Last Whorl Research Articles

Shell morphology and reproductive anatomy of Levantina mardinensis (Gastropoda, Helicidae) from a new locality of Mardin, Türkiye

ABSTRACT The genus Levantina Kobelt, 1871, comprises 25 taxa inhabiting rocky environments across the Middle East. This study focuses on documenting a new location of L. mardinensis Kobelt, 1900, and provides a detailed analysis of its shell morphology and reproductive anatomy, contributing to the knowledge and conservation of this land snail from Mardin, southeastern Türkiye. The distribution of L. mardinensis is widespread in Mardin Province and extends into northern Syria and Iraq. The study provides measurements for previously unreported shell characteristics of specimens from Eskikale (Mardin), including aperture height, aperture width, spire height, and body whorl height, with high-resolution images for visual reference.

A new species of Lysinoe (Gastropoda: Helicoidea) from the Oligocene of Mexico

In her 1945 study on the Tertiary fossil mollusks of northeastern Mexico, Gardner listed only 2 taxa of land snails: Holospira eva Gardner, 1945 and “Helix” sp. The latter is recognized here as a new species of Lysinoe Adams & Adams, 1855 (Helicoidea, Xanthonychidae). The new species can be diagnosed from its congeners by its flattened shell profile, a lower body whorl with a faint angulation on its median portion, a ridge-like angulation around the umbilicus, and a likely wide umbilicus. The species is known to occur in 2 nearby Upper Middle Oligocene outcrops in the eastern part of the state of Nuevo León.

A New Fossil Species of Indolithes gen. nov. from Java, Indonesia (Gastropoda: Fasciolariidae)

A new, moderately large shell of a fossil species from the family Fasciolariidae Gray, 1853 is described from the Middle Miocene at Bengbreng Hill, West Java, Indonesia. The shell of this new species is related to species of the genus Clavilithes Swainson, 1840. The characteristics of a globular body whorl, low spire, and moderately long siphonal canal, distinguish it from species of the genus Clavilithes which have a fusiform shape, high spire, and usually long siphonal canal. Thisleads to its placement in a new genus Indolithes gen. nov. The new fossil species is comparedwithtwo other fossil species of Fasciolariidae from Java, Clavilithes fennemai (K. Martin, 1906) andC. verbeeki (K. Martin, 1895).

Allometry and condition factor of Faunus ater (Cerithioidea: Pachychilidae) from An Estuarine Habitat of Kerala, Southern India

Faunus ater is a pachychilid gastropod known to inhabit brackish water habi-tats of Western Indo-Pacific countries. This study aimed to analyse the mor-phometric relationships and condition factor of F. ater collected from the Eda-va-Nadayara brackish water lake of Kerala, India. Hydrographic parameters of sampling stations were recorded. A total of 1,522 specimens were collected every month from March 2019 to February 2020. The mean values recorded for total length, shell width, body whorl length, opercular length, opercular width, and total weight were 45.38±13.44 mm, 14.47±3.88 mm, 20.81±5.83 mm, 7.71±3.08 mm, 4.62±1.62 mm, and 6.97±3.72 g, respectively. The length-weight relation was obtained as Log W= -1.005+2.871 Log L. The b value (<3) indicated a negative allometric growth of the organism. Regression analysis of other morphometric measurements also showed a positive correla-tion (P<0.001). The analysis of Fulton’s condition factor indicated a state of well-being of F. ater in this habitat, with condition factors ranging from 5.87 to 6.99 spatially and 5.48 to 7.00 temporally. This study provides the first detailed investigation of morphometric relationships and condition factors in F. ater.

Two new enid land snails from Jiuzhaigou County, Sichuan Province, China (Gastropoda: Stylommatophora: Enidae)

AbstractTwo new land snail species of the family Enidae, Serina xirong Chen, Dai, Wu & Ouyang sp. n. and Turanena jiuzhaigouensis Chen, Dai, Wu & Ouyang sp. n., are described from Jiuzhaigou County, Sichuan Province, China based on conchological morphology. Serina xirong can be distinguished from congeneric species by its ribbed teleoconch, and Turanena jiuzhaigouensis can be distinguished from congeneric species by its micro, conic, weakly keeled shell without color stripes before body whorl. This discovery further enhances our understanding of the enid species diversity in Sichuan Province.

