The tripod fish or tripod spiderfish, ''Bathypterois grallator'', is a deep-sea

benthic The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from the Ancient Greek word (), meaning "the depths". ...

fish in the family Ipnopidae found at lower latitudes. It is now an iconic deep-sea fish, being observed and photographed by

submersible A submersible is an underwater vehicle which needs to be transported and supported by a larger ship, watercraft or dock, platform. This distinguishes submersibles from submarines, which are self-supporting and capable of prolonged independent ope ...

s, using elongate fin rays of the tail and pelvic fins to stand on the ooze. ''B. grallator'' is hermaphroditic.

Characteristics

The tripodfish has long, bony rays that extend from the lower lobe of its tail fin and both pelvic fins. ''B. grallator'' is the largest member of its genus, commonly exceeding a

standard length Fish measurement is the measuring of individual fish and various parts of fish anatomy, their anatomies, for data used in many areas of ichthyology, including Taxonomy (biology), taxonomy and fishery biology. Overall length Standard length (SL) is ...

of and reaching

total length Fish measurement is the measuring of individual fish and various parts of their anatomies, for data used in many areas of ichthyology, including taxonomy and fishery biology. Overall length Standard length (SL) is the length of a fish measured f ...

s of up to long. The tripodfish is often seen in its distinctive stance; standing on its three fin extensions (the namesake tripod) on the seabed, facing upstream with the antennae-like pectoral fin rays extended out, waiting for food. Even though the fins are presumably quite stiff to be able to support its weight, observations of swimming fish shows that their fins seem flexible; it is suggested that fluids are pumped into these fins when the fish is 'standing' to make them more rigid. The tripodfish is closely related to the spider fish '' Bathypterois longifilis'', which is similar in appearances and habits but is smaller and has much shorter fin extensions. They are often found standing very close to each other.

Habitat

''Bathypterois grallator'' has been found relatively widely in the Atlantic, Pacific, and Indian oceans from 40°N to 40°S. It is a wide-ranging eurybathic fish found from deep.

Biology

Feeding

The tripodfish faces into the current, waiting for prey to drift by. The fish uses tactile and mechanosensory cues to identify food; it apparently does not have special visual adaptations to help it find food in the low-light environment. When the fish is perched with its long rays on the ocean floor, it can get food without even seeing it. The tripodfish's mouth ends up at just the right height to catch shrimp, tiny fish, and small crustaceans swimming by. They seem to prefer to perch on the mud using much elongated fin rays in their tails and two pelvic fins to stand, facing upstream into the current to ambush with the pectoral fins turned forward so the outthrust projecting fins resemble multiple antennae. The fish senses objects in the water with its front fins. These fins act like hands. Once they feel prey and realize it is edible, the fins knock the food into the fish's mouth. Recorded prey includes

copepod Copepods (; meaning 'oar-feet') are a group of small crustaceans found in nearly every freshwater and saltwater habitat (ecology), habitat. Some species are planktonic (living in the water column), some are benthos, benthic (living on the sedimen ...

s and other planktonic crustaceans, such as

larvae A larva (; : larvae ) is a distinct juvenile form many animals undergo before metamorphosis into their next life stage. Animals with indirect developmental biology, development such as insects, some arachnids, amphibians, or cnidarians typical ...

Reproduction

Each individual has male and female reproductive organs. If two tripodfish happen to meet, they mate. However, if a tripodfish does not find a partner, it makes both sperm and eggs to produce offspring by itself; thus, it is a true

hermaphrodite A hermaphrodite () is a sexually reproducing organism that produces both male and female gametes. Animal species in which individuals are either male or female are gonochoric, which is the opposite of hermaphroditic. The individuals of many ...

.Winner, C. Life on the Edge. Lerner Publications, 2006. , p. 18

References

External links

Australian Museum page on TripodfishVideo showing a tripodfish at 1443m depth
{{Taxonbar, from=Q556906 Ipnopidae Fish described in 1886