Animal Adaptations: Sensory Organs and Protective Structures

Animal Sensory Organs

The Lateral Line System

The lateral line is a specialized sensory organ found in fish and amphibian larvae. It can be identified as longitudinal lines on each side of the animal's body. These lines are formed by a succession of small pores that cross the scales and connect with a long, fluid-filled tube running beneath the skin along the animal's flanks. The inner tube is lined with hair cells, capable of capturing even the smallest water vibrations.

Facial Pits

The facial pit is a thermosensitive organ found in some snakes, such as rattlesnakes. It consists of two structures located between the eyes and mouth. These pits contain receptors capable of capturing infrared radiation, i.e., the heat emitted by other bodies. This allows snakes to detect the presence of other animals even when they cannot see them.

Ampullae of Lorenzini

The Ampullae of Lorenzini are specialized receivers capable of detecting changes in electric fields. They are found on the underside of the snout in certain chondrichthyan fish, including some types of sharks. This type of receptor is also found along the lateral line of a fish from the genus Gymnarchus, which lives in the Nile.

Animal Protective and Skeletal Structures

Porifera (Sponges)

Porifera (sponges) possess a skeletal framework composed of spongin, a tough, elastic fibrillar protein, and/or small mineral spicules. These elements provide consistency and maintain their body shape.

Cnidarians

Cnidarians, such as jellyfish, have soft bodies with a thin, elastic covering. Many polyps, however, are covered with a calcareous outer structure. In the case of coral, these structures can host millions of individuals and reach a large size.

Mollusks

• Gastropod mollusks secrete a shell from their outer mantle, consisting of calcium salts, which protects them. In general, this shell is usually coiled, except in slugs, which have an internal plate located above the respiratory cavity.
• Bivalve mollusks are characterized by two articulated shells (valves), which are closed strongly through the action of two powerful adductor muscles. This keeps the animal inside the shell, protected from predators.
• Some cephalopods, such as cuttlefish, have an internal calcareous shell, called a pen or cuttlebone.

These hard structures in mollusks grow concentrically as the animal's size increases.

Echinoderms

Echinoderms, such as sea urchins, have a skeleton composed of hard, articulated calcareous plates.

Arthropods

Arthropods, like insects, have an external skeleton (exoskeleton) that covers them. The exoskeleton is composed of chitin, a hard and lightweight substance. It consists of separate units linked together, allowing significant animal movement while protecting internal organs and preventing desiccation. In arthropods, muscles attach internally to the exoskeleton to facilitate appendage movements.

Vertebrates

Vertebrates have an internal skeleton made up of hard structures called bones. The skeleton consists of bone tissue, whose intercellular substance is mainly composed of calcium salts. Chondrichthyan fish have a softer skeleton formed of cartilaginous tissue, which is why they are known as cartilaginous fishes.