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At least 469 records · Page 26Linked to original sources
PubMed1999

Evaluation of Costa Rican copepods (Crustacea: Eudecapoda) for larval Aedes aegypti control with special reference to Mesocyclops thermocyclopoides.

This study attempted to find organisms for the biological control of the mosquito Aedes aegypti in Costa Rica. Copepods of the genera Arctodiaptomus, Eucylops, Mesocyclops, Megacyclops, and Thermocyclops were collected in several parts of the country and cultured for laboratory evaluations. Mesocyclops thermocyclopoides was the most successful species in reducing the number of larval Ae. aegypti (7.3 larvae in 24 h at a density of 200 Aedes/liter). Arctodiaptomus dorsalis, Eucyclops cf. bondi, Eucyclops leptacanthus, Megacyclops sp., and Thermocyclops decipens were not effective predators. In cage simulation trials, M. thermocyclopoides showed 100% larval reduction after 4 wk and adult mosquitoes disappeared after 7 wk. The copepod was able to survive in Aechmea sp. bromeliads under laboratory conditions. In field trials under 3 different climatic conditions M. thermocyclopoides survived 2-5 months in bromeliad leaf axils and 3-6 months in used car tires. In tires, this species reduced the number of larval Ae. aegypti 79, 90, and 99% in tropical dry, moderate, and humid climates, respectively. An El Niño phenomenon affected the results by drought, which apparently also caused a decline in the population of the predatory mosquito Toxorhynchites haemorrhoidalis superbus. Considering these severe test conditions, M. thermocyclopoides might be a promising predator for mosquito control in Costa Rica.

Aedes↗
PubMed2000

Adaptative role of carotenoids and carotenoproteins in Cyclops kolensis Lilljeborg (Crustacea: Copepoda) specimens to extremely eutrophical conditions.

The authors, using column, thin-layer, and ion-exchange chromatography, investigated carotenoid and carotenoprotein complex content in Cyclops kolensis specimens from an extremely eutrophic pond. The following carotenoids were found to be present: beta-carotene, beta-cryptoxanthin, lutein epoxide, crustaxanthin, 4'-hydroxyechinenone, canthaxanthin, and astaxanthin. Carotenoprotein complex containing astaxanthin as the prosthetic group name gamma-crustacyanine was purified from Cyclops kolensis individuals examined. The authors justify the adaptative role of these pigments in Cyclops kolensis specimens in extremely eutrophical conditions.

Animals↗
PubMedDate not supplied

Stomatopods (Crustacea: Hoplocarida) from the Gulf of Tehuantepec, Mexico.

A total of 1,173 specimens of Stomatopoda were captured in 27 localities at different depths (20 to 73 m) during three oceanographic cruises in the Mexican Pacific along the continental shelf of the states of Oaxaca and Chiapas. Seven species were identified of the families Eurysquillidae, Lysiosquillidae and Squillidae. Squilla hancocki and Squilla parva were the most abundant species and the most frequently found together. The relationships between total length and carapace length were obtained for these species, which show that males of S. hancocki have a longer carapace length than females having the same total length, whereas for S. parva the opposite occurs. Larger sizes than previously reported were obtained for Lysiosquilla panamica and Squilla mantoidea. Squilla bigelowi was recorded for the first time in the Gulf of Tehuantepec. All the species were found in the intermediate platform (25-60 m); E. veleronis, S. hancocki and S. parva extended their distributions to the external platform (60-120 m), and S. hancocki and S. parva reached the circalittoral zone (10-25 m).

Animals↗
PubMedDate not supplied

[Quantitative analysis of the invasion with gregarinids (Sporozoa: Gregarina) of the euphausiid Thysanoessa raschii (Crustacea: Euphausiacea) from the Barentsev sea].

