Hyale Nilssoni Research Articles

Motile homes: a comparison of the spatial distribution of epibiont communities on Mediterranean sea turtles

Understanding the ecological roles performed by an individual species requires knowledge from a wide range of disciplines; here we analyze the epibiont–host relationship found in marine turtles. During the study we recorded five new species of sea turtle epibiont: Laomedea flexuosa, Caprella fretensis, Hyale nilssoni, Hyale schmidti, Parasinelobus chevreuxi; as part of a total of nine zoological epibionts present on 35 female green turtles (Chelonia mydas) and 100 loggerhead turtles (Caretta caretta) nesting in Cyprus. The two most commonly occurring epibionts were acorn barnacles Chelonibia testudinaria and Chelonibia caretta, with larger specimens of both species recorded on loggerhead turtles. We analyzed the spatial distribution of these two barnacle species upon the carapaces of their hosts. Specimens of C. testudinaria situated on the anterior half of the carapace were larger than those located at the posterior. A significantly larger proportion of loggerhead turtles (52.5%) hosted epibionts in comparison to green turtles (30.3%). All non-barnacle epibionts were associated with either posterior algal mats or carapace scars.

Epiphytic invertebrate assemblages and dichlorvos usage at salmon farms

Dichlorvos (DDVP) is an organophosphate medicine, used to treat farmed salmon infested with ectoparasitic crustacean sea lice. Field evidence was sought for effects of DDVP usage on mid-tide level invertebrate assemblages associated with the macrophyte Ascophylllum nodosum on shores adjacent to salmonid cages. There was no evidence of impoverishment in Ascophyllum communities in general, and non-target crustacean populations in particular, that could be related to de-lousing operations. Acetylcholinesterase activity in Hyale nilssoni was progressively inhibited with increasing DDVP concentrations. There were indications of reduced AChE activity in Hyale and Carcinus maenas and greater resistance to DDVP in animals collected close to the fish farm with greater usage of DDVP.

Osmoregulation in littoral and terrestrial talitroidean amphipods (Crustacea) from Britain

Osmoregulation was investigated in both aerated seawater and on saturated sand in four species of talitrid amphipods, Talitrus saltator (Montagu), Orchestia gammarellus (Pallas), Orchestia cavimana (Heller) and Arcitalitrus dorrieni (Hunt). The Osmoregulation of one species of intertidal hyalid amphipod Hyale nilssoni (Rathke) was also investigated. Appreciable differences were demonstrated in the osmoregulatory abilities of the species. Whilst the marine supralittoral species O. gammarellus and T. saltator demonstrated the ability to hypo-regulate at higher external concentrations ( > 800 mOsm), they hyper-regulated at lower concentrations, maintaining the haemolymph concentration between 750–850 mOsm. The fresh-water and estuarine supralittoral species O. cavimana and the landhopper A. dorrieni did not have this capacity; both these species maintained the haemolymph hyper-osmotic between external concentrations of 50–900 mOsm. The intertidal H. nilssoni also demonstrated this hyper-osmotic regulation pattern. Hyper-regulation in O. cavimana between external concentrations of 15–290 mOsm was at least partially mediated by the production of hypo-osmotic urine from the antennary gland. The landhopper A. dorrieni produced isosmotic urine as did the hyper-hypo regulating O. gammarellus. There was, however, some evidence that hyper-regulating T. saltator may also produce hypo-osmotic urine. Survivals under different acclimation regimes largely reflect the original habitat of the species: the estuarine/marine supralittoral species were tolerant of a wide range of salinities in water and on sand: the freshwater species showed reduced survival at higher salinities (1200 mOsm) but higher survival than its marine relations in freshwater (<20 mOsm). The landhopper was tolerant of a wide range of salinities but survivals at low (<50 mOsm) and high ( > 900 mOsm) salinities were greater on sand than in water. The results are discussed in relation to the habitats of the species and in relation to the presumed evolutionary history of the group as a whole.

Copper and zinc in an ecological series of talitroidean Amphipoda (Crustacea).

Cu and Zn concentrations were determined for the following talitroidean amphipods, Hyale nilssoni (Rathke), Talitrus saltator (Montagu), Talorchestia deshayesii (Audouin), Orchestia mediterranea Costa, O. gammarellus (Pallas), O cavimana Heller and Arcitalitrus dorrieni (Hunt) in September 1986 from sites in W. Britain (mostly Scottish). To minimize size effects, only animals >2mg body dry weight were included in analyses. Only Talorchestia (Cu & Zn) and O. cavimana (Zn) showed any residual relationship between metal concentration and dry weight. Log transformed data for concentrations of each metal against log dry wt. in all species were compared by ANCOVA. Copper and zinc concentrations of males and females were not significantly different in O. gammarellus, O. mediterranea and T. deshayesii, though Cu (but not Zn) concentrations differed with sex in O. cavimana. The order of species when ranked according to an ascending series of Cu concentrations (at standard body weight) reflected their ecological zonation from sea to land closely, with species living proximal to the sea having lowest Cu concentrations. The 6 talitrid species all had similar Zn concentrations but the Zn concentration of H. nilssoni was considerably lower. There was a relationship between Cu and Zn concentrations in individuals of only one species (O. gammarellus). Data on Cu and Zn concentrations for O. gammarellus derived from the same site in September 1983 were almost exctly the same as in September 1986. The possible impact of seasonal variation on haemocyanin levels is discussed.

