POLYPTERUS (BICHIR)

Contents hide

1) Classification of Polypterus (Bichir)

2) Geographical distribution

3) Habit and habitat

4) General Characteristics of Polypterus (Bichir)

5) Ecological Importance:

6) Conservation Status:

7) Special features

8) Identification

Classification of Polypterus (Bichir)

Phylum :- Chordata (Dorsal tubular nerve cord, notochord and gill-slits present.)
Group :- Craniata (Cranium with brain present.)
Sub phylum :- Vertebrata (Vertebral column present.)
Division :- Gnathostomata (Jaws and paired appendages present.)
Super Class :- Pisces (Paired fins, gills and skin with scales.)
Class :- Osteichthyes (Bony fishes. Skin contains dermal scales. Paired lateral fins present. Gills, air bladder present. Cleavage meroblastic.)
Sub-Class :- Palaeopterygii (Ancient fishes. Dermal fin rays numerous. Clavicles present. Nostrils free from mouth cavity.)
Order :- Cladistia (Body slender, scales thick, rhomboid, enamelled. Air bladder lung like.)
Family :- Polypteridae (Pectoral fins lobate, while pelvic fms non-lobate.)
Genus :- Polypterus

Geographical distribution

Polypterus is restricted to tropical Africa, the Nile, Nigeria and Congo. Palaeozoic and Recent (none known species).

Habit and habitat

Polypterus is found in sea water. It becomes active during night. It feeds on small teleosts, batrachians and crustaceans.

General Characteristics of Polypterus (Bichir)

Polypterus is one of the most primitive living bony fish and could be easily regarded as living fossil.
Body divisible into head, trunk and tail.
Body is elongated, cylindrical, measuring 1 metre in length and covered with rhombic ganoid scales.
Surface covering consists of a thin shiny enamel called ganoin.
Head is covered with a horny shield containing tubular nostrils and forwardly lying eyes.
Spiracles present.
There is a fleshy lip on the lower jaw matching that of the upper jaw.
Dorsal fin consists of a series of 5 to 18 isolated finlets composed of single spine-like scales to which are attaches! one or more soft rays.
Pectoral fins, found behind head, are broad rounded and lobed at bases.
Ventral rm backwardly situated. Pelvic fins present.
Caudal fin diphycercal.
Larva possesses plume-like external gills, attached to the hyoid arch, resembling the gills of Amphibian larva.

Ecological Importance:

Predator in Aquatic Ecosystems: Polypterus species are predatory fish that feed on smaller fish, invertebrates, and crustaceans. They help maintain the population balance of these species within their ecosystems, contributing to biodiversity regulation.
Role in Food Webs: As both predator and prey, bichirs play a key role in aquatic food webs. They are preyed upon by larger fish, birds, and mammals, making them an integral part of their ecosystem’s trophic structure.
Indicator of Ecosystem Health: Bichirs are often found in specific freshwater habitats such as swamps, marshes, and slow-moving rivers. Their presence can serve as an indicator of water quality and habitat stability, as they require clean, oxygen-rich water for survival.
Habitat Modifiers: By moving along the substrate and feeding, they may stir up sediments, which can influence nutrient cycling and water clarity in their habitats.

Conservation Status:

Threat Level: Most species of Polypterus are classified as Least Concern by the International Union for Conservation of Nature (IUCN). However, specific species may have varying statuses due to habitat degradation, pollution, and overfishing.
Threats:
- Habitat Loss: The destruction of wetlands, river systems, and other freshwater habitats due to agricultural expansion, deforestation, and urbanization poses a significant threat to Polypterus populations.
- Overfishing: In some areas, Polypterus are harvested for local consumption, ornamental trade, or use in traditional practices, which can lead to population declines.
- Pollution: Water pollution from industrial waste, agricultural runoff, and human activities negatively impacts their habitats.
Conservation Measures:
- Protecting freshwater habitats and reducing pollution can help sustain Polypterus populations.
- Raising awareness about sustainable fishing practices and enforcing regulations in the ornamental fish trade are important steps in conserving these species.
- Restoring degraded wetlands and promoting the conservation of their natural habitats are critical for their long-term survival.

In summary, Polypterus species are ecologically significant as both predator and prey, contributing to the health and balance of freshwater ecosystems. While many species are not currently at high risk, habitat degradation and human activities could threaten their populations, emphasizing the need for proactive conservation measures.

Special features

Polypterus shows combination of primitive and advanced characters. Primitive characters are non-overlapping scales, spiracle, certain skull bones and their arrangement, spiral valve in intestine and the superficial resemblance of paired fins to broad-based crossopterygian fins.
It has also advanced features like dorso-lateral position of nostrils, pyloric caecum in the gut and similar urinogenital system, which bring them closer to bony fishes. The tail is no longer heterocercal. The air bladder though connected with pharynx seems to be respiratory organ but remains non-functional as Polypterus cannot live outside water for a longer period.