Sur quelques Mesocyclops (Crustacea,Copepoda)

Resumé Après un rappel des critères morphologiques qu'il faut considérer en taxonomie des Copépodes du genre Mesocyclops, 14 espèces de ce genre sont décrites our redécrites, à savoir: M. granulatus nov.sp., M. thermocyclopoides, M. isabellae nov.sp., M. Kieferi, M. pehpeiensis, M. ogunnus, M. splendidus, M. brevisetosus, M. borneoensis nov.sp., M. tobae, M. pseudospinosus nov.sp., M. darwini nov.sp., M. notius, et M. australiensis, toutes formes des régions tropicales de l'Asie méridionale ou de l'Australasie.     

Study and modelling of the development of Euterpina acutifrons (Copepoda: harpacticoida)

The larval development of populations initially composed ofnauplii Nl of Euterpina acurifrons (Copepoda: Harpacticoida)is studied in the laboratory. A first experiment in which temperatureis the only varying parameter allows an assessment of inherentvariability of development. A simple mathematical model thenaccounts for the effect of temperature on development. We findresidence times to be almost identical for all developmentalstages, and higher mortality rates in the case of stages N6and Cl. The model also accounts for latency times observed inthe development of populations including larval stages. A secondexperiment, run at constant temperature, shows that a deficientfood supply increases the average residence time of early stages,as well as their variance. Data obtained on a population bredin tanks under unregulated trophic and temperature conditionsshow that the variation with time of the stage composition ofthe population modulates the effect of external factors on thegrowth of the population.     

On the ecology of marine cyclopoid copepods (Crustacea, Copepoda)

The goal of these studies was to improve our understanding ofhow Oithonidae and Oncaeidae can exist in nearly every partof the ocean. In particular, it was intended to obtain quantitativeinformation on reproduction rates and the longevity of adultfemales, and on feeding and growth rates of Oncaeidae. Whenfeeding at relatively high food levels, early copepodids ofOncaea mediterranea ingested     

Molecular phylogeny of the Calanoida (Crustacea: Copepoda)

The order Calanoida includes some of the most successful planktonic groups in both marine and freshwater environments. Due to the morphological complexity of the taxonomic characters in this group, subdivision and phylogenies have been complex and problematic. This study establishes a multi-gene molecular phylogeny of the calanoid copepods based upon small (18S) and large (28S) subunits of nuclear ribosomal RNA genes and mitochondrial encoded cytochrome b and cytochrome c oxidase subunit-I genes, including 29 families from 7 superfamilies of the order. This analysis is more comprehensive than earlier studies in terms of number of families, range of molecular markers, and breadth of taxonomic levels resolved. Patterns of divergence of ribosomal RNA genes are shown to be significantly heterogeneous among superfamilies, providing a likely explanation for disparate results of previous studies. The multi-gene phylogeny recovers a monophyletic Calanoida, as well as the superfamilies Augaptiloidea, Centropagoidea, Bathypontioidea, Eucalanoidea, Spinocalanoidea and Clausocalanoidea. The phylogeny largely agrees with previously-published morphological phylogenies, including e.g., enlargement of the Bathypontioidea to include the Fosshageniidae.     

Platycopia compacta n. sp., the Second Species of Platycopioida (Crustacea: Copepoda) in the Indo-Pacific Region, with Remarks on Development, Feeding, Swimming, and Zoogeography

Platycopia compacta new species (Copepoda: Platycopioida) is described from the hyperbenthic zone in the Tokara Islands, southern Japan. This is the second species of the order in the Indo-Pacific region, and the eighth species of the genus. The present new species is distinguishable from the closely related P. inornata from the Bahamas by (1) the formation of allobasis in the antenna; (2) two unequal setae on the basal exite of the maxillule; (3) the intermaxillipedal process with only 3 pairs of prominences at tip; (4) the fusion of the coxa and basis in leg 3; and (5) the fusion of the second and third endopod segments in female legs 3-5. Copepodid stages III, V, and VI are compared with those of P. orientalis collected from Okinawa, and differ in the developmental patterns of the antennule and legs. The presence of an intermaxillipedal process and gut content analysis revealed that Platycopia is carnivorous. The armature of legs 2-5 of the hyperbenthic genus Platycopia is stouter than that of cavernicolous platycopioids, which indicates that Platycopia may penetrate into loose sediment, whereas the latter group might be more adapted to pelagic life. The horizontal distribution of the genus Platycopia apparently exhibits a full Tethyan track.     

