Egg Cannibalism in a Facultative Polygynous Ant: Conflict for Reproduction or Strategy to Survive?

Abstract

Policing, i.e. all behaviours that prevent a nestmate from reproducing, is currently observed in social insects. It is presumed to have evolved to regulate potential conflicts generated by genetic asymmetries or to enhance colony efficiency by avoiding surplus reproductives and brood. In the ant, Ectatomma tuberculatum, individual queen fecundity was similar in monogynous and polygynous colonies issued from a Mexican population. Egg cannibalism, however, occurred in the polygynous colonies. The stealing and destruction of reproductive queen‐laid eggs involved only nestmate queens, even if they were highly related. No queen appeared to monopolize reproduction in the polygynous colonies. But, the observed value of relatedness among workers differed from the expected value, suggesting an unequal sharing of reproduction between queens. We discussed whether the cannibalism of queen‐laid eggs in E. tuberculatum results from a competition for reproduction among queens or if this phenomenon is related to constraints on nutritional resources.

Juvenile hormone downregulates vitellogenin production in Ectatomma tuberculatum (Hymenoptera: Formicidae) sterile workers

“…JH activates ion channels in ovarian follicular cells, increasing the intercellular space as a result of changes in the architecture of the actin filaments (Ronnau et al, 2015) and facilitating vitellogenin to reach the surface of oocytes, where it is endocytosed Tufail and Takeda, 2009). In this way, the reduction of the circulating vitellogenin in the haemolymph in JH-treated ants may be associated with the uptake of vitellogenin for growing oocytes, since all workers used in the experiment have developing trophic eggs (Hora et al, 2001(Hora et al, , 2007. On the contrary, in S. invicta, the JH peak occurs in queens during the oviposition period (Brent and Vargo, 2003), but in this fire ant, worker are always sterile.…”

“…All colonies were polygynous, containing from two to five queens and more than 30 workers and brood. The colonies were kept at 26±2°C and fed every 2 days with larvae of Tenebrio molitor Linneaus 1758 (Coleoptera: Tenebrionidae), honey, and water ad libitum (Hora et al, 2007).…”

“…The workers are morphologically identical, and the tasks they perform within the colony vary according to age (Champalbert and Lachaud, 1990;Fénéron et al, 1996;Hora et al, 2001). The workers of E. tuberculatum also have active ovaries and produce non-reproductive trophic eggs (Fénéron and Billen, 1996;Hora et al, 2007). Furthermore, they are not able to mate because their spermathecae are not functional (Hora et al, 2001).…”

Behavioral Differentiation and Ovarian Development of Unmated Gynes, Queens, and Workers ofEctatomma vizottoiAlmeida 1987 (Formicidae, Ectatomminae)

“…According to Hora et al [36] queens of E. tuberculatum spend more time protecting the eggs, because they invest a large amount of energy in their production. However, in other members of Ectatomminae, such as E. permagnum [12], only workers were seen protecting the eggs.…”

“…The task "worker-larva food transfer" was performed by both unmated gynes and workers (Table 2). However, in colonies of E. opaciventre [22,23], E. tuberculatum [36] only workers fed the larvae. According to Wilson [1], ants from the subfamilies Myrmicinae, Aneuretinae, Dolichoderinae, and Formicinae exchange regurgitated food, and their intestine is modified to store and distribute food for nestmates, a process called trophallaxis.…”