PJZ_58_3_1187-1193

Introduction

Mollusca are the largest and most diversified phylum in tropical waters, and they consist of a diverse group of soft-bodied organisms and occur in various shapes and colors. They provide the primary food sources for humans and other secondary consumers in the ecosystems (Asakura et al., 2020). Since many molluscs species have significant economic value, other biological indicators, and vital components of the food web and their significance in the ecosystem cannot be understated (Raveendran et al., 2016). Molluscs consume both living and decaying algae and plant materials, which contributes significantly to the ecological processes associated with the decomposition of organic detritus (Kelaher et al., 2007; Nagelkerken et al., 2008). As grazers, gastropods can regulate algal blooms and ephiphyton (Asakura et al., 2020; Keerthana et al., 2023), whereas bivalves, as filter feeders, can aid in the purification of marine waters that have been silted (Chatla and Padmavathi, 2017). According to a report by the Ministry of Environment and Forests (MoEF, 2014), Government of India, in 2014, India is home to a remarkable diversity of molluscan species. Of the approximately 66,535 known species of molluscs worldwide, India hosts 5,169 species, representing a significant portion of global molluscan biodiversity (MoEF, 2014). This figure, which is considered a conservative estimate, underscores the rich and varied ecosystems present in the country, ranging from terrestrial to freshwater and marine environments. The variety of these molluscs, including gastropods and bivalves, is a strong indicator of the health of mangrove ecosystems (Mawardi et al., 2023). Additionally, many bivalves and gastropods are economically significant, providing food for local communities (Zvonareva et al., 2015). Understanding their species diversity and their distribution is key to managing sustainable utilization of resources and ensuring food security. With this background, the current study aimed to compile a comprehensive checklist of molluscs, particularly on gastropods and bivalves, in the mangrove ecosystems of the Thoothukudi coast. This research involves identifying and documenting the biodiversity of molluscs associated with mangroves. This data will be invaluable for forming conservation and management strategies, aiding efforts to conserve and sustain these crucial ecosystems.

Materials and methods

In this study, a comprehensive checklist of molluscs (gastropods and bivalves) in the mangrove region of Thoothukudi was prepared. The quadrant (20 quadrants/site/month) was placed randomly at a distance of every 10 m and the specimens collected fortnightly from three stations: Station-1, Thoothukudi (Roche Park, Lat 8°47’23’’N, Long 78°9’19’’E), Station-2, Palayakayal (Landing centre, Lat 8°40’13’’N, Long 78°6’9’’E), and Station-3, Punnakayal (Landing centre, Lat 8°38’8’’N, Long 78°7’20’’E) from December 2022 to November 2023. Sampling was conducted during low tide to maximize the molluscs, mangrove trees, and land area exposure. Live and dead shells of gastropods and bivalves were hand-picked, and some of them were identified on-site, while others were collected and transferred to the laboratory in an icebox. Molluscs samples were collected along the mangrove ecosystem of the Thoothukudi coast and analyzed following previous research reported by Keerthana et al. (2023). The bivalves and gastropods were separated and labeled individually. Along with standard websites like WoRMS, SeaLifeBase, and Natural History Museum Rotterdam, standard keys released by the Food and Agriculture Organization (Dholakia, 2013; Sonak, 2017) were used to identify the specimens. The recent taxonomic names were checked from websites such as sea life base and WoRMS (world register of marine species).

