Litozamia acares n. sp. and Siphonochelus (Trubatsa) wolffi n. sp. are described from New Caledonia. The radula and the operculum of Litozamia acares are illustrated and described. The classification of Litozamia in Trophoninae is maintained awaiting molecular data to either confirm or modify this decision. Litozamia longior (Verco, 1909) is reinstated as a valid species. The use of the subgenus Choreotyphis Iredale, 1936 is reinstated in Siphonochelus for a single species from eastern Australia, based on differences in shell morphology.
A review is made of the Recent members of the buccinid genus Lirabuccinum Vermeij, 1991, to which is added a new species from the Yellow Sea. Placement in the genus and the family Buccinidae is confirmed on the basis of radular and animal morphology. There is a discussion of shell structure, with reference to the independent development of internal and external spiral sculpture. Lectotype selections are made for Searlesia constricta Dall, 1918, Euthria hokkaidonis Pilsbry, 1901 and E. fuscolabiata E. A. Smith, 1875.
A new alycaeine species, Cipangocharax ananensis n. sp., is described based on specimens collected from calcareous areas in Anan City, Tokushima Prefecture, Japan. Among five Cipangocharax species, the new species closely resembles C.biexcisus and C. kiuchii. However, the new species is distinguished from these two species by having a relatively larger shell, a more expanded and broader aperture with its posterior part depressed by the slightly deflected outer lip margin, the parietal lip adherent to the body whorl, and a thick calcareous operculum with a small papilla. This discovery represents the third Cipangocharax species that is found only in Tokushima Prefecture.
A new vesicomyid species, Calyptogena (Abyssogena) mariana, is described from a depth of 5620 m in the Mariana Trench. It is close to C. (A.) kaikoi Okutani & Métivier, 1986 and C. (A.) southwardae Krylova, Sahling & Janssen, 2010 but separable from them in slight differences of cardinal configuration and also by means of molecular analyses.
We surveyed the land snail fauna of 13 localities including three limestone outcrops in Sabah, Borneo, Malaysia. Land snails were sampled using manual collection and identified to species level where possible. In this study, a total of 39 species was recorded. Species diversity in limestone areas was higher than that in non-calcareous areas. The genus Opisthostoma was found in all the 3 limestone outcrops. A random sample of about 20 shells of this genus from each site contained single but unique taxa among the three limestone outcrops. The three limestone outcrops were isolated by more than 20 km from one another. This result confirmed the high endemicity of this genus. At areas deforested and perturbed by humans, we found two invasive species, Bradybaena similaris (Rang, 1831) and Subulina octona (Bruguière, 1792), which have been widely spread over the world.
The habitats of Potamopyrgus antipodarum at four localities in the Kanto district (Shiobara, Chiba, Banyu Park and Yugawara) and at one location in the Kinki district (Hassaka) were investigated and the relationships between snail density and some environmental factors were analyzed. All field studies were undertaken during August and September in 2007 and 2010. The snails tended to be distributed in shallow water, which is consistent with the general features demonstrated in past studies, and in rather various velocity currents. They were distributed in high densities in a small creek entering Lake Biwa at Hassaka, but not at all in the coastal zone of Lake Biwa. At Shiobara and Yugawara, hot springs discharge into the rivers, but the mean water temperature in summer was less than 25°C, which is the upper limit for P. antipodarum reported in past studies, at all sites at both localities. Therefore, the hot spring discharges may make these areas rather suitable for P. antipodarum by increasing the water temperature from autumn to spring. At Chiba, P. antipodarum occurred in high densities in a creek in which the summer daytime water temperature reached 33.3°C. No clear relationship was determined between snail density and DO, pH, EC, NH4-N, PO4-P and Ca2+. P. antipodarum occurred at high densities in water with DO or Ca2+ concentration values close to the lowest limits reported in past studies. A laboratory experiment for the thermal tolerance of snails showed that all individuals from the Chiba population survived until the end of the experiment (21 days) at 31°C, but all but one snail from Kanro (near Hassaka) had died by the 14th day. The majority of the snails at Kanro were the same haplotype as those at Chiba and therefore may be the same clone. Therefore, it is likely that the high thermal tolerance of the Chiba population reflects their ability to acclimate, rather than a unique characteristic of the genotype of the Chiba population. Based on these results, the potential spread of P. antipodarum through Japan was discussed.
