In order to elucidate the selection of spawning substrate by female cuttlefish Sepia esculenta, their behavior and trigger stimulus during a spawning sequence were examined in indoor tanks. Fe male approaches substrate, spurts water towards substrate, takes sediment in arms, covers eggs with sediment, spurts water towards substrate again, and undergoes egg deposition on substrate to complete one spawning. Females which finished copulation were visually attracted to more visible substrate. The height of a substrate was not an important factor for the attraction. Substrates which swung by the spurting water were not accepted by females. Females exhibited taking sediment even though there was no sediment on the tank bottom. It was concluded that female cuttlefish prefer long, fine, and immobile materials as spawning substrates.

SUMMARY: The sensory basis of the behavior of cuttlefish towards basket traps explains in part the mechanism of capture by the gear. Previous studies have shown that the reaction of cuttlefish Sepia esculenta to basket traps is mediated mainly by vision. In this study, visual factors that attract cuttlefish to basket traps were examined in the laboratory. The reaction of cuttlefish was divided into three processes of recognition, approach, and entry; the frequency and the duration of each process indicated the strength of the reaction. Cuttlefish were most attracted to a basket trap that contrasted most strongly with the background. When the dismantled components of the basket trap were presented as visual targets to cuttlefish, all the components were approached by the cuttlefish, which remained in the internal space. Cuttlefish have a habit of occupying the internal space of a structure and this habit seems to be the main motivation for entry into a trap. Another experiment was carried out to examine the social attraction between individuals inside and outside a trap. Social interference between males and females seems to be part of the mechanism of capture of cuttlefish by basket traps.

Environmental DNA (eDNA) is an increasingly popular tool in biological and ecological studies. As a biproduct of its increasing use, large number of eDNA samples are being collected and stored, that potentially contain information of many non-target species. One potential use for these eDNA samples is a surveillance and early detection of pathogens and parasites that are otherwise difficult to detect. Echinococcus multilocularis is such a parasite with serious zoonotic concern, and whose range has been expanding. If eDNA samples from various studies can be repurposed in detecting the parasite, it can significantly reduce the costs and efforts in surveillance and early detection of the parasite. We designed and tested a new set of primer-probe for detecting E. multilocularis mitochondrial DNA in environmental medium. Using this primer-probe set, we conducted real-time PCR on repurposed eDNA samples collected from three streams flowing through an area of Japan endemic to the parasite. We detected the DNA of E. multilocularis in one of the 128 samples (0.78%). The discovery suggests that while detecting E. multilocularis using eDNA samples is possible, the rate of detection appear to be very low. However, given the naturally low prevalence of the parasite among wild hosts in endemic areas, the repurposed eDNAs may still be a valid option for surveillance in newly introduced areas with the reduced cost and efforts. Further work is needed to assess and improve the effectiveness of using eDNA for detection of E. multilocularis.