Journal of Threatened
Taxa | www.threatenedtaxa.org | 26 February 2025 | 17(2): 26553–26557
ISSN 0974-7907 (Online)
| ISSN 0974-7893 (Print)
https://doi.org/10.11609/jott.9208.17.2.26553–26557
#9208 | Received 13 June
2024 | Final received 30 January 2025 | Finally accepted 06 February 2025
First record of the
sea slug Lobiger serradifalci
(Calcara, 1840) (Gastropoda:
Sacoglossa: Oxynoidae) from
the Indian coast
Dimpal Dodiya 1 & Paresh Poriya
2
1,2 Department of
Zoology, Bahauddin Government Science College,
Junagadh, Gujarat 362001, India.
¹ dodiyadimpal1995@gmail.com, ² pareshporiya@gmail.com
(corresponding author)
Editor: Hari Praved P.,
Cochin University of Science and Technology, Cochin, India.
Date of publication: 26 February 2025 (online & print)
Citation: Dodiya, D. & P. Poriya
(2025). First record of the sea
slug Lobiger serradifalci
(Calcara, 1840) (Gastropoda:
Sacoglossa: Oxynoidae) from
the Indian coast. Journal of Threatened Taxa 17(2):
26553–26557. https://doi.org/10.11609/jott.9208.17.2.26553-26557
Copyright: © Dodiya & Poriya
2025.
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: None.
Competing interests: The authors declare no competing interests.
Acknowledgements: The authors express their gratitude to Dr. R.P. Bhatt, principal of Bahauddin Government Science College, Junagadh, for providing the necessary laboratory resources throughout the study. The authors appreciate the manuscript’s critical review by anonymous reviewers. The first author is thankful to the Education Department of Gujarat State for the SHODH (Scheme of Developing High-Quality Research) fellowship.
Abstract: The present study
confirms the presence of a Sacoglossan (Mollusca)
species, Lobiger serradifalci
(Calcara, 1840), from India. The distribution of this
species has not yet been documented in India. It has been reported from Turkey,
Italy, France, Greece, Israel, and now, for the first time, from the western
coast of India. L. serradifalci was discovered
under green seaweeds in the lower intertidal zone. The species was found to
remain hidden within various types of green seaweeds in the region. The study
provides comprehensive details on its morphology, habitat, and taxonomy.
Keywords: Intertidal Sacoglossans, marine gastropods, sap-sucking sea slugs,
western coast of India.
Gastropod molluscs, which comprise snails and slugs, are incredibly
diversified in terms of species diversity, morphology, habitat, and numerous
other characteristics. They have significant body plan differences and extend
to freshwater, marine, and terrestrial habitats (Bieler 1992). Indian sea slugs
were classified into 361 distinct species (Apte &
Desai 2017), with an additional 33 species reported in the Gulf of Kachchh (Apte et al. 2010) and 24 species reported on a checklist
from several islands and reefs in the Gulf of Kachchh of the Gujarat coast (Rao
& Sastry 2005). There are 95 species found throughout the Gujarat coast;
seven of these are found in Saurashtra (Poriya et al.
2015; Vadher et al. 2020). The food habits of
gastropods include herbivores, omnivores, carnivores, and parasites, some of
which drill through the shells of other animals to feed. One of the few
examples of specialized herbivores in the marine environment is the fascinating
clade of opisthobranch molluscs
known as the Sacoglossans. Each sacoglossan
species is generally associated with a single genus or species of macroalgae
and shows a close evolutionary relationship with its algal host(s) (Krug 2011).
Sacoglossa, also known as the “solar-powered sea
slugs,” are divided into two clades: the shelled families, Oxynooidea,
and the shell-free families, Plakobranchacea (Handeler et al. 2009). The superfamily Oxynooidea
comprises four families, including the Oxynoidae,
which includes sea snails and bubble snails (Bouchet
et al. 2005). Out of the three genera of the Oxynoidae
family, Lobiger (Krohn
1847) comprises only five species: L. nevilli Pilsbry, 1896; L. sagamiensis Baba,
1952; L. serradifalci Calcara,
1840; L. souverbii P. Fischer, 1857; and L.
viridis Pease, 1863 (MolluscaBase
2023). The present study marks the first record of L. serradifalci from the Indian coast, specifically along
the Adri coast of Gujarat. Given its highly cryptic nature, the observation of L.
serradifalci proves to be particularly
challenging, especially when concealed beneath green algae. The elusive nature
of L. serradifalci, combined with its habitats
with green algae, imparts an added layer of difficulty to its discovery. The
species’ predominantly green coloration further camouflages it within its
surroundings, making it one of the most challenging Sacoglossan
species to discern in this coastal ecosystem. This research has provided
information on the habitat, morphology, and systematics of this species.
