Abstract：
Since 2000, a well-established population of the invasive oriental shrimp Palaemon macrodactylus has been present in fully marine conditions in the southwestern Atlantic Ocean (~38° S). To assess the physiological performance of this atypical population restricted to fully marine conditions, we conducted a laboratory experiment in which individuals were transferred from 35 ‰S (local seawater) to 2 ‰S; 5 ‰S; 10 ‰S; 20 ‰S; 50 ‰S and 60‰ for short (6 h), medium (48 h), and long (>504 h) acclimation periods. We measured the time course response of relevant parameters in the shrimp\'s hemolymph; activity of Na+, K+-ATPase (NKA), and V-H+-ATPase (VHA); and muscle water content. Shrimp showed great osmoregulatory plasticity, being able to survive for long periods between 5 ‰S and 50 ‰S, whereas no individual survived after transfer to either 2 ‰S or 60 ‰S. Shrimp hyper-regulated hemolymph osmolality at 5 ‰S and 10 ‰S, hypo-regulated at 35 ‰S and 50 ‰S, and isosmoticity was close to 20 ‰S. Compared to 35 ‰S, prolonged acclimation to 5 ‰S caused a decrease in hemolymph osmolality (~34%) along with sodium and chloride concentrations (~24%); the NKA and VHA activities decreased by ~52% and ~88%, respectively, while muscle water content was tightly regulated. Our results showed that the atypical population of P. macrodactylus studied here lives in a chronic hypo-osmo-ion regulatory state and suggest that fully marine conditions contribute to its poor performance at the lower limit of salinity tolerance (<5 ‰S).
摘要：
自2000年以来，在西南大西洋（〜38°S）的完全海洋条件下，已经存在了公认的入侵东方虾Palaemonmacrodactylus种群。为了评估这种局限于完全海洋条件的非典型种群的生理表现，我们进行了一项实验室实验，将个体从35‰S（当地海水）转移到2‰S；5‰S;10‰S;20‰S;50‰S和60‰（6h），中等（48小时），和长(>504小时)的适应期。我们测量了虾血淋巴中相关参数的时程响应；Na+活性，K+-ATP酶(NKA),和V-H+-ATP酶(VHA);和肌肉含水量。虾表现出很大的渗透调节可塑性，能够在5‰S到50‰S之间长期存活，而转移到2‰S或60‰S后，没有人存活。对虾血淋巴渗透压在5‰S和10‰S时过度调节，在35‰S和50‰S时过度调节，等渗透度接近20‰S。与35‰S相比，长时间适应5‰S会导致血淋巴渗透压降低（〜34％）以及钠和氯化物浓度降低（〜24％）；NKA和VHA活性降低了〜52％和〜88％，分别,而肌肉含水量受到严格控制。我们的结果表明，在这里研究的大型P。的非典型种群生活在慢性低渗透离子调节状态，并表明完全的海洋条件导致其在盐度耐受性下限（<5‰S）下表现不佳。
