Free amino acid pools as effectors of osmostic adjustment in different tissues of the freshwater shrimpmacrobrachiumolfersii(crustacea, decapoda) during long-term salinity acclimation

Abstract

To examine osmotic regulation during long-term acclimation to a hyperosmotic medium, hemolymph osmolality, [Na þ ] and total protein, tissue hydration, and free amino acid (FAA) pools in abdominal muscle, gills, central nervous tissue and hemolymph were quantified in the diadromous freshwater (FW) shrimp, Macrobrachium olfersii, during direct exposure to 21øS seawater over a 20-day period. Hemolymph osmolality and [Na þ ] reach stable maxima within 24 h while total protein is unchanged. Muscle and nerve tissues rapidly lose water while gills hydrate; all tissues attain maximum hydration (þ5%) by 5 days, declining to FW values except for gills. Total FAA are highest in muscle, reach a maximum by 2 days (þ64%), declining to FW values. Gill FAA increase by 110% after 24 h, diminishing to FW values. Nerve FAA increase 187% within 24 h, and remain elevated. Hemolymph FAA decrease (À75%) after 24 h, stabilizing well below the FW concentration. During acclimation, muscle glycine (þ247%), gill taurine (þ253%) and proline (þ150%), and nerve proline (þ426%), glycine (þ415%) and alanine (þ139%) increase, while hemolymph leucine (À70%) decreases. Total FAA pools contribute 10-20% to intracellular (22-70 mmol/kg) and 0.5-2.4% to hemolymph (3-7 mOsm/kg) osmolalities during direct acclimation from FW. These data emphasize the modest participation of FAA pools in intracellular osmotic regulation during physiological adaptation by M. olfersii to osmotic challenge, accentuating the role of anisosmotic extracellular regulation, suggesting that, during the invasion of freshwater by the Crustacea, dependence on intracellular adjustment employing FAA as osmotic effectors, has become progressively reduced.

Effect of salinity on the metabolism and osmoregulation of selected ontogenetic stages of an amazon population of Macrobrachium amazonicum shrimp (Decapoda, Palaemonidae)

“…These amino acids together constitute about 60% of the total of free amino acids, independent on the ontogenetic stage evaluated. The results obtained here are in agreement with the literature that shows that the main amino acids which take part in the osmoregulatory process of crustaceans are the non-essential ones, that means, those obtained through a biosynthetic via and not trough feeding (McNamara et al, 2004;Augusto et al, 2007a, b;Augusto et al, 2009;Faria et al, 2011;Prymaczok et al, 2012;.…”

“…This pattern is different from the one found by some M. amazonicum populations where larvae die in fresh water right after eclosion or in other initial stages of the life cycle. Additionally, data add useful information to aquaculture of M. amazonicum, considered promising specie for commercial cultivation (New et al, 2010;Bentes et al, 2011). The fact that zoeae II canalize greater quantity of energy for osmoregulatory processes when kept in brackish water of 18 may negatively influence their growth and development.…”

“…Among physiological mechanisms which can be investigated, osmoregulation and metabolism have a notable importance for being related to the distribution of the species in different environments. In this sense, osmotic and ionic regulation in crustaceans is composed of two processes, extracellular anisosmotic regulation, responsible for the maintenance of the osmolality and performed by the action epithelial enzymes like Na + /K + -ATPase, V-ATPase, HCO 3 -ATPase, carbonic anhydrase (Freire et al, 2008;Garçon et al, 2013) and intracellular isosmotic regulation, responsible for the maintenance of intracellular media through the adjustment of the concentration intracellular osmolytes, mainly free amino acids (Péqueux, 1995;McNamara et al, 2004;Augusto et al, 2007a, b;Faria et al, 2011). As indiquem que a variabilidade genética das populações ocorre ao nível intraespecífico.…”

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“…In the crab Neohelice granulata, the increase of proteolysisderived amino acids could satisfy gluconeogenesis from amino acids in posterior gills for osmoregulation under stress (Oliveira and da Silva, 2000). In an amphidromous freshwater prawn Macrobrachium olfersii, the amount of free amino acid in gills was increased by 110% after 24 h of salinity stress (McNamara et al, 2004), indicating that the amino acid released from other tissues can be used by the gluconeogenic process in gill for acclimation of salinity stress. Therefore, the amino acids stored in the muscle would be transported to hepatopancreas and gills for gluconeogenesis to cope with salinity stress.…”

Caracterização cinética e molecular da (Na+,K+)-ATPase do tecido branquial do caranguejo Cardisoma guanhumi (Latreille,1825).

“…Um fenômeno de ocorrência geral entre crustáceos decápodes aclimatados é a participação dos aminoácidos livres não essenciais ao controle do volume celular em diferentes tecidos e estágios ontogenéticos (PROSSER, 1973;CLAYBROOK, 1983;CHARMANTIER, 1998;McNAMARA et al, 2004;AUGUSTO et al, 2007). Outra forma de se tornar mais tolerante ao estresse salino é através do acúmulo de osmólitos de baixa massa molecular como as poliaminas (BOUCHEREAU et al, 1999) (JANTARO et al, 2003).…”