. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 374 18 MASAYUKI SAIGUSA Time of day 24. 18 24 FIGURE 3. Temporal patterns of emersion and submersion on the mud flat of the study area at Kasaoka. Solid lines indicate the time from the beginning to the end of tidal influence. Dotted lines show periods at which tidal data were not obtained. Lines ad and bb' connect the sunset times. a river flowing into the Inland Sea was chosen for observation. On the coasts of the Pacific Ocean including the Izu peninsula, the time of moonrise and moonset is close to that of high water, so
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 374 18 MASAYUKI SAIGUSA Time of day 24. 18 24 FIGURE 3. Temporal patterns of emersion and submersion on the mud flat of the study area at Kasaoka. Solid lines indicate the time from the beginning to the end of tidal influence. Dotted lines show periods at which tidal data were not obtained. Lines ad and bb' connect the sunset times. a river flowing into the Inland Sea was chosen for observation. On the coasts of the Pacific Ocean including the Izu peninsula, the time of moonrise and moonset is close to that of high water, so that it is very difficult to determine whether the time of day of larval release coincides with the lunar day or tidal cycle. This paper reports the larval release rhythm of S. haematocheir observed at Kasaoka, Okayama Prefecture, Japan. The causes are presented for the difference in the larval release patterns between the Kasaoka population and the Izu popu- lation, along along with the timing mechanism of incubation and larval release. The relation of larval release rhythm to local tidal conditions is new evidence for the adaptive significance of semilunar reproductive rhythm in estuarine crabs. MATERIALS AND METHODS Larval release by Sesarma haematocheir females was observed in Kasaoka, Okayama Prefecture, from 11 July to 1 August, and from 31 August to 17 Sep- tember 1980. i L riverside area located about 100 m upriver from the Inland Sea was chosen as the study site (Fig. 1). The number of females releasing larvae was counted by an electric torch with six V batteries. From 11 July to 1 August, a 7-8 m range along the water's edge (site A-A') was observed, but from 31 August to 17 September, about a 10 m range (site B-B') was used. Because a boat at A- A' often hindered observation, the site was moved somewhat in Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appear
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