Differentiation of Bulinussenegalensis and Bulinusforskalii Snails in West Africa Using Morphometric Analysis

PurposeAccurate identification of medically important intermediate host and vector species is crucial for understanding disease transmission and control. Identifying Bulinus snails which act as intermediate host species for the transmission of schistosomiasis is typically undertaken using conchological and genital morphology as well as molecular methods.MethodsHere, a landmark-based morphometric analysis of shell morphology was undertaken to determine its utility to distinguish the closely related and morphologically similar sister species Bulinus senegalensis and Bulinus forskalii. The method was developed to increase the accuracy of conchological morphology methods to identify Bulinus species in the field. Both species are found in West Africa, but only B. senegalensis is implicated in the transmission of urogenital schistosomiasis.ResultsWe found when scaled down to the same length, 3-whorl and 4-whorl (juvenile) B. senegalensis shells had a longer spire, narrower body whorl and shorter aperture than B. forskalii. In contrast, 5-whorl (adult) B. senegalensis had a shorter spire, but still had a shorter aperture and narrower body whorl than B. forskalii. Canonical Variate Analysis (CVA) showed minimal overlap between B. senegalensis and B. forskalii for 3-whorl and 4-whorl shells, with a clear separation for 5-whorl shells. Overall, B. senegalensis had a consistently shorter aperture size and narrower body whorl than B. forskalii for all development stages. Spire length was variable depending on the stage of development, with 3-whorl and 4-whorl shells having the opposite trends of adult shells.ConclusionsOur study demonstrates the applicability of landmark-based morphometrics in distinguishing the medically important, Bulinus senegalensis from its morphologically similar sister species, Bulinus forskalii. We recommend using measurements based on spire length, penultimate whorl length, body whorl width and aperture size to differentiate B. senegalensis and B. forskalii, when used with the appropriate information for each shell’s development stage.

Morphological Trait Correlations, Gonadal Development Characteristics and Pleopod Nutrient Compositions of the Whelk Volutharpa perryi perryi

The aim of this study was to clarify the “morphological-trait–body weight” correlation, gonadal development characteristics, and pleopod (main edible part) nutrient composition of the whelk (Volutharpa perryi perryi). Live body mass (BM), soft tissue mass (STM), and eight other morphological traits of the whelk were measured, and path coefficients, correlation indices (R2), and coefficients of determination were then calculated. Gonadal development characteristics were investigated by histological observation. Pleopod nutrient composition was analyzed by standard biochemical assays. The results indicated that (1) shell aperture width (SAW) and body whorl height (BWH) were positively correlated with both live BM and STM (p < 0.01), and shell height (SH) was positively correlated with both live BM and STM (p < 0.01) in male whelks; (2) similar gonadal development characteristics were observed in both female and male whelks; and (3) pleopod nutrient composition was consistent in both female and male whelks, whereas sex-specific variation in pleopod nutrient content was observed in the whelks. The observations in this study will provide theoretical support for the development of the whelk aquaculture industry.

Rediscovery and systematics of the enigmatic genus Helicostoa reveals a new species of sessile freshwater snail with remarkable sexual dimorphism.

Helicostoa sinensis E. Lamy, 1926 is a unique freshwater gastropod species with a sessile habit. This enigmatic species was first found cemented on river limestones from China about 120 years ago and described together with the genus. It was never collected again and has been considered monotypic. Here, we report the rediscovery of Helicostoa from several rivers in China, and describe a second species of this genus based on a comprehensive study. In addition to the unique sessile habit of both species, the new Helicostoa species presents one of the most remarkable cases of sexual dimorphism within molluscs. Only the adult female is sessile and the original aperture of the female is sealed by shell matter or rock, while an opening on the body whorl takes the function of the original aperture. The male is vagile, with a normal aperture. Our results confirm the recently suggested placement of Helicostoa within the family Bithyniidae. The sessility of Helicostoa species is considered as an adaption to the limestone habitat in large rivers. The extreme sexual dimorphism and secondary aperture of females are considered as adaptations to overcome the obstacles for mating and feeding that come with a sessile life style.

