. Animal Ecology. Animal ecology. sponges, and bryozoaiis tiiul no stable anchorage : and rock-inliabiting snails and limpets are quickly buried. Clanis, however, tiiid a sandy bottom suitable, if it is hrmly packed, as they are adapted to burrowing and plowing their way through a loose substratum. They are able also to move through a mud bottom, but where silting is Iieavy they close their valves to avoid an accumulation of silt within the mantle cavity and on the gills. The anodontas seem to be the most tol- erant of mud bottoms. Some of the mayfly naiads, such as Hexagcnia. are adapted to b
. Animal Ecology. Animal ecology. sponges, and bryozoaiis tiiul no stable anchorage : and rock-inliabiting snails and limpets are quickly buried. Clanis, however, tiiid a sandy bottom suitable, if it is hrmly packed, as they are adapted to burrowing and plowing their way through a loose substratum. They are able also to move through a mud bottom, but where silting is Iieavy they close their valves to avoid an accumulation of silt within the mantle cavity and on the gills. The anodontas seem to be the most tol- erant of mud bottoms. Some of the mayfly naiads, such as Hexagcnia. are adapted to burrowing in mud, and the surface of the bottom in shallow water is often closely dotted with the openings of their burrows (Hunt 1953). These burrows are relatively permanent in compact mud but would quickly collapse in loose sand. The genus Caenis is peculiar in possessing covers at the anterior end of the abdomen; they protect the gills from becoming clogged with silt. Midge fly larvae and aquatic annelids exist in mud bottoms: they would be ground to bits among moving sand parti- cles. The pond crayfish will burrow into mud down to water level as a pond dries up, but stream cray- fish will not do so and consequently suffer high mor- tality (Bovbjerg 1952). The bottom is important to invertebrates and vertebrates alike for placement of eggs. Some caddis- fly eggs are fastened to smooth rock surfaces in long strings by a cement-like substance. The eggs of other species occur in jelly-like masses and may be secured to plant stems or other submerged objects. Jelly-like masses of snail eggs are often quite common on the undersides of rocks in riffles. Some fish, such as the fantail darter (Lake 1936). make nests in small cavi- ties under stones, but other species, for instance the rainbow darter (Reeves 1907), creek chub (Reig- hard 1908), and river chub (Reighard 1943), build nests in gravel bottoms in the upper parts of riffles. Some of the suckers (Reighard 1920) spawn in shal
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Keywords: ., bookcentury1900, bookcollectionbiodive, booksubjectanimalecology