Results and discussion

The current study recorded a diverse array of 87 molluscs species belonging to two classes, Gastropoda and Bivalvia, across three selected mangrove stations along the coast of Thoothukudi (Table I). In this study, Station-1 recorded 32 genera and 42 species of molluscs. Station-2 exhibited the highest diversity with 56 genera and 72 species, indicating perhaps a more complex and heterogeneous habitat or less anthropogenic impact. Station 3 had 49 genera and 61 species, suggesting intermediate conditions between the other two stations. These species span 28 families, including Arcidae, Lucinidae, Donacidae, Psammobiidae, Tellinidae, Mytilidae, Margaritidae, Ostreidae, Pinnidae, Cyrenidae, Mactridae, Veneridae, Cerithiidae, Potamididae, Turritellidae, Littorinidae, Naticidae, Columbellidae, Melongenidae, Muricidae, Nassariidae, Tonnidae, Muricidae, Fasciolariidae, Neritidae, Ellobiidae, Chilodontaidae, and Trochidae. The Bivalvia class was represented by 39 species across six orders, 12 families, and 33 genera. The Order Venerida had the highest number of species (12), followed by the Order Cardiida with nine species and the Order Arcida with three species. The significant presence of Venerida and Cardiida indicates the favorable sedimentary conditions in these mangrove areas, which support filter-feeding bivalves. The class gastropoda comprised 48 species belonging to seven orders, 17 families, and 34 genera. The order Caenogastropoda found to be dominant with 19 species, followed by Neogastropoda with nine species. Notably, Euchleus asper was the only species recorded under the order Segueniidae. This diversity reflects the rich ecological niches and the adaptability of gastropods in mangrove ecosystems. Compared with previous studies, Yadav et al. (2019) documented 19 species of gastropods from 13 families and three species of bivalves from 3 families in the mangroves of Paradeep, Northeast India. Similarly, Karthick et al. (2020) reported six species of bivalves from 5 families and 11 species of gastropods from 8 families along the Tiruchendur coast, Southeast India. Chatla and Padmavathi (2017) recorded 23 species of molluscs in the Paleru and Moosy backwaters, Andhra Pradesh, with 16 species from 12 families of Gastropoda and seven species from 5 families of Bivalvia, which was closely related to the present study. Also, Ramanibai and Govindan (2018) identified 34 species of gastropods from 26 families and 17 species of bivalves from 13 families in Pulicat Lagoon, which was comparatively less than the current results. Notably, Boominathan et al. (2012) reported an extensive diversity of 215 molluscs species, comprising 133 gastropods and 77 bivalves, from various mangrove ecosystems across India. These studies collectively highlight molluscs communities’ considerable variation and richness in mangrove habitats across the Indian coastline.

The wide distribution of families such as Ellobiidae, Littorinidae, Potamididae, and Neritidae in this study aligns with findings by Hogarth (2015) and Kantharajan et al. (2017), who reported these families as common in Indo-Pacific and Southeast Asian mangroves. This similarity underscores the ecological importance of these families in mangrove ecosystems, where they play crucial roles in nutrient cycling and as prey for higher trophic levels.

Table I. Checklist of molluscs: gastropods and bivalves of the mangrove ecosystems of the Thoothukudi coast.

