Journal of Threatened
Taxa | www.threatenedtaxa.org | 26 June 2026 | 18(6): 29120–29126
ISSN 0974-7907 (Online) | ISSN 0974-7893 (Print)
https://doi.org/10.11609/jott.10328.18.6.29120-29126
#10328 | Received 23 December 2025 | Final received 25 March 2026|
Finally accepted 18 May 2026
An evasive naticid surfaces in
India: first confirmed report of Gennaeosinum
perobliquum (Dautzenberg
& Fischer, 1907) (Gastropoda: Naticidae)
Aparna Mishra 1, Sanjaya
Dalai 2, Roberto Ardovini 3, N.V.
Subba Rao 4 &
Dipti Raut 5
1,2,5 Centre of Excellence in
Environment and Public Health, Environmental Science Laboratory, Department of
Zoology, Ravenshaw University, Cuttack, Odisha 753003, India.
3 Department of Information
Technology, ITIS FERMI ROMA Technical Institute, Rome 00135, Italy.
4 Molluscan Section, Zoological
Survey of India, New Alipore, Kolkata, West Bengal 700053, India.
1 aparnamishra839@gmail.com, 2
s.dalai1996@gmail.com, 3 roberto_ardovini@fastwebnet.it, 4
subbarao_nalluri@hotmail.com, 5 diptiraut@ravenshawuniversity.ac.in
(corresponding author)
Editor: Han Raven, Naturalis Biodiversity Center,
Leiden, Netherlands. Date of publication: 26 June 2026
(online & print)
Citation:
Mishra, A., S. Dalai, R. Ardovini, N.V.S. Rao &
D. Raut (2026). An evasive naticid surfaces in India: first confirmed report of Gennaeosinum perobliquum (Dautzenberg & Fischer, 1907) (Gastropoda:
Naticidae). Journal of Threatened Taxa 18(6): 29120–29126. https://doi.org/10.11609/jott.10328.18.6.29120-29126
Copyright: © Mishra et al. 2026. Creative Commons Attribution 4.0 International License.
JoTT allows unrestricted use, reproduction, and
distribution of this article in any medium by providing adequate credit to the
author(s) and the source of publication.
Funding: The first author AM acknowledges the financial research support provided by the Council of Scientific &
Industrial
Research, New Delhi, India (File no. 09/1036(24086)/2025EMR-1 dated 13/10/2025).
Competing interests: The authors declare no competing interests.
Author details: Aparna Mishra: a Ph.D research scholar with research interest in benthic ecology and focus on molluscan taxonomy. Sanjaya Dalai: a Ph.D research scholar with research interest in benthic ecology and focus on molluscan taxonomy. Roberto Ardovini: professor at ITIS Fermi Roma
(Technical Institute of Information Technology, Rome), specializing in malacology and conchology, with a focus on the taxonomy and description of marine gastropods and bivalves. His work includes descriptions of new species and contributions to global shell inventories. N.V. Subba Rao: scientist and Former Head of the Molluscan Section, Zoological Survey of India. Expertise in the taxonomy, systematics, and faunal documentation of Indian molluscs across marine, freshwater, and terrestrial habitats. Landmark works are foundational reference material for Indian malacology. Dipti Raut: professor of Zoology at Ravenshaw University, Cuttack, Odisha, India. Research focuses on macrobenthic Community ecology. Work integrates environmental monitoring with Marine biodiversity documentation.
Author contribution: Conceptualization: Dipti Raut, N. V. Subba Rao; Methodology: Dipti Raut, Aparna Mishra, Sanjaya Dalai; Data Collection: Sanjaya Dalai, Aparna Mishra, Roberto Ardovini; Data Analysis: Aparna Mishra, Sanjaya Dalai, Roberto Ardovini; Writing Original Draft: Aparna Mishra, Sanjaya Dalai; Writing Review and Editing: Dipti Raut, N. V. Subba Rao, Roberto Ardovini; Supervision: Dipti Raut
Acknowledgments: The first author AM acknowledging the financial research support provided by the Council of Scientific & Industrial Research, New
Delhi, India (File no. 09/1036(24086)/2025EMR-1 dated 13/10/2025). The authors are thankful to the Department of Zoology, Ravenshaw University, Cuttack, Odisha, India, for the laboratory facilities. The anonymous reviewers’ comments greatly improved the manuscript.
