Influence of Host Gender on Infection Rate, Density and Distribution of the Parasitic Fungus,Hesperomyces virescens,on the Multicolored Asian Lady Beetle,Harmonia axyridis

Abstract

Hesperomyces virescens Thaxter (Laboulbeniales: Laboulbeniaceae) is a parasitic fungus that infects lady beetles (Coleoptera: Coccinellidae) via horizontal transmission between adults at overwintering and feeding sites. The differential behavior of male and female hosts could have profound effects on intensity of infection and positioning of fungus on the host's integument. The influence of host gender on infection rate, density and distribution of this parasite on the multicolored Asian lady beetle, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), was determined at a feeding site. Adult H. axyridis were sampled from pecan, Carya illinoinensis (Wangenh.) K. Koch, trees in northern Mississippi, USA, during summer and early fall 2003–2004. Results indicated that the behavior of male or female beetles on pecan trees had only a limited effect on the intensity of infection. When averaged over the entire season, the percentage of H. axyridis infected with H. virescens was not influenced by host gender. In 2003, a seasonal average of 54 and 39% of males and females, respectively, were infected; whereas in 2004, 36 and 41% of male and female beetles, respectively, were infected. The percentage of males infected with H. virescens was correlated with the number of males captured at the site in 2003; infection rate decreased as male abundance increased. Infection rate did not correlate with female abundance in 2003 or male or female abundance in 2004. Host gender had a considerable effect on the density and distribution of the fungus. Hesperomyces virescens mature thalli were denser on male rather than female beetles. Also, thallus density was often greatest on the elytra, meso- and metathorax, and abdomen of males and elytra of females, than on other body parts, in 2003. In 2003 and 2004, approximately 59 and 97% and 67 and 96% of males and females, respectively, had mature thalli distributed on the elytra. Prevalence of H. virescens thalli on the dorsum of H. axyridis females suggests that mating behavior is important in fungal transmission. However, prevalence of thalli on the dorsum of H. axyridis males suggests that behaviors other than mating contribute to the transmission of H. virescens onto male beetles. Spread of H. virescens ascospores from infected to uninfected H. axyridis adults of different generations, at feeding sites, might be vital to maintaining stable populations of the fungus.

Harmonia axyridis (Coleoptera: Coccinellidae) as a host of the parasitic fungus Hesperomyces virescens (Ascomycota: Laboulbeniales, Laboulbeniaceae): A case report and short review

“…This difference indicates that an important but not the only way in which H. virescens is transmitted between hosts is during mating. The importance of mating for the transmission of the parasite is reported by other researchers (Welch et al, 2001;Garcés & Williams, 2004;Harwood et al, 2006a;Riddick, 2006) along with other kinds of direct contact between hosts, especially when they aggregate during winter (Riddick & Schaefer, 2005;Nalepa & Weir, 2007).…”

“…Sexual transmission is probably the most important way in which H. virescens is transmitted, and this is often indicated by the different distribution of the parasite thalli on male and female hosts. Males tend to bear most thalli on their ventroposterior surface and females on their dorsoposterior surface (Welch et al, 2001;Garcés & Williams, 2004;Harwood et al, 2006a;Riddick, 2006;this study). Of the non-sexual direct contacts among hosts that may result in parasite transmission probably the most important is that which occurs in overwintering aggregations (Riddick & Schaefer, 2005;Nalepa & Weir, 2007).…”

“…The association between H. axyridis and H. virescens was first reported in Ohio (USA) in 2002 (Garcés & Williams, 2004) and subsequently at many localities in eastern and central United States, with the percentage parasitization often reaching 70-100% (Riddick & Schaefer, 2005;Harwood et al, 2006a, b;Riddick, 2006Riddick, , 2010Nalepa & Weir, 2007;Riddick & Cottrell, 2010).…”

Rickia wasmannii increases the need for water in Myrmica scabrinodis (Ascomycota: Laboulbeniales; Hymenoptera: Formicidae)

“…They are sometimes 65 considered to be a neutral factor (Garcia et al, 2010;Lapeva-66 Gjonova and Santamaria, 2011;Whisler, 1968), or to cause little 67 to no harm (Benjamin, 1971;Majewski, 1994;Santamaria, 1998;68 Scheloske, 1969). Negative effects are also mentioned (Benjamin,69 1971; Nalepa and Weir, 2007;Raak-van den Berg et al, 2014;70 Riddick, 2010Riddick, , 2006. Gemeno et al (2004) found some negative 71 effects of a Laboulbeniales fungus on a cockroach and Strandberg 72 and Tucker (1974) in an earwig species.…”

Laboulbeniales (Ascomycota) of the Boston Harbor Islands I: Species Parasitizing Coccinellidae and Staphylinidae, with Comments on Typification

“…Although some studies have suggested that insects infected with Laboulbeniales do not experience adverse effects on their fitness (Benjamin 1971, Scheloske 1969, Whisler 1968, negative effects on hosts have been reported (Báthori et al 2015;Kamburov et al 1967;Riddick 2006Riddick , 2010Strandberg and Tucker 1974). Laboulbeniales can alter reproductive behaviors of infected hosts, such as oviposition patterns (Strandberg and Tucker 1974), and cause injury to the host's appendages and abdominal tissues (Gemeno et al 2004, Thaxter 1908.…”