Synchronous and Non-Synchronous Semelparity in Sibling Species of Pulmonates

Diverse life histories have been documented in terrestrial pulmonates, which inhabit different regions in climate. Life history traits are often phenotypically plastic and vary depending on the environment. Thus, surveys using designs that control for the confounding effects of environment are needed to evaluate the evolutionary differences between populations of closely related species in the wild. We examined the life histories of sibling species of terrestrial pulmonate within two regions of similar climates. Bradybaena pellucida (BP) is endemic to Japanese islands, and has recently been expanding its distribution northeastward, whereas B. similaris (BS) has been introduced by humans into temperate and tropical regions worldwide. We found that these species exhibit discrete differences in population dynamics and life cycle, despite their close relatedness. The annual life cycle of BP is synchronized among individuals in a population. Thus, BP is univoltine with discontinuous generation. In contrast, BS individuals do not synchronize their growth or reproduction, and thus exhibit overlapping generations. Our results indicate that synchronized and non-synchronized population dynamics diverge relatively rapidly in semelparous pulmonates. This type of difference has not been documented in pulmonate life history, and may have been overlooked because only a few studies have explicitly compared life cycles of closely related species within the same climate. Our results provide a basis for further studies of life history evolution in pulmonates.ArticleZOOLOGICAL SCIENCE. 32(4):372-377 (2015)journal articl

A new species of Gudeodiscus Páll-Gergely, 2013 from China, with extraordinary conchological and anatomical features (Gastropoda, Pulmonata, Plectopylidae)

A new species of the Plectopylidae, Gudeodiscus longiplica is described from northern Guangxi Province, southern China. The shell, anatomical and radular characters are figured and described. This new species is characterized by long plicae on its parietal shell wall, which have not been observed in any other Gudeodiscus species. In contrast, the long parietal plicae are characteristic for the genera Plectopylis and Chersaecia, which mainly inhabit Thailand and Myanmar. These two genera are, however, only distantly related to the new species, as other characters (anatomy, protoconch sculpture, parietal plicae) suggest. The male portion of the genital structure of the new species is characterized by two separate penial caeca with different lengths, but similar in outer and inner structure. The relevance of this anatomical character is discussed. Gudeodiscus longiplica sp. n. occurs sympatrically with Gudeodiscus soosi Páll-Gergely, 2013. The anatomy and radula characters of the latter species are also described and figured.ArticleZooKeys.564:1-19(2016)journal articl

Description of two new Ecuadorian Zilchistrophia Weyrauch, 1960, with the clarification of the systematic position of the genus based on anatomical data (Gastropoda, Stylommatophora, Scolodontidae)

Two new species of the genus Zilchistrophia Weyrauch, 1960 are described from Eastern Ecuadorian rain forest: Zilchistrophia hilaryae sp. n. and Z. shiwiarorum sp. n. These two new species extend the distribution of the genus considerably northwards, because congeners have been reported from Peru only. For the first time we present anatomical data (radula, buccal mass, morphology of the foot and the genital structure) of Zilchistrophia species. According to these, the genus belongs to the family Scolodontidae, subfamily Scolodontinae (=“Systrophiini”). The previously assumed systematic relationship of Zilchistrophia with the Asian Corillidae and Plectopylidae based on the similarly looking palatal plicae is not supported.ArticleZooKeys.453:1-17(2014)journal articl

A new Chinese species of Eostrobilops Pilsbry, 1927 with a checklist of Eostrobilops and Enteroplax Gude, 1897 species (Gastropoda, Pulmonata, Strobilopsidae)

Eostrobilops humicolus Páll-Gergely & Hunyadi, sp. n. is described from Guangxi Province, China. It is characterized by the combination of a small shell (diameter: 2.3–2.4 mm), strongly ribbed dorsal surface, an infraparietal lamella not reaching the callus, and long basal folds. The new species is found approximately 500 and 800 km from the two nearest species E. infrequens (northern Vietnam), and E. diodontina (Hunan, China), respectively. A checklist of extant Eostrobilops Pilsbry, 1927 and Enteroplax Gude, 1899 species is provided. Enteroplax yaeyamensis Habe & Chinen, 1974, Enteroplax kanjiokuboi Minato & Tada, 1992 and Enteroplax taiwanica Minato & Tada, 1992 are moved to the genus Eostrobilops because of the lack of an elevated parietal callus and a peripheral thread. A map showing all Eostrobilops records is provided.ArticleZOOKEYS. (508):85-95 (2015)journal articl

Chiral Speciation in Terrestrial Pulmonate Snails

On the basis of data in the literature, the percentages of dextral versus sinistral species of snails have been calculated for western Europe, Turkey, North America (north of Mexico), and Japan. When the family of Clausiliidae is represented, about a quarter of all snail species may be sinistral, whereas less than one per cent of the species may be sinistral where that family does not occur. The number of single-gene speciation events on the basis of chirality, resulting in the origin of mirror image species, is not closely linked to the percentage of sinistral versus dextral species in a particular region. Turkey is nevertheless exceptional by both a high percentage of sinistral species and a high number of speciation events resulting in mirror image species. Shell morphology and genetic background may influence the ease of chirality-linked speciation, whereas sinistrality may additionally be selected against by internal selection. For the Clausiliidae, the fossil record and the recent fauna suggest that successful reversals in coiling direction occurred with a frequency of once every three to four million years

Fitness Consequences of Reciprocally Asymmetric Hybridization Between Simultaneous Hermaphrodites