On the foraging and feeding ability of Oithona davisae (Crustacea,Copepoda)

Growth experiments with macrophytes revealed anomalies in the growth and development of Najas intermedia. Further analyses showed that these anomalies were caused by differences between the male and female plants. To examine the gender-related differences, the results of two field experiments and a phenological monitoring programme were analysed. The field experiments were conducted in four different lakes in Southern Germany. Over the course of 2 years, eight different sediments were used to research the interaction between the gender and the growth of N. intermedia plants. The phenological monitoring programme, on the other hand, was focused on the development of three different populations of N. intermedia in three Southern German lakes. The results of the experiments revealed significant differences in the gender-related development: Depending on the environmental conditions, male plants grew between 20 and 40% faster than female plants. Additionally, the male plants developed flowers earlier in the vegetation period and died before the female plants. As a result, male and female plants coexisted in the same lake only for a short period of time. This might be a strategy to reduce the competitive pressure between the genders and to gain an advantage over rival species.     

Energy budget of the female harpacticoid Tisbe carolinensis (Copepoda,Crustacea)

Partitioning of the ingested energy in harpacticoid Tisbe carolinesis was investigated with ¹⁴C labelled diatom Cylindrotheca sp. (Strain N-1) as food source under laboratory conditions (salinity 30 ppt, 24 ± 1.5°C). Over a 24 hr period, egg sacs and fecal pellets produced per T. carolinesis were 0.64 and 1.19, respectively. Radioactivity measured in the body accounted for 49.1% of the ingested radioisotope, whilst 42.3% of the energy was channneled into reproduction. Respiration and excretion took up 4.9% of the energy and the rest, 3.7%, went into fecal pellets.     

On Neodiaptomus schmackeri (Poppe & Richard, 1892) (Crustacea,Copepoda)

Neodiaptomus schmackeri and related species are redescribed. The synonymy of this species with N. strigilipes and N. handeli is discussed.     

Zoogeography of parasitic Copepoda of the New Zealand region

The islands of New Zealand are believed to be fragments from the Gondwanaland supercontinent that are now over 2 000 km from either Australia or Antarctica. Despite this, the marine fish parasitic copepod fauna is neither isolated nor distinctive, but reflects the southward extension of the tropical Indo-Pacific fauna and also the circumpolar element. Only one of the 49 known genera, representing 18 families, is endemic and speciation within all the families is low.Although the origin of the marine fish parasitic copepod fauna can be explained in terms of host dispersal patterns, the derivation of the euryhahne endemic Abergasilus and the freshwater Paeonodes and Thersitina is still an enigma.The copepod associates of the invertebrates are still virtually unknown and no conclusions can be drawn.     

The cyclopid (Crustacea,Copepoda) fauna of the inland waters of Israel

Four species of the genusMesocyclops (Cyclopoida: Cyclopidae) are reported from Israel:Mesocyclops kieferi Van de Velde, 1984,Mesocyclops aequatorialis similis Van de Velde, 1984,Mesocyclops ogunnus Onabamiro, 1957 andMesocyclops arcanus n.sp. The new species, close toM. kieferi, is described and some remarks are given for the other species.     

Three Variable Arenopontia Species (Crustacea, Copepoda) from Panamá

Three species of the genus Arenopontia (Cylindropsyllidae) from the Pacific and Atlantic coast of Panamá are presented. Two of them are A. trisetosa Mielke and A. peteruxi Mielke, both of which were described for the first time from the Galápagos Islands. The third species is tentatively identified as A. gussoae Cottarelli previously reported from an interstitial habitat in Cuba.     

Mesocyclops (Crustacea, Copepoda, Cyclopidae) in the South Pacific islands

Based mainly on recently collected material, we discuss the taxonomy and zoogeography of a (sub)tropical genus, Mesocyclops, in the South Pacific. A new species, Mesocyclops roberti sp. nov. is described from Fiji and the Wallis Islands. New data on the geographic distribution and morphology are reported for Mesocyclops medialis, Mesocyclops woutersi and Mesocyclops aspericornis. Phylogenetic reconstructions coding the intraspecifically variable characters by three different methods (unordered, unscaled and scaled coding) support close relationship of M. roberti with two Australian species (Mesocyclops brooksi and Mesocyclops notius). Both the “unordered” and “scaled” analyses show monophyly of a group composed of Australian (Mesocyclops australiensis, M. brooksi, M. notius, and Mesocyclops pubiventris) and South Pacific (M. medialis and M. roberti sp. nov.) taxa. None of the analyses supports a sister relationship of M. roberti with M. medialis (New Caledonia, Vanuatu), the only other species restricted to South Pacific, which suggests that Mesocyclops invaded the South Pacific from Australia at least twice. The sister relationship of the Australian-South Pacific clade remains unresolved, yet all reconstructions suggest a link with Asian Mesocyclops sp.     