S. No	Species name	Common name	Sampling stations	No. recorded	Size range (cm)	Utility
Phylum: Mollusca; Class: Bivalvia; Subclass: Autobranchia
Infraclass: Pteriomorphia; Order: Arcida; Family: Arcidae
1	Larkinia grandis (Broderip & Sowerby, 1829)*	Mangrove cockle	TH	106	1.8 - 2.7	-
2	Tegillarca granosa (Linnaeus, 1758)*	Blood cockle	TH, PA, PU	138	1.5 – 2.4	C
3	Barbatia sp., (Gray, 1842)*	Ark clam	PA, PU	184	2.6 – 3.5	-
Infraclass: Heteroconchia; Order: Lucinida; Family: Lucinidae
4	Anodontia alba (Link, 1807) *	Buttercup lucine	TH, PA, PU	162	1.2 – 2.6	-
5	Anodontia edentula (Linnaeus, 1758) *	Toothless lucine	TH, PA	136	1.6 - 2.8	C
6	Loripes orbiculatus (Poli, 1795)*	Pale lucine	PA, PU	155	1.9 – 2.6	-
	Order: Cardiida; Family: Donacidae
7	Donax incarnates (Gmelin, 1791)*	Fleshy donax	PA, PU	142	2.3 – 2.7	-
8	Latona sordida (Hanley, 1845)*	Beam clams	PA, PU	112	2.2 – 3.3	-
9	Donax pulchellus (Hanley, 1843)*	Beautiful donax	PA, PU	128	1.2 – 2.5	-
10	Hecuba scortum (Linnaeus, 1758)*	Leather donax	PA, PU	146	4.5 – 7.9	-
11	Donax semisulcatus (Hanley, 1843)*	Half striated donax	PA, PU	118	3.5 – 4.6	-
12	Hiatula planulata (Reeve, 1857)*	Sunset clams	TH, PA	122	3.6 – 8.5	-
13	Alaona ala (Hanley, 1845)*	Tellin clams	TH, PA, PU	102	2.4 – 3.6	-
14	Ardeamya petitiana (d’Orbigny, 1845)*	Not found	TH, PA	98	2.1 – 2.8	-
15	Serratina fissa (Spengler, 1798)*	Not found	PA, PU	114	1.9 – 2.5	-
Infraclass: Pteriomorphia
	Order: Mytilida; Family: Mytilidae
16	Byssogerdius striatulus (Hanley, 1843)*	Not found	PA, PU	116	2.7 – 3.5	-
17	Mytella strigata (Hanley, 1843)*	Charru mussel	PA, PU	124	1.8 – 3.4	-
18	Perna perna (Linnaeus, 1758)*	Brown mussel	PA, PU	143	5.3 – 8.1	HC
19	Perna viridis (Linnaeus, 1758)*	Green mussel	TH, PA, PU	187	7.6 – 9.8	HC
	Order: Ostreida; Family: Margaritidae
20	Pinctada imbricata (Roding, 1798)*	Atlantic pearl oyster	TH, PA, PU	248	2.6 – 5.5	HC
21	Magallana cuttackensis (Newton and Smith, 1912)*	True oysters	TH, PA, PU	270	7.2 – 8.9	-
22	Magallana bilineata (Roding, 1798)*	Philippine cupped oyster	TH, PA, PU	176	5.6 – 7.8	C
23	Ostrea edulis (Linnaeus, 1758)*	Edible oyster	PA, PU	142	3.8 – 6.2	C
24	Saccostrea cuccullata (Born, 1758)*	Hooded oyster	PA, PU	164	3.4 – 5.7	C
25	Pinna sp., (Linnaeus, 1758)*	Pen shells	TH, PA	126	7.3 – 9.5	C
Infraclass: Heteroconchia
	Order: Venerida; Family: Cyrenidae
26	Villorita cyprinoides (Gray, 1825)#	Black clam	PA, PU	246	2.8 – 3.6	-
	Family: Mactridae
27	Mactra grandis (Gmelin, 1791)*	Plain Trough shell	PA, PU	360	4.5 – 5.1	C
	Family: Venerida
28	Chamelea gallina (Linnaeus, 1758)*	Stripped Venus clam	TH, PA	288	2.6 – 3.9	C
29	Circe scripta (Linnaeus, 1758)*	Script venus	TH	152	3.6 – 4.2	-
30	Eucallista purpurata (Lamarck, 1818)*	Purple amiantis	PA, PU	134	4.1 – 4.6	-
31	Gafrarium pectinatum (Linnaeus, 1758)*	Comb venus	TH, PA, PU	211	3.9 – 4.4	-
			Table continued on next page...........
S. No	Species name	Common name	Sampling stations	No. recorded	Size range (cm)	Utility
32	Lliochione subrugosa (Wood, 1828)*	Venus clams	PA, PU	168	3.1 – 3.7	-
33	Marcia opima (Gmelin, 1791)*	Fertile venus	TH, PA, PU	144	3.5 – 3.9	-
34	Meretrix casta (Gmelin, 1791)*	Backwater hard clam	TH, PA, PU	432	3.7 – 4.6	-
35	Meretrix meretrix (Linnaeus, 1758)*	Asiatic hard clam	TH, PA, PU	582	3.6 – 4.3	C
36	Paratapes textile (Gmelin, 1791)*	Textile venus	TH, PA	142	3.2 – 3.8	C
37	Pelecyora trigona (Reeve, 1850)*	Trigonal dosinia	PA, PU	151	2.8 – 3.6	-
38	Protapes gallus (Gmelin, 1791)*	Rooster venus	PA, PU	173	3.5 – 5.2	C
39	Sunetta menstrualis (Menke, 1843)*	Mauve sunetta	TH, PU	132	2.6 – 3.5	SF
Phylum: Mollusca; Class: Gastropoda
	Order: Caenogastropoda Family: Cerithiidae
40	Cerithium atratum (Born, 1778)*	Dark cerith	TH, PA, PU	678	1.8 – 2.5	-
41	Cerithium coralium (Kiener, 1841)*	Coral cerith	TH, PA	799	1.6 – 2.2	C
42	Cerithium lutosum (Menke, 1828)*	Variable cerith	TH, PA, PU	822	1.5 – 2.0	-
43	Cerithium traillii (Sowerby, 1855)*	Traills cerith	TH, PA	756	2.1 – 2.8	-
44	Clypeomorus batillariaeformis (Habe and Kosuge, 1966)*	Necklace or channeled cerith	TH, PA	528	2.3 – 2.9	-
