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PubMed2006

Seasonal and vertical patterns of egg-laying by the freshwater fish louse Argulus foliaceus (Crustacea: Branchiura).

Argulus foliaceus is a damaging fish ectoparasite for which new control measures are being developed based on egg-removal. In an attempt to develop further understanding of seasonal and vertical egg-laying patterns in this parasite, egg-laying activity was monitored over the period 14 April to 17 November 2003 in 2 rainbow trout Oncorhynchus mykiss fisheries in Northern Ireland, UK. At Site 1, egg-laying was continuous from 21 April to 17 November, when water temperature was above 8 to 10 degrees C. At Site 2, egg-laying was continuous from 4 June to 29 October. In the early months of the season, egg-laying was recorded mainly within the top 1 m of the water column; however, a significant shift to deep water egg-laying was recorded between 7 July and 17 November at Site 1 and between 20 August and 29 October at Site 2. Egg clutches were preferentially laid at depths of up to 8.5 m during this time (Site 2), a feature of egg-laying hitherto unappreciated. Temperature and dissolved oxygen did not differ significantly among depths, but there was an increase in water clarity over time. However, the precise environmental triggers for deep water egg-laying are still unclear. These new insights into the reproductive behaviour of this species will be useful in developing control methods based on egg-removal.

Animals↗
PubMed1976

Hemolymph iron in Crustacea decapoda during the intermolt cycle.

A study on the iron content in the hemolymph of Austropotamobius pallipes and Carcinus maenas has been made. The hemolymph iron content and the total iron binding capacity were investigated in males and females of both species. The values obtained for hemolymph iron content in the males were between 154 and 430 mug/100/ml and in the females between 134 and 431 mug/100/ml. The total iron binding capacity for the males was between 472 and 762 mug/100/ml and for the females between 390 and 698 mug/100/ml. The variations occurring in both parameters during different stages of the intermolt were also studied. The first increase in hemolymph iron coincides with the postmolt stage. During the intermolt, the need for iron decreases as the rate of tissue synthesis becomes lower. Finally an enormous increase in the hemolymph iron content was observed during the molt.

Animals↗
PubMed1999

Discapseudes holthuisi (Crustacea: Tanaidacea) as an intermediate host of Caballerorhynchus lamothei (Acanthocephala: Cavisomidae).

The intermediate host of the acanthocephalan Caballerorhynchus lamothei Salgado-Maldonado, 1977, is reported for the first time. Cystacanths of C. lamothei were found in the hemocoel of the tanaid shrimp Discapseudes holthuisi Bacescu and Gutu, 1975, in Alvarado and Sontecomapan lagoons, Veracruz, Mexico. This is the first report of a palaeacanthocephalan using a tanaid shrimp as an intermediate host. Prevalence by locality, shrimp length, sex and developmental stage, and an analysis of the distribution of number of cystacanths per host are presented. A higher prevalence, and percentage of multiple infections and larger host size were found in Alvarado Lagoon.

Acanthocephala↗
PubMed1999

[Toxic effect of DDT, chlordane and water from the Ignacio Ramírez dam (Mexico), on Daphnia magna (Crustacea: Daphnidae)].

Chlorodiphenylnitrichloroethane (DDT) and chlordane (CLO) are currently used in Mexico to control malaria and termites. From 1990 to 1996 a total of 27 ton of DDT and 508 of CLO were imported. We establish a methodology to determine their environmental impact in a Mexican dam (Ignacio Ramírez). The toxic effect of DDT and CLO were evaluated on the o-demethylase (OD) and acethycholinesterase activities (AchA) of the cladoceran Daphnia magna exposed to different concentrations of the insecticides solved in water from three sites. Their effect on the AchA and OD activities, and so the CL50 were used as exposure bioindicators to determine the more polluted sites. The physicochemical characteristics of water and the biodiversity of the dam test sites were considered. The station near the floodgate has toxicity potential because enzymatic activities were modified. We suggest the use of AchA and OD activities measure in the cladoceran to evaluate the toxicity of a water body polluted by organochlorate insecticides.

Acetylcholinesterase↗
PubMed2000

Histology of the hepatopancreas of the freshwater prawn Palaemonetes argentinus (Crustacea, Caridea).

