The potential role of phoresy in the evolution of parasitism: radiolabelling (tritium) evidence from an astigmatid mite

Abstract

Using tritium as a radiolabel marker of interspecific fluid transfer, we present experimental evidence that the heteromorphie deutonymph of an astigmatid mite (Hemisarcoptes cooremani) acquires materials (at least water) directly from the haemolymph of its beetle host (Chilocorus cacti). This acquisition is above that obtained from atmospheric vapour. The material acquired from the host is necessary for the completion of the ontogeny of H. cooremani and is likely procured through the action of the caudal ventral suckers of the heteromorphic dentonymph (hypopus). On gross morphological criteria, this mite-beetle relationship was previously defined as phoretic (for dispersal). Scanning electron photomicrographs of the physical relationship between the hypopodes and the beetles shed light on the 'parasitic' nature of the hypopus ofH. cooremani. Our findings are discussed in terms of the evolution of parasitism from a free-living astignmtid form. This transition into parasitism is facilitated by the heteromorphie hypopus and represents a classic 'wolf-insheep's-clothing' strategy. The heteromorph retains the characteristic phoretic morphology while exploiting the host in transit.

Positive and negative effects of phoretic mites on the reproductive output of an invasive bark beetle

“…Mites often travel upon bark beetles as a hypopus (a nymphal stage specialised with sucker plates or grasping organs for dispersal). A hypopus has no mouthparts, but studies suggest that some mite species may nevertheless extract nutrients from their host in this form (Houck and Cohen 1995). Using tritium radiolabelling, Houck and Cohen (1995) showed that material passed from Chilocorus cacti Linnaeus (Coleoptera: Coccinellidae) beetles into their attached astigmatid hypopodes through a small wound made by the ventral sucker plate of the mite.…”

“…A hypopus has no mouthparts, but studies suggest that some mite species may nevertheless extract nutrients from their host in this form (Houck and Cohen 1995). Using tritium radiolabelling, Houck and Cohen (1995) showed that material passed from Chilocorus cacti Linnaeus (Coleoptera: Coccinellidae) beetles into their attached astigmatid hypopodes through a small wound made by the ventral sucker plate of the mite. Thus, although they appear morphologically passive, these mites are functionally capable of parasitising their host.…”

“…Phoresy is often described as a form of commensalism, with the assumption that the host is unaffected by the interaction. However, the host is often strongly influenced by its phoretic companions due to the close association of the ectosymbiont (Houck and Cohen 1995). Phoretic ectosymbionts often synchronise with their host's life cycle and must stay close to potential hosts in order to disperse (Okabe and Makino 2008).…”

“…Phoretic ectosymbionts often synchronise with their host's life cycle and must stay close to potential hosts in order to disperse (Okabe and Makino 2008). In some cases, this close association becomes mutualistic, but in most studies the interaction is costly to the host (Houck and Cohen 1995), and thus is more appropriately deemed parasitic. Costs can include reduction in host mating success (Forbes 1993), amplification of required reproductive and parental effort (Møller 1990), and increased offspring mortality (Lindquist 1969;Blackman and Evans 1994).…”

A sex-specific tri-trophic-level effect in a phoretic association

“…The minimal and optimal contact times required for the apolysis of Hemisarcoptes coccophagus Meyer are 2 and 4-6 days, respectively (Izraylevich and Gerson, 1995a). During this contact hypopodes may obtain essential apolysis-inducing materials from the beetles' elytra, as shown for the Hemisarcoptes cooremani (Thomas) phoretic on Chilocorus cacti (L.) (Houck and Cohen, 1995).…”