Revision of the African species of the genus Mesocyclops Sars, 1914 (Copepoda: Cyclopidae)

A revision is made of the African Mesocyclops species, based on type material (when extant) and on collections from various parts in Africa.Diagnostic characteristics are: presence or absence of spinule patterns on antennular segments, structure of the hyaline membrane of the 17th antennular segment, spine pattern on the basipodite of the antenna, armature of the maxillulary palp, presence or absence of a spine on the basipodite of P₁, armature of the connecting lamella, coxopodite and basipodite of P₄, armature of the apical spines of Enp₃P₄, armature of the last thoracic segment, genital segment and the other abdominal segments, armature of the furcal rami and structure of the receptaculum seminis.First, the taxonomical status of M. leuckarti (Claus) is redefined; this species does not occur in Africa and its geographical range is restricted to Europe and the western part of Northern Asia. On the African continent, twelve other taxa are found. Four are described as new to science: M. kieferi sp.n., M. dussarti sp.n., M. spinosus sp.n. and M. aequatorialis similis subsp.n. The remainder are: M. major Sars, M. tenuisaccus (Sars), M. paludosus Lindberg, M. salinus Onabamiro, M. ogunnus Onabamiro, M. aspericornis (Daday), M. rarus Kiefer and M. aequatorialis aequatorialis (Kiefer).Their geographical distribution is discussed. Eleven taxa are restricted to the African continent (including the Arabian Peninsula and the Canary Islands). One taxon is also found in the Oriental Region. Madagascan representatives are briefly mentioned.The importance of breeding and cross-breeding experiments should be stressed in copepod taxonomy. Experiments were performed on African species and M. leuckarti to evaluate the morphological characters used in the present study, and intraspecific morphological variability was examined up to and including the third generation (Van de Velde, in press).In future one should critically reconsider the so-called cosmopolitan species; they may indeed represent a complex of related taxa, each with a geographical range more restricted than that of the species-complex itself.Abstracted from the author's Ph.D. thesis, State University of Ghent, 1982.Abstracted from the author's Ph.D. thesis, State University of Ghent, 1982.     

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 swimming and feeding behavior of Mesocyclops

The swimming and feeding behaviors of Mesocyclops are described from a review of the literature and personal observations. Mesocyclops exhibits considerable behavioral flexibility in response to environmental stimuli. Mesocyclops edax exhibits an increase in horizontal looping behavior at high prey densities, and performs a tight vertical looping behavior in response to the loss of captured prey. Ingestion rates by Mesocyclops are a complex function of prey density, morphology, and behavior in addition to prey size. Vertebrate predators induce a rapid escape response in Mesocyclops and may be responsible at least in part for their extensive diel vertical migrations. The complex behavioral patterns of Mesocyclops suggest that its distribution and abundance in nature will be distinctly nonrandom and influenced as much by its own behavioral responses as by other external physical factors such as water circulation patterns.     

A new Oriental species of Mesocyclops (Copepoda: Cyclopidae)

Mesocyclops ferjemurami sp. nov. is described from Central Vietnam, North India and Sri Lanka. It differs from all congeners in having a unique spinule ornamentation on the caudal surface of the antennary basipodite: the `leuckarti-type' spinule pattern is supplemented with a group of spinules at the height of implantation of the medial setae, and proximal to this group a triangular spinule field occurs, the longest side of which runs more or less parallel to the oblique row of tiny spinules starting at distal half of the medial rim. It is suggested that Mesocyclops ferjemurami is closely related to Mesocyclops pehpeiensis Hu, 1943 and Mesocyclops papuensis Van de Velde, 1987.     

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.     

Mesocyclops thermocyclopoides species-group: redefinition and content

Within the genus Mesocyclops the thermocyclopoides species-group is defined on the basis of the presence of spiniform armature on the maxillar coxa. Examination of nineteen, mainly Palaeotropical species of Mesocyclops and nine representatives of the closely related genus Thermocyclops revealed, that the coxal part of the maxillar syncoxa of the species recently unified in the thermocyclopoides group is adorned with distinct rows of big spinules on its frontal surface. This character, with only one known exception in South Indian M. cf. papuensis, is absent in other species of Mesocyclops and all the Thermocyclops studied here. These species have no spinules on the maxillar coxa at all or very tiny scattered ones.     

Mesocyclops dissimilis n. sp. from Lake Biwa,Japan (Copepoda,Cyclopoida)

The status of the Mesocyclops from lake Biwa is reexamined and a new species, Mesocyclops dissimilis n. sp., distinct from M. thermocyclopoides Harada, 1931, is described.     

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.     

Respiratory metabolism during embryonic subitaneous and diapause development in Pontella mediterranea (Crustacea,Copepoda)

Oxygen consumption and ATP content are reported for the planktonic marine copepod Pontella mediterranea during normal and diapause embryonic development. In subitaneous embryos that hatched without delay within 48 h, O₂ uptake increased linearly after spawning to reach maximum levels about 25 h later. By contrast, ATP levels were initially very high but decreased rapidly within the next 5 h to reach stable values thereafter. In diapause embryos, O₂ consumption followed the typical U-shaped curve described for insect diapause. An initial period of prediapause, which lasted for about 25 days, was characterized by elevated O₂ uptake. This was followed by a period of diapause in which O₂ consumption dropped to 25% of the values recorded during prediapause. This protracted period of dormancy, which lasted about 4 to 5 months, was followed by a period of high O₂ consumption possibly due to the breaking of diapause and resumption in development. ATP content during the pre-diapause period showed a similar trend as in subitaneous embryos with high initial levels that decreased with time for the first 20 days and remained stable afterwards.Abbreviations E embryo - EDTA ethylenediamine-tetraacetic acid - PCA perchloric acid - SW sea water - TEM transmission electron microscopy     

