Effects of trophic‐eggs on offspring performance and rivalry in a sub‐social bug

Abstract

performance and rivalry in a sub-social bug. Á/ Oikos 107: 28 Á/35.Trophic eggs, which are inviable and usually function as a food supply for offspring, have been regarded as extended parental investment or the outcome of parent Á/ offspring conflict in sibling oophagy. Adomerus triguttulus (Heteroptera: Cydnidae) is a sub-social bug showing a complex pattern of maternal care, including progressive provisioning of host seeds and trophic-egg production. To investigate the functions of trophic eggs, we removed trophic eggs from clutches under different resource conditions. The longevity of nymphs was greatly extended by feeding upon trophic eggs when seeds were excluded. When seeds were provided, trophic-egg feeding by nymphs enhanced their development, but there were no significant effects on brood survival. Some viable eggs were also fed upon by sibling nymphs. However, there was no difference in the proportion of viable eggs consumed between clutches with and without trophic eggs. Females lay viable eggs within the first oviposition day. The synchronous hatching resulting from this oviposition mode seems to prevent sibcannibalism. The body size of females affected their relative investment in trophic eggs; larger females produced more viable eggs with relatively fewer trophic eggs. The functions and adaptive allocation of trophic eggs are discussed in light of the two hypotheses mentioned above.

Morphology of trophic eggs and ovarian dynamics in the subsocial bug Adomerus triguttulus (Heteroptera: Cydnidae)

“…They produce inviable trophic eggs and add them to the viable egg masses (Nakahira 1994). Nymphs feed upon the trophic eggs within a day after hatching (Kudo and Nakahira 2004). The trophic-egg feeding by hatched nymphs enhances their growth and survival (Kudo and Nakahira 2004).…”

“…Nymphs feed upon the trophic eggs within a day after hatching (Kudo and Nakahira 2004). The trophic-egg feeding by hatched nymphs enhances their growth and survival (Kudo and Nakahira 2004). After hatching occurs, the females show progressive provisioning: they temporarily leave their broods and transport seeds to feed them.…”

“…In addition to the lower cost of production, the smaller size of A. triguttulus trophic eggs may have resulted from unequal resource allocation among eggs within clutches in relation to such predation risks (Kudo and Nakahira 2004). Eggs on the peripheral surface of clutches are more vulnerable and thus females should invest less in such eggs than in those in the centre (Mappes et al 1997;Kudo 2001).…”

“…Like other subsocial cydnid bugs (Filippi et al 2001), A. triguttulus females show complex maternal care of eggs and nymphs (Nakahira 1992(Nakahira , 1994. The nymphs feed upon trophic eggs soon after hatching and gain nutritional benefits (Kudo and Nakahira 2004). Kudo and Nakahira (2005) have shown that females can adjust trophic-egg production in an adaptive manner: they increase relative trophic-egg investment under poor food-resource conditions.…”

Maternal-care behaviour inAdomerus variegatus(Hemiptera: Cydnidae)

“…The bugs with extended parental behavior are: Sehirus cinctus cinctus (Palisot de Beauvois) (Sites & McPherson 1982;Agrawal et al 2004Agrawal et al , 2005; Adomerus triguttulus (Motchulsky) (Kudo & Nakahira 2004Kudo et al 2006;Nakahira & Kudo 2008); Adomerus variegatus (Signoret) (Mukai et al 2010); Canthophorus niveimarginatus Scott (Sehirinae) (Filippi et al 2009;Baba et al 2011); and the most studied Parastrachia japonensis Scott (Parastrachidae) (Tachikawa & Schaefer 1985;Tsukamoto & Tojo 1992;Tsukamoto et al 1994;Filippi et al 1995aFilippi et al , 1995bFilippi et al , 2000aFilippi et al , 2000bFilippi et al , 2001Filippi et al , 2002Filippi et al , 2005Nomakuchi et al 1998;Hironaka et al 2005Hironaka et al , 2007aHironaka et al , 2007bHironaka et al , 2007cTojo et al 2005). In a laboratory experiment adults and nymphs of Adrisa magna Uhler were observed to carry seeds of Sophora japonica L. (Leguminosae) to shelter places allowing communal feeding and possible provisioning for nymphs (Takeuchi & Tamura 2000).…”