. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 650 RUSSELL-HUNTER, APLEY AND HUNTER specimens of Melampus can be drowned by prolonged submergence. It appears that Melampus is unable to use an exposed gas bubble as a "physical gill" for sus- tained diving, as can be done in certain pulmonate genera (including Lymnaea, Physa and Planorbarius} \vhich have become "readapted" for aquatic life in fresh waters (see Russell Hunter, 1953b; Henderson, 1963; Russell Hunter, 1964). Given this inability to live submerged, and the general topography of salt marshes
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 650 RUSSELL-HUNTER, APLEY AND HUNTER specimens of Melampus can be drowned by prolonged submergence. It appears that Melampus is unable to use an exposed gas bubble as a "physical gill" for sus- tained diving, as can be done in certain pulmonate genera (including Lymnaea, Physa and Planorbarius} \vhich have become "readapted" for aquatic life in fresh waters (see Russell Hunter, 1953b; Henderson, 1963; Russell Hunter, 1964). Given this inability to live submerged, and the general topography of salt marshes, it is clear why adults of Melampus do not migrate down to lower zones of the littoral for reproduction as do some sympatric arthropods. On the other hand, the relatively primitive pattern of reproduction in Mclatnpus involves the spawn- ing of large numbers of small eggs which yield planktonic larvae on hatching. o o 9 9 .mil. SPAT GROWTH SETTLEMENT PLANKTONIC VEUGEH HATCHING DEVELOPMENT EGG-LAYING ~] COPULATION ^'. AGGREGATION ^\j. 10 20 JUNE 10 20 AUGUST I 10 20 SEPTEMBER FIGURE 10. Semilunar periodicity in reproduction and early life-cycle of Melampus at Little Sippewisset. The diagram is based on the actual timings and observations of the "three-cycle" reproductive period of summer 1966, except for the spat growth which is interpo- lated from the more extensive spat data of 1970. At the top of the figure lunar phases are shown conventionally, with below them a record of those high tides which exceeded a vertical height of feet (the height of the top of the Mc!uinf>iis zone in Fig. 8). At the bottom of the figure, the thicker portions of the base-line indicate times when the population of Melampus was dispersed. Three cycles of aggregation, copulation and egg-laying occur at semilunar intervals. Hatching and settlement also show semilunar synchronization. Three kinds of triangles are used to distinguish successive modal sizes for the three cohorts of spat
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
