Stomach Nematodes (Mastophorus muris) in Rats (Rattus rattus) Are Associated with Coconut (Cocos nucifera) Habitat at Palmyra Atoll

Abstract

Black rats ( Rattus rattus ) and their stomach nematodes (Mastophorus muris) were historically introduced to islets at Palmyra Atoll in the central Pacific Line Islands. To investigate patterns of parasitism, we trapped rats and quantified nematodes on 13 islets of various sizes and habitat types. Most rats were parasitized (59%) with an average of 12 worms per infected rat. Islet size did not greatly influence parasite population biology. Nematodes also did not appear to affect rat condition (weight to skull length). The only strong and consistent factor associated with the mean abundance of nematodes in rats was habitat (dominant cover and locally dominant plant species). Thus, nematodes were much more abundant in rats from sites dominated by coconut trees (Cocos nucifera). Coconut trees may also be an introduced species at Palmyra Atoll.

Biology and Impacts of Pacific Island Invasive Species. 11.Rattus rattus,the Black Rat (Rodentia: Muridae)

“…Also in Hawai'i, ear mites (Notoedres muris) that cause ear lesions can infect 26% of the R. rattus population in some forests but other populations suffer very little (<2%) infection (Shiels 2010). Intestinal worms (helminths), likely the nematode Mastophorus muris, are common in wild R. rattus on many Pacific islands (Fall et al 1971, Sugihara 1997, Shiels 2010, and the majority of the R. rattus captured were parasitized by this worm on Palmyra Atoll ( Lafferty et al 2010) and on Rangitoto Island, New Zealand (Miller and Miller 1995). Because the nematodes M. muris and Physoloptera getula have obligate life cycles involving arthropods as intermediate hosts, R. rattus is likely infected directly by eating its arthropod prey (Miller and Miller 1995).…”

Local extinction of the Asian tiger mosquito ( Aedes albopictus ) following rat eradication on Palmyra Atoll

“…In fact, Aedes is not the only putative secondary extinction associated with the Palmyra rat eradication. Most rats on Palmyra were parasitized with a rodent-specific stomach nematode [ 20 ], which must have also gone extinct on the atoll after rat eradication. These changes in the Palmyra food web show how removing introduced rats can have unintended indirect effects, including eradicating an introduced disease vector.…”

A nematomorph parasite explains variation in terrestrial subsidies to trout streams in Japan

“…Forest type can affect parasites in other systems for unknown reasons. For instance, stomach nematodes in rats are more abundant in coconut plantations than native forests (Lafferty et al 2010). Previous studies have not found an effect of landscape type on nematomorphs (Hanelt et al 2001).…”