Species distinctions: Deep-Sea Anglerfish:
Weight: n/a
Body length: female, 0.8 to 1.0 m ( 32.0 to 40.0 in); male, 0.1 m (4.0 in)
Diet: fish
Distinctive qualities: live at great depths in sea; black in colour; possess a light-emitting "lure" which acts as a fishing pole to catch prey; in a few species, the male is tiny and lives as a parasite of the much larger female.

With approximately one hundred and fifty species, anglerfish are some of the oddest fish to be observed, living in the deeper regions of the seas. Most are round in shape, of modest size and appear to be black in colour, with sharp teeth in a large mouth, eyes positioned at the top of the head, and are equipped with a rod and light to catch prey.

However, the relationship between the male and the female which is also of particular interest: the male is a tiny, free-swimming fish when young, except he lacks a digestive system. When adulthood is reached, he finds a female and attaches himself to her skin by his teeth, allowing the skin of the female to grow around his body as he deteriorates. Gradually, his blood vessels fuse with hers and his nourishment is provided for by the female, similar to the mammalian foetus which is fed by being attached to its mother’s placenta. The male continues to live as an external, parasitic, sperm-providing affixation of the female.

Physics Application(s):

Bioluminescence: The very large female, equipped with a complete set of organs, digestive system, and fins, is also equipped with an external growth from the top of the head: a form of rod-like appendage with a luminous end. It is compared to a fishing rod that has a lure of light attached, which may be used for the very same reason: in order to catch other fish, the lure may be used to attract the prey and bring it close to the mouth, where the anglerfish catches it in her mouth and feeds.

Anemaw [Animal Electromagnetism and Waves] © Elizabeth Gerrow 2002 .