Footballfish

Footballfish are a unique family of deep-sea anglerfishes. They belong to the family Himantolophidae. These fish are known for their globose, or ball-like, body shapes. They live in the dark mesopelagic and bathypelagic zones of the ocean. You can find them in the Atlantic, Indian, and Pacific Oceans. They are also found in the Southern Ocean. Because they live in such deep water, food is very hard to find.

To survive in the dark, female footballfish use a clever hunting method. They possess a specialized organ called an esca. This esca contains bioluminescent bacteria, which are tiny living things that produce light. The female uses this light to lure prey toward her. Once the prey is close, she strikes with her mouth. Her teeth curve backward to ensure that any prey cannot escape. She eats whatever she can fit into her mouth, including fish, squid, and crustaceans.

There are currently 23 recognized species within the genus Himantolophus. Scientists organize these species into several distinct groups. These include the groenlandicus group and the appelii group. Other groups are the nigricornis, albinares, cornifer, brevirostris, and rostratus groups. Most of these groups were identified by looking at the morphology, or physical form, of adult females. However, the brevirostris and rostratus groups were determined using only the characteristics of males.

The history of studying these fish began in the 19th century. In 1837, the Norwegian zoologist Johan Reinhardt first described the species Himantolophus groenlandicus. He identified this species after it washed ashore near Godthaab in Greenland. The name Himantolophus comes from Greek words. It combines "himantos," meaning a leather strap or leash, with "lophus," meaning a crest or tuft. This likely refers to the thick, leathery illicium, or the stalk holding the light, seen in some species. Later, in 1861, Theodore Gill established the family Himantolophidae.

Footballfish exhibit significant sexual dimorphism, which means males and females look very different. The metamorphosed females have a well-developed lower jaw that sticks out past the snout. They also have a wide vomer, a bone in the mouth, that lacks teeth. Larger females may have conical spines scattered across their heads and bodies. In contrast, the males are much smaller than the females. For example, in the species H. groenlandicus, the maximum standard length for a female is much larger than that of a male.

The males have specific adaptations to help them find mates in the vast, dark ocean. They possess a large olfactory system, which is a highly developed sense of smell. They use their sideways-pointing nostrils to detect females. Once a male finds a female, he uses specialized teeth to attach to her. He has between 16 and 31 denticular teeth on his snout and 20 to 50 on his chin. Unlike some other members of the suborder Ceratioidei, these males are free-living and non-parasitic. They attach to the female but do not fuse her body to theirs.

Understanding the life cycle of the footballfish requires looking at their earliest stages. The larvae are round and have a swollen appearance to their skin. Their pectoral fins do not extend past their dorsal or anal fins. Female larvae possess a small, club-shaped rudimentary illicium. The eggs and larvae are pelagic, meaning they live in the open water column. This life cycle connects the footballfish to the broader biological systems of the deep sea. Their ability to find food and mates in such a sparse environment is a remarkable feat of evolution.