Host Castration as a Parasitic Strategy

Abstract

Rothschild (1941b,c) proposed increased host growth as the selective advantage of parasitic castration for trematodes castrating their first intermediate host, Peringia ulvae. She demonstrated a positive correlation between frequency of parasitism and host size, which led her to postulate that parasitized hosts grew faster and to a larger size than non-parasitized ones. This, she said, should result in increased fitness of the parasite, since the number of cercariae produced by a snail is proportionate to its size. However, an alternative hypothesis to that of increased host growth has been offered by Hartnoll (Hartnoll, 1967), to explain crustacean castration. He postulated that the typical sacculinization effects are produced by the parasite, which benefits from the resulting physiological and behavioral changes. These changes apparently result in all parasitized individuals, regardless of sex, behaving like ovigerous females; such individuals do not reproduce while they are parasitized, but they provide protection and ventilation to the parasites which occupy the external location usually 335

Cheating the cheater: domatia loss minimizes the effects of ant castration in an Amazonian ant-plant

“…In that sense, the energetic loss to the plant is less than if attacks occurred only after flowers had matured or after fruit set. This castration behavior is probably beneficial for the ant colony, because it increases nesting space (Yu and Pierce 1998;Yu 2001), given the likely trade-off between plant growth and reproduction (Baudoin 1975;Clay 1990;Yu and Pierce 1998;Stanton et al 1999;Kover 2000;Yu 2001). Because both leaves and flowers of H. myrmecophila are produced at the branch tips (Fig.…”

“…To house ants, these plants have evolved special hollow structures, know as domatia, in which ants nest (Janzen 1966;Beattie 1985;Benson 1985). Many ant-plants also provide food to their associated ants, in the form of nectar or food bodies (Janzen 1966;Baudoin 1975;Janzen 1975;O'Dowd 1980;Beattie 1985;Vasconcelos 1991). In exchange, ants often protect plants against herbivores (Janzen 1966;McKey 1984;Benson 1985;Vasconcelos 1991;Davidson and McKey 1993;Fonseca 1994;Federle et al 1998), against encroaching vines and competing plants (Janzen 1966;Benson 1985;Davidson and McKey 1993;Federle et al 1998), or provide nutrients essential for plant growth (Janzen 1966;Treseder et al 1995).…”

Subtle effect of Xenos vesparum (Xenidae, Strepsiptera) on the reproductive apparatus of its male host: Parasite or parasitoid?

“…Parasitic castrators (or sterilizers) are organisms that manage to exploit the reproductive pathways of the host for their own development and reproductive output: they do so by diverting energy from gonad development or by secreting castrating hormones (Kuris, 1974;Baudoin, 1975;Hechinger et al, 2009;Lefèvre et al, 2009a). Parasitic castrators can also influence host morphology, behaviour and the evolution of host life history traits (Lafferty, 1993a;Hiroki et al, 2004;Hughes et al, 2004;Beani et al, 2011).…”

The unavoidable costs and unexpected benefits of parasitism: Population and metapopulation models of parasite-mediated competition

“…Empirical and theoretical studies suggest that reproduction and immunity represent two competing needs in the host's overall resource allocation strategy (Sheldon and Verhulst, 1996;Zerofsky et al, 2005;Zuk and Stoehr, 2002). While reproduction is obviously essential for population persistence, infections can greatly reduce survival or cause sterility such that resources allocated to reproduction are effectively wasted (Baudoin, 1975;Clay, 1991;Ebert et al, 2004;Lively, 1987;Roy, 1993;Roy and Bierzychudek, 1993). Because reproduction and immunity are both expensive (Kraaijeveld et al, 2002;Reznick, 1985), the way in which a host allocates resources can have a dramatic effect on the host's fitness.…”