Material and Method
The specimens of sacoglossans, referred to as the genus Lobiger,
were occasionally observed in the intertidal zone of the coast during field
visits. The specimen was collected from a tide pool on the Adri coast (21.60194
˚ N, 70.47611 ˚E) on January 22, 2024 (Image 1A). The Adri coast is located on
the west coast of India and has a mixed type of intertidal habitat with rocky
outcrops studded with sand (Image 1B). The supratidal zone is covered with
sand; the upper, middle, and lower intertidal zones are rocky-sandy. A single
sample was collected, cleaned and preserved in a 10% buffered formalin
solution. The morphological characteristics of the species were observed using
a stereo zoom microscope (Model S.N.-391). The voucher specimen was deposited
at the Museum of the Department of Zoology, Bahauddin
Government Science College, Junagadh. Standard references were used for
identification, including Calcara (1840), Gonor (1961), Thompson (1988), Jensen (1996), and Furfaro et al. (2020). We used the WoRMS
database (2023) to determine this species’ current taxonomic status on MolluscaBase.
Results and Discussion
Systematics
Phylum: Mollusca
Linnaeus, 1758
Class: Gastropoda Cuvier, 1797
Order: Sacoglossa Ihering, 1876
Family: Oxynoidae Stoliczka, 1868
Genus: Lobiger Krohn, 1847
Species: Lobiger serradifalci (Calcara, 1840)
Synonyms (taken from WoRMS)
Lobiger serradifalci (Calcara
1840), Bulla serradifalci (Calcara
1840), Lobiger philippi
(Krohn, 1847)
Morphological
Description
The specimen is 20 mm
in length, with a light yellow coloration across its
entire body and a greenish hue beneath the shell (Image 2B). The external shell
is translucent, showing the clear grass-green colour
of the underlying mantle and the rhinophores are one pair (Image 2A). There are
a few scattered white papillae on the head and tentacles (Image 2A). The foot
and perfectly smooth body were completely covered in green seaweed, indicating
that the species prefers seaweed-covered rocky substrates. The two pairs of
parapodia are large and small, smooth, stumpy, and flattened, with white on
surface and green & yellow inside, almost invariably fused together, and
have pinkish dorsal edges (Image 2A,B). The parapodia
lobe is long compared to the shell, which is highly elevated and slightly
tipped backward and the outer side is white with brown speckling (Image 2D).
The foot’s region features tubercles, and in addition, the tail has a median
ridge covered by two comparative, less lateral ridges (Image 2A,C). The body sides are smoother than those above the level
of the parapodia lobes and have less developed tubercles.
Habitat
The specimen was
found beneath green seaweeds Caulerpa racemosa and Ulva Lactuca
(Image 1C) in the lower intertidal zone, which had large, deep-tide pools and
areas covered with various kinds of seaweed.
Geographical
Distribution
The present study
confirms the presence of Lobiger serradifalci on the Indian coast. It was first reported
from the Bay of Palermo, Mediterranean Sea (Calcara
1840); the Turkish coast (Pruvot-Fols 1954); Palermo,
Messina, Naples, Marseilles, the Balearic Islands, and Banyuls
(Wirz-Mangold & Wyss, 1958); the Bay of Mersin
(formerly Icel) in the Eastern Mediterranean and on
the southern coast of Turkey (Swennen 1961); Villefranche-sur-Mer (Alpes-Maritimes), France (Gonor 1961); Israel (Barash & Danin
1982); Taranto (Perrone 1983); Aghios Andreas (Ionian
Sea), Greece (Thompson 1988); the Salento Peninsula in Southeast Italy (Furfaro et al. 2020).
Remarks
The morphological
characteristics of L. serradifalci align with
previous observations made by Thompson (1988). Externally, L. serradifalci bears a resemblance to the Lobiger souverbii
species, as both inhabit Caulerpa fronds
and exhibit an elongated green body with a shell (Marcus 1977; Jensen &
Clark 1983). L. serradifalci has a light
grass-green body, flattened & in-rolled parapodia, and a pink-white
exterior with brown speckling. In contrast, L. souverbii
presents distinctive morphological features, including parapodial margins that
are red with dots. The mantle is yellowish-green in color beneath its
transparent shell, with several shorter blue lines scattered throughout the
dorsal surface. L. souverbii also possesses
two pairs of long, upright parapodia (Ichikawa 1993). L. serradifalci
resembles another saccoglossan species, Lobiger viridis.
Its whole body is bright yellow in colour and one
pair of short rhinophores are present above the animal’s mouth. Species have
been commonly found on the Indian coast, like Poshitra
Reef, Ashaba Island, the Gulf of Kachchh, and Andaman
Island (Parasharya 2012; Apte
& Desai 2017). It is possible that L. serradifalci
is present in intertidal habitats but due to its close resemblance, it may have
been overlooked and misidentified as L. viridis
in a previous study.
The earliest study
indicated Caulerpa racemosa
as food of L. serradifalci (Marcus 1977;
Jensen & Clark 1983). Few studies have also reported the phylogenetic
relationship between Sacoglossans and their food
plants (Kay 1968; Clark & Busacca 1978). All
shelled Sacoglossans use Caulerpa
sp. as their main food source, which demonstrates the phylogenetic
relationships between Sacoglossa and their food
plants (Jensen 1997; Parsons 1994). L. serradifalci
also uses Caulerpa sp. (Swennen 1961), including Caulerpa
prolifera (Gonor 1961; Gavagnin et al. 1994), and C. racemosa
(Marcus 1977; Jensen & Clark 1983) as a main food source. During the
present study, species were also found beneath the green seaweed C. racemosa habitat in the lower intertidal zone of the
Adri coast.
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