Abstract: This study provides the first
record of the naticid species Gennaeosinum perobliquum in Indian waters. Previously documented from Vietnam,
Indonesia, and South Africa, G. perobliquum
was collected during a benthic survey, from the intertidal zone of Chandipur, Balasore, Odisha, on
the eastern coast of India. A clear
description of the shell morphology is provided, along with detailed
morphometric and imaging analyses. By comparing G. perobliquum
with related naticid species found in India, this work aims to refine taxonomic
understanding and contribute to knowledge of naticid biodiversity in the
region. This newly documented record not only expands the known geographic
distribution of G. perobliquum but also
underscores the importance of continued benthic faunal surveys for further
exploration of molluscan biodiversity in the Bay of Bengal and adjacent
regions.
Keywords: Bay of Bengal, benthos, Chandipur, first record, geographic distribution, Indian
waters, intertidal, mollusc biodiversity, moon
shells, Odisha.
Abbreviation: TSL—Total Shell Length | WB—Width
of the last whorl | HB—Height of the last whorl | SL—Spire Length |
CL—Columella Length | UL—Length of the Umbilical callus | (AW)a—Aperture
Width towards anterior side | (AW)b—Aperture Width towards posterior
side | dd—Dead specimen | RZEVB—Ravenshaw University
Zoology Environmental Science Budhabalanga Estuary |
ZSI M—Zoological Survey of India Mollusca.
Introduction
Members of the cosmopolitan
family Naticidae within the phylum Mollusca and class
Gastropoda inhabit a wide range of environments, from
intertidal to the deep sea. Commonly called moon shells, these oval-shaped
predatory gastropods are known for their distinctive drilling behavior, which
they use to prey on various bivalves and gastropods. They typically dwell in sandy and muddy
substrates, where they remain hidden (Huelsken et al.
2008). The Naticidae family includes four
subfamilies, 38 genera, and about 260–270 species (Kabat 1996; WoRMS 2025).
The genus Gennaeosinum
Iredale, 1929, comprises three valid species. Kilburn
(1976) classified it as a subgenus of Eunaticina;
Gennaeosinum is consistently
characterized by a thick funicle, a feature absent in
all Eunaticina species. Although 36 Naticidae species across 12 genera have been documented in
India, no Gennaeosinum species has been
reported from the region (Tripathy et al. 2024). This
study documents the first record of Gennaeosinum
perobliquum (Dautzenberg
& Fischer, 1907) in the Bay of Bengal, expanding its known distribution. Gennaeosinum
perobliquum was described initially from
“Ben-Son” (probably Binh Son, south of Da Nang) in
Vietnam (Dautzenberg & Fischer 1907) and later
recorded from Durban, Kwazulu-Natal, South Africa (Kilburn 1976) and Indonesia
(Bakker et al. 2026). This species is often misidentified as Eunaticina papilla (Gmelin,
1791) due to similar spiral lirae patterns. As detailed here, G. perobliquum can be reliably distinguished from Eunaticina species occurring in India.
A recent study (Mishra et al.
2024) identified the naticid Sinum laevigatum (Lamarck, 1822) along Odisha’s coast,
underscoring the need for further research on Naticidae
in this region. Consequently, extensive surveys were conducted along Odisha’s
entire coastline, with particular focus on the intertidal zone of Chandipur, where specimens were collected.
This study not only adds G. perobliquum to the list of species known in Indian
waters but also highlights the rich malacofaunal diversity present along the
largely unexplored eastern coast of India. It provides a thorough examination
of the specimen, including the holotype description and comparative analyses
with closely related species, aiming to mitigate future taxonomic ambiguities.
Enhanced photographic documentation and detailed morphometric measurements are
included to enrich the understanding of shell sculpture and address existing
gaps in the literature.
Materials
and Methods
A survey was conducted in the Chandipur intertidal region (21.455° N, 87.045° E) (Figure
1) during September 2025. Samples were randomly collected during low tide by
hand-picking and stored; dead specimens were placed in ziplock
pouches, and live specimens were preserved in 4% formalin. Dead specimens were
carefully washed, air-dried, and sorted. Sediment samples were obtained through
manual excavation using a hand shovel for the purpose of analyzing soil
texture. Morphometric measurements were obtained using a dial caliper (Safeseed, China; resolution 0.1 mm, accuracy ± 0.2 mm),
while shell surface structures were examined under a stereo microscope (Leica
E24W, Germany). Specimen photographs were captured with a Nikon Z 30 camera (MC
50 mm / 2.8 f). Following vouchering, specimens were deposited in the
Environmental Science Laboratory, Department of Zoology, Ravenshaw University,
Cuttack, Odisha, India.
Morphological identification was
performed based on the holotype description (Dautzenberg
& Fischer 1907), supplemented by additional information from Kilburn
(1976). A critical comparison was made with other naticids reported from India,
as documented by Rao (2003). The taxonomic status was verified through the
World Register of Marine Species (WoRMS 2025).
