Fish classification

Fish classification: Fish are vertebrate animals that inhabit aquatic environments, both freshwater and saltwater. They are known for their diversity, as they present a wide range of shapes, sizes and habits. Fish classification is a fundamental part of biology, as it helps us to understand the differences and similarities between the various species that make up this group. In general terms, fishes are classified into two major groups: osteocytes (bony fishes) and chondrichthyans (cartilaginous fishes).

Osteiectes: Bony fishes

Osteiectes, also known as bony fishes, are the largest group of fishes and comprise the majority of known species. These fishes have an internal skeleton composed mainly of bone, which gives them a stiffer and stronger structure.

Main characteristics of Osteiectes:

Bony skeleton: Unlike cartilaginous fishes, osteiectes have a skeleton made up of bones.

Gills with operculum: The gills of osteiectes are protected by a bony structure called operculum, which facilitates respiration.

Limbs with bony rays: Their fins are supported by bony rays, which provide support and mobility.

Ctenoid or cycloid scales: Most osteocytes have two types: ctenoid (serrated edges) or cycloid (smooth edges).

Diversity of shapes and sizes: This group ranges from small fish such as sardines to large predators such as tuna.

Examples of Osteiectes:

Tuna (Thunnus spp.): one of the best known fish, highly prized in cooking.

Sardine (Sardina pilchardus): Small and abundant, essential in the marine food chain.

Cod (Gadus morhua): Cold water fish, famous for its role in world gastronomy.

Seahorse (Hippocampus spp.): Known for its unique shape and curious reproductive behavior.

Chondrichthyans: Cartilaginous fishes

Chondrichthyans, or cartilaginous fish, include some of the most feared and fascinating species in the oceans, such as sharks and rays. The main distinguishing feature of this group is that they have a skeleton made of cartilage instead of bone.

Main characteristics of chondrichthyans:

Cartilaginous skeleton: Unlike osteocytes, chondrichthyans have a skeleton formed by cartilage, which is lighter and more flexible.

Absence of operculum: These fish lack an operculum to protect their gills. Instead, the gills are exposed through gill slits.

Rough skin: The skin of chondrichthyans is covered with placoid scales, which have a rough texture and help reduce friction with the water.

Internal fertilization: Many chondrichthyans, such as sharks, have an internal fertilization process, through a structure called a clasper, analogous to the mammalian penis.

Sharp, replaceable teeth: Sharks, in particular, are known for their sharp, replaceable teeth throughout their lives.

Examples of chondrichthyans:

Great white shark (Carcharodon carcharias): One of the oceans’ most formidable predators.

Manta ray (Manta birostris): Known for its large wingspan and filter feeding habits.

Chimera (Chimaera monstrosa): little known cartilaginous fish, with a characteristic appearance and deep-sea habits.

Importance of classification

The classification of fishes into osteocytes and chondrichthyans is crucial for the biology, ecology and conservation of these species. Knowing the differences between these groups allows a better understanding of their habits, their role in aquatic ecosystems and the threats they face. In addition, this classification helps to identify and study the myriad species of fish, allowing scientists and conservationists to develop more effective strategies for their preservation.

Fish are important in the aquatic ecosystem and in human life, scientific study or biodiversity that we must protect. Through a detailed knowledge of their classification, we can ensure that these animals continue to thrive in the world’s waters.