Seaweed-associated animal communities in the Firth of Clyde, with special reference to the population biology of the amphipod Hyale nilssoni (Rathke)

SynopisPresent knowledge of animal communities associated with the algae of the Firth of Clyde is briefly reviewed. New work is presented on Hyale nilssoni (Rathke), the commonest amphipod inhabiting high littoral seaweeds, which describes the life-history characteristics over three years of a population associated with Pelvetia. Seasonal changes in growth rate, sex ratio and breeding status are described. Fecundity is investigated and data on brood and egg sizes compared with populations from other latitudes. The dynamic equilibrium between the grazer (Hyale) and the grazed (Pelvetia) is described.

The Fine Structure of the Pore Canals of the Talitrid Amphipod Hyale Nilssoni Rathke

ABSTRACT The pore canals of the talitrid amphipod Hyale nilssoni are described by transmission electronmicroscopy and compared with the pore canals previously described for three species of the gammarid amphipod Gammarus. Structural similarities between the pore canals of the two genera include the presence of an elongate tubular portion that dilates near the junction of the exocuticle with the inner epicuticle, and a cavity in the epicuticle that provides continuity between the animal's surface and the rest of the pore canal. Differences include the presence, in Hyale, of a greater degree of fusion between adjacent elements of the system, and of an anastomosing arrangement of tubules that occupies a series of narrow spaces just below the inner epicuticle. These tubules are derived from the most distal portions of the dilatations and communicate with the cavities in the epicuticle by narrow channels. The significance of the pore canals of Hyale is discussed.

Some Observations on the Life History of the Amphipod Crustacean, Hyale nilssoni (Rathke), in New Hampshire

Hyale nilssoni is an intertidal amphipod at open coastal and estuarine habitats in New Hampshire. Two juvenile recruitment peaks occurred during the year (spring and summerfall), with these peaks occurring earlier in the estuary. The spring peak coincided with increasing water temperature at both locations. Body sizes at the two habitats tended to be inversely related to water temperature resulting in a greater body size on the open coast. Energy demands on the animal associated with the fluctuating water temperatures and salinities likely attributed to the smaller body size of the animal in the estuarine population.

Effects of experimental oil exposure on the fauna associated withCorallina officinalisL. in intertidal rock pools

Field and laboratory experiments on the effects of small-scale pollution by unweathered Ekofisk crude oil on the fauna of intertidal rock pools were carried out in western Norway. Ecological results indicate an immediate effect at community level, followed by rapid recovery. A similar pattern is also valid for biological accumulation and degradation of oil components by Patella vulgata L. Behavioural tests demonstrate differences in responses to oil among species. Amphipods (Hyale nilssoni Rathke, H. pontica Rathke, Stenothoe monoculoides Bate, and Amphithoe rubricata Montagu) are generally more sensitive than isopods, tanaidaceans, and decapods. The importance of the microdistribution of species within habitat (Corallina officinalis) is discussed in relation to adaptive strategies.

The apparent rôle of temperature in breeding initiation and winter population structure in Hyale nilssoni Rathke (Amphipoda): Field observations 1972–1983

Data are presented on the population structure of Hyale nilssoni Rathke (an amphipod inhabitant of high littoral seaweeds) over the period of breeding initiation (late February) of 11 yr. By sampling, as near as possible, the same date annually, photoperiodic effects are controlled. The percentage of ovigerous females on this date was significantly correlated with post-winter solstice mean sea temperature. February sex ratios (M : F) did not correlate with either preceding August or September mean sea temperature such as would have been expected was sex determination temperature sensitive. Sex ratio, however, was significantly positively related to mean winter sea temperatures, with warmer winters having male-dominated Hyale populations in late February. Behavioural hypotheses involving amphipod migration and/or size specific elimination of larger males (c.f. females) during harsher winters are offered in explanation. Population size-frequency distributions over 11 yr were remarkably consistent. Male size was more heterogeneous between years than female size. Mean male size (late February) proved to be significantly negatively correlated with mean winter sea temperatures. Mean female size showed no significant relationship. Given that large males are necessary for precopulatory carrying behaviour it is important that, as shown, they are available to initiate spring breeding, even after harsh winters.

The epifaunal communities of Pelvetia canaliculata and Fucus spiralis

The distribution, size and abundance of Pelvetia canaliculata (L.) and Fucus spiralis L. and the epifaunal communities associated with these two high shore fucoid algae have been studied at several contrasting sites in North Wales. Several environmental parameters were measured at each site and correlated with the distribution of the algae and their associated fauna. These weeds, which occur in perhaps the harshest zone of the shore, support exceedingly impoverished epifaunal communities in which the amphipod Hyale nilssoni (Rathke), small littorinids and acarines predominate. This contrasts markedly with the extremely diverse epifaunal communities associated with algae situated lower in the intertidal zone.