45	Clypeomorus bifasciata (Sowerby, 1855)*	Sea snail or mud snail	PA, PU	711	1.4 – 2.3	-
46	Pseudovertagus clava (Gmelin, 1791)*	Cerithids	PA, PU	432	1.3 – 2.5	-
47	Rhinoclavis kochi (Philippi, 1848)*	Kochi’s cerith	PA, PU	620	2.1 – 3.1	-
	Family: Potamididae
48	Cerithidea anticipata (Iredale, 1929)*	Sea snail or mud snail	TH	384	2.4 – 3.6	-
49	Pirenella alata (Philippi, 1849)*	Mud whelks	TH, PU	512	2.2 – 2.8	-
50	Pirenella arabica (Reid, 2016)*	Not found	TH, PA	488	1.8 – 3.0	-
51	Pirenella cancellata (Ozawa and Reid, 2016)*	Not found	TH, PA	311	1.7 – 2.3	-
52	Pirenella cingulata (Gmelin, 1791)*	Hom snails	TH, PA, PU	454	1.6 – 2.4	C
53	Pirenella conica (Blainville, 1829)*	Not found	TH, PA	208	1.1 – 1.4	-
54	Pirenella microptera (Kiener, 1841) *	Not found	TH, PA	334	1.3 – 2.5	-
55	Pirenella retifera (Sowerby, 1855) *	Mangrove whelk	PA, PU	386	1.0 – 1.8	-
56	Terebralia palustris (Linnaeus, 1767)*	Giant mangrove whelk	TH, PA	212	2.0 – 2.9	-
57	Terebralia sulcata (Born, 1778)*	Sulcate swamp cerith	PA, PU	188	2.2 – 2.8	-
	Family: Turritellidae
58	Turritella acutangula (Linnaeus, 1758)*	Tower shells	PA, PU	122	6.3 – 7.9	-
	Order: Littorinimorpha
	Family: Cymatiidae
59	Lotoria triangularis (Perry, 1811)*	Perry’s Triton	TH, PA	134	4.2 – 5.8	-
60	Ranularia testudinaria (Adams and Reeve, 1850)*	Tortoise Triton	TH, PA	128	5.4 – 6.9	-
61	Naria ocellata (Linnaeus, 1758)*	Ocellate cowry	PA, PU	106	2.5 – 3.1	-
	Family: Littorinidae
62	Littoraria scabra (Linnaeus, 1758)*	Mangrove periwinkle	TH, PA	154	1.4 – 2.8	-
63	Eunaticina papilla (Gmelin, 1791)*	Papilla moon snail	PA, PU	96	2.1 – 3.6	-
	Family: Tonnidae
64	Tonna galea (Linnaeus, 1758)*	Giant tun	TH	45	5.7 – 7.3	C
	Order: Neogastropoda Family: Columbellidae
65	Euplica scripta (Lamarck, 1822)*	Dotted dove shell	PA, PU	168	2.2 – 2.8	-
	Family: Melongenidae
66	Volegalea cochlidium (Linnaeus, 1758)*	Spiral melongena	TH	105	5.2 – 7.3	-
			Table continued on next page...........
S. No	Species name	Common name	Sampling stations	No. recorded	Size range (cm)	Utility
	Family: Muricidae
67	Trophon plicatus (Lightfoot, 1786) *	Murex snails or rock snails	PA, PU	172	4.1 – 5.3	-
	Family: Nassariidae
68	Nassaria coromandelica (Smith, 1894)*	Indian Phos	PA, PU	122	3.3 – 4.5	-
69	Nassarius stolatus (Gmelin, 1791)*	Nassa mud snails or dog whelks	PA, PU	138	2.4 – 2.8	-
70	Phrontis tiarula (Kiener, 1841)*	Western mud nassa	PA, PU	145	1.5 – 1.9	-
71	Tritia reticulata (Linnaeus, 1758)*	Netted dog-whelk	PA, PU	136	2.1 – 2.7	-
	Family: Muricidae
72	Murex trapa (Roding, 1798)*	Rare spined murex	TH, PU	58	6.2 – 6.8	C
	Family: Fasciolariidae
73	Fusinus longissimus (Gmelin, 1791)*	Long spindle	TH	48	10.5–12.6	-
Subclass: Neritimorpha
	Order: Cycloneritida; Family: Neritidae
74	Clithon olivaceum (Recluz, 1843)*	Nerites	PA, PU	164	2.1 – 2.6	-
75	Clithon oualaniense (Lesson, 1831)*	Guamanian nerite	PA, PU	131	0.7 – 1.1	-
76	Nerita polita (Linnaeus, 1758)*	Turbo snail	PA, PU	138	2.5 – 3.2	C
77	Neritodryas dubia (Gmelin, 1791)*	Nerites	PA, PU	123	1.9 – 2.5	-
78	Vitta virginea (Linnaeus, 1758)*	Virgin nerites	PA, PU	118	0.9 – 2.2	-
79	Vittina waigiensis (Lesson, 1831)*	Red racer nerite snail	PU	132	1.6 – 2.3	-
Subclass: Heterobranchia; Infraclass: Euthyneura
	Order: Ellobiida; Family: Ellobiidae
80	Allochroa bronnii (Philippi, 1846)*	Hallow shelled snails	PU	145	1.8 – 2.6	-
81	Cassidula aurisfelis (Bruguiere, 1789)*	Cat ear helmet snail	TH, PA,PU	112	1.2 – 2.5	-
82	Cassidula labrella (Deshayes, 1830)*	Not found	PU	135	1.6 – 2.3	-
83	Cassidula nucleus (Gmelin, 1791)*	Banded	TH, PU	108	1.3 – 2.2	-
84	Melampus adamsianus (Pfeiffer, 1855)*	Salt march snail	PA, PU	118	1.7 – 2.3	-
Subclass: Vetigastropoda
	Order: Seguenziida; Family: Chilodontaidae
85	Euchelus asper (Gmelin, 1791)*	Sea snail	TH, PA	138	1.2 – 2.5	-
	Order: Trochida; Family: Trochidae
86	Trochus cariniferus (Reeve, 1842)*	Small sea snail	TH,	126	1.0 – 2.2	-
87	Umbonium vestiarium (Linnaeus, 1758)*	Button top snail	TH, PU	134	1.3 – 1.8	C

