Surbida K L, Wright J C
Department of Biology, Pomona College, 609 North College Avenue, Claremont, CA 91711, USA.
Physiol Biochem Zool. 2001 Nov-Dec;74(6):894-906. doi: 10.1086/324474.
Marsupial development in terrestrial isopods subjects embryos to potential physiological stresses, including desiccation, osmotic variation, and high ammonia concentrations. In this study, we investigated tolerance of osmotic extremes, total ammonia, and pH in developmental stages of Armadillidium vulgare cultured in vitro. Marsupial stages were classified as stage 1 (chorionated eggs), stage 2 (having shed the chorion), and stage 3 (mancas). All stages showed wide but differing tolerance ranges. Stage 1 eggs possess the greatest ammonia tolerance, with high 7-d survival in 150 mM total ammonia, and a wide pH tolerance range. Mancas show the widest osmotic tolerance (100-1,400 mosm x kg(-1)) and display proficient hemolymph osmoregulation over this range. Stage 2 eggs reveal the narrowest tolerance ranges for all three parameters but still qualify as eurytopic. Silver staining revealed two distinct ion-transporting tissues in the developmental stages: a median band on the vitelline membrane of stage 1 and stage 2 eggs, corresponding in location to the embryonic dorsal organ, and the posterior three pairs of pleopodal endopodites in mancas. Gravid females do not downregulate ammonia but show efficient regulation of marsupial fluid pH and downregulation of osmolality during dehydration, both of which will provide additional protection to the marsupial young.
陆生等足类动物的有袋发育使胚胎面临潜在的生理压力，包括脱水、渗透压变化和高氨浓度。在本研究中，我们调查了体外培养的普通鼠妇发育阶段对极端渗透压、总氨和pH值的耐受性。有袋阶段分为1期（带卵壳的卵）、2期（已蜕去卵壳）和3期（初孵幼体）。所有阶段都表现出宽泛但不同的耐受范围。1期卵具有最强的氨耐受性，在总氨浓度为150 mM时7天存活率较高，且pH耐受范围较宽。初孵幼体表现出最宽的渗透压耐受性（100 - 1400 mosm×kg⁻¹），并在该范围内表现出良好的血淋巴渗透压调节能力。2期卵在所有三个参数上的耐受范围最窄，但仍可归类为广适性。银染显示发育阶段有两种不同的离子转运组织：1期和2期卵的卵黄膜上的一条中线带，其位置与胚胎背器官相对应，以及初孵幼体后三对腹足内肢。怀孕雌体不会下调氨含量，但在脱水过程中对有袋液pH值进行有效调节并下调渗透压，这两者都将为有袋幼体提供额外保护。
