Based on my experience to study the parasites of different aquatic animals, I proposed a new science, aquaparasitology, in 1989 when I was a scientist at the Hokkaido Fisheries Experimental Station in Japan. This science aims to clarify various aspects of the biology of parasites infecting aquatic invertebrates and vertebrates and has a wider perspective than fish parasitology. Since only limited information is available on the parasites of aquatic invertebrates, it is desired to study those parasites intensively.

Anura, a living amphibian group without tail on its adult, are the largest order of the extant Amphibia. They are commonly known as frogs and are widely distributed ranging from the tropics to subarctic regions. Since there are few traits available for species identification, a diverse approach is essential for systematic study of this group. This paper aims to provide a brief overview of taxonomic history of Japanese frogs, as well as technique and perspective approach, with a special focus on the recent studies on the spring- and subterranean-stream-breeding frogs.

Two species of rocky reef dwelling mantis shrimps of Gonodactyloidea are reported on the basis of materials from the nearshore environment of Honshu Island, Japan. Chorisquilla orientalis Hwang, Ahyong, and Kim, 2018 (Protosquillidae), originally described from Korean and Japanese waters, was recently discovered in additional localities of western to central Honshu, including Tottori, Shizuoka, and Kanagawa Prefectures. Taku spinosocarinatus (Fukuda, 1909) (Takuidae), originally described from Kanagawa Prefecture, was likewise discovered for the first time in Tottori Prefecture, on the western coast of the Sea of Japan; though it has been recorded from a more northern locality along the same coast. Previous Japanese records of these two species, which have been reported under different scientific and Japanese names, are herein revised, and proper Japanese names for them are proposed. Notes on the live coloration of the two species are also provided based on newly collected specimens.

The trematode parasite Botulus microporus (Monticelli, 1889) is reported for the first time on the coast of Japanese mainland. The host fish Alepisaurus ferox Lowe, 1833 which had washed ashore was sampled on the coast of Shizuoka Prefecture, Suruga Bay, Japan. Its digestive tube was dissected in the laboratory, and an adult trematode was detected from the host intestine. The trematode was identified as B. microporus based on morphological characteristics.

The opecoelid trematode Pedunculacetabulum opisthorchis Yamaguti, 1934 has been reported from marine fish in coastal regions in Japan, whereas its larvae have never been reported. In this study, three adults of P. opisthorchis were obtained from Oplegnathus fasciatus (Temminck & Schlegel, 1844) captured in Aomori, Mie, and Ehime Prefectures, Japan. Partial sequences of the nuclear 28S rDNA from two of the three adults, as well as that of mitochondrial COI from one, were determined as DNA barcodes. Molecular comparisons revealed the conspecificity between P. opisthorchis and the unidentified metacercaria previously reported from the staurozoan cnidarian Haliclystus tenuis Kishinouye, 1910 in Hokkaido, Japan. The staurozoan cnidarian is thought to act as the second intermediate or paratenic host of P. opisthorchis.

An Indo-Pacific worm goby (Gobiidae), Caragobius urolepis (Bleeker, 1852) inhabits soft mud bottoms near river mouths. In Japanese waters, this species has previously been recorded only from the Ryukyu Islands, viz., Amami-oshima, Okinawa-jima, Ishigaki-jima, and Iriomote-jima islands. In this study, 72 specimens [10.8–44.1 mm in standard length (SL)] were collected from Miyazaki Prefecture, Kyushu, southern Japan. Thus, the presently reported specimens represent the northernmost records of the species. These specimens were collected in Miyazaki Prefecture between October 2023 and November 2024. Specimens over 40 mm SL were collected only in the summer of 2024, while only smaller specimens (10.8–36.6 mm SL: mean 21.7 mm) were observed in the autumn and spring. The large females (40.9–44.1 mm SL) with developed yellow ovaries were also collected in July 2024. Examination of the specimens from Miyazaki Prefecture revealed that some body parts changed their proportions with growth; the head length (HL), pre-dorsal length, and pre-pelvic length relative to SL decrease with growth, while the pre-dorsal length and pre-pelvic length relative to HL increase with growth.

The wild boar Sus scrofa, a globally widespread invasive species, has been increasingly recognized as a driver of ecosystem change through its rooting behavior and omnivorous diet. However, its ecological impact on faunal communities, especially in Asia, remains poorly documented. Here, we summarize results from our unpublished field experiment, which evaluated the effects of wild boar density on ground-nesting birds using artificial nests and eggs in evergreen broad-leaved forests at five study sites (four islands and one mainland site) in the Seto Inland Sea, western Japan. Across the study sites, nest destruction or egg predation was observed in 1.3–98.7% of nests, with higher rates occurring in areas with greater wild boar relative abundance index (RAI). Camera traps identified wild boars as the main nest predators in high-RAI sites. These results strongly suggest that wild boars function as active nest predators and may significantly reduce the breeding success of ground-nesting birds. Our findings highlight the urgent need to incorporate ecosystem-based perspectives into wild boar management policies in Japan, following the example of sika deer Cervus nippon management, where population thresholds for ecosystem impact have been established. Proactive and evidence-based strategies are needed to prevent potentially irreversible ecological degradation caused by wild boar overabundance.