Macrobrachium Borellii Research Articles

GENETIC DIVERSITY OF POPULATIONS OF THE FRESH-WATER SHRIMP MACROBRACHIUM BORELLII (CARIDEA: PALAEMONIDAE) EVALUATED BY RAPD ANALYSIS

ABSTRACT We evaluated the genetic diversity of 2 populations of the pampean fresh-water shrimp Macrobrachium borellii at its most southern geographical distribution by means of the PCR-based technique RAPD (random amplified polymorphic DNA). As a result of either small population size, greater degree of isolation, or greater inbreeding, genetic diversity was lower in an artificial pond population than in a population from a small tributary of the Rio de la Plata. The high level of diversity scored in this species with RAPD markers is striking in comparison to the low H values reported by other authors for decapods, including Macrobrachium rosenbergii, with allozyme markers. These results demostrate that RAPD polymorphisms can be useful measures of diversity in these taxa.

Palmitic acid metabolism in hepatopancreas of the freshwater shrimp Macrobrachium borellii

1. 1. The palmitic acid fate as substrate for the synthesis of either glycerides or other fatty acids was studied in vivo and in the microsomal fraction from hepatopancreas of Macrobrachium borellii. 2. 2. Most of the palmitic acid administered in vivo circulated to the hepatopancreas, being incorporated mainly in the triacylglycerol (TG) fraction. 3. 3. Palmitic acid transformations into palmitoleic, stearic and oleic acids were observed in the hepatopancreas. 4. 4. The in vitro biosynthesis of TG in hepatopancreas was more active than in other tissues. In the microsomal fraction, palmitic acid was also incorporated mainly in TG, and followed the α-glycerophosphate pathway.

Effect of environmental temperature on mitochondrial β-oxidation activity in gills and hepatopancreas of the freshwater shrimp Macrobrachium borellii

1. 1. To elucidate the effect of environmental temperature on mitochondrial palmitic (16:0) and oleic (18:1 n-9) fatty acid β-oxidation of the freshwater shrimp Macrobrachium borellii, groups of animals were maintained at 11 and 29°C, respectively. 2. 2. These are the extreme temperatures of the water stream that they inhabit. After 21 days of acclimation, gills and hepatopancreas mitochondria were isolated and their oxidative capabilities were measured. 3. 3. There were no significant changes in mitochondrial fatty acid β-oxidation activity in gills and hepatopancreas of animals acclimated at 11°C, compared with controls (16–20°C) 4. 4. An increment in the fatty acid β-oxidation in those animals acclimated at 20°C was observed. It was several-fold higher compared to controls. 5. 5. Acclimation affects the optimal temperature for β-oxidation specific activity. 6. 6. There were no differences in the lipid rotational mobility ( r) of mitochondrial membranes as a consequence of temperature acclimation.

Lipid classes' consumption related to fasting and thermal stress in the shrimp Macrobrachium borellii

1. 1. The effect of the environmental temperature on lipids of unfed and fed shrimps, was studied. Lipid and fatty acid classes from the hepatopancreas, gills and muscle, were analyzed. 2. 2. Each organ responds in a different way to food deprivation or to changes in the water temperature. The hepatopancreas is the main organ where lipids are stored and great variations are observed. 3. 3. A 4-week fasting did not modify energetic lipid levels of the hepatopancreas either at low environmental temperature (13°C) or moderate temperature (14–20°C). In contrast, a significant consumption of triacylglycerols and free fatty acids at high temperature (29°C) was found. 4. 4. Consumption of neutral lipids due to thermal stress also appeared in the fed animals. 5. 5. The changes in the fatty acid composition could be attributed to those found in the lipids they belong to. Besides, such changes partially reflected the composition of the diet.

O ciclo da intermuda em Macrobrachium borellii (Nobili, 1896) (Crustacea, Decapoda, Palaemonidae): a influência da temperatura e do comprimento do animal

Foram realizados estudos de laboratório sobre o camarão de água doce do sul do Brasil Macrobrachium borellii (Nobili, 1896). Foram analisadas as relações entre as médias das temperaturas e a duração do ciclo de intermuda e entre o tamanho do corpo do animal e a duração do ciclo.

Lipid characterization and distribution among tissues of the freshwater crustacean Macrobrachium borellii during an annual cycle

1. 1. Lipid and fatty acid seasonal distribution from tissues of the freshwater shrimp Macrobrachium borelli was studied. 2. 2. Female gonads and hepatopancreas were the organs with the highest lipid percentages. They were mainly composed of triacylglycerols, with oleic acid as the major fatty acid. 3. 3. Total lipids and triacylglycerols from ovarian tissue increased during sexual maturation and they presented a peak during winter in hepatopancreas. 4. 4. Phospholipids were the dominant lipids in muscle. They were mainly constituted by eicosapentaenoic, oleic and arachidonic acids. 5. 5. The w3:w6 acid ratio was more than 1, which is very high compared to other freshwater invertebrates.