Foster Clarice, Amado Enelise M, Souza Marta M, Freire Carolina A
Departamento de Fisiologia, Setor de Ciências Biológicas, Universidade Federal do Paraná, Curitiba, PR, Brazil.
J Exp Zool A Ecol Genet Physiol. 2010 Feb 1;313(2):80-94. doi: 10.1002/jez.575.
Decapod crustaceans occupy various aquatic habitats. In freshwater they are osmoregulators, while marine species are typically osmoconformers. Freshwater crustaceans are derived from marine ancestors. The hypothesis tested here was that osmoregulators, which can rely on salt transport by interface epithelia to prevent extracellular disturbance, would have a lower capacity of tissue water regulation when compared with osmoconformers. Four species of decapod crustaceans (the marine osmoconformer crab Hepatus pudibundus, and three osmoregulators of different habitats) have been exposed in vivo to a salinity challenge, for up to 24 hr. Osmoregulators were: the estuarine shrimp Palaemon pandaliformis, the diadromous freshwater shrimp Macrobrachium acanthurus, and the hololimnetic red crab Dilocarcinus pagei. H. pudibundus displayed hemolymph dilution already after 0.5 hr in 25 per thousand, reaching approximately 30% reduction in osmolality, but its muscle degree of hydration did not increase. To make the different in vivo salinity challenges directly comparable, the ratio between the maximum change in muscle hydration with respect to the control value measured for the species and the maximum change in hemolymph osmolality was calculated (x 1,000): H. pudibundus (25 per thousand, 8.1% kg H(2)O/mOsm x 10(3))>P. pandaliformis (2 per thousand, 9.2)>M. acanthurus (30 per thousand, 12.6)>P. pandaliformis (35 per thousand, 16.7)>D. pagei (7 per thousand, 60.4). Muscle slices submitted in vitro to a 30% osmotic challenge confirmed in vivo results. Thus, the estuarine/freshwater osmoregulators displayed a lower capacity to hold muscle tissue water than the marine osmoconformer, despite undergoing narrower variations in hemolymph osmolality.
十足目甲壳动物栖息于各种水生环境中。在淡水中，它们是渗透压调节者，而海洋物种通常是渗透压顺应者。淡水甲壳动物起源于海洋祖先。此处所验证的假设是，与渗透压顺应者相比，能够依靠界面上皮细胞进行盐分运输以防止细胞外干扰的渗透压调节者，其组织水分调节能力较低。四种十足目甲壳动物（海洋渗透压顺应者螃蟹裸肝蟹，以及三种不同栖息地的渗透压调节者）被活体暴露于盐度挑战中长达24小时。渗透压调节者分别是：河口虾潘氏长臂虾、洄游性淡水虾棘臂沼虾，以及全湖性红蟹帕氏溪蟹。裸肝蟹在25‰盐度下暴露0.5小时后就出现了血淋巴稀释，渗透压降低了约30%，但其肌肉水合程度并未增加。为了使不同的活体盐度挑战具有直接可比性，计算了物种肌肉水合相对于对照值的最大变化与血淋巴渗透压最大变化之间的比率（×1000）：裸肝蟹（25‰，8.1% kg H₂O/mOsm×10³）>潘氏长臂虾（2‰，9.2）>棘臂沼虾（30‰，12.6）>潘氏长臂虾（35‰，16.7）>帕氏溪蟹（7‰，60.4）。体外接受30%渗透压挑战的肌肉切片证实了活体实验结果。因此，尽管河口/淡水渗透压调节者血淋巴渗透压变化较小，但与海洋渗透压顺应者相比，它们保持肌肉组织水分的能力较低。