Depending on fitness consequences, hybridization may rescue inbred populations; generate premating barriers, reproductive interference, or hybrid species; or extinguish a species. However, the fitness of hybrids is unpredictable without direct quantification of their performance in fitness components across multiple generations. The land snails Bradybaena pellucida and B. similaris, which are indigenous and non-indigenous in Japan, respectively, copulate with each other simultaneously and reciprocally. However, only B. pellucida produces hybrids, because it ends mating by removing the penis before transferring a spermatophore, while B. similaris inseminates B. pellucida. To evaluate the strength of an intrinsic postzygotic barrier against the hybrids produced by B. pellucida, we conducted breeding experiments in the laboratory and measured six life-history traits: (1) growth rate, (2) body weight at maturity, (3) number of days to first oviposition after being permitted to mate, (4) clutch size, (5) fecundity, and (6) hatchability. We also calculated the relative intrinsic fitness based on five of these trait values (excluding clutch size). F(1) hybrids exhibited heterosis in growth rate, body weight at maturity and relative intrinsic fitness. F(2) hybrids also showed heterosis in body weight at maturity. Nevertheless, the F(2) hybrids produced significantly fewer progeny than the mid-point value of the parental species. Thus, the F(2) hybrids exhibited weak out-breeding depression in reproduction, offsetting their vigor in body size. These results indicate that only a weak postzygotic barrier, contrasting with strong F(1) heterosis, has evolved during genetic divergence of the two sibling species in allopatry.ArticleZOOLOGICAL SCIENCE. 26(3):191-196 (2009)journal articl

The family Plectopylidae (Gastropoda, Pulmonata) in Laos with the description of two new genera and a new species

Previously only a single plectopylid species, Helix laomontana L. Pfeiffer, 1862 was reported from Laos. Here we erect Naggsia Páll-Gergely & Muratov, gen. n. for H. laomontana based on the description of its reproductive anatomy and radula. Another species, Hunyadiscus saurini Páll-Gergely, gen. & sp. n. is described from Northern Laos based on conchological data. Helix (Plectopylis) andersoni Blanford, 1869, which is known from the Burmese-Chinese border region, is also classified within Hunyadiscus Páll-Gergely, gen. n. A third species, Gudeodiscus (Gudeodiscus) messageri raheemi Páll-Gergely & Hunyadi, 2015 is reported from Laos for the first time. The new localities represent the westernmost sites of the genus Gudeodiscus. The reproductive anatomy of the latter species is described.ArticleZooKeys.592:1-26(2016)journal articl

Left–Right Reversal Recurrently Evolved Regardless of Diaphanous-Related Formin Gene Duplication or Loss in Snails

Bilateria exhibit whole-body handedness in internal structure. This left–right polarity is evolutionarily conserved with virtually no reversed extant lineage, except in molluscan Gastropoda. Phylogenetically independent snail groups contain both clockwise-coiled (dextral) and counterclockwise-coiled (sinistral) taxa that are reversed from each other in bilateral handedness as well as in coiling direction. Within freshwater Hygrophila, Lymnaea with derived dextrality have diaphanous related formin (diaph) gene duplicates, while basal sinistral groups possess one diaph gene. In terrestrial Stylommatophora, dextral Bradybaena also have diaph duplicates. Defective maternal expression of one of those duplicates gives rise to sinistral hatchlings in Lymnaea and handedness-mixed broods in Bradybaena, through polarity change in spiral cleavage of embryos. These findings led to the hypothesis that diaph duplication was crucial for the evolution of dextrality by reversal. The present study discovered that diaph duplication independently occurred four times and its duplicate became lost twice in gastropods. The dextrality of Bradybaena represents the ancestral handedness conserved across gastropods, unlike the derived dextrality of Lymnaea. Sinistral lineages recurrently evolved by reversal regardless of whether diaph had been duplicated. Amongst the seven formin gene subfamilies, diaph has most thoroughly been conserved across eukaryotes of the 14 metazoan phyla and choanoflagellate. Severe embryonic mortalities resulting from insufficient expression of the duplicate in both of Bradybaena and Lymnaea also support that diaph duplicates bare general roles for cytoskeletal dynamics other than controlling spiralian handedness. Our study rules out the possibility that diaph duplication or loss played a primary role for reversal evolution.journal articl

Seven new hypselostomatid species from China, including some of the world's smallest land snails (Gastropoda, Pulmonata, Orthurethra)

Seven new species of Hypselostomatidae are described from the Chinese province Guangxi: Angustopila dominikae Páll-Gergely & Hunyadi, sp. n., A. fabella Páll-Gergely & Hunyadi, sp. n., A. subelevata Páll-Gergely & Hunyadi, sp. n., A. szekeresi Páll-Gergely & Hunyadi, sp. n., Hypselostoma socialis Páll-Gergely & Hunyadi, sp. n., H. lacrima Páll-Gergely & Hunyadi, sp. n. and Krobylos sinensis Páll-Gergely & Hunyadi, sp. n. The latter species is reported from three localities. All other new species are known only from the type locality. Specimens nearly identical to the type specimens of Angustopila huoyani Jochum, Slapnik & Páll-Gergely, 2014 were found in a cave in northern Guangxi, 500 km from the type locality. Adult individuals of Angustopila subelevata sp. n. (shell height = 0.83–0.91 mm, mean = 0.87 mm) and A. dominikae sp. n. (shell height of the holotype = 0.86 mm) represent the smallest known members of the Hypselostomatidae, and thus are amongst the smallest land snails ever reported. We note that Pyramidula laosensis Saurin, 1953 might also belong to Krobylos. Paraboysidia neglecta van Benthem Jutting, 1961, which was previously included in Angustopila, is classified in Hypselostoma.ArticleZOOKEYS. (523):31-62 (2015)journal articl