Population traits of two species of oysters, Saccostrea cucullata (= S. mordax) and Saccostrea kegaki were investigated every year from 1991 to 2011. The study site was located near the northern limit and around the center of the geographic ranges of S. cucullata and S. kegaki, respectively. The recruitments of these species fluctuated significantly year to year. The new recruits of S. cucullata often disappeared before joining into the older-year cohort, whereas those of S. kegaki constantly merged with the older-year cohort. The growth increment in shell length of S. cucullata was 5–10 mm / year up to 40 mm in shell length and that of S. kegaki was 5 mm / year up to 15 mm, and the growth of the both species slowed down subsequently. The age of S. cucullata of 60 mm in size and that of S. kegakiof 20 mm in size were estimated to be 15 and 4 years, respectively. The ratio of dead empty shells of these species in the field decreased in winter when the density of their predator, muricid gastropods, decreased. The ratio of empty shells with holes drilled by the muricids was 36% for S. cucullata and 30% for S. kegaki. Of these shells, the proportion of juveniles (<10 mm) was 83% in S. cucullata and 8% in S. kegaki. The survivorship curves suggested that the mortality of juveniles of S. cucullata was higher than that of S. kegaki. Mass mortality of S. cucullata occurred after a period of extremely low air temperature in January, 2011, during which the temperature was the lowest in the last 30 years. In contrast, the effect of this cold wave on S. kegaki was not serious. The decrease in air temperature was drastic compared to that in the water temperature, and the mortality of S. cucullata was higher at higher littoral levels, suggesting a more serious effect from air temperature than from water temperature. The population ecology of Saccostrea cucullata thus shows characteristics of a tropical species at the northern front of its range, in that the recruitment was inconsistent and the adults were vulnerable to episodic cold weather, compared to the temperate congeneric species S. kegaki.
The karyotypes of three lotic snails, Semisulcospira kurodai, S. habei and S. fluvialis were surveyed at 3 localities in Japan, including the type locality of respective species. The observed diploid chromosome number was as follows: Semisulcospira kurodai 36, S. habei 18, S. fluvialis 26. Chromosome numbers and karyotypes were different from one another. Their karyotypes were different from three lotic species reported previously.
Here, we examined the suitability of the largemouth bass, Micropterus salmoides; common freshwater goby, Rhinogobius spp. (Rhinogobius sp. OR); and tadpoles of the American bullfrog, Rana catesbeiana as hosts for glochidia of the freshwater unionid mussel Unio douglasiae nipponensis. The hosts, to which the glochidia were attached for 2 h (density of glochidia: 500–1000 individuals/L), were cultured in tanks (6 L, 28 ± 0.5°C) for 16 days. The glochidia and juveniles that became detached from the hosts were counted daily. The juveniles appeared for 7 to 15 days after the glochidia became attached to the goby. Therefore, Rhinogobius spp. was apparently a suitable host on which over 74% of the attached glochidia metamorphosed to juveniles. However, only dead glochidia were observed between the first and forth days for the largemouth bass, and neither glochidia nor juveniles were observed for the American bullfrog. These alien species were apparently unsuitable hosts for U. douglasiae nipponensis.
Breeding season of Anemina arcaeformis was studied in a small creek at Osato-cho, in Kumagaya City, Saitama Prefecture, Japan. In September, females began to incubate eggs in their outer gills. Glochidia hatched until the beginning of January, and then females discharged them from late January to April, mainly in March.