; presumably an aid in deposit feeding (Crane, 1941). I collected and examined 457 0. gaudichaudii from four beaches in Corcovado National Park, located on the Osa Peninsula on the Pacific coast of Costa Rica. The locations were: Punta