Enrique M. Rodríguez

Inhibitory effects of cadmium on carbonic anhydrase activity and ionic regulation of the estuarine crab Chasmagnathus granulata (Decapoda, Grapsidae).

This work was aimed at evaluating the gill carbonic anhydrase (CA) activity of the estuarine crab Chasmagnathus granulata exposed in vivo to cadmium, at different salinities. The in vivo effect of the specific inhibitor acetazolamide (AZ) was also assayed. Besides, the inhibition of CA activity by different heavy metals (cadmium, copper, zinc) and AZ were evaluated under in vitro conditions. For the in vivo assays, adult males were acclimated to salinities of 2.5 or 30/1000. The corresponding 96-h LC50 of cadmium was 2.69 mg l-1 at 2.5/1000, and > 50 mg l-1 at 30/1000. Cadmium only caused a significant lower CA activity than control at 2.5/1000. EC50 for CA inhibition was estimated to be 1.59 mg l-1 at 2.5/1000. Statistical differences in Na+ hemolymphatic levels (P < 0.05) were only detected at 2.5/1000, between 0 and 1.25 mg l-1 of cadmium, but no statistical differences were observed for Cl- levels at any assayed salinity. As CA inhibition registered at 2.5/1000 was followed by only changes in Na+ concentration, it is likely that cadmium exposure could differentially affect ions permeability, among others factors. The concentrations that inhibited in vitro 50% of enzymatic activity (IC50) were 2.15 x 10(-5), 1.62 x 10(-5), 3.75 x 10(-6) and 4.4 x 10(-10) M for cadmium, copper, zinc and AZ, respectively. The comparison with IC50 values of other aquatic species, indicates a higher CA sensitivity for C. granulata to pollutants.

JUVENILE HATCHING AND MATERNAL CARE IN AEGLA URUGUAYANA (ANOMURA, AEGLIDAE)

Abstract Ovigerous females of Aegla uruguayana were observed in the laboratory during the egg incubation period, under controlled conditions. Hatching of juveniles was characterized by a high degree of asynchrony and ranged from three to four days for most females. Maternal care of juveniles was also seen. During the first day after hatching, juveniles remained living on the ventral side of the abdomen of females, while during the second and third days they were able to explore the surroundings next to the female body, finally separating from her on the third or fourth day of life. No special structures in juveniles for attaching to females were seen. Both the asynchronous hatching and maternal care in A. uruguayana were in many aspects closer to similar processes observed in freshwater astacoid crayfishes than to the ones observed in other anomurans, being the way in which juveniles of A. uruguayana are linked to their mothers, as well as the absence of moulting while they remain with their mothers, which are similar to processes reported for freshwater brachyuran crabs.

Effects of serotonin and fluoxetine on blood glucose regulation in two decapod species

One of the best known crustacean hormones is the crustacean hyperglycemic hormone (CHH). However, the mechanisms involved in hormone release in these animals are poorly understood, and thus constitute the central objective of the present study. Different groups of crustaceans belonging to diverse taxa (Chasmagnathus granulata, a grapsid crab and Orconectes limosus, an astacid) were injected with serotonin, fluoxetine, or a mixture of both, and glycemic values (C. granulata and O. limosus) and CHH levels (O. limosus) were determined after 2 h in either submerged animals or animals exposed to atmospheric air. Both serotonin and fluoxetine caused significant hyperglycemia (P<0.05) after injection into the blood sinus of the two species, an effect enhanced after exposure to atmospheric air. In C. granulata blood glucose increased from 6.1 to 43.3 and 11.4 mg/100 ml in submerged animals and from 5.7 to 55.2 and 22.5 mg/100 ml in air-exposed animals after treatment with serotonin and fluoxetine, respectively. In O. limosus the increases were from 1.2 to 59.7 and 135.2 mg/100 ml in submerged animals and from 2.5 to 200.3 and 193.6 mg/100 ml in air-exposed animals after treatment with serotonin and fluoxetine, respectively. Serotonin and fluoxetine also caused a significant increase in the circulating levels of CHH in O. limosus, from 11.9 to 43 and 45.7 fmol/ml in submerged animals and from 13.2 to 32.6 and 45.7 fmol/ml in air-exposed animals, respectively, thus confirming their action as neuroregulators in these invertebrates.