The aim of this study is to describe the histological structure of the hepatopancreas of P. argentinus in intermoult stage in order to provide a baseline for future analysis of its modifications as indicator of environmental stress. Adults at sexual rest of both sexes were collected from Sotelo stream, tributary of Mar Chiquita lagoon, Argentina (38 degrees S 55 degrees W). P. argentinus hepatopancreas was studied by using histological techniques. The hepatopancreas is a bilaterally bilobed brown-yellowish organ. The structure is formed by a mass of blind tubules, with scarce intertubular space. Each tubule consists of a cylindrical epithelial layer surrounded by a basal lamina and myoepithelial cells. Four cellular types were recognized which represent E (embryonic), F (fibrillar), R (resorptive) and B (blisterlike) cells of other decapods. E-cells were found in mitosis and some F-cells had signs of cellular death. B-cells were observed in different phases of holocrine secretion and some groups of desquamated cells appeared at medial and proximal zones, revealing an important cellular turnover rate. According to these observations F, R and B cells are differentiated independently from E-cells.

Animals↗
PubMed2001

Changes in the hepatopancreas histology of Palaemonetes argentinus (Crustacea, Caridea) during moult.

The present work describes the histological changes in the hepatopancreas of Palaemonetes argentinus during the moulting cycle. The hepatopancreas of individuals at different moult stages were dissected and studied using histological techniques. The hepatopancreas in intermoult presents four typical cell types (E, F, R and B) and follows the general plan of the rest of decapods. During early premoult (D1), there is an important secretory activity and many R-cells have several subapical vacuoles and are highly columnar. In early postmoult (A), B-cells are confined to the proximal zone of the tubules. Some of the tubules show a folded basal lamina in late premoult and postmoult. Degenerative desquamation occurs at the proximal zone of the tubules in all the stages, this zone being replenished by mitosis of E cells. Mucopolysaccharides and glycogen reserves are more abundant in premoult than in the rest of the cycle. Cellular height increased in premoult and decreased towards the intermoult, stage of more stability. R-cells are the most abundant, and F-cells do not change significantly through the cycle. The observations suggest that the hepatopancreas of P. argentinus undergoes a significant dynamic and cellular turn over rate in relation to moult.

Animals↗
PubMed2001

[Growth of Artenia franciscana and A. persimilis (Crustacea, Anostraca) under controlled conditions].

Growth (length) was compared in A. franciscana populations from Utah, United States of America, and Yape, Chile, and A. persimilis (population from Salinas de Hidalgo, Argentina), cultured under controlled conditions (24 degrees C, seawater 35 g/l, fed with Chaetoceros calcitrans). There were significant differences among all stages of A. franciscana (Utah) and A. persimilis, whereas we found significant differences only in two stages of A. persimilis and A. franciscana (Yape); both A. franciscana had similar total lengths in all stages analyzed. Habitat adaptations could explain these results.

Animals↗
PubMed1979

[Coagulation of hemolymph in Crustacea. Electrophoretic demonstration of a plasmatic component in the course of hemostasis in a group A crustacean (Cancer pagurus)].

Coagulation assays in vitro of plasmatic extract from Cancer pagurus reveal the existence of a plasmatic coagulation in this species which was considered as yet as lacking a such process. Electrophoretical analysis of this extract before and after coagulation shows the presence of a plasmatic component probably involved in the formation of the clot.

Animals↗
PubMedDate not supplied

[Abundance and body size of Menippe mercenaria (Crustacea: Brachyura), in artificial refuges in Quintana Roo, Mexico].

In Florida and Cuba the stone crab Menippe mercenaria (Say, 1818) is under strong fishing-pressure; nevertheless in the Mexican Caribbean it is considered as sub-utilized and poorly known resource. Artificial shelters ("condominios cubanos") were used to study relative abundance, age structure, claw length-carapace amplitude relation, and population in three seasons and four sectors at Bahía Ascension, Quintana Roo, Mexico. The abundance varied according to the sector and sampling season: population was higher in the south and during the north wind ("Nortes") season (January to March). The carapace amplitude was directly proportional to claw length (r2 = 0.83, 0.97 and 0.89; p < 0.05 in females, males and total, respectively). The results suggest that specimens with 37.5 and 67.5 mm of carapace amplitude are the most limited regarding refuge availability in the Bay.

Animals↗
PubMed2002

[Euphausiids (Crustacea: Melacostraca) from the southern Mexican Caribbean Sea].