The “Bothropoma” species in the Red Sea

The use of the genus Bothropoma for Red Sea colloniid species is incorrect. Of the four presumptive Red Sea species one of them usually indicated as Bothropoma bellula (H. Adams, 1873) is not a Colloniinae but probably belongs to the subfamily Liotopomatinae and is here considered a junior synonym of Depressipoma (?) pentegoniostoma (Carpenter, 1856). The shells of the other species are to be attributed to the genus Neocollonia and are very variable, but in general they can be distinguished on the basis of the development of three major spiral cords of the body whorl: Neocollonia pilula (Dunker, 1860) has a rounded profile without any protruding spiral cord and Neocollonia isseli (Thiele, 1924) has a rounded/angulated shell mainly with first spiral cord here termed number 1 protruding. These two Neocollonia may even be extreme morphs of the same species, but only molecular investigation will allow testing this hypothesis. Neocollonia munda (H. Adams, 1873) has a slightly flattened body whorl with similarly prominent spiral cords here named number 2 and 3. I consider the recently described species Neocollonia diversicolor, N. splendida and N. kantori (all Poppe Tagaro & Huang, 2023) within the intraspecific variation of N. pilula and thus junior synonyms.

A new species of Coccoglypta Pilsbry, 1895 from China (Gastropoda, Camaenidae)

ABSTRACT A new camaenid land snail species: Coccoglypta limenghuai Chen, Xie, Dai & Wu, n. sp. is described from Yaan City, Sichuan Province, China based on morphology and phylogenetic analysis. Coccoglypta ellenstrongae Thach & Huber, 2021 is treated as a junior synonym of Acusta toyenmongaiensis Rolle, 1911. Coccoglypta limenghuai is morphologically different from the congeneric species by the depressed conical shell, strongly keeled and almost flat whorls and a shallow groove-like depression below the keel of the body whorl. The habitat of the species has been severely damaged and it survives only within an area of a few hundred square metres. Further attention and protection should be given to it in the future. urn:lsid:zoobank.org:pub:DC52A2B4-096C-4CC8-B986-29C789696F3C.

A Review of Neodilatilabrum Dekkers, 2008 (Mollusca: Neostromboidae: Strombidae) Resulting in a New Species from Japan

The genus Neodilatilabrum contains taxa that are both morphologically stable across their ranges, while others are highly plastic, making the choice of discerning characteristics critical to achieving taxonomic stability. A new species of Neodilatilabrum from Japan is presented here. Neodilatilabrum tasminae n. sp. lacks the axial shoulder rib on the body whorl found in N. robustum and N. sowerbyorum. The angulate shoulders of N. succinctum differentiate that taxon from N. tasminae. Neodilatilabrum simanoki is placed within the synonymy of N. sowerbyorum, and N. boucheti is placed under the synonymy of N. robustum. This revision provides the basis from which more detailed studies into the complex variability of species, both locally and across their ranges, to be undertaken.

A new species of Anauchen Pilsbry, 1917 from Guangxi, China (Gastropoda: Stylommatophora: Hypselostomatidae)

Anauchen whitteni sp. nov. is described and illustrated based on specimens collected in Guangxi Zhuang Autonomous Region, southwestern China. The new species is diagnosed by havinh four apertural barriers and a rounded body whorl.

Fusceulimoides kohtsukai gen. et sp. nov., a Minute Eulimid Gastropod Parasitic on the Little Brittle Star Ophiactis savignyi in Central Japan.

Gastropods of over a dozen genera in the family Eulimidae have been identified as parasites of brittle stars, and many more remain to be discovered and described for a comprehensive understanding of the evolutionary history of their host-parasite relationships. In this study, we describe Fusceulimoides kohtsukai gen. et sp. nov., parasitic on the little brittle star, Ophiactis savignyi (Ophiactidae), in Kanagawa, central Japan. The new genus is distinguished from other eulimid genera by the combination of following seven conchological characters: (1) a very small size of up to 1.7 mm high, (2) a colorless translucent appearance, (3) a conical pupiform shape with a paucispiral protoconch, (4) slightly convex teleoconch whorls, (5) a remarkably large body whorl occupying 65-70% of the total shell height, (6) a broad, somewhat squarish and laterally expanded aperture with a strongly curved outer lip, and (7) a developed parietal callus without an indentation or depression in the umbilical area. A multi-locus molecular phylogeny revealed its distant relationship to Hemiliostraca + Pyramidelloides, a previously known clade of ophiuroid parasites, thereby suggesting multiple origins of this host-parasite association in Eulimidae.

