Topic
Gammarus roeseli
About: Gammarus roeseli is a research topic. Over the lifetime, 91 publications have been published within this topic receiving 4301 citations. The topic is also known as: Gammarus roeseli.
Papers published on a yearly basis
Papers
1 Jan 1977
TL;DR: The Gammarus pulex-group is revised, based on rich material from Europe, North Africa, Asia minor and adjacent areas, and certain stable characters can be distinguished within some taxa, such as the structure of the mandibular palp.
Abstract: 2) These freshwater species can be classified in three artificial groups: (a) the G. pulex-group (species without dorsal carina and with dense setation on pereiopods 3 and 4 and uropod 3), (b) the G. balcanicus-group (species without dorsal carina and poorly setose pereiopods 3 and 4 and uropod 3) and (c) the G. roeseli-group (species with dorsal carina). These groups are merely artificial ones since transitive (intermediate) species do exist. Moreover, the origin of the species is not known, so that polyphyly is not excluded. 3) In the present work the Gammarus pulex-group is revised, based on rich material from Europe, North Africa, Asia minor and adjacent areas. 4) The taxonomic differences between the various species are usually small but distinct and stable. This is especially evident in mixed populations of two or more species. In those populations no intermediates between the taxa have been observed. 5) In some cases, morphological differences between two species are hardly discernible although reproductive isolation is present (e.g. G. fossarum and G. wautieri). 6) Hybridization experiments can solve taxonomic problems and test the taxonomic value of morphological differences between populations. Such experiments between many Asiatic and European populations might clarify their taxonomic status. 7) The taxonomic characters may largely be variable within one population as well as in different populations of the same species. 8) Characters that are very stable in one species can be largely variable in other species (e.g. presence of calceoli, length of rami of uropod 3). Nevertheless we can distinguish certain stable characters (e.g. the structure of the mandibular palp), but also instable ones (e.g. the number of dorsal and lateral spines on the urosomites) in all species. 9) Gammarus pulex has given rise to several isolated populations, adapted to subterranean life (being blind or having enlarged eyes). These populations are considered distinct subspecies. 10) Within some taxa (e.g. G. fossarum and G. p. pulex) morphologically aberrant populations can be found. Since these populations do successfully cross-breed and are sympatric they must be considered mere variations. 11) We had serious problems to determine the identity of several Gammarus species, especially from Asia Minor, because of the impossibility to obtain literature and type material of some Russian authors. (So we cannot exclude the possibility that our species described from Asia might be identical with a species formerly described by a Russian author). 12) For all species, except the most common ones, complete lists of all localities studied are given. Moreover, in 3 maps the distribution of the various species and subspecies is illustrated. 13) It was not possible to illustrate all morphological details of every taxon mentioned in the present work. Only G. pulex, the type species of the genus Gammarus and the nominal form of the entire group, is figured completely. For the other taxa, only those parts are illustrated that are fundamentally different from those of G. p. pulex.
271 citations
TL;DR: This work compared the reaction to light and vertical distribution of individuals infected with both parasites to those of individuals harbouring a single parasite species and uninfected ones under controlled conditions and discussed the results in relation to the occurrence of active avoidance or hijacking between conflicting manipulative parasites.
Abstract: When two parasite species are manipulators and have different definitive hosts, there is a potential for conflict between them. Selection may then exist for either avoiding hosts infected with conflicting parasites, or for hijacking, i.e. competitive processes to gain control of the intermediate host. The evidence for both phenomena depends largely on the study of the relative competitive abilities of parasites within their common intermediate host. We studied the effects of simultaneous infection by a fish acanthocephalan parasite, Pomphorhynchus laevis, and a bird acanthocephalan parasite, Polymorphus minutus, on the behaviour of their common intermediate host, the amphipod Gammarus pulex. We compared the reaction to light and vertical distribution of individuals infected with both parasites to those of individuals harbouring a single parasite species and uninfected ones under controlled conditions. Compared to uninfected gammarids that were photophobic and tended to remain at the bottom of the water column, P. laevis-infected gammarids were attracted to light, whereas P. minutus-infected individuals showed a modified vertical distribution and were swimming closer to the water surface. The effects of both P. laevis and P. minutus appeared to be dependent only on their presence, not on their intensity. Depending on the behavioural trait under study, however, the outcome of the antagonism between P. laevis and P. minutus differed. The vertical distribution of gammarids harbouring both parasites was half-way between those of P. laevis- and P. minutus-infected individuals, whereas P. laevis was able to induce altered reaction to light even in the presence of P. minutus. We discuss our results in relation to the occurrence of active avoidance or hijacking between conflicting manipulative parasites and provide some recommendations for future research.
150 citations
TL;DR: The results suggest that the predatory behaviour of invasive gammarids, in particular of D. villosus, may have contributed to the decline of some macroinvertebrate taxa in some European streams.
