Siluriformes

Siluriformes belongs to the class of bony fishes, with 34 families, 310 genera and about 2,316 species. China has 13 families, 32 genera and 132 species. All Siluriformes are bottom-dwelling carnivorous fish, many of which are important edible fish and also common game fish. Most of them live in freshwater, and only the family of Siluriformes is widely distributed in tropical and subtropical waters. The characteristic of Siluriformes fish is their long body shape, and most of the groups are naked and scaleless.

I. Introduction to Siluriformes (Catfishes)

1. Definition and Key Characteristics

• Taxonomic Scope
  Siluriformes, commonly called “catfishes,” is a large order of primarily freshwater fishes. Over 3,000 described species are found on most continents (except Antarctica), mainly in inland or brackish waters. A few species venture into coastal marine environments.

• Morphological Traits

• Barbels (“Whiskers”): Most catfishes have 1–4 pairs of barbels around the mouth, aiding in tactile and chemical sensing (the iconic “cat-like” whiskers).

• Reduced or Absent Scales: Many have skin without typical fish scales; some are covered in bony plates (e.g., armor catfishes in Callichthyidae or Loricariidae). A mucus-covered body is common.

• Fins: A short dorsal fin (often with a stout spine) is typical; many also possess an adipose fin (a small fin between the dorsal and caudal fin).

• Skeletal Features: Unique skull and shoulder girdle structures, along with special adaptations in jaw bones.

• Habits and Lifestyles

• Benthopelagic Feeding: Many are bottom-dwelling and often nocturnal, relying on barbels and taste receptors to locate prey in turbid waters.

• Dietary Variety: Ranging from carnivorous (small fishes, crustaceans), herbivorous/algae-grazing, detritivorous (consuming organic matter), or specialized (e.g., parasite-like candirus).

2. Ecological and Economic Importance

• Freshwater Ecosystem Role
  As benthic feeders with varied diets, catfishes regulate invertebrate populations and help recycle organic debris, contributing to healthy aquatic systems.

• Fisheries and Aquaculture
  Many catfish species (e.g., African sharptooth catfish, channel catfish) are farmed extensively for food; others (e.g., “plecos,” corydoras catfish) are prized in the ornamental trade.

• Cultural and Recreational Aspects
  Catfish are popular in recreational angling. In some regions, they hold cultural significance (e.g., local folklore linking catfish to natural phenomena).

II. Evolutionary History

1. Origins and Fossil Record

• The earliest catfish fossils date from the Late Cretaceous to Paleogene eras. Shifts in Earth’s climates, river patterns, and continental layouts allowed catfishes to diversify and adapt to different freshwater niches.

• These early catfishes already showed benthic adaptations, shaping the basis for the modern Siluriformes variety.

1. Global Differentiation and Multiple Radiations

• Continental drift and glacial/interglacial cycles caused repeated isolation in basins, leading to independent evolutionary lineages in the Americas, Africa, Asia, and parts of Australia.

• Particularly high diversity is found in South America’s Amazon Basin and its tributaries, Africa’s rivers (e.g., Nile, Congo), and Southeast Asian waterways.

1. Modern Molecular Phylogenetics

• Genetic analyses reveal complexities and potential non-monophyly in some large families, prompting ongoing taxonomic revisions (e.g., splitting “Loricariidae,” “Siluridae,” or reclassifying certain subfamilies).

• Newly identified families and genera show the tremendous phylogenetic depth within Siluriformes.

III. Major Families and Representative Genera

Below is a table of some notable catfish families, with select genera and example species. Classification can vary across sources due to ongoing revisions, so consider these groupings as a general reference.

(A) Widely Distributed Families

(B) Regional Families of Interest

(Note: Pangasiidae [Pangasiid catfishes]—including the popular “basa” or “pangasius” in aquaculture—may be grouped here or recognized separately.)

(C) Additional Families and Unique Groups

• Plotosidae (Eel-tailed Catfishes): “Sea catfishes” with elongated tail, found in Indo-Pacific coastal zones and occasionally in rivers.

• Heteropneustidae (Airsac Catfishes): e.g., Indian stinging catfish (Heteropneustes fossilis), with venomous spines and high tolerance to low oxygen.

• Trichomycteridae (Parasitic/“candiru” catfishes): Notable for species like the candiru in the Amazon, known for entering gill cavities or orifices of larger organisms.

IV. Conclusion

1. Multiple Origins and Global Spread

• Since the Cretaceous–Paleogene, catfishes have diversified into nearly all the world’s major freshwater systems, showing numerous morphological and ecological adaptations (e.g., accessory breathing in Clariidae, bony plates in Loricariidae).

1. Ecological and Economic Roles

• As benthic or night-feeding fishes, many Siluriformes species help manage invertebrate populations and recycle organic matter in aquatic systems.

• They play a substantial role in commercial fisheries, aquaculture, and ornamental fish markets (e.g., African sharptooth catfish, channel catfish, “plecos,” cory catfish).

1. Conservation Challenges

• Habitat fragmentation (dams), pollution, overfishing, and invasive species are threats to various catfish species worldwide.

• Lack of data on certain deep-river or specialized species hinders effective conservation; large tropical basins (Amazon, Mekong, Yangtze) face urgent management issues.

Summary

The above overview introduces the historical development, main families and ecological status of the Siluriformes, aiming to help you understand the systematic classification and diversity of fish in this order. If you need more in-depth species-level information, such as morphological characteristics, geographical distribution, conservation status, etc., you can refer to regional fish records, professional aquatic materials and the latest molecular systematic literature. I hope that this "Siluriformes Classification Encyclopedia" can provide you with clear and practical popular science and search materials.