Question

In Macrobrachium rosenbergii males, how many common morphotypes are observed?

• A. Two
• B. One
• C. Six
• D. Three

Hint:

Remember the three male morphotypes of M. rosenbergii by their claw development: Small Male (translucent claws) \( \rightarrow \) Orange Claw (intermediate size) \( \rightarrow \) Blue Claw (large, dominant).

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
The giant freshwater prawn, Macrobrachium rosenbergii, exhibits a complex social hierarchy among adult males.
This hierarchy is defined by the development of three distinct male morphotypes, each possessing unique physical and behavioral characteristics.

Step 2: Detailed Explanation:
The three male morphotypes observed in adult populations of Macrobrachium rosenbergii are:
1. Small Male (SM):
These are small, highly mobile prawns with translucent claws.
They use a sneak-mating strategy, hiding near larger males to fertilize females without being detected.
They grow rapidly and can transition into the next morphotype.
2. Orange Claw (OC):
These are medium-sized prawns with bright orange claws.
They grow rapidly but are socially dominated by the larger blue claw males.
Once they reach a certain size, they undergo a rapid molt to transition into the final blue claw morphotype.
3. Blue Claw (BC):
These are the largest, most dominant males, characterized by long, dark blue claws.
They protect harems of receptive females and defend their territories from other males.
They grow slowly once they reach this terminal stage.
This social structure can lead to uneven growth in prawn ponds, which is an important factor in harvest management.

Step 3: Final Answer:
Adult male M. rosenbergii develop into three distinct morphotypes (SM, OC, and BC).
Thus, the correct choice is (D).