Male vs Female Crabs
When male and female crabs are considered, it might appear to be a little difficult task to identify the males and females separately. That is mainly due to the slightly exhibited sexual dimorphism in crabs. However, their sexually dimorphic characters could be understood if a close look is set forth. Understanding about the male and female would be highly important for the captive breeders, as the crabs have become an important food item with a great taste for humans.
Body Size: There are some characteristics to be paid attention in understanding the sexual dimorphism of crabs. One of the most prominent differences between males and females is the size. Male crabs are larger than female crabs, but there should be individuals from both sexes in order to compare the size difference between them.
Claws: The size of their claws could be a very important character to distinguish the males from females, as the male crabs have larger claws than females do. Fiddler crabs could be stated as the best example to express this particular difference. It is described that the male fiddler crabs pose attractively to their females by waving the extra-large claw to be selected as the sexual partner.
Colouration: Colouration patterns of the two sexes vary in some species of crabs. Despite the fact that males are usually more colourful than females, crabs do not always have prettier males than females, but their colouration patterns should be studied and understood. As an example, the tips of the claws are red in female blue crabs while those are blue in males.
Abdomen, Pleon: The shape of the pleon or the abdomen of crabs is one of the most convincing indications that would enable to distinguish males from females. The pleon of males is narrow and triangular whereas females have a broad and round abdomen. However, their abdomen is usually not observed from the top of a crab. Therefore, the crab has to be manhandled and turned upside down in order to distinguish their sexes.
Parental Care: Crabs being an invertebrate group of animals, it would be important to notice the behaviour of parental care, which is usually common for the higher vertebrates. The female crab, after mating with a male, carries a pouch with thousands of eggs on her abdomen. Most of these eggs would not become adults, but the survival of hatchlings is increased considerably because of this behaviour. The shape of the abdomen of females, discussed above, is very important for this behaviour. Thus, it could be envisaged that males do not company the females in caring for the young. In addition, the females carrying hatchlings can be easily observed from the top, as the young ones usually run all over the mother’s body.
Male vs Female Crabs
In summary, the most important differences between male and female crabs could be laid out as follows.
• Males are larger and heavier than females.
• The claws are larger in males than in females.
• Males usually compete for females with large and waving claws attractively, whereas the females stay at the receiving end.
• There are colouration differences between males and females depending on the species.
• Abdomen is broad and round in females, but males have a narrow and triangular shaped abdomen.
• Females take part in parental care by sheltering but not the males.