Author: Chewy Editors

An ecological concept called “The Pyramid of Numbers” shows the relative abundance of the various organisms that form a food chain. The organisms that far outstrip all the others in terms of total weight (biomass) are the green plants, which form the base of the pyramid. They are known as “producers,” reflecting the fact that they constitute the first and most significant component on which all the other members of the pyramid depend, either directly or indirectly. Without green plants, there would be no life on earth. Plants are so important because they “capture” the sunlight’s energy and photosynthesize it by binding carbon dioxide and water to produce carbohydrates, one of the basic foods that all living things require. Although animals must obtain carbohydrates, they cannot produce it as plants and some bacteria do. Lacking the ability to photosynthesize, animals must hence become consumers. Herbivores obtain carbohydrates by consuming plants directly. Carnivores and piscivores consume other animals, including some that consume plants. And so it goes on up the pyramid, with each level generally being represented by a progressively lower number of consumers. A typical example from the fish world would be as follows. Free-floating green algae (a producer) could be eaten by a water flea (Daphnia). Thus, the Daphnia becomes the primary consumer (the first to eat the producer). If a small fish eats the Daphnia, the fish is a secondary consumer (it consumes the producer’s nutrients through a primary consumer). That fish could later be eaten by a tertiary consumer, such as a pike. The pike, if small, could be consumed by a heron, or if large, could be fished by an angler and later eaten — and so on. Clearly, it takes numerous free-floating algae to sustain a single Daphnia. Fewer (but still quite numerous) Daphnia would be required by a mosquitofish. It would take even fewer mosquitofish to feed a pike, etc. It is this relationship that gives the Pyramid of Numbers its characteristic shape, particularly when biomass is substituted for actual numbers; for example, a single Daphnia weighs less (has a lower biomass) than the total number of algae it eats over a lifetime. We are all part of this intricate relationship.

A fish swimming upside down normally indicates a serious ailment and a near-term appointment with the Great Aquatic Paradise. But one unusual fish, the upside-down catfish (Synodontis nigriventris), is quite adept at gracefully gliding upside down with the greatest of ease. Due to a remarkable physiology, the seemingly bizarre swimming habits of this fish are actually quite normal, rather than being an indicator of a life-threatening illness. These fish are able to perform underwater acrobatics, including knife edges, barrel rolls and their extended namesake posture. In a still fish aquarium, these fish are able to remain motionless in an upside-down position for what seems to be an indefinite period of time. Synodontis nigriventris received its Greek and Latin binomial names from its tooth and jaw formation, and unusual dark belly coloration. The genus name Synodontis means “together teeth,” and the species name nigriventris means “dark abdomen.” Normally, the dorsal pigmentation of a fish is darker than the ventral side, and it is speculated that this is to provide visual obscuration from predators. But the ventral side of the upside-down catfish is dark, indicating this fish has chromatically adapted camouflage for extended upside-down swimming near the water’s surface. The upside-down catfish is a peaceful, schooling fish that grows to about 4 inches in length and is ideally suited for a community tank with other species of a similar temperament. Of the six S. nigriventris in my collection, slight coloration differences (white or yellowish base color mixed with dark brown and black marbling) are observable under bright lighting. Random white dots create a stunning sparkling effect on this beautiful fish. Reference material and hobbyist reports indicate these fish are tolerant of a wide range of water conditions (pH 6.0 to 7.5) and temperatures ranging from 71 to 82 degrees Fahrenheit. Synodontis nigriventris is of the order Siluriformes and part of the Mochokidae family. It shares the order Siluriformes with the popular Corydoras, having distinctive ray finnage, cat-whiskerlike barbels and a scaleless body. Synodontis nigriventris has been collected from Malebo Pool in the Congo River Basin and in many tributaries, such as the Lekenie River in the Odzala National Park in the Republic of the Congo. The Lekenie River is a clear to tea-colored waterway with a sand and fine quartz gravel substrate.