Abstract
Radula in all melongeninae species is rather uniform and characterized by bicuspid lateral teeth with strongly curved cusps and sub rectangular rachidians, bearing usually 3 cusps. The aim of the present study was to describe the radula of 2 Pugilina cochlidium populations using SEM. The radula in 2 species proves itself as a rachiglossate type showing the radular formula of 1 + R + 1. The first population hasthe central tooth wide with sharp cusps equal in length, emanate from posterior margin of tooth base. The lateral teeth have 2 cusps and are long, sharp, pointed and bent towards the rachidian tooth. Whereas the second population, the central tooth is narrow with sharp cusps equal in length, emanate from posterior margin of tooth base. The lateral teeth have 2 cusps and are broad, longer, sharp, pointed and bent towards the rachidian tooth. They are typically sickle shaped with broad strong base. In both populations the rachidian tooth is subquadrate with 3 big cusps in the middle, but in the second population the base of the rachidian is concave while in the first population it is straight. In the present study the median rachidian of the second population, has a broad basal region when compared to first. This similar observation has been made in Chicoreus virgineus ponderosus and Siratus virgineus ponderosus. In the present study, since 2 populations exhibit the same generalized rachiglossate pattern it does not offer much scope for systematic diagnosis below generic level.
Highlights
The morphology of the radula, the chitinous strip of teeth found in molluscs, has traditionally been one of the most commonly used sources of data for studies on molluscan systematics (Brusca and Brusca, 2002; Moore, 2006; Fernandes et al, 2013)
Radula of second population is of typical rachiglossate type with several rows of teeth and proves the radular formula is 1 + R + 1
The radula is of typical rachiglossate type and the radular formula is 1 + R + 1 (Teso and Pastorino, 2011) this type of radula is highly evolved next to toxoglossate type (Eisapour et al, 2015) in general the central or rachidian tooth is tricuspid having 3 large pointed sharp cusps the median cusp of the median rachidian tooth is some what shorter than the lateral cusps the median cusp is sharp and pointed straight towards the anterior end (Teso and Pastorino, 2011; Eisapour et al, 2015)
Summary
The morphology of the radula, the chitinous strip of teeth found in molluscs, has traditionally been one of the most commonly used sources of data for studies on molluscan systematics (Brusca and Brusca, 2002; Moore, 2006; Fernandes et al, 2013). Research on functional morphology of the molluscs radula has focused attention on the obvious food-preparing and food gathering operation of the teeth and their relationship. This requires some knowledge on the radula and its functioning. The radula has been recognized as an important morphological criterion for the taxonomic allocation of species. It shows general similarities on familial and generic levels with consistent differences on the species level. There have been many studies on the gastropod radula, where the radular characters are generally considered constant within the species or that individual variation does not exceed the difference between species (Fretter and Graham, 1994). Many studies have demonstrated that the radular characters are modified by many factors as seasonal changes, sexual differences, age were reported (Maes, 1966; Fujioka, 1984a, b, 1985a, b, c)
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