Adaptive significance of the gregarious phase in nymphs of a wolf spider, Pardosa pseudoannulata (Araneae : Lycosidae)

概要

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In many spider species, spiderlings spend several days aggregated in a mass immediately after emerging from the egg sac. During this period, which is called the gregarious phase, spiderlings do not eat. In this study, we conducted two experiments to clarify the benefits of the gregarious phase in a wolf spider, Pardosa pseudoannulata Boes. et Str. In one experiment, we examined the effect of the fasting period on spiderling development (duration until molting to the next instar and increment of carapace width). The fasting period was set at 1d in one treatment and at 5d in another treatment. In a second experiment, we examined the effect of aggregation on spiderling development. In one treatment, spiderlings were individually reared from the next day of emerging from the egg sac. In another treatment, spiderlings were allowed to aggregate for 5d before being reared individually. In both treatments, the fasting period was set at 5d. Spiderlings that fasted for 5d molted after a significantly shorter feeding period than those that fasted for 1d, although we observed no effects of aggregation. The feeding period corresponds to the post-gregarious period when females no longer guard their spiderlings. Our results suggest that the gregarious phase functions to shorten the postgregarious period during which the spiderlings are exposed to natural enemies.
日本応用動物昆虫学会の論文
2005-11-25