Sexual dimorphism in shell shape: is Pomacea canaliculata an exception or an example among Neotropical apple snails?

Sexual dimorphism has often been recorded in apple snails (Caenogastropoda Ampullariidae), but reports are concentrated in a few species, either invasive or with biocontrol potential, which sugests some taxonomic bias. To find out evolutionary and ecological correlates of sexual dimorphism it is necessary to detect and quantify it but also is important to detect its absence. Our aims were to confirm or not the existence of sexual dimorphism in shell shape of Felipponea neritiniformis and Asolene platae, using Pomacea canaliculata as reference and applying the same methodology (landmark-based geometric morphometrics) and statistical power. Significant intersexual differences were only found in P. canaliculata and, in a lesser degree, in F. neritiniformis: males have larger apertures relative to body whorl and more rounded apertural outer edges than females. Female shells are larger in F. neritiniformis and P. canaliculata, but not in A. platae. Using comparable methodologies and statistical power, sexual dimorphism in shell shape is detectable in some apple snails but not in others. Interspecific variation in sexual dimorphism in the Ampullariidae is not only due to taxonomic bias and deserves more research to establish the main patterns and possible causes.

A new volute, Ericusa ngayawang sp. nov. (Gastropoda: Volutidae), from the Miocene of South Australia.

Ericusa ngayawang sp. nov. is described from shells preserved in the Middle Miocene Cadell Formation in the western Murray Basin of South Australia. At the time the Murray Basin was part of the Southeastern Australian Marine Biogeographic Province. Ericusa ngayawang is a small heavily costate species of Ericusa with clear affinities to the Early Miocene E. atkinsoni of Victoria and Tasmania but can be distinguished from it by its smaller size, more slender proportions and its heavily costate body whorl. Ericusa atkinsoni and its relative, E. macroptera, inhabited the basins to the east of the Murray Basin during the Late Oligocene and Early Miocene but were extinct there before the end of the Burdigalian Stage of the Early Miocene. The persistence of E. ngayawang into the Langhian Stage of the Middle Miocene is another piece of evidence for partial biogeographic isolation of the western Murray Basin from the rest of the Southeastern Australian Province during the Miocene.

Occurrence and Preservation of Gastropod Shells in Recent Riverine and Estuarine Sediments of Chennai, SE-India

Objectives: The distribution of aquatic gastropod shells was investigated in riverine and coastal sediments of Chennai, India. Next to taxonomic identification, the shell preservation was characterized and quantified with a taphonomic grade. Methods: Sediments of the Adyar and Cooum rivers as well as of coastal backwaters of the metropolitan area were taken down to a maximum depth of 81 cm using a handheld geoslicer and inspected by optical and electron microscopy. Taphonomic features (i.e. exfoliation, external luster, cracking, fragmentation, edge preservation, bioerosion, encrustation) reflecting different destructive post-mortem processes were observed, individually ranked and averaged in a composite taphonomic grade for each specimen. Results: Shells and shell fragments of various families occur with markedly different abundances between 63.7 and < 1% (in decreasing order Potamididae, Bithyniidae, Stenothyridae, Planorbidae, Thiaridae, Bullinidae, Nassariidae, Neritidae, Paludomidae). Their distribution invokes salinity as a major factor controlling occurrence in a habitat. The lack of larger and globose shells in freshwater river sediments may reflect the preference of stagnant water habitats and limited preservation in sedimentary transport. The predominance of Pirenella cingulata among the shells found in sediments of brackish environments probably reflects mechanical robustness and its extreme abundance in tidal flats. Due to post-mortem destruction most shells are incomplete. Roughly 25% of all specimens are almost complete shells not only showing spire and body whorl but at least in part also apex and/or aperture and outer lip. More than 50% represent spires or combinations of apex and spire. Composite taphonomic grades for gastropod families show a large range and reach high values. The lowest grades, indicative of best preservation, are observed for Stenothyra blanfordiana and Bithynia sp. Novelty: The distribution of gastropods in riverine and coastal environments represents a valuable ecosystem characteristic. Shell preservation shown here for sediments of Chennai is the basis for retrospective environmental characterization. Keywords: Gastropods; shells; river sediments; taphonomy; Chennai

