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Setae on the foreleg of a mayfly. Annelid setae are stiff bristles present on the body. They help, for example, earthworms to attach to the surface and prevent backsliding during peristaltic motion. These hairs make it difficult to pull a worm straight from the ground. Setae in oligochaetes (a group including earthworms) are largely composed of ...
A chaeta or cheta (from Ancient Greek χαίτη (khaítē) 'crest, mane, flowing hair'; pl. chaetae) is a chitinous bristle or seta found on annelid worms, although the term is also frequently used to describe similar structures in other invertebrates such as arthropods.
Nereis is a genus of polychaete worms in the family Nereididae. It comprises many species, most of which are marine. Nereis possess setae and parapodia for locomotion and gas exchange. [1] They may have two types of setae, which are found on the parapodia. Acicular setae provide support.
Drawing of the statocyst system Statocysts (ss) and statolith (sl) inside the head of sea snail Gigantopelta chessoia. The statocyst is a balance sensory receptor present in some aquatic invertebrates, including bivalves, [1] cnidarians, [2] ctenophorans, [3] echinoderms, [4] cephalopods, [5] [6] crustaceans, [7] and gastropods, [8] A similar structure is also found in Xenoturbella. [9]
In some groups, such as the scale worms (e.g. Polynoidae), the dorsal cirrus is modified into a scale (or elytron). [ 2 ] In most species, the anteriormost segments may be specialised into the head region and prostomium , which can result in the modification of those parapodia, loss of chaetae and elongation of the cirri into anterior-facing ...
For much of the year, these worms look like any other burrow-dwelling polychaete, but as the breeding season approaches, the worm undergoes a remarkable transformation as new, specialized segments begin to grow from its rear end until the worm can be clearly divided into two halves. The front half, the atoke, is asexual.
Two mature Tubifex worms undergo copulation by joining ventral and anterior surfaces together with their anterior ends pointing opposite directions. Thus, the spermathecal opening of each worm is nearer to the male apertures of another worm. The penial setae of one worm penetrate into the tissues of other worm and thus the conjugants are held ...
Aphrodita aculeata, the sea mouse, is a marine polychaete worm found in the North Atlantic, the North Sea, the Baltic Sea and the Mediterranean. The sea mouse normally lies buried head-first in the sand. It has been found at depths of over 3,000 metres (9,800 ft). [2]