Portia Spider Anatomy

Portia spiders are hunting spiders and are among the most numerous spider species in the world. They belong to the jumping spider family called Salticidae. Jumping spiders are easily distinguished from other spiders because they have two forward facing eyes, flanked by two smaller ones, and a pair of 'lesser' eyes on the sides of the head. They have superior vision compared to sight other spider species and can see in colour, even in ultra violet.

The anatomy of the Portia spider is divided into a cephalothorax and abdomen, covered by a chitinous exoskeleton. The cephalothorax or prosoma is a fusion of the head and thorax. The top of the cephalothorax is the covered by a carapace while the underside is by a sternum. All eight segmented legs are attached to the cephalothorax. The limbs do not have muscles and are extended by changing the pressure of hemolymph. Specialised hairs known as setae on their legs enable them to detect scents, sounds and vibrations.

At the front of the cephalothorax are the pedipalps, jaws and side moving fangs. Specialised pedipalps are used by males for mating purposes. Small maxillae at the base of pedipalps are used to bring food into the mouth. The prosoma also houses the brain, eight eyes, venom glands, and venom canals.

The abdomen includes the heart, lungs, digestive tubule, ovaries, testes, and silk glands. Two plates on the underside of the abdomen called the epigastric plates cover the book lungs. Respiration takes place through two haemolymph-filled book lungs and a trachea near the spinnerets. A short distance in front the epigastric plates is the epigyne, which leads to the oviduct. Just before the spinnerets is a usually a single opening, the trachea. At the end of the abdomen are the spinnerets, and depending on the species, there are about eight spinnerets.

Like most arthropods the Portia spider has an open circulatory system. Instead of having a system of veins and true blood, they have simple tubular heart that pumps haemolymph throughout the body. Haemolymph is blood-like fluid containing hemocyanin and is similar to haemoglobin, which gives the blood a slight blue colour. The excretion anatomy of the Portia spider is basic. The Malpighian tubules remove waste products such as nitrates and ammonia out of the haemolymph, to be disposed off through the anus.

Captured prey is immobilised and digested by injected venom. The dissolved prey is sucked into the mouth by the straw-like pharynx organ. Liquefied food enters the sucking stomach from the esophagus and then branches into digestive cecum, distributing nutrients to the legs, and other parts of the body. The sucking stomach also leads to the intestines, opening into the anus.

Reproduction takes place sexually. On the underside is the epigyne, which is a chitinous, brownish plate with two openings. The ovaries are connected to the exterior of the abdomen via the oviduct that ends at the epigyne. The grooves and ducts in the epigyne store sperm.

The reproductive anatomy of male Portia spiders is typical of spiders - the pedipalps are enlarged at the ends. The pedipalps are rubbed on the underside, transferring sperm from the epigastric furrow. When the male spider finds a mate, and providing she does not eat him first, he inserts his pedipalps into her epigyne, fertilising her eggs.