Morphological Identification of Babylonia spirata (Linnaeus, 1758) from Tuticorin Coast, Gulf of Mannar Introduction

The taxonomy is an integral part of any biological study. Scientific studies involving a taxon must have an accurate identification of that taxon. In the past, morphology alone sometimes fails as an effective identifier of species [1]. In the cases of morphologically similar species, or where the specimens are derived from larval or juvenile life stages, the usefulness of traditional methods of comparative morphology could be limited [2]. Furthermore, traditional taxonomy is heavily dependent on specialists whose knowledge is usually lost when they retire, thus there is a need for a novel scheme that would preserve taxonomic information and knowledge and make these more accessible [3].

The order Neogastropoda is one of the most abundant and diverse groups of marine gastropods, around more than 5200 species [4]. The number of families recognized within Neogastropoda varies to a great extent from 15 to 34 [5]. It is generally accepted that evolution of the order, as well as that of other gastropod species was determined mainly by the changes in the anatomy of the digestive system, while the similarity of shells is often the result of convergence [6]. Much attention has been paid to the anatomy of the digestive system and current phylogenetic analyses of the higher classification of Neogastropoda have been based mainly on anatomical characters of the digestive system especially on the foregut [7-9]. Similarly, discrimination of the families within the Neogastropoda has traditionally been based on radular and other foregut characters. The stomach of Neogastropoda remains a poorly studied structure. Only very few publications dedicated entirely to stomach morphology and its comparative analysis. For gastropod tissues, however there is only very few information available on the morphological status. Therefore, in this study the morphological status of B. spirata was carried out.

Sample of Babylonia spirata (Linnaeus, 1758)

Live animals of B. spirata were collected from Therespuram coast, Tuticorin, Tamil Nadu, India (800 48’N; 780 94’E). Immediately after the collection, samples were stored in the ice box and brought to the laboratory. Then, the species were identified based on their morphological characters.

Morphological examination of Babylonia spirata

Morphological characteristics of the shell and internal tissue were also examined.

Morphological description of the Babylonia spirata

The whelks were categorized under the order of Neogastropoda and family Buccinidae. They are mostly carnivorous and scavengers. In India B. spirata were observed to be landed, mostly in the bottom trawls and rarely in crab net.

Habitat: It thrives well on muddy bottom of marine environment. Whereas salinity below 19ppt was observed to be lethal. The Babylonia species mostly preferred in coarse sand.

Food: It is a carnivore and readily accepts calm meat as food.

Growth: The laboratory studies indicated that the settlement after a day old juvenile have attained are average shell length 1.58mm, average total weight 0.009g attain of an average shell length of about 34.3mm and the total weight of 9.137g.

Head: The body is externally divided into three regions viz, head, foot and visceral mass. The head was observed to be bilaterally symmetrical with a pair of black coloured eyes at the base of the lateral side. The colour of the head is brown with blackish pigmentation.

Tentacles: Two pairs of contractile cephalic tentacles are present on either side of the snout which measure about 3mm and 5mm in length. It depends upon the size of the animal.

figure 1:Dorsal view of Babylonia spirata.

figure 2:Ventral view of Babylonia spirata.

Shell: The shell of B. spirata was observed to be thick, void with a horny surface. The shell shows a characteristic colour pattern and consisted of regular spiral rows of round bright brownish patches on a white background. The apex of the shell the oldest part and showed a reverse coiling. The umbilicus was found to be either closed or open. It has a smooth surface. Its apex (spire) was observed to be well elevated with conical shape and the in flatted whorls are inflated. The whorls are six or seven in number and lie very close to each other (Figure 1 & 2).

Foot: The foot is a muscular organ with a broad ventral creeping sole occurring on the ventral side of the head. It has reddish brown pigmentation and is capable of expansion and concentration. The animal having the shell length of about 60mm possessed of about 32mm. Whereas it measures about 50-70mm in length and 40- 50mm in width during contraction (Figure 3).

Mantle: The mantle encircles the neck region of the animal like a collar. It was observed to be broad dorsally and its width narrows down rapidly towards the posterior region, where it forms a slight ridge-like structure. Posteriorly, it possesses a continuous wall continuous with the visceral mass. Whereas, anteriorly the dorsal side of the mantle is drawn out into a siphon, which extends thorough the siphoned canal exteriorly. Its edge involves in the secretion of the shell and plays a major role in their glandular and sensory activities (Figure 3).

figure 3:Digestive system of B. spirata.

Operculum: The operculum was found to be at the poster dorsal region of the foot. It is oval in shape horny and chitinous in nature with a terminal nucleus. The concentric rings called lines of growth surround the nucleus. The operculum has 8 to 10mm concentric bands. The numbers of bands are lesser and appear to be a transparent in the immature forms. The adult B. spirata operculum has a maximum length and width ranged from 32mm and 18mm with clean line growth (Figure 4).

figure 4:Anterior and Posterior view of operculum of B. spirata.

Visceral complex: The distal end of the hind region of the body is occupied by the visceral mass; which contains the stomach, the digestive diverticula and gonads. The stomach is irregular in shape, elongated in anterior-posterior direction, embedded in the anterior region of the midget gland. The midget gland occupies the major part of the visceral mass. The gonad covers the stomach on the dorsal side and it exhibits different colours in accordance with the reproductive phase of the animal.

Reproduction