Reproductive consequences of female size in haematophagous ectoparasites

Abstract

To test relationships between maternal size, egg size and size of new offspring, we studied (a) the effect of maternal size on egg size and number, and maternal survival after oviposition and (b) the effect of egg size on the duration of development and new imago size in three flea species (Xenopsylla ramesis, Synosternus cleopatrae, Parapulex chephrenis) with varying host and habitat specificity. In general, the number and size of eggs as well as total egg volume appeared to be independent of maternal body size. There was no trade-off between egg number and size. However, female body size was related to post-oviposition survival, with larger females surviving longer after oviposition than smaller females. In addition, females that produced more eggs died faster after oviposition in X. ramesis but not in the two other species. There were no significant size differences between eggs that developed into new imagoes and eggs that did not survive. Survivorship of male and female eggs did not differ; however, new adult females were significantly larger than new adult males. Female, but not male, new imagoes exhibited a significant positive relationship between egg size and duration of preimaginal development in all three species, with larger eggs developing faster than smaller eggs. In X. ramesis and S. cleopatrae, faster developing eggs also developed into larger new imagoes. We conclude that these patterns were largely consistent among the three flea species, suggesting that they result from the same mechanisms and are weakly affected by the ecological specialization of a given species.

Parasite performance and host alternation: is there a negative effect in host-specific and host-opportunistic parasites?

“…Faster development of S. cleopatrae pre-imago under host alternation is likely associated with larger eggs (Kiefer et al 2016). However, shorter pre-imaginal development of smaller eggs produced by X. conformis fed on alternating hosts contradicts patterns found earlier in a congeneric flea (Xenopsylla ramesis; Kiefer et al 2016). This can be an indication of a trade-off between egg size and egg provisioning.…”

“…In other words, consumption of blood from a non-preferred host resulted in decreased egg production and smaller egg size (but see Khokhlova et al 2013) even if blood from a preferred host was consumed as well. However, smaller egg size does not necessarily lead to decreased viability of new imagoes or smaller new imago (at least, in P. chephrenis ; Kiefer et al 2016). This is because maternal investment into offspring is associated not only with egg size, but also with egg provisioning (e.g.…”

“…Consequently, larvae that hatch earlier may have a competitive advantage over those that hatch later. Faster development of S. cleopatrae pre-imago under host alternation is likely associated with larger eggs (Kiefer et al 2016). However, shorter pre-imaginal development of smaller eggs produced by X. conformis fed on alternating hosts contradicts patterns found earlier in a congeneric flea ( Xenopsylla ramesis ; Kiefer et al 2016).…”

Harrison's rule scales up to entire parasite assemblages but is determined by environmental factors

“…For example, Poulin (2007) argued that host body size can be an important evolutionary driver for parasite size because larger hosts may provide greater resources to parasites. In fleas, body size was found to correlate positively with post‐oviposition female survival and, thus, with higher lifetime fecundity (Kiefer et al., 2016). Consequently, natural selection may favour larger parasite bodies if sufficient resources are available (e.g.…”

“…(2017) found a lack of support for the rule in only one of four guilds of avian lice investigated. Until the present, Harrison's rule has been investigated at the population and species level (Johnson et al., 2005; Morand et al., 1996; Villa et al., 2018; Yamagishi et al., 2014), and the causes for a positive relationship between parasite and host body size are still debated (Kiefer et al., 2016; Morand et al., 2000; Poulin, 2007).…”