TH, Thoothukudi; PA, Palayakayal; PU, Punnakayal; #, least concern; *, not evaluated; C, commercial; HC, highly commercial; SF, subsistence fisheries.

The diversity and distribution of molluscs recorded in this study underscore the ecological richness of the mangrove habitats along the Thoothukudi coast. The findings contribute valuable data to understanding molluscs diversity in Indian mangroves and highlight the need for ongoing conservation efforts to protect these vital ecosystems against environmental and anthropogenic pressures. Further comparative studies across different geographic regions and long-term monitoring are essential to understand the impacts of climate change and habitat degradation on molluscs communities in mangrove ecosystems.

Ravindran and Rajesh (2013) catalogued three species of gastropods spanning three genera from Punnakayal. Among these, the utility status of 16 species was classified under the commercial category, with an additional three species falling into the high commercial category and one species designated for subsistence fisheries. Intriguingly, an analysis of the international union for conservation of nature (IUCN) status unveiled that nearly all species (86) were categorized as not evaluated (NE), with only one species listed under the least concern (LC) category (Table I). Mangroves serve as indispensable habitats for numerous coastal wildlife, offering crucial breeding sites and nursery grounds. In this intricate web of coastal ecology, bivalves and gastropods emerge as pivotal players, influencing the dynamics of mangrove ecosystems. Despite their significance, our understanding of the molluscan species inhabiting mangrove environments remains limited. The study area, bordered by salt pans, industrial activities, and other anthropogenic influences, highlights the urgent need for ongoing ecosystem monitoring. Such care is imperative to safeguard these invaluable resources and ensure sustainability amidst rising environmental pressures. Regular monitoring efforts can furnish invaluable insights into the health of mangrove ecosystems, facilitating informed conservation strategies to preserve these vital habitats for future generations. This study suggests monitoring mangroves and their faunal biodiversity to maintain the sustained health of the ecosystem.

Declarations

Acknowledgment

All authors thank the Dean, Fisheries College and Research Institute, Thoothukudi and the Vice-Chancellor, Tamil Nadu Dr. J. Jayalalithaa Fisheries University, Nagapattinam, Tamil Nadu, India, for providing necessary facilities and support.

Funding

Tamil Nadu Dr. J. Jayalalithaa Fisheries University, Nagapattinam – 611 002.

IRB approval

This article has approved by review committee members of Fisheries College and Research Institute, Tamil Nadu Dr. J. Jayalalithaa Fisheries University, Thoothukudi – 628 008, Tamil Nadu, India.

Ethical approval

No animals were harmed during the entire research.

Statement of conflict of interest

The authors have declared no conflict of interest.

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