Abstract: The Ponto-Caspian gammarids Dikerogammarus villosus SOVINSKIJ and Echinogammarus ischnus STEBBING have invaded Central-European streams in the early 1990s. Declines in macroinvertebrates have been observed since the arrival of invasive species. To elucidate the predatory impact of gammarids on the macroinvertebrate community, we conducted laboratory experiments with macroinvertebrate prey taxa and native and invasive gammarids as predators. Dikerogammarus villosus, which is known to be a strong predator, consumed more and a broader range of prey than E. ischnus or the native gammarids, Gammarus pulex L. and Gammarus roeseli GERVAIS. Echinogammarus ischnus consumed a somewhat higher amount of prey organisms than G. pulex and a higher number and a broader range than G. roeseli. Adult D. villosus consumed up to 25 mg macroinvertebrate biomass (wet weight) per day which corresponds to approximately 1/3 of their own biomass. Chironomid larvae were preferred by all gammarids tested. Taking into account that gammarids density may surpass 1000 ind m-2, our results suggest that the predatory behaviour of invasive gammarids, in particular of D. villosus, may have contributed to the decline of some macroinvertebrate taxa in some European streams.
115 citations
TL;DR: Mathematical functions developed in long-term laboratory experiments at different constant temperatures were combined with daily water temperatures for 1991–93 in eight Austrian streams and rivers to simulate the complex life histories and reproductive capacities of two freshwater amphipods: Gammarus fossarum and G. roeseli.
Abstract: SUMMARY 1. Mathematical functions developed in long-term laboratory experiments at different constant temperatures were combined with daily water temperatures for 1991–93 in eight Austrian streams and rivers to simulate the complex life histories and reproductive capacities of two freshwater amphipods: Gammarus fossarum and G. roeseli. The functions describe brood development times, hatching success, times taken to reach sexual maturity, growth, and fecundity. The sex ratio was assumed to be 0.5 and an autumn–winter reproductive resting period was based on observations of six river populations. Simulations included summer-cold mountain streams, summer-warm lowland rivers, watercourses fed by groundwater or influenced by heated effluents, and varying amplitudes of change within each year. 2. A FORTRAN 77 computer program calculated growth from birth to sexual maturity of first-generation females born on the first day of each calendar month in 1991, and the numbers of offspring successfully released from the maternal broodpouch in successive broods. At the 1991–93 regimes of temperature, individual G. fossarum released 127–208 offspring and G. roeseli released 120–169 in seven or eight successive broods during life spans of less than 2 years in six rivers. Life spans extended into a third year in the relatively cool River Salzach (mean temperature 7.5 � C). They were not completed in the very cold River Steyr (mean 5.6, range 2.5–7.9 � C), where G. fossarum produced five broods (totalling 120 offspring) and G. roeseli only two broods (totalling 28 offspring) in the 3-year period. Except in the Steyr, some offspring grew rapidly to maturity and produced several second-generation broods during the simulation period; in the warmest rivers some thirdgeneration broods were also produced. Birth dates, early or late in the year, influenced the subsequent production of broods and young, depending on temperature regimes in particular rivers. Total numbers of offspring produced by the second and third generations represent the theoretical reproductive capacities of G. fossarum and G. roeseli. Minimum and maximum estimates mostly ranged from 100 to 17 300, were larger for G. fossarum except in the warmest river (March), where temperatures rose above 20 � C for 56–78 days in summer, and largest (maximum 37 600) in the River Voeckla heated by discharge from a power-station (mean 11.5 � C). Results from the simulations agree with preliminary assessments of relative abundances for G. fossarum and G. roeseli in several of the study
100 citations
1 Jan 2000
TL;DR: In this article, the authors compared the prevalence and behavioural influence of a fish acanthocephalan parasite, Pomphorhynchus laevis, in two species of amphipods, Gammarus pulex and gammarus roeseli in sympatry in the river Ouche (Burgundy, eastern France).
Abstract: Although various species of acanthocephalan parasites can increase the vulnerability of their amphipod intermediate hosts to predation, particularly by altering their photophobic behaviour, their influence on the structure of amphipod communities and the success of invader species has so far received little attention. We compared the prevalence and behavioural influence of a fish acanthocephalan parasite, Pomphorhynchus laevis, in two species of amphipods, Gammarus pulex and Gammarus roeseli in sympatry in the river Ouche (Burgundy, eastern France). There, G. pulex is a resident species, whereas G. roeseli is a recent coloniser. Both uninfected G. pulex and G. roeseli were strongly photophobic, although less so in the invading species. However, there was no significant difference in reaction to light between infected and uninfected G. roeseli, whereas infected G. pulex were strongly photophilic. We discuss our results in relation to the parasite’s ability to manipulate invading host species, the possibility that resistant individuals have been selected during the invasion process, and the role that acanthocephalan parasites can play in shaping the structure of amphipod communities. q 2000 Australian Society for Parasitology Inc. Published by Elsevier Science Ltd. All rights reserved.
88 citations
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