User:Soap/crabs

The males of the green spoonworm are tiny and cannot eat; they instead rely on the females for all food needs. Another one is, of course, the rhizocephalan barnacles that eat crabs. The male barnacle has no mouth but can sense the location of females in the water. Once a female is found, the male attaches and loses all body parts other than its germ-making cells.

Some n trematodes have males signficantly larger than females but both seem to be capable of feeding autonomously. In the water, the trematode swims towards the chemical signals secreted by skin and then enters the skin. According to [Evolutionary Ecology of Parasites: Second Edition], the male schistosoma parasite is shorter than the female but much thicker, and therefore has a significantly heavier body weight. This allows the female worm to fit inside the male. The female has apparently lost much of her muyscle mass, showing similarities with parasitic evolution, but still retains the ability to feed independently. the female worm can migrate through skin, blood vessels, etc, but apptly relies on the male for locomotion after maturing indo the adult phase.

- I believe that the male anglerfish, and the male barnacle, never develop a digestive system of their own and thus never actually eat anything; their nutrition is provided through the blood vessels of the female. Thus, it could be argued that this goes even beyond parasitism and the males of these species are just accessory organs of the female, having less of an independent existence than even a parasite. One difference between the two, however, is that the male anglerfish still passes sperm to the female in the conventional fish manner, since they mate externally; whereas the male barnacle simply inserts himself into the female's body and fertilizes her internally.

Nevertheless, the sources refer to this as parasit(ic|ism) reliably.

As above, the male loses all body parts other than his reproductive tissue ... so what happens to the rest of his body? Do the free-floating remnant males just automatically die after "mating"? Will research more when possible.

Other nptes
The progression of lifestages of some parasitic crustaceans has been described as retrogressive metamorphosis because the larvae have complex bodies but the adult is a worm similar in form to creatures that the crustaceans had evolved from hudnredfs of millions of years earlier.