The composition, abundance and distribution of euphausiids from the southern part of the Mexican Caribbean Sea (August 1986) were sampled during the ARCOMM I cruise on board the R/V "Justo Sierra" of UNAM. Sampling was done using a Bongo-net (0.5 mm mesh size) performing oblique hauls from 200 m to the surface at 28 stations. Of the total euphausiid numbers, the most abundant species was Stylocheiron carinatum (49%), followed by Euphausia americana (9.8%) and E. tenera with (7.8%). The highest total density and that of the three most abundant species occurred during the night sampling, and probably was related to vertical migration patterns. The Bray-Curtis index revealed three station assemblages, related to the day-night variations of the euphausiid community. Species were distributed mainly in the oceanic area, and were absent in the neritic zones. The local fauna shows a strong affinity for the euphausiid community of the Gulf of Mexico and other areas of the Caribbean Sea. Four species are considered to be new records for the western Caribbean Sea.

Animals↗
PubMed2002

[Allozymatic variation in crustacea Artemia franciscana (Anostraca: Artemiidae) of Freat Salt Lake in different experimental conditions].

Starch gel electrophoresis was used to analyze the allelic variability of four polymorphic loci (Lap-2, Lap-3, Pgm and Gpi) from a single population of Artemia franciscana (Kellogg, 1906) from the Great Salt Lake (Utah, USA), cultured under eight different experimental conditions. The organisms were cultured to the adult stage under a 2 x 2 x 2 experimental design (22 and 30 degrees C; 30 and 60 ppt salinity; and Dunaliella sp. and Spirulina sp. as food). There were significant differences in allele frequencies at each locus and the mean expected heterozygosity (He) varied from 0.236 to 0.447. Therefore, the hypothesis of no allelic differences among treatments is rejected. With relation to a possible correlation between genetic variability and the phenotypic characteristics, the results show that there is probably a synergic effect between the different salinities and temperatures on the survival of heterozygous organisms in the different loci.

Alleles↗
PubMed2003

[Molecular genetic diagnostics of some Daphnia species (Crustacea, Cladocera) from the Volga river].

Population genetic structure of the widespread Daphnia species from Kuibyshev and Saratov reservoirs was examined by use of RAPD-PCR technique with four mitochondrial DNA (16S rRNA) specific primers. One of the examined Daphnia clones from the Volga region appeared to be conspecific to the North American Daphnia galeata, while another clone was most likely a hybrid between D. galeata and D. cucullata.

Animals↗
PubMedDate not supplied

How do fish ectoparasites Argulus spp. (Crustacea: Branchiura) match with their hosts at the behavioural and ecological scales?

Features of the Argulus foliaceus and A. coregoni life cycles including spatial distribution and hatching patterns of the resting eggs as well as their host searching behaviour were analyzed on the basis of field and experimental data obtained in lakes and a fish farm in the Central Finland. Published data on behaviour and ecology of these parasites were also used. The main point of this analysis was an ecological adjustment of the life cycles of parasites to that of their fish hosts at different spatial and temporal scales. Due to different spatial distribution of overwintering eggs, the newly hatched larvae of A. coregoni are more likely to attach to salmonids, which are their main hosts, while A. foliaceus to percids and cyprinids. The main peak of argulid hatching occurs in late spring-early summer and coincides with the period when most of freshwater fishes concentrate close to the shore, either for spawning, or, foraging. Nevertheless, despite the general coincidence, the parasite-host encounter rate could still be very low. The main peak of hatching is followed by a long "tail". We suggest that under fluctuating and uncertain environmental conditions characterised by both abiotic stochasticity and poor predictability of the hosts, an optimal recruitment strategy is to hedge a bet, with a proportion of eggs synchronously hatching and a proportion remaining dormant and hatching at much lower rate during an extended period. One of the main behavioural adaptations to match with the hosts is all-over-the-day searching activity of argulids. The boreal A. coregoni relies primarily on vision, which is most effective in transparent waters during long polar days in summer. Vision is also important in the behavioural repertoire of the temperate A. foliaceus in the light, but olfaction and mechanoreception in the dark provide the highest host searching rate. The two generally sympatric species of argulids segregated on the finer habitat scale. Partially overlapping on salmonid hosts, they prefer ecologically distinct categories of fish, and use different microhabitats for egg laying and searching for hosts.

Animals↗