Result
Systematics
Family: Naticidae
Guilding, 1834
Subfamily: Sininae
Woodring, 1928
Genus: Gennaeosinum Iredale, 1929
Type species: Gennaeosinum
peleum Iredale,
1929 (type by original designation)
Gennaeosinum perobliquum (Dautzenberg & H. Fischer,
1907) (Image 1A–H)
Chresonomy
Sigaretus (Eunaticina)
perobliquus Dautzenberg
& H. Fischer, 1907: p. 178, pl. 5,
figures 4–5.
Eunaticina papilla (non Gmelin); Kensley,
1973: 93, fig. 323.
Eunaticina (Gennaeosinum)
perobliqua (Dautzenberg
& Fischer, 1907) - Kilburn 1976; p. 872, figure. 22 (c).
Eunaticina (Gennaeosinum)
perobliqua (Dautzenberg
& Fischer, 1907) - Bakker H, Gill A, Creuwels J
(2026). Naturalis Biodiversity Center (NL) -
Mollusca. Naturalis Biodiversity Center. Occurrence
dataset https://doi.org/10.15468/yefvnk accessed via GBIF.org on 2026-05-05.
https://www.gbif.org/occurrence/2444340122.
Type Locality: “Ben-Son” (probably Binh Son, south of Da Nang) in northern Vietnam
IUCN status: Not Evaluated.
Material examined: Two specimens (dd), Accession number: RZEVB18 (TSL 13.5 mm, WB 10.2 mm);
RZEVB19 (TSL 13.9 mm, WB
10.5 mm) were examined from the Chandipur
intertidal, Balasore, Odisha, eastern coast of India
(21.455° N, 87.045° E), coll. Sanjaya
Dalai & Aparna Mishra.
Additional material studied: Figured type material of Sigaretus (Eunaticina)
perobliquus Dautzenberg & Fischer, 1907 (images
examined from Dautzenberg & Fischer 1907; p. 178,
pl. 5, figure 4–5).
Topotype of Eunaticina
papilla (Gmelin, 1791) (Zoological Survey of
India, Registration number ZSI M 22150/4).
Specimen of Eunaticina
linnaeana (Récluz,
1843) (Zoological Survey of India, Kolkata, Registration number M25925/5).
Description: Shell solid, white, moderately
elongated oval; aperture strongly prosocline. Low, depressed spire with blunt
tip; deep suture. Protoconch slightly convex, smooth,
glossy white with brown tinge; two whorls. Transition to teleoconch
not well defined; feeble spiral ribs present. Teleoconch
with two whorls, last whorl highly convex much larger than previous whorls. Teleoconch surface initially smooth, later marked by strong
arc-like growth lines; faint spiral ribs becoming distinct and unevenly
distributed on last whorl. Around 9–10 spiral ribs on penultimate whorl,
separated by shallow, broad interspaces. Ribs more elevated below suture,
flattening with lower interspaces on last whorl. Spiral ribs become denser
towards base; growth lines become stronger towards outer lip. Spiral threads
continue into inner side of umbilical groove. Aperture semicircular, wider
anteriorly. Inner lip almost straight, slight concavity towards parietal
region; anterior region curved. Thick parietal callus extends over umbilicus,
forming a funicle that covers umbilicus backwardly. Funicle divided by shallow
groove. Wide open anteriorly, deep umbilical groove. Operculum corneous.
Remarks: A thick callus pad covers the
umbilical groove and the funicle, which has a shallow groove that divides it
into two. These are the key identification features that confirm the first
report of the genus Gennaeosinum and the
species G. perobliquum from India. The
multi-spiral protoconch with two whorls signifies a
planktonic veliger larval stage (Vendetti, 2007).
This developmental form implies improved dispersal abilities; therefore a large distribution area is to be expected.
Distribution: From Vietnam (Holotype) through
Indonesia (GBIF) and India to South Africa (Kilburn, 1976) (Figure 2).
Locality within India: Chandipur
Intertidal, Balasore, Odisha, east coast of India,
present study (Figure 2).
Habitat: The species has repeatedly been
recorded from shallow water. Chandipur’s intertidal
stretch shows diverse sedimentary conditions, with a silty mudflat in the
middle region. The upper intertidal region has a coarse,
sandy substratum, encompassing high diversity.
Discussion
Identification of Naticidae can be challenging because of their highly
cryptic morphology and very minor interspecific variation (Sharma et al. 2021).
