Paramyxean–microsporidian co-infection in amphipods: Is the consensus that Microsporidia can feminise their hosts presumptive?

A Widespread and Distinctive Form of Amphipod Intersexuality Not Induced by Known Feminising Parasites

“…These findings suggest the male intersex phenotypes should not be considered stages on a single spectrum of intersexuality. Rather, they support the hypothesis that internal and external intersexuality are divergent phenotypes with separate causal mechanisms Short et al, 2012], leading to the hypothesis that both male intersex phenotypes are stages on a single spectrum of intersexuality resulting from parasite-induced incomplete feminisation .…”

“…We also use a microarray to find the intersex phenotypes possess distinct testicular transcriptomic profiles. Finally, we establish that, unlike external intersexuality, internal intersexuality is not associated with infection by any feminising parasite known to infect amphipods [Cordaux et al, 2001;Short et al, 2012].…”

“…Additionally, the phenotype might result from an early infection that failed to establish but left an ovotestis as a developmental legacy. However, this hypothesis is weakened by findings showing that populations uninfected by feminising parasites possess high levels of internal intersexuality [Yang et al, 2011;Short et al, 2012]. It is known that E. marinus sex determination is influenced by day length and a link between intersexuality and environmental sex determination in amphipods has been documented [Dunn et al, 1990[Dunn et al, , 1996.…”

“…The DNA quality was confirmed by PCR amplification of a host gene as previously described [Yang et al, 2011;Short et al, 2012]. The samples were screened using previously described PCR assays for the presence of general microsporidia, the microsporidian Dictyocoela duebenum [Yang et al, 2011], paramyxean parasites , and Wolbachia bacteria [Werren and Windsor, 2000;Cordaux et al, 2001].…”

“…For example, while external intersex males sampled from a site in Scotland (Inverkeithing) present high coinfection (85-86%) with feminising parasites, normal males present very low infection levels (2-3%) [Ford et al, 2006;Short et al, 2012]. However, despite the low infection levels, examination of a range of morphometric characters (including multiple coxal plate measurements and gnathopod, eye and head length) of Inverkeithing animals suggest normal males still present a demasculinised phenotype [Ford et al, 2004].…”