An occurrence of the gregarinids in the gastrointestinal tract of euphausiid Thysanoessa raschii was studied in summer 1982 and winter 1983 in the southern part of the Barents Sea. The infection rates of T. raschii with gregarinids was 0% in winter and 89.4% in summer. The highest level of infection was 1035 gregarinida per crustacean. The level of infection was found to be related mainly to be food composition (no gregarinids was found in euphausiids with copepods in stomach, the high level--in crustaceans with phytoplankton in the gastrointestinal tract).

Animals↗
PubMedDate not supplied

Fine silver staining analysis of the nucleolar organizer regions during oogenesis in Penaeus kerathurus (Crustacea, Decapoda).

In previtellogenic oocytes, nucleoli showed segregated components, with the dense fibrillar component (DFC) appearing highly developed and presenting several fibrillar centers (FC). The granular component (GC) was less developed and formed a wide-spaced reticulum. Only the DFC appeared stained by silver, with higher intensities being found at its periphery. During early vitellogenesis, the nucleolar components were kept segregated but both the DFC and the GC enlarged, without evident changes being noticed in the silver staining pattern. In mid and late vitellogenesis, the nucleoli showed integrated components, with the DFC being intermeshed with the GC. Both nucleolar components were highly developed, no evident FC were noticed, and silver stained the DFC in a heterogeneous pattern. During cortical vesicle formation, the nuclear chromatin condensed and nucleoli appeared disintegrated, showing high levels of accelerated exportation of silver stained materials. Results suggest that the size of the DFC is kept high and the size of the GC kept low (low rDNA transcription levels and RNP exportation accelerated), in the segregated nucleoli of the previtellogenic oocyte, as the cell stores nuages but shows absence of rough endoplasmic reticulum and thus low protein svnthesis; that the size of the DFC and of the GC is increased in the segregated nucleoli of early vitellogenic oocytes (intermediate levels of rDNA transcription and of protein synthesis), which is in accordance with the appearance of the rough endoplasmic reticulum and of yolk vesicles formed with endogenous and exogenous sources; that during mid and late vitellogenesis the DFC and the GC appear highly developed and integrated (high levels of rDNA transcription and of protein synthesis) as the rough endoplasmic reticulum expands and the large yolk vesicles grow by endogenous synthesis; and that chromatin condense and nucleoli disintegrate (very low levels of rDNA transcription with accelerated RNP exportation) when cortical vesicles are formed.

Animals↗
PubMed2001

The evolutionary transformation of phyllopodous to stenopodous limbs in the Branchiopoda (Crustacea)--is there a common mechanism for early limb development in arthropods?

Arthropods and in particular crustaceans show a great diversity concerning their limb morphology. This makes the homologization of limbs and their parts and our understanding of evolutionary transformations of these limb types problematical. To address these problems we undertook a comparative study of the limb development of two representatives of branchiopod crustaceans, one with phyllopodous the other with stenopodous trunk limbs. The trunk limb ontogeny of a 'larger branchiopod', Cyclestheria hislopi ('Conchostraca') and the raptorial cladoceran Leptodora kindtii (Haplopoda) has been examined by various methods such as SEM, Hoechst fluorescent stain and expression of the Distal-less gene. The early ontogeny of the trunk limbs in C. hislopi and L. kindtii is similar. In both species the limbs are formed as ventrally placed, elongate, subdivided limb buds. However, in C. hislopi, the portions of the early limb bud end up constituting the endites and the endopod of the phyllopodous filtratory limb in the adult, whereas in L. kindtii, similar limb bud portions end up constituting the actual segments in the segmented, stenopodous, and raptorial trunk limbs of the adults. Hence, the portions of the limbs corresponding to the endites of the phyllopodous trunk limbs in C. hislopi (and other 'larger branchiopods') are homologous to the segments of the stenopodous trunk limbs in L. kindtii. It is most parsimonious to assume that the segmented trunk limbs in L. kindtii have developed from phyllopodous limbs with endites and not vice versa. This study has demonstrated at least one way in which segmented limbs have been derived from phyllopodous, multi-lobate limbs during evolution. Similar pathways can be assumed for the evolution of stenopodous, segmented and uniramous limbs in other crustaceans. Irrespective of the differences in the adult limb morphology, the early patterning of arthropod limbs seems to follow a similar principle.

