First record of the genus Pseudaeginella Mayer, 1890 (Crustacea, Amphipoda, Caprellidae) with a new species from Korean waters.

A new species of the genus Pseudaeginella Mayer, 1890 belonging to the family Caprellidae Leach, 1814 was collected from the South Sea in Korea. Pseudaeginellacarinaspinosasp. nov. is morphologically similar to related congeners belonging to the genera Paradeutella Mayer, 1890 and Pseudaeginella, in having dorsal projections on pereonites, triarticulate mandibular palp, small or absent molar, and uniarticulate pereopods 3 and 4. However, this new species is distinguished from its congeners by the position and size of dorsal projection. This is the first record of Pseudaeginella from the Northwest Pacific region, including Korea, and a key to species of the genus Pseudaeginella is also provided.

A new species of the genus Opisa Boeck, 1876 (Crustacea, Amphipoda, Opisidae) and a new record for Opisatakafuminakanoi from the East Sea, South Korea.

Two species of the opisid genus Opisa have been collected from the East Sea of South Korea, one of them described as Opisaparvimana sp. nov.. The new species, O.parvimana sp. nov. is similar to O.odontochela; however, it can be clearly distinguished from this species because it has 12 blunt robust setae in the palm of gnathopod 1. The other collected species, Opisatakafuminakanoi Narahara-Nakano, Kakui & Tomikawa, 2016 is previously known from Japanese waters (southeast of Akkeshi Bay, Hokkaido). Both species are illustrated and compared to related species. A key to Opisa species is also provided.

Two new species of the genus Microlysias (Crustacea, Amphipoda, Tryphosidae) from Korean Waters.

Two new species of the genus Microlysias Stebbing, 1918 belonging to the family Tryphosidae Lowry Stoddard, 1997 were collected from shallow Korean waters. The two new species are described as Microlysias rectangulatus and M. triangulus. The new species M. rectangulatus sp. nov. is similar to M. xenokeras, M. soela, and Orchomenella japonica. However, the new species can be distinguished from these species by having a subrectangular peduncular article 5 of antenna 2 and an elongated article 1 of the mandibular palp, nearly equal to palp article 3. M. triangulus sp. nov. is similar to M. xenokeras and M. soela. However, this species is characterized by the triangular shaped peduncular article 5 of antenna 2 and the slender propodus of gnathopod 1. These species are illustrated and compared to related species.

A new Gammarus species (Crustacea, Amphipoda, Gammaridae) from Northwestern Islands, South Korea.

A new species, Gammarus baengnyeongensis sp. nov., belonging to the family Gammaridae Leach, 1814 was collected from the Baengnyeongdo and Daecheongdo islands in South Korea. This new species is characterized by the flagellum of antenna 2 with calceoli, and the length ratio of outer ramus to inner ramus of uropod 3. Descriptions of diagnostic characteristics of the species are provided in the text. We performed statistical analysis to confirm the significance of morphological differences of interspecies. Additionally, we compare the new species to related species by the partial sequence of the mitochondrial cytochrome c oxidase subunit 1 (CO1) gene. Genetic distances between the new species and closely related species rated from 29.1-40.8%, which highly supports Gammarus baengnyeongensis sp. nov. as a valid species. In this study, we add one new Gammarus species in Korean waters.

A new species of Monoliropus Mayer, 1903 (Crustacea, Amphipoda, Caprellidae) from Korean waters.

A new species of the genus Monoliropus belonging to the family Caprellidae was collected from the Yellow Sea, Korea. The new species differs from Monoliropusagilis Mayer, 1903, Monoliropuskazemii Momtazi & Sari, 2013, and Triprotellaamica Arimoto, 1970 as follows: 1) gnathopod 1 subrectangular; 2) pereonites 2-3 with acute triangular processes anterolaterally; 3) mandibular palp, apical article with four simple setae subdistally. The new species is fully illustrated and extensively compared with related species. This is the first record of the genus Monoliropus from Korean waters. A key to Monoliropus species is also given.

Arginine vasotocin (AVT) triggers courtship behavior without exposure to external stimuli and modulates the olfactory response of male Hynobius leechii salamanders.

To study the function of arginine vasotocin (AVT) in a specific courtship behavior (body undulation) in male Hynobius leechii, we injected various doses of AVT or an AVT V1a or V2 receptor antagonist into breeding and non-breeding males. After these injections, we placed the males alone or with breeding females in Petri dishes and measured the incidence and frequency of body undulation. Additionally, to test whether AVT modulates the olfactory response of males, we exposed breeding males that were injected with AVT to female odors and measured the same response. Both breeding and non-breeding males intraperitoneally injected with 50 or 100 µg of AVT exhibited body undulation. Additionally, breeding males intraperitoneally injected with 50 or 100 µg of AVT exhibited an increased frequency of body undulation when exposed to female odors. The intraperitoneal injection of 5, 25, or 50 µg of the AVT V1a or V2 receptor antagonist did not significantly decrease the incidence or frequency of body undulation of 100 µg AVT-injected breeding males. However, in a post-hoc experiment, the breeding males that were subcutaneously injected with 100 µg of the AVT V1a receptor antagonist exhibited a significant decrease in the frequency of body undulation, induced by exposure to females. Additionally, a central injection of 1 µg of AVT into the brain induced body undulation in breeding males. Our results show that AVT not only induces a specific courtship behavior in male H. leechii via AVT V1a receptors but also modulates the olfactory response.