Evidence for widespread Wolbachia infection in isopod crustaceans: molecular identification and host feminization

Abstract

Wolbachia are maternally inherited, intracellular, alpha proteobacteria that infect a wide range of arthropods. They cause three kinds of reproductive alterations in their hosts: cytoplasmic incompatibility, parthenogenesis and feminization. There have been many studies of the distribution of Wolbachia in arthropods, but very few crustacean species are known to be infected. We investigated the prevalence of Wolbachia in 85 species from ¢ve crustacean orders. Twenty-two isopod species were found to carry these bacteria. The bacteria were found mainly in terrestrial species, suggesting that Wolbachia came from a continental environment. The evolutionary relationships between these Wolbachia strains were determined by sequencing bacterial genes and by interspeci¢c transfers. All the bacteria associated with isopods belonged to the Wolbachiae B group, based on 16S rDNA sequence data. All the terrestrial isopod symbionts in this group except one formed an independent clade. The results of interspeci¢c transfers show evidence of specialization of Wolbachia symbionts to their isopod hosts. They also suggest that host species plays a more important role than bacterial phylogeny in determining the phenotype induced by Wolbachia infection.

Cloning and sequencing of wsp encoding gene fragments reveals a diversity of co-infecting Wolbachia strains in Acromyrmex leafcutter ants

“…However, adaptation to the physiology of a specific ant host seems more likely, and would be in agreement with the general pattern that other ants tend to be infected by a limited set of closely related Wolbachia strains . Host specialisation has also been suggested for parthenogenesis inducing Wolbachia of Trichogramma wasps, where a single wsp clade occurs in nine different host species (Schilthuizen and Stouthamer, 1997), and for feminizing Wolbachia of isopods, where a similar clustering within the Wolbachia phylogeny has been shown (Bouchon et al, 1998). Sometimes the Acromyrmex species also share closely related strains (the InvB strains in echinatior, insinuator, and octospinosus and the InvA strains in echinatior and octospinosus) and in this case it cannot unequivocally be inferred that the bacteria were inherited from a common ancestor or acquired by horizontal transmission, after speciation had occurred.…”

Wolbachiainfection frequencies in insects: evidence of a global equilibrium?

“…The surveys were for lower Central America (Panama), temperate Europe (Britain) and temperate North America (Indiana). Some surveys of other insects have recently been published (Bouchon et al 1998;Hariri et al 1998;Wenseleers et al 1998). However, these were focused upon groups where there was some prior knowledge of Wolbachia infections and, therefore, the infection frequencies are likely to be biased upwards.…”

“…Two (designated A and B) are found in arthropods (Werren et al 1995a;Zhou et al 1998), including insects, crustacean isopods (Bouchon et al 1998) and mites ( Johanowicz & Hoy 1995;Breeuwer 1997), and the other two (designated C and D) are found in nematodes (Bandi et al 1998). A ¢fth subgroup (designated E) has recently been proposed based on a 16S rDNA sequence for a Wolbachia found in a collembolan, a primitive insect (Vandekerckhove et al 1999).…”

How many species are infected withWolbachia? Cryptic sex ratio distorters revealed to be common by intensive sampling

“…Strains that cause cytoplasmic incompatibility typically occur at a high prevalence, often near ¢xation. Parthenogenesis inducers and feminizers both range from a fairly low prevalence to ¢xation in females (Rigaud 1997;Stouthamer 1997;Bouchon et al 1998). However, male killers typically occur in 1^30% of females , although much higher prevalences have been known (Jiggins et al 2000a).…”