Natural development time of Eodiaptomus japonicus (Copepoda: Calanoida) in Lake Biwa

Seasonal and ontogenetic changes in natural development timewere studied for Eodiaptomus japonicus in Lake Biwa in 1986and 1987. Wild individuals in a certain developmental stagewere collected, fed on natural food and examined until theyhad moulted twice. Natural development times fluctuated irrespectiveof temperature from May to October. Food deficiency delayeddevelopment in all feeding stages, and food availability probablydetermined natural development time. Serious food limitationraised mortality in copepodid stage I. In November developmentwas delayed even with enough food. The development of E.japonicuswas almost isochronal except for a short prefeeding naupliarstage I and a long copepodid stage V.     

Effects of temperature on life history traits of Eodiaptomus japonicus (Copepoda: Calanoida) from Lake Biwa (Japan)

Effects of temperature on life history traits of the dominant calanoid Eodiaptomus japonicus were examined to evaluate its population dynamics in Lake Biwa (Japan). Embryonic and post-embryonic development times and reproduction were determined in the laboratory at four temperatures (10, 15, 20 and 25 °C) and under ad libitum food condition. Post-embryonic development time of E. japonicus from hatching to adult female decreased with increasing temperature from 67.9 to 15.1 days. Males reached the adult stage 1–6 days earlier than the females. Only 15 % of the individuals survived until the adult stage at 10 °C, while 40 % did so at >15 °C. Egg production also depended on temperature. A power function of temperature on instantaneous growth rate predicted a value of <0.06 day^?1 when water temperature was below 10 °C, suggesting that E. japonicus retards its growth during winter. The null value obtained at 8.6 °C for the computed population growth rate supports the idea of an overwintering strategy. Responses of life history traits to temperature suggested that in conditions where there was no food limitation, E. japonicus in Lake Biwa would be able to take advantage of the rise of temperature predicted in the context of global climate change.     

Eodiaptomus shihi n. sp. (Copepoda,Calanoida) from central India

Eodiaptomus shihi n. sp. is described from the material collected from Gandhisagar reservoir, River Narmada and a hillpool in the Madhya Pradesh State of central India. The salient features of this new species include: in female, the left metasomal wing is strongly developed, and the endopodite in leg 5 is 2-segmented and longer than first exopodite-segment; in male, the right caudal ramus is armed with a tooth-like chitinous structure near ventro-distal region, and in right leg 5, the basis is devoid of any hyaline lobe on inner margin and the first exopodite-segment is produced into a large spinous process at disto-outer corner.     

Combined effects of temperature and food concentration on growth and reproduction of Eodiaptomus japonicus (Copepoda: Calanoida) from Lake Biwa (Japan)

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Development of Acartia clausi (Copepoda,Calanoida) cultured at different conditions of temperature and food

The pelagic copepod Acartia clausi Giesbrecht was bred 3 times from nauplius stages I and II to maturity at 5, 10, 15 and 20 °C and 4 different rations of autotrophic and heterotrophic food. The rate of development of copepods increased with increasing temperature and food level. At the highest food level the stage duration was almost constant through most stages, but development was not quite isochronal. Particularly at lower food concentrations stage duration became progressively longer with increasing stage of development. The relation between development time and temperature is described by Blehrádek's functions at different food levels. These relations predict a generation time of about 50 days at spring bloom conditions and only slightly less during summer due to food limitation. Comparison with estimates in the field from the literature suggests hat food is often limiting during summer conditions.     

On Gaussia Wolfenden (Copepoda,Calanoida, Metridinidae)

Aspects of the female genital segment with and without attached couplers and enclosed spermatophores are studied of Gaussia specimens collected in the SW Atlantic and SE Pacific. A new species found in the SW Atlantic, Gaussia asymmetrica, is proposed.     

Oogenesis in Centropages typicus (Copepoda, Calanoida)

We carried out a complete study of oogenesis in Centropages typicus using structural, ultrastructural and cytochemical data. The usual stages of oogenesis, i.e. germinative phase, premeiosis, primary and secondary vitellogenesis, were found. The latter two stages were the most typical. Primary vitellogenesis consisted of endogenous yolk accumulations; these substances, probably of lipoprotein or lipoglycoprotein nature, were produced at the granular endoplasmic reticulum level and then stocked in the reticulum cavities. During secondary vitellogenesis, endogenous yolk production continued, but we mainly observed the development of exogenous yolk accumulation (lipid droplets and protein globules) in the ooplasm. These accumulations resulted from the fusion of very numerous pinocytotic vesicles arising from the oolemma and containing substances probably brought to the oocytes by the hemolymph. The effect of various proteases on the vitellus globules caused a more or less marked digestion of their contents, tending to prove their protein nature. The end of vitellogenesis was marked by the appearance of vacuolar formations with dense lamellae which could correspond to cortical granules.     

