Fishes constitute a class of vertebrates. (animals with limbs with digits). They evolved from aquatic craniate animals with gills and no true spine. They have a closed-loop circulatory system and a variety of mechanisms for breathing oxygen. Some species can survive for protracted periods on land or in oxygen-depleted water.
Bony fishes comprise 45 orders and over 28,000 species, constituting a diverse superclass of vertebrates. They have predominantly skeletal skeletons and can be divided into ray-finned (Actinopterygii) and lobe-finned (Pisces) groups. (Sarcopterygii).
The earliest known bony fish lived in the Late Silurian period, 425 million years ago. The Guiyu oneiric had ray-fins and lobe-fins, but lobe-fins became less common during the Permian Period.
Actinopterygians have a complex skeleton composed of skull and pectoral girdle bones. Their heads and jaws are designed to accommodate their typically carnivorous diets. They have a pair of gill openings and an operculum covering the gills.
During the Paleozoic Era, a multitude of jawless fish species evolved. They ranged in size from small freshwater fish to two-meter-long marine agnathans.
These early jawless vertebrates possessed paired pectoral fins, a sclerotic ring around the eye, and internal bony supports for gill arches. Some groups formed these structures at maximal capacity, while others did so before reaching this stage of development.
Some of these later groups of jawless fish also had light-sensitive pineal organs beneath the orifice between their cranium bones. (like the lamprey). These organs were not used for visual perception but rather for transmitting information about the quantity of light in a given environment to the brain.
Chondrichthyans, or cartilaginous fishes, are a class of vertebrates with cartilage-based skeletons. In contrast, osteichthyans, or bony fishes, have skeletons composed of bone tissue.
Sharks (Elasmobranchs), skates, and rays are examples of Chondrichthyes. In addition, they consist of delusions, which are deep-water species that diverged from shark lineages during the Devonian period.
Cartilaginous fish are distinct from bony fish in that they lack pharyngeal jaws. Instead, they possess an oral mandible to grasp and assimilate food.
Ampullae is another distinguishing characteristic of cartilaginous fish. These are specialized sensory cells that detect the electrical charges their prey emits. They are found near the mouth or snout of sharks and stingrays. The animal also uses the ampullae to communicate with its environment.
Based on their water classification, fishes are divided into two major categories. Freshwater fish inhabit rivers and lakes, while saltwater fish inhabit oceans and seas.
Most ichthyoplankton develop from ova into larvae. (immature forms). Larval fishes feed endogenously or from within, allowing them to obtain the necessary nutrients for growth and development without leaving their egg sac.
Larval mortality is widely believed to be size-dependent, indicating that faster-growing individuals within a population have a reduced risk of being killed by predators. This hypothesis is predicated primarily on the theory that larger larvae have superior swimming abilities and extended swim times, reducing the time they are exposed to predators during their larval period.
There are an enormous variety of fish species. Some are tiny, while others can reach great heights! Many people maintain fish as pets, an excellent method to interest children in the marine environment. However, selecting species that can accommodate your tank or aquarium is essential.
It is a common misconception that fish are solitary creatures, but this is false! Certain fish, including cichlids, are social and exist in partnerships. A fish begins as an embryo, develops into a larva, and becomes a fry. The sauté stage may last a few days, weeks, or even months.