Silva W R, Giaretta A A
Laboratório de Taxonomia, Sistemática e Ecologia Comportamental de Anuros Neotropicais, Instituto de Biologia, Universidade Federal de Uberlândia, Uberlândia, MG, Brazil.
Braz J Biol. 2008 May;68(2):403-7. doi: 10.1590/s1519-69842008000200024.
Leptodactylus labyrinthicus tadpoles reach a large size in the nest through consumption of trophic eggs. We previously suggested that the trophic eggs are laid just after amplexus has finished, but our new data do not support this hypothesis. We also present further details on the natural history of the species with regard to breeding activity, spawning site, retreats and the ability of tadpoles in preying upon fully-growth heterospecific tadpoles. We also show that the tadpoles are mainly nocturnal and take diurnal refuges. We collected the data in Brazil in three localities within the Cerrado Biome. We examined burrows used by L. labyrinthicus males, verified if females still contained mature eggs just after released from amplexus, and tested the ability of tadpoles in preying fully-growth heterospecific tadpoles. Field observations and experiments were conducted on tadpole activity time, hiding behaviour and level of susceptibility to predation by the bird leaf-scrapers in four sheltering situations. Reproduction could start before the first rains; this may be advantageous by allowing the tadpoles to exploit eggs of other frogs. We found one floating nest built in a temporary pool. The nest of the species is normally circumscribed in an excavated basin beside the water body. Adult males were found during the day with their head-out of the entrance of underwater burrows, which were perforations through dense root mats beside calling/spawning sites. Probably, these burrows in permanently water-filled soil are actively excavated by males. Females released all their eggs during the amplexus, so trophic eggs are not produced by the currently-accepted mechanism. Fully-grown heterospecific tadpoles were not preyed upon by L. labyrinthicus tadpoles, which can prey only slow-moving newly hatched ones. Field tadpoles took shelter under mud/dead leaves during daylight and became exposed on the bottom at night. Free-ranging leaf-scrapers removed dead leaves from a pool with their beaks and preyed upon tadpoles. In the experiments, the tadpoles sheltered under gravel/leaves during daylight, but they were exposed at night. Leaf-scrapers ate all exposed tadpoles, but no tadpole of the gravel/leaves trays was consumed. Hence the nocturnal habits and use of diurnal refuges may protect the tadpoles from visual predators, such as the leaf-scrapers.
迷宫姬蛙蝌蚪通过食用营养卵在巢穴中长到很大的体型。我们之前认为营养卵是在抱对结束后立即产下的，但我们的新数据并不支持这一假设。我们还提供了关于该物种自然史的更多细节，涉及繁殖活动、产卵地点、避难所，以及蝌蚪捕食完全成长的异种蝌蚪的能力。我们还表明，蝌蚪主要在夜间活动，并在白天寻找避难所。我们在巴西塞拉多生物群落的三个地点收集了数据。我们检查了迷宫姬蛙雄性使用的洞穴，核实了雌性在从抱对中解脱出来后是否仍含有成熟的卵，并测试了蝌蚪捕食完全成长的异种蝌蚪 的能力。我们在四种遮蔽情况下对蝌蚪的活动时间、隐藏行为以及对食叶鸟类捕食的易感性水平进行了实地观察和实验。繁殖可能在第一场雨之前就开始；这可能具有优势，因为这样蝌蚪就能利用其他青蛙的卵。我们在一个临时水塘中发现了一个漂浮的巢穴。该物种的巢穴通常位于水体旁挖掘出的水池中。白天发现成年雄性时，它们的头伸出水下洞穴的入口，这些洞穴是穿过鸣叫/产卵地点旁茂密根垫的穿孔。可能，这些位于常年积水土壤中的洞穴是雄性主动挖掘的。雌性在抱对期间产下所有的卵，所以营养卵不是通过目前公认的机制产生的。迷宫姬蛙蝌蚪不会捕食完全成长的异种蝌蚪，它们只能捕食行动缓慢的新孵化蝌蚪。野外的蝌蚪在白天躲在泥/枯叶下面，晚上则暴露在水底。自由放养的食叶鸟用喙从水塘中啄走枯叶并捕食蝌蚪。在实验中，蝌蚪白天躲在砾石/树叶下面，但晚上会暴露出来。食叶鸟吃掉了所有暴露在外的蝌蚪，但砾石/树叶托盘里的蝌蚪没有被吃掉。因此，夜间活动的习性和白天寻找避难所的行为可能会保护蝌蚪免受视觉捕食者的侵害，比如食叶鸟。