Animals↗
PubMedDate not supplied

[Effect of the parasitic dinoflagellate Ellobiopsis chattoni (Protozoa: Mastigophora) on the winter mortality of the calanoid copepod Calanus finmarchicus (Crustacea: Copepoda) in the Norwegian Sea].

We studied the effects of the parasitic dinoflagellate Ellobiopsis chattoni on the winter mortality of natural population of the calanoid copepod Calanus finmarchicus in the Norwegian Sea (materials was collected in March-April 1989 and September 1990). Dinoflagellate infection occurred during autumn (the infection rates of copepods with E. chattoni was 15%, as average). Average mortality rate in C. finmarchicus was about 0.08% per day, or about one-tenth of total mortality in winter period.

Animals↗
PubMed2002

Microanatomical characteristics of marginal ommatidia in three different size-classes of the semi-terrestrial isopod Ligia exotica (Crustacea; Isopoda).

The aims of this paper have been (a) to characterize marginal ommatidia from different eye regions through a detailed description of their distinct ultrastructural features in three different size-classes of L. exotica, and (b) to compare microanatomical characteristics of the marginal ommatidia with those of ommatidia of the same eye, but located further centrally. On the basis of transverse as well as longitudinal sections we conclude that new ommatidia are added from a crescentic dorso-anterio-ventral edge of the eye and that maturing ommatidia go through a sequence in which originally the nuclei of cone-, pigment-, and retinula cells are arranged in three separate layers. At the beginning of the microvillar development, the organization of the corresponding rhabdomeres is still quite different (much less regular) from that of those rhabdomeres that make up the mature rhabdom. Marginal ommatidia always possess smaller diameters than more centrally located ones and retinal screening pigment granules are most apparent in the retinula cells only after the first microvilli have appeared. The diameters of rhabdom microvilli (approx. 55 nm) do not differ in ommatidia from the five investigated eye regions in small specimens (< 1.5 cm body length), but show a tendency to be slightly wider in the anterior (= frontal or rostral) regions of the eye (approx. 65 nm) in larger specimens (> 2.0 cm body length).

Animals↗
PubMed2003

Testosterone metabolism in the estuarine mysid Neomysis integer (Crustacea; Mysidacea) following tributyltin exposure.

Current evidence suggests that the biocide tributyltin (TBT) causes the development of imposex, a state of pseudohermaphrodism in which females exhibit functional secondary male characteristics, by altering the biotransformation or elimination of testosterone. Imposex in gastropods following TBT exposure is the most complete example of the effects of an endocrine disrupter on marine invertebrates. Previous studies have demonstrated that the estuarine mysid Neomysis integer converts testosterone into multiple polar and nonpolar metabolites resulting from both phase I and phase II biotransformations. In this study, the effects of TBT chloride (TBTCl) on the phase I and II testosterone metabolism of N. integer were evaluated. The TBTCl was highly toxic to N. integer (96-h median lethal concentration [LC50] of 164 ng/L). To assess the effects on testosterone metabolism, mysids were exposed for 96 h to different concentrations of TBTCl (control, 10, 100, and 1,000 ng/L), and testosterone elimination as polar hydroxylated, nonpolar oxido-reduced, and glucose- and sulfate-conjugated metabolites was examined. The TBTCl differentially affected testosterone metabolism. The effect of TBTCl on phase I metabolism was unclear and has been shown to vary among species, likely depending on the inducibility or presence of certain P450 isozyme families. Reductase activity and metabolic androgenization were induced in the 10-ng/L treatment, whereas higher concentrations resulted in a reduction of sulfate conjugation. The exact mechanisms underlying TBT-induced imposex and alterations in the steroid metabolism need to be further elucidated.

Animals↗