In India, three genera of the Sininae subfamily are
represented: Eunaticina P. Fischer, 1885,
Sigatica O. Meyer & Aldrich, 1886, Sinum Röding, 1798. The
genus Gennaeosinum herein reported is
the fourth, represented by a single species. The aforementioned three genera
are unique in several ways. Eunaticina differs
from Sinum by its auricular, more depressed
shape and wider aperture. Gennaeosinum is similar to Eunaticina
and was treated as its subgenus by Kilburn (1976). Gennaeosinum
is differentiated from Eunaticina by a thick
callus pad in the parietal region, which is absent in Eunaticina.
Gennaeosinum includes three species: G. intercisum Iredale, 1931, G.
peleum Iredale, 1929,
and G. perobliquum (Dautzenberg
& Fischer, 1907). Kilburn included several other species, namely G. kraussi (E.A. Smith, 1902) and G. linguifera Thiele, 1925, but now G. kraussi is accepted as Eunaticina
kraussi whereas G. linguifera
is accepted as Natica Linguifera. This work confirmed the first report of the
Gennaeosinum genus and the species G.
perobliquum from Indian marine waters.
Previously, this species was found in the western and central Indo-Pacific
regions. It now extends its range into the Bay of Bengal. There are few
descriptions or images of the species besides the original description, which
has excellent figures. Kilburn (1976) did not provide an illustration. The
Indian specimens align with the original description and Kilburn’s description
of the features of the South African specimen.
The species can be confused with
two Eunaticina species well known from the
Indo-West Pacific: E. papilla (Gmelin, 1791)
and E. linnaeana (Récluz,
1843). Kilburn (1976) compared G. perobliquum
with E. linnaeana, but the specimens are more
similar to E. papilla. Eunaticina linnaeana is larger and broadly ovate, while G. perobliquum is smaller and moderately ovate. Both have
low spires, but the conical shape distinguishes the latter. Eunaticina
linnaeana has fine spiral grooves, whereas G. perobliquum is ornamented with well-developed, flat
spiral ribs. Eunaticina
linnaeana has an aperture that is wider,
elongated, and larger, giving it a distinct look compared to the semicircular
opening in G. perobliquum. Eunaticina
linnaeana has frequently been misidentified as
E. papilla, leading to similar confusion with G. perobliquum.
E. papilla has an exserted spire, shallow suture,
and ovate aperture. G. perobliquum resembles E.
papilla in size, spiral ribs, and moderately large aperture. Distinctively,
G. perobliquum stands out from both Eunaticina species because it features a thick
callus pad in the parietal region, divided into two by a shallow groove, a
feature always absents in Eunaticina.
Various factors influence the
dispersal of naticid species in Indian marine waters. Oceanic currents and
ballast water from ships play a major role (Ruiz et al. 2000; Cowen & Sponaugle 2009; Treml et al.
2015). The Bay of Bengal, located in the northern Indian Ocean, shares
environmental and habitat characteristics with the central and western
Indo-Pacific marine regions. These include high sea surface temperatures, a
variety of coastal and open-water habitats, and rich biodiversity, all
characteristic of tropical Indo-West Pacific ecosystems (Spalding et al.
2007). Climate change and rising sea
temperatures are likely to shift the ecological niches of these species. This
could extend their distribution beyond previously established ranges
(Wallingford & Sorte 2022; Lin et al. 2024).
Changes in species distribution may be hard to establish due to a lack of
comprehensive surveys and challenges in species identification, especially
given the cryptic nature of Gennaeosinum perobliquum (D’Souza & Shenoy 2023). Research on the Naticidae
family in India has been limited, particularly along the eastern coast. This
highlights the need for further exploration, including the collection of live
specimens and the establishment of a DNA database to elucidate intraspecific
and interspecific relationships among Indian naticid species.
Conclusion
The discovery of G. perobliquum underscores significant connections among
molluscan fauna in the Indo-West Pacific and highlights the urgent need for a
comprehensive taxonomic review of naticid species in India. This study also
confirms the limited exploration of malacofaunal diversity along the eastern
coast. Additionally, this record expands the regional species list and deepens
the understanding of biogeographical patterns in the Indo-West Pacific. These
findings are crucial for developing effective conservation strategies and for
protecting biodiversity in the region.
Table 1. Morphometrics of Gennaeosinum perobliquum collected from Odisha.
|
Specimen |
TSL |
WB |
HB |
SL |
CL |
UL |
(AW)a |
(AW)p |
|
RZEVB18 |
13.5 |
10.2 |
7.8 |
3.8 |
11.3 |
4.0 |
6.8 |
3.9 |
|
RZEVB19 |
13.9 |
10.5 |
8.9 |
3.9 |
11.0 |
3.8 |
7.4 |
4.3 |
For
figures & image - - click here for full PDF
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