Evidence for Carbonate System Mediated Shape Shift in an Intertidal Predatory Gastropod

Phenotypic plasticity represents an important first-line organism response to newly introduced or changing environmental constraints. Knowledge about structural responses to environmental stressors could thus be an essential measure to predict species and ecosystem responses to a world in change. In this study, we combined morphometric analyses with environmental modelling to identify direct shape responses of the predatory gastropod Nucella lapillus to large-scale variability in sea surface temperature and the carbonate system. Our models suggest that the state of the carbonate system and, more specifically, the substrate inhibitor ratio ([HCO3−][H+]−1) (SIR) has a dominant effect on the shell shape of this intertidal muricid. Populations in regions with a lower SIR tend to form narrower shells with a higher spire to body whorl ratio, whereas populations in areas with a higher SIR form wider shells with a much lower spire to body whorl ratio. These results indicate that a widespread phenotypic response of N. lapillus to continuing ocean acidification can be expected, potentially altering the phenotypic response pattern to predator or wave exposure regimes with profound implications for North Atlantic rocky shore communities.

The first record of the family Parvaplustridae (Gastropoda, Heterobranchia) from hydrothermal vent fields of the Piip Volcano, Bering Sea with the description of a new species of the genus Parvaplustrum

A new species, Parvaplustrum wareni sp. nov. (Parvaplustridae), collected in the area of the submarine Piip Volcano, the northwestern Bering Sea, at depths of 400–472 m, has been described on materials obtained during the research cruises #75 and #82 aboard the R/V Akademik M.A. Lavrentiev. This is the first record of the family in the Bering Sea. Parvaplustrum wareni sp. nov. is found around hydrothermal vents, where it forms aggregations with population densities of up to 6000–31 000 ind./m2. Parvaplustrum wareni sp. nov. differs from the other species of the genus by its globose shell, jaw morphology, and by the absence of spiral sculpture on the body whorl. In addition to the morphology, molecular data on mitochondrial (cytochrome c oxidase subunit I and 16S rRNA) and nuclear (histone H3 and 28S rRNA) markers were used. We assume that P. wareni sp. nov. feeds on bacterial mats, scooping them up with its petaliform radular teeth. The presence of bacteria-like filaments on gill lamellae suggests the possibility of an epibiotic association which needs further study. In addition to the Bering Sea, the range of this new species covers also the Hydrate Ridge, off Oregon (northeastern Pacific), where specimens were previously identified as P. cadieni.

A revision of Doxanderina Dekkers and Maxwell, 2020 (Gastropoda: Neostromboidae: Strombidae): The extant Doxander Wenz, 1940 and a new species from Queensland

In this study, the extant Doxanderina species are addressed. Species contained within Doxander are examined based on type material, and a new species from Queensland is recognised. Comparisons are made based on morphology. This revision recognises six species in the Doxander complex: D. campbellii, D. entropi, D. japonicus, D. queenslandicus nov. sp, D. operosus, and D. vittatus. Doxander queenslandicus is most similar to D. vittatus from Indonesia, but differs in the body whorl being more dorso-laterally compressed, having a terminal point of the anterior canal which does not extend past the outer lip as in D. vittatus, and the presence of a dorsal knob on the shoulder of D. queenslandicus.

Studies in Canarium urceus (Linnaeus, 1758) Part 6: A new Canarium species from the Andaman Sea (Gastropoda: Strombidae) and discussion on related species

This part of the Canarium (Canarium) urceus-complex (Linnaeus, 1758) review after Abbott’s revision (Abbott, 1960) revision examines material from the Andaman Sea. At present, material from that region has been synonymised under the name Canarium (Canarium) urceus (Linnaeus, 1758). Canarium (Canarium) andamanense new species is known from the Andamanian Subprovince, a semi enclosed basin that is centered on the Andaman Sea and enclosed by the west coasts of Myanmar and Thailand and the Mergui Archipelago in the east, to the northern Malacca Strait in the south, and to the Andaman and Nicobar Islands in the west. This species is recognized and differentiated by solid, sturdy shells with a triangular body whorl, large knobs on the shoulder and bright orange aperture. This study further confirms that there is a high degree of bioregionalisation within the Canarium complex.