Kyoto, Japan -- Like many parasites, nematomorphs are known to manipulate the behavior of their hosts to complete their life cycles. Also known as horsehair worms, among other names, these creatures develop in their hosts' body cavities and lure their terrestrial arthropod victims into the water where the parasites then reproduce. Some species have even been observed to induce positive phototaxis, attracting the host toward horizontally polarized light reflected on the water's surface.

Given that some parasites, including nematomorphs, target nocturnal hosts, a team of researchers at Kyoto University wondered if parasites manipulate their nocturnal hosts in sync with the lunar cycle. If such a manipulation mechanism has been conserved across nematomorph lineages, the team hypothesized that water-entry behavior in nocturnal hosts infected by Gordius and Gordionus nematomorphs may be more prevalent during the full moon, and sparse during the new moon.

From August to October during nights of the full and new moon, the researchers sampled camel crickets floating on the water in a small artificial pond in the Kiso River system in Nagano prefecture, where they also found large numbers of nematomorphs. In addition, they examined the stomach contents of salmonid fish in a nearby forested stream, treating the fish as fellow field researchers that continuously survey the river, day and night.

Marine plastic debris can persist for long periods and gradually break down into microplastics that are difficult to remove. Researchers from Ritsumeikan University used a system dynamics model to examine how reducing marine plastic inputs and varying the timing and intensity of cleanup could affect plastic accumulation by 2050. The findings show that halting plastic inputs is essential but insufficient on its own. Earlier cleanup of legacy macroplastics can reduce accumulation, but at higher costs.