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On segments three to five there is usually one spine in the first line. First line spines are larger and sharper to very sharp on larger individuals, above 40 mm (1.6 in). A second line of spines is generally poorly developed, being absent to tiny in smaller animals, under 30 mm (1.2 in), and tiny to small on larger specimens.
Pontastacus leptodactylus, [2] the Danube crayfish, [3] Galician crayfish, [3] Turkish crayfish [4] or narrow-clawed crayfish, is a relatively large and economically important species of crayfish native to fresh and brackish waters in eastern Europe and western Asia, mainly in the Pontic–Caspian region, among others including the basins of the Black Sea, and the Danube, Dnieper, Don and ...
Rostrum (from Latin rostrum, meaning beak) is a term used in anatomy for several kinds of hard, beak-like structures projecting out from the head or mouth of an animal. Despite some visual similarity, many of these are phylogenetically unrelated structures in widely varying species.
The rostrum is short and in individuals over 50 mm (2.0 in) OCL usually does not reach the base of the third antenna segment. In those measuring 20–140 mm (0.79–5.51 in) OCL the rostrum is to the base or midpoint of that segment and, in some under 20 mm (0.79 in), goes to the end of the third segment. [4]
Compared to other species of crayfish in its range, L. chimera is a sizable crayfish. On average, adults of this species range from about 9.5 to 11.8 centimeters (or 3.7 to 4.7 inches) in body length, measuring from the anterior tip of the rostrum to the posterior tip of the telson.
The Dougherty Plain cave crayfish grows to a length of about 53 millimetres (2.1 in) with antennae twice this length. It is a colourless species with unpigmented eyes, segmented cephalothorax and abdomen, a pair of slender chelae (claws) with a row or two of tubercles and long slender appendages.
The Hell Creek Crayfish lacks pigment in its body and does not have eyes. It reaches an overall body length of 2.5 to 3.0 inches. [3] It has a convergent rostrum, which is the beak-like shell located between the crayfish's eyes. [5] Its areola is narrow, and if a cervical spine is present, it is very small.
The prementum closes the preoral cavity from behind. Terminally, it bears four lobes, two inner glossae, and two outer paraglossae, which are collectively known as the ligula. One or both pairs of lobes may be absent or they may be fused to form a single median process. A palp arises from each side of the prementum, often being three-segmented ...