Four species of Chicomurex are discussed and illustrated. Two new species are described from the Philippines, with geographical distribution extending to New Caledonia for one. Chicomurex gloriosus (Shikama, 1977) is reinstated as a valid name and C. venustulus (Rehder & Wilson, 1975) is restricted to the Marquesas Islands. Seven species are listed from the Philippines.
Satsuma ferruginea (Pilsbry, 1900) has been known to display geographic variation in epiphallic flagellum morphology. Around the type locality of the species, i.e., Kagawa and Okayama Prefectures, rod-like and hook-like flagellum forms are recorded. Our field survey and molecular phylogenetic analysis showed that the two forms have parapatric distributions and likely have limited gene flow at the present. The hook-form populations correspond to S. ferruginea, and rod-form species is here described as S. akiratadai n. sp. The new species had likely been an endemic of the islands around the Bisan Straits, because the current distribution is limited to small islands and hilly terrain areas in the Okayama Plain that had been separate islands before an increase in sedimentation activity and land reclamation since the 6th Century. The new species occurs on forest floors in arid environments on small islands and hills in coastal areas, suggesting that the species likely diverged from S. ferruginea and adapted to the more arid climate that is common in the island areas of the Seto Inland Sea.
Vitrea politissima n. sp. is described from south-western Turkey (Isparta Vilayet, Uluborlu). Shell characters suggest that the new species is closely related to other species that have a large shell and wide umbilicus such as Vitrea ernesti, V. ephesina, V. klemmi and V. sossellai. Our analysis of biogeography in the genus based on literature indicates that rockassociated species are frequently confined to small areas, whereas relatively widely distributed species are not associated with habitats on or under rocks. This cannot be explained by limited availability of rock habitats in small areas and instead suggests that the distribution ranges of rock-associated species may be limited by their small dispersal rates relative to those of other congeneric species. This study demonstrates that advancements in systematics and in faunal and ecological surveys provide an opportunity to gain useful insights into the pattern and process of biogeography.
In order to determine the influence of environmental factors on the distribution patterns of sandy shore swash zone bivalves, especially Donax semigranosus, 59 sandy shore sites were examined along the Japan Sea coast of Honshu. In total, 664 individuals of 12 bivalve species were obtained using core samplers. Among them, D. semigranosus was the most dominant species (86.6%). Bivalves were sampled at 24 sites, and D. semigranosus was observed at 16 sites. Multivariate regression models were applied to explain the presence (or absence) of all bivalves, the number of bivalve species, the presence (or absence) of D. semigranosus, and the abundance of D. semigranosus. As explanatory variables, 13 environmental factors were used for the analyses. Minimizing AIC for each regression model enabled identification of the critical environmental factors. In the range of this study, effects of the length of the sandy shore and salinity were detected in all four models. Several additional factors were included in each model. Anthropogenic factors such as the presence of artificial shore protection and the resulting fragmentation of the sandy shore habitat were predicted to negatively affect the presence and diversity of the shore bivalves. Different sets of critical factors were detected for the presence/absence model and the abundance model for D. semigranosus. Considering that most of the reproductive individuals in the D. semigranosus population are one year old, critical assessment of the environmental factors relating to recruitment and subsequent survival processes are important for the stable existence of the population.
This is the first report on the left-right reversal arrangement of organs in Sinanodonta lauta glochidia. A glochidial larva possesses a pair of subtriangular-shaped shells, a pair of claw-like hooks with spines at the ventral margin, internal and external glochidial threads, four pairs of sensory hair tufts and one adductor muscle. The arrangement of the internal thread and the origin of the external thread is asymmetric between the pair of valves. As a result of examination of approximately 50 glochidia by light microscopy, one was observed with the internal thread and the origin of the external thread positioned on the left valve. These morphological features are positioned on the right valve in normal glochidia. The relative position of these threads between abnormal and normal glochidia represents a left-right reversal.
A rare terrestrial gastropod species, Japonia inouei, is newly recorded from Mie Prefecture, central Honshu, Japan. A living specimen was collected in Ogisu Valley, Suzuka City, in 2013. A brief morphological examination was carried out on this specimen, and compared with conspecific and allied species collected from adjacent areas. Five diagnostic characters were recognized in the present specimen: 1) two rows of petal-like periostracal hairs on the periphery of the body whorl, 2) blackish coloration of the head-foot, 3) a taenioglossate radula with relatively few cusps, 4) a grayish white penis with dully acute tip, 5) ball-like feces containing plant tissues in the intestine. Examination of additional specimens of J. inouei collected from the Kii Peninsula revealed that there is a considerable variation in the morphology of the petal-like periostracal hairs. Although the present specimen possesses distally expanding hairs with a smooth surface, most specimens from the Kii Peninsula possess similarly shaped hairs but with a striated surface. In addition, larger and more aged specimens from the Kii Peninsula tend to have narrower hairs, suggesting age-related change in their shape. However, a population from Kushimoto-cho comprises specimens of similar sizes with both wide and narrow hairs, and it is also probable that the difference may be ascribed to intraspecific variation. The present record represents a considerable north- and eastward range expansion of this species to Mie Prefecture. The lack of previous records in this area can be attributed to the fact that the morphology of the periostracal hairs is the only morphological character that distinguishes this species from its allies, and specimens possessing hairs in good condition are extremely rare, like the species itself. It is thus necessary to reconsider the distributions of this and allied species in the western part of Honshu, where more than two species are potentially distributed sympatrically, based on the careful examination of periostracal hairs.