Interesting Creatures… The Flea

May 30, 2021 Interesting Creatures in Guyana, News

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Kaieteur News – Fleas are wingless insects, 1.5 to 3.3 millimetres (1⁄16 to 1⁄8 inch) long, that are agile, usually dark coloured (for example, the reddish-brown of the cat flea), with a proboscis, or stylet, adapted to feeding by piercing the skin and sucking their host’s blood through their epipharynx. Flea legs end in strong claws that are adapted to grasp a host.
Unlike other insects, fleas do not possess compound eyes but instead only have simple eyespots with a single biconvex lens; some species lack eyes altogether. https://en.wikipedia.org/wiki/Flea – cite_note-2 Their bodies are laterally compressed, permitting easy movement through the hairs or feathers on the host’s body. The flea body is covered with hard plates called sclerites. These sclerites are covered with many hairs and short spines directed backward, which also assist its movements on the host. The tough body is able to withstand great pressure, likely an adaptation to survive attempts to eliminate them by scratching.
Fleas lay tiny, white, oval eggs. The larvae are small and pale, have bristles covering their worm-like bodies, lack eyes and have mouth parts adapted to chewing. The larvae feed on organic matter, especially the feces of mature fleas, which contain dried blood. Adults feed only on fresh blood.
Jumping
Their legs are long, the hind pair well adapted for jumping; a flea can jump vertically up to 18 cm (7 in) and horizontally up to 33 cm (13 in), making the flea one of the best jumpers of all known animals (relative to body size), second only to the froghopper. The flea jump is so rapid and forceful that it exceeds the capabilities of muscle and instead of relying on direct muscle power, fleas store muscle energy in a pad of the elastic protein named resilin before releasing it rapidly (like a human using a bow and arrow). Immediately before the jump, muscles contract and deform the resilin pad, slowly storing energy, which can then be released extremely rapidly to power leg extension for propulsion. To prevent premature release of energy or motions of the leg, the flea employs a “catch mechanism.” Early in the jump, the tendon of the primary jumping muscle passes slightly behind the coxa-trochanter joint, generating a torque, which holds the joint closed with the leg close to the body. To trigger jumping, another muscle pulls the tendon forward until it passes the joint axis, generating the opposite torque to extend the leg and power the jump by release of stored energy. The actual take off has been shown by high-speed video to be from the tibiae and tarsi rather than from the trochantera (knees).
Life cycle and development
Fleas are holometabolous insects, going through the four-lifecycle stages of egg, larva, pupa and imago (adult). In most species, neither female nor male fleas are fully mature when they first emerge but must feed on blood before they become capable of reproduction. The first blood meal triggers the maturation of the ovaries in females and the dissolution of the testicular plug in males and copulation soon follows. Some species breed all year round while others synchronise their activities with their hosts’ life cycles or with local environmental factors and climatic conditions. Flea populations consist of roughly 50 percent eggs, 35 percent larvae, 10 percent pupae and 5 percent adults.
Direct effects of bites
In many species, fleas are principally a nuisance to their hosts, causing an itching sensation, which in turn causes the host to try to remove the pest by biting, pecking or scratching. Fleas are not simply a source of annoyance, however. Flea bites cause a slightly raised, swollen, irritating nodule to form on the epidermis at the site of each bite, with a single puncture point at the center, like a mosquito bite. This can lead to an eczematous itchy skin disease called flea allergy dermatitis, which is common in many host species, including dogs and cats. The bites often appear in clusters or lines of two bites, and can remain itchy and inflamed for up to several weeks afterwards. Fleas can lead to secondary hair loss as a result of frequent scratching and biting by the animal. They can also cause anemia in extreme cases.
As a vector
Fleas are vectors for viral, bacterial and rickettsial diseases of humans and other animals, as well as of protozoan and helminth parasites. Bacterial diseases carried by fleas include murine or endemic typhus and bubonic plague. Fleas can transmit Rickettsia typhi, Rickettsia felis, Bartonella henselae, and the myxomatosis virus. They can carry Hymenolepiasis tapeworms and Trypanosome protozoans. The chigoe flea or jigger (Tunga penetrans) causes the disease tungiasis, a major public health problem around the world. Fleas that specialise as parasites on specific mammals may use other mammals as hosts; thus, cat and dog fleas may bite humans. (Source: Wikipedia)

 

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