Size Relationship of the Ectoparasite Tachaea chinensis in the Host Shrimp Palaemon paucidens From Shiga Prefecture, Japan

Host selection and potential predation in the host-parasite interaction between the isopod Tachaea chinensis and freshwater host species

“…nipponense after being released into a tank, which indicates that it has strong visual capabilities ( Nagasawa and Fujimoto, 2021 ). Similar observations were made in another study, which concluded that the isopod might be incorporating different sensory mechanisms to locate its host; however, the sensory attractant was difficult to pinpoint in both studies owing to the presence of different sensory stimuli in the experimental tank (e.g., visual, chemical, and tactile) ( Khalfan et al, 2022 ).…”

“…Tachaea chinensis ranged from 4 mm to 10 mm in body length. The ratio of the isopod body length to host carapace length was set between 0.7 and 1.0, as such a ratio is optimal to promote size selection in this parasite ( Khalfan et al, 2023 ). The isopods were starved for 24 h prior to experimentation.…”

“…The isopods were starved for 24 h prior to experimentation. All provided choice pairs had similar carapace lengths (e.g., those of shrimps) to avoid selection results being influenced by differences in host species sizes ( Khalfan et al, 2023 ).…”

“…Similar findings were observed by Ota (2019) , who concluded that the small-sized shrimp, Neocaridina spp., may not offer adequate space for the isopod to safely attach itself. Khalfan et al (2023) , using behavioral experiments, further elucidated this hypothesis and concluded that 0.7–1.0 ratios of parasite body length to host shrimp carapace length appeared to be preferred by the isopod T. chinensis , because it provides adequate space for safe attachment while avoiding potential consumption by the available host shrimps. In the same study, the authors found that relatively large size differences between the parasite body length and host shrimp carapace length resulted in the disappearance of the isopod from the experimental tank, potentially via predation by the large host shrimp.…”

“…However, host size and overall surface area could resemble determinant factors for a successful association. In one study, individuals of T. chinensis were always found on host shrimps that are slightly larger in carapace length compared to its own body length ( Khalfan et al, 2022 ). Similar findings were observed by Ota (2019) , who concluded that the small-sized shrimp, Neocaridina spp., may not offer adequate space for the isopod to safely attach itself.…”