Ovarian growth in the crab Chasmagnathus granulata induced by hormones and neuroregulators throughout the year. In vivo and in vitro studies

Abstract The hormones 17α-hydroxyprogesterone and juvenile hormone III (JHIII), as well as the dopaminergic antagonist spiperone, were assayed both in vivo and in vitro on adult females of the estuarine crab Chasmagnathus granulata at different times of the year. All the chemicals were administered both by injection and by incorporation into the food. Each of these in vivo assays lasted 1 month, and they were done during three different periods of the year, in accordance with the reproductive cycle of this crab (pre-, post- and reproductive periods). Spiperone and progesterone were always administered at a dose of 10 −8 mol/crab, while JHIII at 10 −7 mol/crab. The assays done during the reproductive period (spring and summer) yielded a significantly higher gonadosomatic index (GSI) than that of the concurrent control for all the chemicals assayed, whether injected or incorporated into the food. During the pre-reproductive period (winter), only progesterone and JHIII increased the GSI, while for the post-reproductive period (autumn), only spiperone and progesterone did so. These differences may be related to the phases of the annual reproductive cycle that is synchronized by both external and internal stimuli. In vitro assays that involved a 24-h incubation of isolated pieces of ovary from females sampled during the reproductive period were also done. A significant increase of leucine uptake by the ovary fragments was observed by merely adding either progesterone or JHIII to the incubation medium, but a similar effect of spiperone was only observed when thoracic ganglion (TG) was also added. Spiperone was also able to reverse the inhibitory effect caused by eyestalk tissue (ET) added to medium. The results of these in vitro assays support the hypothesis, previously suggested, about the inhibitory role of dopamine in crustacean reproduction acting on neuroendocrine organs such as TG and ET.

Effects of Glyphosate and Polyoxyethylenamine on Growth and Energetic Reserves in the Freshwater Crayfish Cherax quadricarinatus (Decapoda, Parastacidae)

Freshwater crayfish Cherax quadricarinatus have a high commercial value and are cultured in farms where they are potentially exposed to pesticides. Therefore, we examined the sublethal effects of a 50-day exposure to glyphosate acid and polyoxyethylenamine (POEA), both alone and in a 3:1 mixture, on the growth and energetic reserves in muscle, hepatopancreas and hemolymph of growing juvenile crayfish. Exposure to two different glyphosate and POEA mixtures caused lower somatic growth and decreased muscle protein levels. These effects, caused by both compounds interacting in the mixture, could also be synergistic because they were expressed even at the lowest concentration. The decrease in protein levels could be related to the greater use of other energy reserves. This hypothesis is supported by the decrease in muscle glycogen stores due to glyphosate exposure and the decrease in lipid reserves associated with exposure to POEA.

Population features of Microphrys bicornutus Latreille, 1825 (Brachyura, Majidae) from Isla Margarita, Venezuela

The aim of this study is to characterize the population biology (sex ratio, size structure, relative growth of reproductive characters and realised fecundity) of the crab Microphrys bicornutusfrom Isla Margarita, Venezuela. Nearly 100 crabs were collected and fixed monthly during 1998. In the laboratory, crabs were sexed and measured: maximum carapace length, chelae length, chelae and abdomen width for females and first pleopod length for males. Additionally, 96 ovigerous females were collected to determine fecundity. The following measurements were taken for each female: body wet weight (BWW), body dry weight (BDW), egg wet weight (EWW), egg dry weight (EDW) and number of eggs (NE). The following determinations were made: relative fecundity (RF) = NE/BDW and reproductive output (RO) = (EDW/ BDW) × 100. Relative size at the onset of maturity (RSOM) was calculated as minimum ovigerous female/females maximum size. The results indicate that the sex ratio is nearly 1:1 during the entire year. Ovigerous females and moulted males and females were observed throughout the year. Size frequency distribution and size at the onset of sexual maturity, estimated by relative growth of the sexual secondary characters and RSOM value, differed from those estimated in studies done in Jamaica and Buchuaco, Venezuela.

