A genotoxicity study on Talitrus saltator (Crustacea, Amphipoda) exposed to lead and benzo(a)pyrene

Sandy beaches are ecosystems often subjected to a variety of pollution sources, including heavy metals and polycyclic aromatic hydrocarbons, largely due to improper human activities. The sandhopper Talitrus saltator s. l. (Montagu, 1808) typically lives on supralittoral shores where it plays an important ecological role. The purpose of this study was to investigate DNA damage levels on hemocytes of T. saltator by means of the Comet assay. Firstly, we tested the sensitivity and reproducibility of the Comet assay on hemocytes of T. saltator after in vitro exposure (1 h) to the genotoxicant methyl methanesulfonate (MMS). The data demonstrated a DNA damage (defined as % DNA tail) related to MMS exposure in a concentration-dependent manner. Next, we carried out the assay on hemocytes of T. saltator that were exposed in vivo (24 h and 7 days) to: a) lead (Pb), b) benzo(a)pyrene (B(a)P), c) mixtures of them. Our data on exposure to Pb or B(a)P showed DNA damage on the hemocytes of T. saltator in a concentration-dependent manner, but apparently with a non-synergistic effect of exposure to their mixtures. Our results provide a background for further studies in order to verify the applicability of Comet assay on T. saltator for assessing genotoxicity levels in sandy beaches subjected to pollutio

Variation of genetic and behavioural traits in the sandhopper Talitrus saltator (Crustacea Amphipoda) along a dynamic sand beach

In an attempt to unravel the possible relationships among coastal stability, genetic variability and orientation behaviour in the sandhopper Talitrus saltator, we have screened four subpopulations of this species. Sandhoppers along 3 km of a dynamic sand beach were studied for orientation performance (i.e. adherence to the seaward theoretical escape direction (TED)) and sequence variation for a fragment of the mitochondrial (mt) gene encoding for the cytochrome oxidase Subunit I (COI). The sampling sites differed in the stability of the shoreline (from severely eroded to accreting). Analysis of molecular variance (AMOVA) revealed significant subdivisions among the four locations. The subpopulation sampled at the most eroded point showed no haplotype diversity and had the highest scatter in orientation. Genetic diversity increased with decreasing erosion. Orientation performances were best where the beach is in dynamic equilibrium, and were progressively more scattered at the accreting points. Multiple linear regression analyses demonstrated that the variables and factors that affected orientation significantly were daytime, global solar radiation, sex of individuals and haplotype diversity. Environmental factors are likely to influence sandhopper behaviour on a short and medium time scale (i.e. from single individual life span to a few generations). The data also suggest that temporal stability of the shoreline has a positive effect on the genetic variability of the resident sandhopper populations

Supralittoral amphipod abundances across habitats on Mediterranean temperate beaches

Community complexity and abiotic conditions are key components of environmental heterogeneity that affect the abundance and distribution of species. In this study we evaluated how environmental conditions affect abundances of supralittoral amphipods (Talitridae) in four habitats (sandy beach, rivermouth, wrack and lakeshore), along the Italian peninsula in the Mediterranean Sea. All samplings covered a 12 month period, and used the same sampling methodology thereby enabling comparison of abundances and species composition and richness. Four species (Talitrus saltator (Montagu, 1808), Orchestia gammarellus (Pallas, 1766), O. montagui Audouin 1826, O. cf. cavimana Heller 1865) were collected in the different habitats, but most species were found or were abundant in only one of the four habitats. Abundances of talitrids (numbers per sampling hour) differed significantly among the habitats with highest abundances found in the wrack and on the riverbank in proximity to an estuary, and lowest abundances observed on four sandy beach sites. Environmental conditions (temperature, moisture, substrate penetrability) differed among the habitats and were associated with some of the among-site variability in abundances. Our findings demonstrate that talitrids thrive better in some supralittoral habitats than others, and that some habitats could be considered to be "hotspots" of talitrid ecology and biodiversity.Community complexity and abiotic conditions are key components of environmental heterogeneity that affect the abundance and distribution of species. In this study we evaluated how environmental conditions affect abundances of supralittoral amphipods (Talitridae) in four habitats (sandy beach, rivermouth, wrack and lakeshore), along the Italian peninsula in the Mediterranean Sea. All samplings covered a 12 month period, and used the same sampling methodology thereby enabling comparison of abundances and species composition and richness. Four species (Talitrus saltator (Montagu, 1808), Orchestia gammarellus (Pallas, 1766), O. montagui Audouin 1826, O. cf. cavimana Heller 1865) were collected in the different habitats, but most species were found or were abundant in only one of the four habitats. Abundances of talitrids (numbers per sampling hour) differed significantly among the habitats with highest abundances found in the wrack and on the riverbank in proximity to an estuary, and lowe

