Sacculina Barnacle Infested Crab | Tonga

This is a small crab infested with a Sacculina barnacle parasite, a genus of barnacles that is a parasitic castrator of crabs. These barnacles are pelagic during their larval stage. Female larvae seek out host crabs. Once a suitable host is located, the female barnacle attaches to a joint area, molts into a form known as a kentrogon, and then injects its soft body into the crab, discarding its hard shell in the process. Once inside, the Sacculina develops into two parts: the interna, which comprises root-like threads that wrap around the crab’s internal organs; and the externa, which is a bulbous reproductive organ that protrudes from the crab’s abdomen, as pictured here. Male Sacculina barnacles inject themselves into a pocket in the female’s body in order to undertake the sole function of producing spermatozoa to fertilize the female. In other words, the male becomes parasitic to the female, which is parasitic to the crab. Once infected, a crab is unable to molt, though it otherwise functions normally. Nutrition that the crab ingests is siphoned off by the barnacle. Even more amazing, when a female Sacculina sets upon a male crab, as pictured here, it sterilizes the crab and causes the male crab to release hormones that cause the shape of the body to change such that it more resembles a female crab, with wider, flatter abdomen. The formerly male crab can even act like a female, performing female mating dances. When the female Sacculina is ready to release her brood into the water, she causes her host crab to do exactly what a female crab would normally do to release her own eggs. Namely, the crab finds high ground, grooms the brooding pouch on its abdomen and shoots out clouds of larvae via the hole visible at the center of the abdominal area, using its claws to stir the water to assist the newborn larvae, in this case barnacle larvae, not crabs. Once infected, a crab devotes its life to the reproduction of Sacculina. There are more than 100 species of Saccu

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Filename: sacculina-barnacle-infested-male-crab-tonga-201808-2748.tif
Copyright: Copyright Tony Wu. All rights reserved. No duplication, reproduction or usage without prior written permission.
Image Size: 5236x3491 / 52.3MB; https://www.photoshelter.com/support/license#rm; https://www.tony-wu.com/contact-tony-wu; Crustacean Sacculina Barnacle Animalia Arthropoda Crustacea Maxillipoda Cirripedia Rhizocephala Sacculinidae Sacculina sp. Parasite South Pacific Tonga Vava’u
Contained in galleries: Tonga, Crustaceans

This is a small crab infested with a Sacculina barnacle parasite, a genus of barnacles that is a parasitic castrator of crabs. These barnacles are pelagic during their larval stage. Female larvae seek out host crabs. Once a suitable host is located, the female barnacle attaches to a joint area, molts into a form known as a kentrogon, and then injects its soft body into the crab, discarding its hard shell in the process. Once inside, the Sacculina develops into two parts: the interna, which comprises root-like threads that wrap around the crab’s internal organs; and the externa, which is a bulbous reproductive organ that protrudes from the crab’s abdomen, as pictured here. Male Sacculina barnacles inject themselves into a pocket in the female’s body in order to undertake the sole function of producing spermatozoa to fertilize the female. In other words, the male becomes parasitic to the female, which is parasitic to the crab. Once infected, a crab is unable to molt, though it otherwise functions normally. Nutrition that the crab ingests is siphoned off by the barnacle. Even more amazing, when a female Sacculina sets upon a male crab, as pictured here, it sterilizes the crab and causes the male crab to release hormones that cause the shape of the body to change such that it more resembles a female crab, with wider, flatter abdomen. The formerly male crab can even act like a female, performing female mating dances. When the female Sacculina is ready to release her brood into the water, she causes her host crab to do exactly what a female crab would normally do to release her own eggs. Namely, the crab finds high ground, grooms the brooding pouch on its abdomen and shoots out clouds of larvae via the hole visible at the center of the abdominal area, using its claws to stir the water to assist the newborn larvae, in this case barnacle larvae, not crabs. Once infected, a crab devotes its life to the reproduction of Sacculina. There are more than 100 species of Saccu