Macrobrachium nobilii

Lore & Background

Macrobrachium nobilii is distributed in South East India, New Caledonia, Gavataks, and Tuamotu Island. In India, it is reported from freshwater lakes of Chengalpattu District of Tamil Nadu and from the river Cauvery between Mettur Dam and Poomphuhar Estuary. Its common name 'stone prawn' reflects its affinity for substrates such as stones and pebbles found at the bottom of its habitat.

This species is characterized by its prominent or elongated second pair of chelate appendages, in which the carpus is distinctly larger than the merus. The large chela have teeth on the proximal part of the cutting edges. In the rostrum, the first four or five teeth are situated behind the posterior orbital margin.

Biologically, Macrobrachium nobilii is diecdysic, moulting and breeding once every 18–22 days. Males are larger than females. An average female incubates about 2200 eggs per clutch for a period of 14 days. On completion of development, eggs hatch in irregular batches within 6 days. The larvae passively drift to the estuary to complete development, after which juveniles actively migrate back to freshwater grounds.

Reader's Guide

Macrobrachium nobilii holds significance as a freshwater shrimp species with a distinct ecological role, particularly its reliance on stony substrates, which gives it the local name 'stone prawn.' Its distribution across South East India, New Caledonia, Gavataks, and Tuamotu Island indicates a broad but specific habitat range. The species' life cycle is notable for its diecdysic moulting and breeding pattern, occurring every 18–22 days, and its reproductive strategy involves females incubating about 2200 eggs per clutch for 14 days. The larval drift to estuaries and subsequent juvenile migration back to freshwater grounds highlight a complex life history tied to both freshwater and estuarine environments. The morphological feature of an elongated second pair of chelate appendages, with the carpus larger than the merus and teeth on the cutting edges, distinguishes it from related species. This combination of distribution, reproductive biology, and physical traits contributes to its legacy as a well-documented example of a freshwater prawn adapted to specific substrates and life-cycle transitions.

Did You Know?

• Macrobrachium nobilii is locally known as 'stone prawn' due to its affinity for stony or pebbly substrates.
• Males of this species are larger than females, with a reported body weight of 12676 mg versus 7178 mg for females.
• After hatching, larvae passively drift to the estuary, and juveniles later actively migrate back to freshwater grounds.