Date: June 30th, 8;00am
Today's fish of the day is the bottle-nosed elephantfish!
The bottle-nosed elephantfish, also known as the eastern bottle-nosed mormyrid, freshwater dolphin fish, and scientific name mormyrus longirostris, is a mostly unknown fish. Found across Western Africa in Eastern flowing rivers, such as the Niger, Congo, and Senegal river systems. In and around cave systems with soft dirt bottoms across these deep freshwater rivers, where they hide in weedy vegetation. Populations migrate often, but unlike many fish in their family, not on a set schedule. Instead these fish migrate irregularly, as they are poor swimmers, and struggle in areas of high current, forcing them to move to avoid it during the rainy season.
The elephantfish superfamily, Mormyridae, not to be confused with the marine elephant fish, which is a kind of chimaera. This family is known for being quite odd, as they have a unique sound processing system found in no other vertebrate, and the males are the only vertebrates to produce sperm cells without a flagella. They are also known for their weakly electric effect, which they use to sense prey and predators. Electric fields can be found in many different animals, most of which being aquatic. These are split into pulse type, and wave type, pulse type being characterized by long intervals of electrical discharge, and the wave type being made up of smaller connected pulses. The elephantfish family is known for their usage of pulse type electrical sensing, as they have a grouped retina that can only view red light. This, paired with their habit of living in areas of muddy or otherwise low visibility waters forces them to rely heavily on electrical sensing. This is what causes many to compare them to the Southern American electrical fish. The Gymnotiforms order, which forms the electrical organs by the exact same amino acid substitution, despite being separated by 60 million years of evolution. These organs being formed from the same muscle along the caudal tail.
The bottle-nosed elephantfish is active at night, hunting for small invertebrates, lizards, eggs,weeds, and fish. These are found through the electrical organ. This can be broken into two parts, one of which being specialized cells along the fish, which are used to sense and read back information from electrical signals. The second part is the sender, which sends pulsing signals from the tail, which then can read electrical signals sent by the muscle cells of moving animals. This is what allows them the find prey and predators! Other than this, the bottle nosed elephantfish is quite normal for their family. Named for the elongated and rounded body, with a large nose like structure. They can grow up to 75cm or 30inches, although maternity is achieved at 35cm in length.
The reproductive and lifecycle behaviors of this fish are rather unknown, as it is particularly tricky to convince them to breed in captivity. In the wild, these fish are observed carrying as many as 10,000-70,000 eggs at a time, which will be laid during the rainy season, as the elephantfish populations are temporarily stuck in small areas on low current. These fish have been seen with courtship displays, made up of complex swimming patterns to attract females. After which eggs are lain in vegetation and the male will guard them. This behavior extends after the eggs hatch, with male bottle-nosed elephant fish remaining several weeks after the fry are born. These fish will go on to live anywhere from 6-10 years, although there are claims of captive fish living to 15, if kept particularly well.
That's the bottle-nose elephantfish, everybody! I hope you had a wonderful time learning about them!