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Abstract

This study aims to elucidate the physical evidence of the moulting stages and the characteristics of ecdysteroid levels in the moulting cycle of Neocaridina denticulata sinensis. From hatching to the first complete pleopod development, N. denticulata sinensis moults 14 times at 25°C in the laboratory. The whole process was divided into four stages based on the moulting characteristics during the various intervals. Using the structural changes of the telson and Drach’s classification system, four moulting periods (postmoult, intermoult, premoult, and ecdysis) were recognized. In addition, based on the changes of the setal lumen, internal cone, and the epidermis, the premoult period was further divided into five substages (D0, D1, D2, D3, and D4). Despite similar fluctuation patterns in mature males and females, significant differences of haemolymph ecdysteroid titers were revealed in postmoult, intermoult, and premoult. These works will provide an important additional reference for the exploration of the moulting mechanism in crustaceans.

In: Crustaceana

Abstract

The biodiversity of copepods as examined in the present study is based on an oceanographic survey conducted on two ecosystems along the Algerian coast (central and eastern) in the early autumn of 2014. During that investigation, the thermocline was present at shallow depth, extending between 30 and 80 m. A total of 49 species were recorded in the samples, belonging to 20 families, among which six families, Calanidae, Eucalanidae, Metridinidae, Oithonidae, Paracalanidae, and Temoridae, appeared to be dominant. The total abundance of zooplankton at the 13 stations was less than 600 ind/m3. Two geographic groupings have been distinguished: stations in the central sector (group 1) are in opposition to the other stations in the eastern sector (group 2). The quantitative levels of copepods are less abundant in the east (234.15 ind/m3) than in the centre (334.99 ind/m3). In the central regions, the trophic organization is dominated by omnivores (73.02%), with an inferior co-dominance of carnivores (14.02%) and herbivores (12.95%). In the east, copepods with omnivorous behaviour are strongly represented (82.14%), followed by phytophagous (13.85%) and carnivorous (4.01%) species. The distribution of the abundances over the copepod communities was found to be linked to the temperature, salinity, North Atlantic Oscillation (NAO) index, and phytoplankton biomass.

In: Crustaceana

Abstract

The species name Kovalevskiella elisabethae n. sp. is proposed for a new taxon of a Recent ostracod found in interstitial sediments of the alluvial plain of the Danube in the surroundings of Vienna, Austria. The main characters that differentiate Kovalevskiella elisabethae n. sp. from its congeners K. bulgarica, K. cvetkovi, K. dani, K. rudjakovi and K. phreaticola are based on the morphology and chaetotaxy of antennula, antenna and mandible. Important diagnostic characters of the new species are the 5-segmented antennula, the presence of 2 setae on the posterior margin of its fourth segment, the presence of only 1 seta (besides the conjoined seta and aesthetasc) on its last segment, as well as the presence of 1 seta on the basis and 3 on the endopodite of the mandibula. An identification key for the Recent species of the genus is provided.

In: Crustaceana