THE ADAPTIVE VALUE OF OFFSPRING SIZE AMONG FRESH-WATER MUSSELS (BIVALVIA, UNIONOIDEA)
THE ADAPTIVE VALUE OF OFFSPRING SIZE AMONG FRESH-WATER MUSSELS (BIVALVIA, UNIONOIDEA)
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DOI：
10.2307/5270
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发表时间：
1994-10-01
影响因子：
4.8
通讯作者：
BAUER, G
中科院分区：
文献类型：
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作者：
BAUER, G
1.蚌类的钩介幼虫必须附着在宿主鱼身上才能通过寄生阶段。钩介体的大小是物种特异性的：从C。0.05 mm到c. 0.45 mm壳长。钩介体的大小和数量之间存在一种平衡关系，钩介体小的种类繁殖力高，钩介体小的种类繁殖力低。似乎没有异速生长的限制钩毛的大小。系统发育的限制似乎是次要的（也许除了Margaritiferidae）。此外，繁殖类型（长期或短期繁殖者）或栖息地类型对水流没有影响。有袋类的数量和类型（四只有袋类、两只有袋类、两只有袋类在后鳃后部）似乎也与钩突的大小无关。形态因子“钩介壳”和生态因子“寄主范围”（寄主鱼科数）是重要的。有钩的钩虫比无钩的钩虫大。它们经常附着在坚韧的宿主组织上，因此必须很强大。钩介体的大小也随着宿主范围的增加而增加。这种关系可能是由于寄生阶段的持续时间和宿主免疫防御的相互作用而演变的。分析表明，钩介体的大小是一个重要组成部分，在一个连续的进化中的繁殖策略之间的Unionoidea。一端的代表是Margaritiferidae，具有小钩介，高生育力，长寄生期，在宿主上长时间生长和狭窄的宿主范围。它们对栖息地的适应性很强。一些无齿蚌属物种代表了另一端，具有大钩介体、低生育力、不参与生长的短寄生期和大宿主范围。它们生活在各种各样的栖息地。
1. The glochidia (larvae) of the freshwater mussels Unionoidea must attach to a host fish to pass through their parasitic stage. Glochidial size is species-specific: varying from c. 0.05 mm to c. 0.45 mm shell length.2. There is a trade-off between size and number such that fertility is high in species with small glochidia and vice versa.3. There appear to be no allometric constraints on glochidial size. Phylogenetic constraints seem to be of minor importance (perhaps with the exception of the Margaritiferidae). Furthermore, no influence can be shown for the breeding type (long- or short-term breeder) or the habitat type with respect to the water current. The number and type of marsupia (four marsupia, two marsupia, two marsupia on the posterior part of demibranchs) also does not seem to be related to glochidial size.4. The morphological factor 'hook on the glochidial shell' and the ecological factor 'host range' (number of host fish families) are of importance. Glochidia with a hook are larger than unhooked ones. They frequently attach to tough host tissues and therefore have to be powerful. Glochidial size also increases as the host range increases. This relationship probably evolved because of an interplay of the duration of the parasitic stage and the host's immunological defences.5. The analyses suggest that glochidial size is a crucial component in the evolution of a continuum of reproductive strategies among the Unionoidea. Representatives of one end of the continuum are the Margaritiferidae with small glochidia, high fertility, long parasitic stage, protracted growth on the host and narrow host range. They are highly specialized with respect to the habitat. Some Anodonta species represent the opposite end with large glochidia, low fertility, short parasitic stage with no growth being involved and large host range. They live in a variety of habitats.