Cannibalism studies on eggs and newly hatched caterpillars in a wild population of Ascia monuste (Godart) (Lepidoptera, Pieridae)

Abstract

RESUMO. Estudos do canibalismo de ovos e lagartas recém-eclodidas em uma população selvagem de Ascia monuste (Godart) (Lepidoptera, Pieridae). Ascia monuste, conhecida como lagarta da couve, é especialista em Brassicaceae e considerada herbívora; no entanto, pratica canibalismo. Os experimentos realizados neste trabalho visaram quantificar a ocorrência de canibalismo em A. monuste, verificar se o canibalismo interfere na performance da espécie e se o canibalismo é influenciado pelo tamanho da população. Os parâmetros utilizados para avaliar a performance foram tempo de desenvolvimento, tamanho e peso do adulto, fecundidade, oviposição e sobrevivência. O canibalismo ocorreu em todos os ínstares larvais. Houve uma tendência de aumento da prática de canibalismo com o aumento do número de coespecíficos (presas potenciais). O canibalismo ocorreu com maior intensidade em larvas no final do desenvolvimento larval. De um modo geral, o canibalismo não interferiu na performance da população. A hipótese mais provável para a ocorrência de canibalismo nas circustâncias estudadas neste trabalho seria a de o canibalismo ter função de controle populacional. PALAVRAS-CHAVE.Ascia monuste; Brassica oleracea; canibalismo; controle populacional; lagarta-da-couve.ABSTRACT. Ascia monuste (Godart), also known as cabbage caterpillar, is considered herbivorous and specialist in Brassicaceae; however, it performs cannibalism. Experiments carried out in this work aimed to quantify the cannibalism occurrence in A. monuste, to verify whether cannibalism interferes in the species performance and to check whether cannibalism is influenced by the population size. The parameters used in order to evaluate the performance were time of development, adults weight and size, fecundity, oviposition and survival rate. Cannibalism occurred in all larval instars. There was a tendency to increase the cannibalism practice as the number of co-specific increased (potential preys). Cannibalism was more intense in larvae at the end of larval development. Generally, cannibalism did not interfere in the population performance. The most probable hypothesis for the occurrence of cannibalism in the conditions here studied would be the hypothesis of cannibalism as having the function of population control.

Egg cannibalism in Ascia monuste in the field; opportunistic, preferential and very frequent

“…Experiments involving cannibalism in the present species in laboratory conditions (Zago-Braga and Zucoloto 2005) showed that there was a positive correlation between the number of potential conspecific preys and cannibalism rate in A. monuste. Another important aspect to be considered is that when NHC ingest their own egg shells as soon as they hatch and before eating the vegetable diet (Barros-Bellanda and Zucoloto 2001), there is an acceptance / recognition of eggs as food at the very beginning of development, showing that physical and/or chemical stimuli for the egg ingestion process exist, which can be used again whenever opportunity arises.…”

A non‐pollinating moth inflicts higher seed predation than two co‐pollinators in an obligate pollination mutualism

“…Alternatively, the low incidence of fruits producing more than one adult pollinator could be explained by traits relating not to the plant, but to the pollinators themselves. For example, many Lepidoptera larvae are known to indulge in opportunistic cannibalism when at high densities (Pierce, ; Kakimoto et al ., ; Zago‐Braga & Zucoloto, ). Such behaviours have a variety of possible benefits to the developing larvae, including increased survival, development rate and adult fecundity (Kakimoto et al ., ).…”

“…Under lottery models, the species with the highest growth rates will inevitably drive the less competitive species to extinction over time (Chesson & Warner, 1981). According to the competition versus colonisation model of species coexistence, stable coexistence of competing species can only occur where each of the two species has the higher population growth rates, and is the superior competitor, under certain environmental conditions (Yu & Wilson, 2001).…”

Effects of sex, host-plant deprivation and presence of conspecific immatures on the cannibalistic behavior of wild Ascia monuste orseis (Godart) (Lepidoptera, Pieridae)

“…Both containers were kept in an incubator at 29 ± 2 º C; with a fluorescent lamp (400 lux) on 10:14 (L:D) cycle and 75% humidity (Felipe & Zucoloto 1993). Fourth and fifth instar caterpillars were used in the experiments because (1) oldest caterpillars exhibit greater power of predation due to the greater mobility and the physical structure of its jaws (Zago-Braga & Zucoloto 2004), (2) in these instars, the caterpillars tend to feed solitariously, similar condition to the present experiments and (3) food deprivation of 24 hours in the 4 th instar -required condition for the experiment realization -is not lethal to larvae (Barros-Bellanda & Zucoloto 2003).…”

“…Afterwards, females were dissected in saline solution. Ovaries were separated and oocytes counted including the terminal ovalled regions from the ovaries (n = 20) (Zago-Braga & Zucoloto 2004). Statistical analysis used the Kruskal-Wallis and the Student-Newman-Keuls tests, with ␣ = 0.05.…”