Search results for "Asellus"

EFFECTS OF ACANTHOCEPHALUS LUCII (ACANTHOCEPHALA) ON INTERMEDIATE HOST SURVIVAL AND GROWTH: IMPLICATIONS FOR EXPLOITATION STRATEGIES

2007

Intermediate host exploitation by parasites is presumably constrained by the need to maintain host viability until transmission occurs. The relationship between parasitism and host survival, though, likely varies as the energetic requirements of parasites change during ontogeny. An experimental infection of an acanthocephalan (Acanthocephalus lucii) in its isopod intermediate host (Asellus aquaticus) was conducted to investigate host survival and growth throughout the course of parasite development. Individual isopods were infected by exposure to fish feces containing parasite eggs. Isopods exposed to A. lucii had reduced survival, but only early in the infection. Mean infection intensity w…

Acanthocephalan size and sex affect the modification of intermediate host colouration

2009

Parasitology, 136 (8)

Nouvelles données sur les Asellidae épigés d’Extrême-Orient (Crustacea, Isopoda, Asellota)

1995

Numerous samples of oculate Asellus from eastern Siberia and the Japanese Islands, one from southern China, and one from Alaska, have been studied. The epigean fresh waters of this large Asiatic region generally harbour populations identified as Asellus (Asellus) hilgendorfii Bovallius, 1886, or some of its geographical forms previously considered as species, subspecies, or not yet named. The “hilgendorfii” complex seems to possess the dimension of a superspecies. A new pigmented-oculate species, Asellus (Asellus) levanidovorum is sympatric with A. (A.) hilgendorfii in the lake Bolon region (lower part of the Amur River basin) and is present also in the Sakhalin and Kunashir Islands. Its co…

2021

Interactions between organisms and their environments are central to how biological diversity arises and how natural populations and ecosystems respond to environmental change. These interactions involve processes by which phenotypes are affected by or respond to external conditions (e.g., via phenotypic plasticity or natural selection) as well as processes by which organisms reciprocally interact with the environment (e.g., via eco-evolutionary feedbacks). Organism-environment interactions can be highly dynamic and operate on different hierarchical levels, from genes and phenotypes to populations, communities, and ecosystems. Therefore, the study of organism-environment interactions requir…

Quantification of sexual dimorphism in Asellus aquaticus (Crustacea: Isopoda) using outline approaches

2002

A marked sexual dimorphism is often observed in arthropods species in which males perform precopulatory mate guarding. It is generally thought to reflect the influence of sexual selection. Until now, sexual dimorphisms associated with mate guarding have mainly been qualitatively described. However, assessing the effects of sexual selection on sexual dimorphims requires a preliminary quantitative assessment of differences in morphology between sexes. Using Fourier analyses, we tested if morphological dimorphisms could be quantitatively assessed in the isopod Asellus aquaticus. In addition, we checked whether sexual dimorphism in shape was exclusively related to mate guarding through consider…

Nouvelles données sur le genre Bragasellus (Crustacea: Isopoda: Asellidae

1996

From now on, the genus Bragasellus Henry & Magniez, 1968 includes 2 oculated and 17 stygobiotic species. As a natural and monophyletic taxonomic unit, we consider it a good genus. Its original area corresponds to the north-west quarter of the Iberian Peninsula. Secondarily, this area has extended eastward, using mainly the alluvial channels of hydrographic systems (Ríos Douro + Ebro and tributaries), finally reaching the underground waters of several Mediterranean rivers. This active expansion is exclusively due to the migration of two stygobiotic sibling species: B. lagari Henry & Magniez, 1973 towards the high basin of the Río Tajo, then downstream to the basins of the Ríos Jucar and Turi…

Multidimensionality and intra-individual variation in host manipulation by an acanthocephalan

2008

Parasitology, 135 (5)

Isopodes Aselloïdes stygobies d’Espagne récoltés par J. Notenboom et I. Meijers, III — Le genre Proasellus: A — Espèces oculées ou microphtalmes

1992

Samples collected in underground waters of Spain by Ine Meijers and Jos Notenboom demonstrated the presence of some oculated asellids previously known: Proasellus coiffaiti, P. coxalis, and P. meridianus, and also four new stygophilous species, more or less depigmented, with different stages of regression of the ocular system: P. beticus n. sp., P. ortizi n. sp., P. aragonensis n. sp., and P. ebrensis n. sp. These forms represent relict populations of ancient epigean species. The anophthalmous species of the Aquitanian Basin, Pyrenees, and Iberian Peninsula are more closely related to P. beticus and P. ortizi than to the Recent epigean species P. coxalis and P. meridianus.

Density‐dependent influence of male characters on mate‐locating efficiency and pairing success in the waterlouse Asellus aquaticus: an experimental s…

2005

Population density is likely to determine the form of competition in which males are engaged for access to females. At low density, scramble competition should be of paramount importance because of the low probability of encounter between males and females. Consequently, sexual selection should favour characters that allow rapid detection of females. Conversely, at high population density, sexual selection should favour attributes that raise the fighting ability of males because of the more frequent contacts between males. These general predictions were tested in this study for the precopulatory mate-guarding isopod, Asellus aquaticus. In this species, male-biased sexual dimorphisms are rep…

Differences in parasite susceptibility and costs of resistance between naturally exposed and unexposed host populations

2009

It is generally assumed that resistance to parasitism entails costs. Consequently, hosts evolving in the absence of parasites are predicted to invest less in costly resistance mechanisms than hosts consistently exposed to parasites. This prediction has, however, rarely been tested in natural populations. We studied the susceptibility of three naïve, three parasitized and one recently isolated Asellus aquaticus isopod populations to an acanthocephalan parasite. We found that parasitized populations, with the exception of the isopod population sympatric with the parasite strain used, were less susceptible to the parasite than the naïve populations. Exposed but uninfected (resistant) isopods f…