Differential toxicity of copper, zinc, and lead during the embryonic development of Chasmagnathus granulatus (Brachyura, Varunidae).

Ovigerous females of the estuarine crab Chasmagnathus granulatus were exposed to copper (0.01 and 1 mg/L), zinc (0.05, 1, and 10 mg/L), or lead (0.01 and 1 mg/L) during early, late, or whole embryonic development. None of the assayed heavy metals produced a significant mortality of females, neither a decrease in the number of hatched larvae nor a decrease in the egg incubation time, but several morphological abnormalities were detected in hatched larvae. The abnormalities were classified in three categories: eye, body pigmentary, and body morphological abnormalities. Those larvae with eye and body pigmentary abnormalities, particularly those involving retinal pigments and chromatophores, showed the highest incidence by exposure to the assayed metals. In addition, embryos were more susceptible to copper and zinc during the late period of development, whereas the effect of lead was greater during the early period of embryogenesis. Some teratogenic effects observed in C. granulatus embryos exposed to heavy metals, particularly the hypertrophy and hypopigmentation of eyes observed in the laboratory at a lead concentration as low as that reported for the natural environment, could be considered as sensitive biomarkers for this kind of pollutant.

Effects of lead and cadmium on hatching of the southern king crab Lithodes santolla (Decapoda, Anomura)

Summary Eggs of the king crab Lithodes santolla were exposed to cadmium (0.2 and 2 mg/1) and lead (0.16 and 1.6 mg/1) for 30 days. Concentrations used represented 1/10 and 1 of the respective LC50 values for zoea I of the studied species. Proportion of larvae hatching, meantime of eclosion and proportion of abnormal larvae were recorded. Abnormalities detected were hydropsy; small size; and atrophy of dorsal, rostral and telson spines, as well as atrophy of pereiopods and telson setae. The mean time of eclosion was inversely correlated to the incidence of structural abnormalities such as atrophy of spines and setae. These results suggest that both cadmium and lead caused an early eclosion of underdeveloped larvae, but while cadmium caused also a significant increase in hatching rate, lead produced a significant decrease in the proportion of larvae hatching.

Fecundity and Brood Biomass Investment in the Estuarine Crab Chasmagnathus Granulatus Dana, 1851 (Decapoda, Brachyura, Grapsidae)

Number of brooded eggs and wet and dry brood weights were measured in the estuarine crab, Chasmagnathus granulatus. Best correlations for all reproductive variables were found with respect to female wet body weight, but while the best fitted model was logarithmic for broods having uneyed embryos (UE), a linear model corresponded to eyed embryo (EE) broods. For UE, larger females invested in each brooded egg 8.4% more of dry biomass than smaller females, in accordance with the logarithmic model adjusted. Overall fecundity was estimated in 26790±9936 eggs/brood/female. Biomass investment in reproduction was estimated in 7.1 % (dry weight basis) and 9.3% (wet weigh basis). Egg dry weight decreased throughout embryonic development, in accordance with metabolic requirements of embryos, while a higher water content was noted in EE, probably related to tissue solvation during development and/or increase of the osmotic pressure needed for hatching.

Effects of salinity on the toxicity of parathion to the estuarine crab Chasmagnathus granulata (Decapoda, Grapsidae)

The crab community of Buenos Aires Province, Argentina extends along the coast of Samborombon Bay. Since this is an estuarine environment, there are strong diel and seasonal fluctuations in water salinity which requires special physiological adaptations of the animals that live in this habitat. One of the common species of crabs of this community is Chasmagnathus granulata, which shows euryhaline and osmoregulatory features that render it a good model for the study of parathion toxicity at different salinities. Parathion is a widely used pesticide in Argentina, and it is able to reach Samborombon Bay from neighboring croplands through several rivers and artificial channels flowing into it.