The freshwater Calanoida (Crustacea: Copepoda) of Thailand

14 Species of freshwater Calanoida in Thailand are reported in this study. The most common species is Neodiaptomus botulifer. Most of these belong to the Southeast Asian species, the remainder are either Indian or East Asian copepods. The zoogeographical demarcation of copepods in Thailand is not very distinct due to its interconnecting riverine and reservoir systems as well as frequent flood. The peculiarity of the Thai Calanoida and their distribution is discussed in a Southeast Asia context. A taxonomic key to the Thai Calanoida is formulated.     

The diminution of heterochromatic chromosomal segments in Cyclops (Crustacea,Copepoda)

The chromosomes of Cyclops divulsus, C. furcifer, and C. strenuus, like those of several other Copepods, undergo a striking diminution of chromatin early in embryogenesis. The process is restricted to the presumptive soma cells and occurs at the 5th cleavage in C. divulsus, at the 6th and 7th in C. furcifer, and at the 4th in C. strenuus. The eliminated chromatin derives from the excision of heterochromatic chromosome segments (H-segments). Their chromosomal location is different in the three investigated species: Whereas in C. divulsus and C. furcifer the H-segments form large blocks — exclusively terminal in the former and terminal as well as kinetochoric in the latter — the germ line heterochromatin in C. strenuus is scattered all along the chromosomes. Extensive polymorphism exists with respect to the length of the terminal H-segments in C. furcifer, and with respect to the overall content of heterochromatin in the chromosomes of C. strenuus. In a local race of C. strenuus an extreme form of dimorphism has been found which is sex limited: females as a rule are heterozygous for an entire set of large (heterochromatin-rich), and a second set of small chromosomes in their germ line. Males are homozygous for the large set. In the first three cleavage divisions the H-polymorphism is solely expressed through differences of chromosome length. Following diminution the differences between homologous have disappeared. Feulgen cytophotometry demonstrates that in the three species the 1C DNA value for the germ line, as measured in sperm, is about twice that measured in somatic mitoses (germ line/soma C-values in picograms of DNA: C. strenuus 2.2/0.9, C. furcifer 2.9/1.44, C. divulsus 3.1/1.8). — The data imply that chromatin diminution is based on a mechanism which allows specific DNA segments, regardless of their location and size, to be cut out from the chromosomes without affecting the structural continuity of the remaining DNA. This mechanism may be analogous to that of prokaryotic DNA excision.     

Freshwater Crustacea (Cladocera,Copepoda) of Iceland: taxonomy,ecology, and biogeography

Of the many types of freshwater bodies across Iceland (e.g., lakes, springs, rivers, and ponds), greater effort has been invested in researching the freshwater Crustacea (Cladocera, Copepoda) of more permanent, larger, and deeper water bodies than on smaller or more ephemeral sites. To address this, we described the fauna of 12 shallow freshwater bodies distributed from the coast to the central highlands of Iceland. We identified 16 species in 11 genera belonging to six families of Cladocera, and 12 species in eight genera belonging to four families of Copepoda. Five of the species we identified (Alona werestschagini, Cyclops vicinus, Daphnia cristata, Diacyclops abyssicola, and Heterocope borealis) represent new distribution records for Iceland, increasing the number of species now known from this region to 34 Cladocera and 38 Copepoda taxa. Additionally, we discuss the taxonomy of some species with doubtful taxonomical status. Six crustacean taxocenes are described, each characterized by the dominance of different taxa, with bottom sediment characteristics best explaining species assemblage structure. We evaluated the relationships between Icelandic Cladocera and Copepoda faunas and those of the adjacent Svalbard, Faroe, and Shetland Islands, Greenland, and the mainland Norway. The taxonomic composition of the Icelandic fauna is dominated by widely distributed Holarctic, and secondarily Palaearctic and Nearctic species, and is more similar to the faunas of the major North Atlantic islands (64.2–71.8 % similarity) than it is to that of continental Norway.