Atyopsis spinipes is a freshwater shrimp species found in streams and rivers on tropical and subtropical Pacific islands. Juveniles of A. spinipes are also found in temperate regions of Japan, but adults are not, suggesting that juveniles do not successfully overwinter there. The present study investigated the low temperature tolerance of A. spinipes juveniles as a basis for predicting the northern limits of the species' geographical range under global warming. Artificially raised juveniles were cultured in containers in which the temperature was adjusted to decrease from 20°C by 1°C every 48 h until all test juveniles had died. The survival rates of the juveniles largely declined below 16–17°C, and all died at around 12°C. The mean lethal temperature for juveniles was 14–15°C, which appears to be higher than winter temperatures in temperate regions and equivalent to those in the subtropical islands of Japan. A winter temperature of around 15°C may be the limit for successful overwintering by A. spinipes juveniles.
The mysids Siriella sp., Anchialina lobata, Heteromysis domusmaris and H. kaufersteinae sp. nov. were extracted from sponges sampled in shallow water at the coast of Lizard Island. The range of A. lobata is extended ≥5400 km along waterways from the coast of SW-Australia to the Coral Sea off NE-Australia. Heteromysis domusmaris is first recorded from nature; this species was previously known only from coral reef aquaria. Heteromysis kaufersteinae sp. nov. differs from closely related species of the subgenus Olivemysis by the basal segment of the antennular trunk being furnished with a mid-dorsal lobe bearing a blade-like spine (modified seta), in combination with an unsegmented antennal scale, the disto-mesial edge of eyestalks bearing a tooth-like projection, by the numbers of segments of the carpopropodus of thoracic endopods 5–8, and by the numbers of spines on modified male pleopods 3–4.
One and two specimens of Argulus japonicus Thiele, 1900 were collected from the body surface of big-scaled redfin Pseudaspius hakonensis (Günther, 1877) (Cypriniformes: Leuciscidae) in the Babame River, Akita Prefecture, and Lake Jusan, Aomori Prefecture, northern Honshu, Japan, respectively. This is two new prefecture records in Japan and a new host record for A. japonicus. Lake Jusan is the northernmost collection locality of this parasite in Japan recorded from wild fishes. As Lake Jusan is a brackish water lake and big-scaled redfin is known to migrate from fresh to salt waters, and since A. japonicus completes its life cycle in fresh waters, we infer that the two individuals of A. japonicus parasitized the big-scaled redfin in an inflowing river, then this fish was collected along with the surviving argulid individuals after migrating to the lake. The collection of A. japonicus in Lake Jusan represents the second record for the species from brackish water lakes in Japan.
