Frog Sexual Dimorphism
தவளைகளின் பால் ஈருருமை
Sexual dimorphism in Rana tigrina is not an aesthetic choice; it is a reproductive necessity. Misidentify the sex, and you miss the mechanism of amplexus. Do not confuse these external markers with internal gonadal development.
The idea
Male frogs possess vocal sacs and copulatory pads on the first digit of the forelimbs. These structures are strictly absent in females. Vocal sacs amplify sound for mate attraction, while copulatory pads facilitate firm gripping during amplexus. These are the primary external morphological indicators of sex.
Why it matters
These structures exist to facilitate mating and reproduction, specifically for sound production to attract mates and for gripping during amplexus.
NEET lens
NEET focuses on the location of copulatory pads: the first digit of the forelimb. Do not confuse this with hindlimbs. Expect 'Match the Following' or 'True/False' statements regarding these morphological traits. Memorize: Vocal sacs and pads are exclusive to males.
Clinical significance
In evolutionary biology, the failure of these secondary sexual characteristics leads to reproductive isolation. If vocal sacs fail, the male cannot signal fitness, leading to a collapse in population recruitment. This is a classic example of how morphology dictates species survival.
Introduction
Sexual dimorphism in frogs refers to the visible physical differences between male and female frogs, helping identify sex externally.
Core concept
Male frog features: vocal sacs (for croaking/calling females), nuptial pads on first digit of forelimbs (for gripping female during amplexus), slightly smaller than female. Female frog: larger, rounder (more abdominal space for eggs), no vocal sacs, no nuptial pads.
Go deeper
Amplexus is the mating position where the male mounts the female and grips her with forelimbs (using nuptial pads). External fertilization occurs as female lays eggs in water and male simultaneously releases sperm.
From Class 10
You've seen frogs and know males and females look slightly different. These external differences are called sexual dimorphism.