Impact of selective predation by Mesocyclops pehpeiensis on a zooplankton community: experimental analysis using mesocosms

Predation by cyclopoid copepods is an important factor affecting zooplankton communities in freshwater habitats. Experiments provide strong evidence of the role of selective predation by cyclopoid copepods in structuring zooplankton communities. To assess the predation impact of a cyclopoid copepod, Mesocyclops pehpeiensis, we conducted a mesocosm experiment using 20-l polyethylene tanks in which the density of the predator and the food available to herbivorous zooplankton varied. M. pehpeiensis had a notable but selective effect on the zooplankton community. The population of a small cladoceran, Bosmina fatalis was affected negatively, but M. pehpeiensis did not have any apparent impact on the population dynamics of another Bosmina species, B. longirostris. On the other hand, the population of small rotifers responded positively to the presence of M. pehpeiensis, and their densities increased in mesocosms with a high density of M. pehpeiensis. It seems that suppression of B. fatalis by M. pehpeiensis predation indirectly affected rotifers by releasing them from competition with B. fatalis. The results suggest that copepod predation is a powerful factor regulating zooplankton communities directly and indirectly.     

Phenology of dormancy in a Virginia population ofMesocyclops edax (Crustacea: Copepoda)

The abundance and age structure of a Virginia, USA population ofMesocyclops edax that undergoes dormancy in an eutrophic lake was investigated from October 1988 through March 1989. During the fall all instars ofM. edax were present in the water column. By early December, only CI-CIV instars were found. M. edax was not found in the water column in January, but sediment cores in February revealed the presence of CIV's and adult females distributed predominantly at 0–3 cm and in lesser abundance at 3–6 cm. NoM. edax were found below 6 cm. By early March animals in the sediments emerged from dormancy and colonized the water column; CIV's and adult females predominated while CV's and adult males were present in small numbers. Dormancy of both juvenile and adult instars within one population is unusual among animal species. Life histories including multiple dormant stages may be more important for the adaptive evolution of cyclopoid copepods than calanoid copepods in freshwater habitats.     

Esteval phenology of an Acanthocyclops (Crustacea,Copepoda) in a Colorado tarn with remarks on the vernalis-robustus complex

Weekly mean lenghts of adult female Acanthocyclops robustus ranged between 1.14 and 1.41 mm in a Colorado alpine lake during the summer of 1966. The smallest animals occurred in late September and the largest in mid-August, corresponding to development in warm and cool water, respectively. The males also declined in mean length during the course of the summer and were about 70% of the length of the females on any date. About 75% of the females possessed a 3.4.4.4 spine formula; 8%, 2.3.3.3 and 17% an anomalous formula. Eight-one percent of the males had a 3.4.4.4 formula; 7%, 2.3.3.3 and 12% were anomalous. Morphological variation, and breeding experiments performed by Price (1958) suggest that A. robustus and A. vernalis as defined by Kiefer (1976) are likely species complexes, rather than just two species.     

Halicyclops korodiensis Onabamiro (Crustacea,Copepoda) in the estuary of the Warri River,Nigeria, West Africa

Halicyclops korodiensis Onabamiro was recorded in plankton samples of the brackish waters of the Warri River, Nigeria, West Africa. It is redescribed and figured.     

Life history traits of the tropical freshwater copepod Mesocyclops longisetus (Crustacea: Copepoda)

The life history traits of a tropical copepod population of Mesocyclops longisetus were measured in the laboratory under defined and controlled culture conditions. Egg duration times at 25 and 30 °C were 42.1 and 29.6 hours, respectively. Development times from nauplius I to adult females and males were 22.3 and 18.3 days, respectively. Body sizes (cephalothorax length) of adult females and males were 1.00 and 0.60 mm, respectively. Clutch size averaged 70.2 eggs. Comparison of these traits with those of its congeners reveals considerable life history variation in the genus Mesocyclops. Lipid analyses of early stage eggs showed that the percent composition of triglycerides to total lipid in M. longisetus (22%) is similar to that of Mesocyclops edax (17%) and daphniid cladocerans, but only half that of a marine calanoid copepod. We suggest that zooplankton may adapt to different resource environments by either adjusting their egg size or altering the proportion of lipid that is readily available for metabolic energy of embryos and nauplii. The diverse arrays of zooplankton life histories may be explained in part by adaptations in lipid metabolism in response to the level and predictability of resources.     

The membrane systems of the cardiac muscle cell of Euchaeta norvegica Boeck (Crustacea,Copepoda)

Summary The membrane systems of the cardiac muscle cell of the copepod Euchaeta norvegica Boeck are described. The heart wall, which is between 0.12 and 1.36 m thick, consists of an epicardium and a single layer of muscle cells. Invaginations of the sarcolemma forming transverse tubules have been found at all levels of the sarcomere with the exception of the H-band level. The longitudinal tubules of the same system are closely associated with the sarcoplasmic reticulum to form interior couplings at the A-I level of the sarcomere. Triadic couplings at the Z band level were not seen in E. norvegica, but peripheral couplings were demonstrated. Nexuses were found in the intercalated discs.     

Morfologia y taxonomia de los Mesocyclops (Crustacea: Copepoda: Cyclopoida) de Mexico

A fundamental review of all species and subspecies of Mesocyclopsencountered in the territory of Mexico, a biogeographical transitionzone where the Neotropical Region bounds the Nearctic Regionin the south. The book begins with a sketch of the history of