13课

lesson 13

The Biology of Salmonids (Ⅲ) 鲑科鱼类的生物学

Smolt 刚入海的鲑鳟鱼 Osmosis 渗透（作用 Dilemma 困境

Lethal 致死的 Sodium

chloride 氯化钠 Shipwrecked

mariner 失事船上的水手

Isosmotic 等渗的 Metamorphosis 变态作用 Convalescence

period 恢复期，康复期

Retina 视网膜 Thyroid 甲状腺 Hyperactive 兴奋的，活动过度的

Slim 细长的 Feeding rate Vaccination 接种疫苗

Vaccine 疫苗 Enteric 肠道的 Ichtyyophthirius

multifiliis 多子小瓜虫

Strain 菌株 Vibriosis 弧菌病 Surveillance 监视，监督

tumour 肿瘤 Plethora 多血症 Derangement 错乱，发狂

Lymphopenia 淋巴细胞减少 Salmo trutta L 欧鲑，河鳟 Versatile 多才多艺

Neutrophilia 中性细胞减少 Prolactina 催乳素 Salmo salar L 大西洋鲑

Pregnancy 怀孕，怀卵 Thymus 胸腺 Lymphocyte 淋巴细胞

Spleen 脾脏 Monocyte 单核细胞 Macrophage 巨噬细胞

Granulocyte 粒细胞 Inflammation 炎症 Pathogen 病原

Salt and water balance and smoltification：水盐平衡和银化

A characteristic feature of the life cycle of salmon and trout is that it involves living both in fresh

water and sea water. Spawning is in fresh water and the young grow in fresh water. Some species

or populations never migrate to sea but most reach a stage known as the smolt stage when the

fish is capable of surviving in the sea. For most fish species that live either in sea water or fresh

water transfer to the other medium is lethal, death occurring within a few hours. Many fish can

only tolerate very minor changes in salinity.

生命周期的鲑鱼和鳟鱼的典型特征是，它涉及生活在淡水和海水。产卵是在淡水中，年轻人在淡水中生长。一些物种或种群永远不会迁移到大海，但最达到称为小鲑鱼阶段，当鱼能够存活在海中的一个阶段。对于生活在海水或淡水转移至其他培养基中的大多数鱼类致死，死亡否发生几个小时之内。很多鱼只能在盐度容忍非常轻微的修改。

The problem for a fish in living either in sea water or fresh water is the gills of necessity are

exposed to the surrounding water. The gills are large in area, are filled with blood and are

designed to allow maximum diffusion of materials between blood and water. The natural

concentration of salts in fish blood is intermediate between that of sea water and fresh water

一条鱼在生活在海水或淡水问题是必要性的鳃部必要性的暴露在周围的水。鳃在面积很大，充满了血液和旨在允许最大扩散的血和水之间的材料。天然鱼类血液中盐的浓度是介于海水与淡水

In fresh water salts constantly diffuse out and water enters continuously by osmosis. In fresh

water there is therefore a tendency for the blood to become diluted and for the fish to swell up

with fresh water. This is counteracted in two ways. The kidneys produce vast quantities of dilute

urine to get rid of water continuously as it floods in across the gills. Salt loss is compensated for

by active uptake of salt, particularly sodium chloride through the gills. This takes place through

special cells known as chloride cells. Other salts are taken up through the gut wall from the diet

or drinking water. The fish is able to take up salts from extremely low concentrations but survival

is not possible in absolutely pure distilled water.

在淡水环境中盐不断漫出来了，水进入不断通过渗透作用。在淡水环境中因此有一种倾向，血液就变得稀释和膨胀起来的淡水的鱼。这被抵消以两种方式。肾脏产生大量稀释尿液，摆脱水不断因为它淹没在跨越鳃。盐损失由活跃吸收盐，尤其是氯化钠通过鳃的补偿。这是通过特殊的细胞称为氯细胞发生的。其他的盐会跟进通过肠道壁从饮食或喝水。鱼是能够拿起从极低浓度的盐，但生存是不可能在绝对纯净的蒸馏水。

In sea water fish suffer the well known dilemma of shipwrecked mariners in being surrounded by

water unfit to drink. The blood of salmonids has a salt composition barely distinguishable from

that of humans. Humans must drink fresh water to counteract the effects of dehydration. In the

fish dehydration is rapid and there is continuous loss of water through the gills by osmosis. This

loss of water is compensated for by drinking and further loss of water is avoided by virtual

cessation of urine production by the kidneys. This process would lead to loading of the body with

excess salt but the fish have a mechanism not available to humans for expelling salt from the

body.

在海水鱼类遭遇海难船员在被四面环水不适合饮用的众所周知的困境。鲑科鱼类的血液有盐的成分几乎无法辨别人类。人类一定要喝新鲜的水，以抗衡脱水的影响。这种鱼体内脱水是快速，水通过鳃渗透法制备连续的损失。由饮酒补偿这一损失的水，进一步冷却水损失的避免虚拟停止尿液生产由肾脏排泄。这一过程会导致加载过多的盐与身体但鱼有不提供给人类的驱逐盐从身体机制。

In sea water chloride cells of the gills actively excrete sodium salts. It is not clear whether it is the

same cells as were responsible for salt uptake in fresh water which reverse their function or new

cells that grow when the fish moves into sea water. Certainly salmon when entering sea water

have acquired many additional chloride cells in the gills.

在海水中的鳃氯细胞积极分泌钠盐。不明确的是，是否同一细胞作为负责盐的摄入，在淡水中扭转其功能或成长时鱼移入海的新细胞。当然大马哈鱼进入海水时获得了许多额外的氯细胞的鳃里。

Thus transfer between fresh water and sea water involves effective reversal of the function of the

kidneys and the gills. Particularly in the gills salt transport is very energy-demanding and this has

led to the speculation that fish grow fastest in water of salinity equal to that of blood, isosmotic,

which is about 30 % sea water. Although some experiments seem to confirm this idea it is not

really borne out under commercial conditions. Often diseased fish with gill or skin damage,