Life history and temporal distribution of Orchestia sp. cf. cavimana (Amphipoda, Talitridae) on a lake shore in central Italy

The life history of the amphipod Orchestia sp. cf. cavimana (Heller, 1865) was studied throughout the course of a year with monthly samplings and the use of pitfall traps along the shores of Lake Albano in central Italy. The data thus obtained showed two peaks in abundance (the first in June and the second in October) and a minimum capture frequency in February. Egg-bearing females were recorded in spring and late summer, whilst recruitment occurred from spring to autumn, with maximum in June and October. The data collected also indicated the presence of a positive correlation between the abundance of talitrids and both temperature and sediment moisture. Morphological analysis enabled the identification of four different cohorts (with a lifespan of the species of approximately 12-15 months) all four of which remained distinguishable throughout the course of the year. It, moreover, enabled sex determination in individuals of 5 or more millimetres. The subsequent distribution indicated that, when significant, the sex ratio was female biased and that maximum size was greater in males. In particular, maximum sizes were recorded in spring for both males and females and were of 17.5 and 13.0 mm, respectively. Furthermore, the total body length recorded for egg-bearing females was positively correlated with the number of eggs in their brood pouch. (C) 2009 Elsevier GmbH. All rights reserved

Life history of the talitrid amphipod Macarorchestia remyi (Schellenberg, 1950) on a Tyrrhenian sandy beach, Italy

In this study, we analysed the life cycle and some aspects of the reproductive biology of the talitrid amphipod Macarorchestia remyi (Schellenberg, 1950) on a sandy beach in central Italy (Tyrrhenian Sea). The species is strongly associated with rotting wood carried by the sea. The animals were sampled once a month by hand over 1 year (May 2006-April 2007) and a total of 3,484 individuals were collected. Results showed the occurrence of intersexes in addition to males and females (n = 268) and a sex ratio always in favour of females. Breeding peaked twice during the year and the number of eggs in the ventral brood chamber ranged from 3 to 19. Linear regression analysis showed a positive correlation between total length of ovigerous females and the number of eggs they carried. The mean length of both mature males and mature females was 6 mm, while the maximum length was 13 mm. The presence of two cohorts during the year was also identified. Our results suggest that, despite the ephemeral habitats where the species lives, the population is stable over time and its life cycle does not differ in relation to other talitrid species that live on beaches

ALLOZYMES AND mtDNA REVEAL TWO DIVERGENT LINEAGES IN ORCHESTIA CAVIMANA (AMPHIPODA: TALITRIDAE)

We report on allozyme and mitochondrial DNA variation in 13 populations of the supralittoral amphipod Orchestia cavimana. The species colonizes fresh and brackish shores of Northern Africa, Near East and throughout Europe. Populations were sampled across a large part of the species range (Cyprus, Turkey, northern and southern Italy, United Kingdom and Germany), including the type locality (Cyprus). Both sets of molecular markers agree in identifying two divergent lineages. A first lineage includes populations from Cyprus and Turkey. A second genetically homogeneous lineage groups Italian, English and German populations. Genetic divergence between the two lineages is high (D-Nei = 0.720 +/- 0.06 for allozymes and K2P = 0.191 +/- 0.001 for mitochondrial DNA) and comparable to that among morphologically distinct congeneric species reported for the same set of molecular markers

Exploratory analysis of talitrid population genetics as an indicator of the quality of sandy beaches

Allozymic variation was studied at 23 loci in 10 populations of Talitrus saltator, two populations of Talorchestia deshayesii and two populations of Talorchestia brito from the Mediterranean and Baltic Seas. Levels of genetic differentiation among the three species showed a close relationship between T. saltator and T. deshayesii, whereas T. brito was more genetically differentiated. Within T. saltator, it was possible to recognise two main clusters, the first grouping consisting of Baltic, Tyrrhenian and North African populations, the second comprising Adriatic and East Mediterranean populations. Talitrus saltator populations were generally characterised by low levels of gene flow (Nm < 1). The relationship between Nm and geographic distances was analysed to test for an isolation by distance pattern in the spatial genetic variation. Isolation by distance was detected at the scale of the whole Mediterranean, with geographic distance explaining about 50% of the variance in gene flow. The North African populations showed an island model of genetic structuring; this result is mainly due to the anomalous genetic pattern of a population from a Tunisian beach (Tabarka) highly exploited for tourism. Human activities, which may influence T. saltator population dynamics, are believed to be responsible for the observed pattern of genetic variation in North Africa