The complete postembryonic development of Tropodiaptomus informis Kiefer, 1936 (Copepoda:Calanoida) reared in the laboratory

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First observations on the biology of Clausocalanus furcatus (Copepoda, Calanoida)

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Post-embryonic developmental plasticity of Arctodiaptomus salinus (Copepoda: Calanoida) at different temperatures

Ephemeral and semi-permanent saline wetlands undergo frequentunpredictable disturbances such as episodes of high salinityor desiccation. Organisms living in these systems are adaptedto survive and develop in very fluctuating and unpredictableconditions and, therefore, could help us to understand lifecycle strategies and plasticity in the context of global warming.Arctodiaptomus salinus is a common species occurring in suchenvironments and is often the main constituent of their zooplanktoncommunity, which is characterized by low diversity and shorttrophic webs. Despite the qualitative and quantitative importanceof A. salinus in these systems, no attention has been paid tothe effect of temperature on its population dynamics. For thisreason, variability in post-embryonic development times andstage-specific mortality of A. salinus were studied for thetemperature-range over which this species occurs. Mortalitywas higher in earlier naupliar and first copepodite stages.The highest developmental variability and mortality occurredat the highest temperature. Developmental instability couldexplain the high variability at high temperatures and the fluctuatingspeed of development throughout the successive stages. The interactionbetween mortality and developmental variability might be animportant mechanism ensuring persistence of A. salinus populationsin these fluctuating and stressing environments.     

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Larval stages of Neodiaptomus lindbergi Brehm, 1953 (Copepoda,Calanoida)

All the postembryonic developmental instars of Neodiaptomus lindbergi Brehm, 1953, reared in the laboratory from eggs, are described and illustrated. Further, the larval affinities of this species vis-a-vis certain other Indian diaptomid species are mentioned.     

On nine Tropodiaptomus-species (Copepoda,Calanoida) from equatorial East Africa

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The species composition of copepods of the genus Pseudocalanusthat dominate the zooplankton in Avachinskaya Bay was studied from samples collected in 1988. Three species were identified: P. minutus(Kröyer), P. newmani(Frost), and P. acuspes(Giesbrecht). The latter species is the first record for the fauna of the northwestern Pacific Ocean. Synonymy and original figures are given; the seasonal variations in the morphometric features and characteristics of Pseudocalanusare discussed.     

Molecular phylogeny of the Calanoida (Crustacea: Copepoda)

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The freshwater Calanoida (Crustacea: Copepoda) of Thailand

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Contrasting effects of a cladoceran (Daphnia galeata) and a calanoid copepod (Eodiaptomus japonicus) on algal and microbial plankton in a Japanese lake, Lake Biwa

Macrozooplankton may affect algal and microbial plankton directly through grazing or predation and indirectly through nutrient regeneration. They may also affect potential prey positively by removing alternative predators. Here, we examined the effects of a cladoceran (Daphnia) and a calanoid copepod (Eodiaptomus) on algal and microbial plankton in a Japanese lake using in situ experiments in which we manipulated the nutrient supply and biomass of these macrozooplankton. The response of algal and microbial plankton to macrozooplankton was diverse and varied depending on the level of nutrient supply. Eodiaptomus seemed to feed mainly on large algae (>20 µm) and microzooplankton, while direct grazing by Daphnia on algae, bacteria, heterotrophic nanoflagellates (HNF), and microzooplankton (ciliates, heliozoa, and rotifers) was pronounced. Trophic linkages within these microbial plankton was also suggested; bacteria were grazed by HNF and these in turn were grazed by microzooplankton. When the nutrient supply was high, both HNF and microzooplankton were exposed to higher amounts of algae and lower bacterial abundance. Moreover, nutrient regeneration by daphnids and Eodiaptomus copepods seemed to differentially stimulate the growth of algae and bacteria. The results suggest that the relationship between macrozooplankton and microbial plankton cannot be fully understood without taking into consideration not only the feeding characteristics of the macrozooplankton, but also the food web structure, the subsidized algal resource, and nutrient regeneration from the macrozooplankton.     

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All the postembryonic developmental instars of Phyllodiaptomus blanci (Guerne & Richard, 1896), reared in the laboratory, are described and illustrated. The larval affinities of this species vis-a-vis certain other diaptomid species are mentioned.