A Scanning Electron Microscopic Study on the Appendage Morphology of Astacus leptodactylus (Eschscholtz, 1823) and Pacifastacus leniusculus (Daña, 1852) (Crustácea:Decapoda: Astacoidea)

Abstract

Estudio en Microscopio Electrónico de SUMMARY:This study compares the morphology of rostrum, pereipods 1,2,4 and mouthparts of juvenile Astacus leptodactylus with those of Pacifastacus leniusculus. Differences in morphology were observed, in particular with regard to the mouthparts e.g. including setal armature and number of teeth on the mandible. In general, the shape of the rostra in the two species is similar in that both taper to a point with a pair of sharp spines distally. Laterally the rostrum of A. leptodactylus is bordered by a regular row of setae, which is not so well defined in P. leniusculus. The observations also showed that in addition to an increase in size, changes in morphology in the feeding apparatus between the developmental stages of the two species were present. It was concluded that both species have similar rostra, but different setal patterns and there are differences between the two species in the armature of mouthparts as development progresses. Therefore, important differences in the morphology of mouthparts between P. leniusculus and A. leptodactylus and in the different stages of the species might cause a difference in the feeding behavior and food choice of the species.KEY WORDS: Appendages; Astacus; Crayfish; Mouthparts; Pacifastacus; Scanning electron microscope. INTRODUCTIONThe signal crayfish, Pacifastacus leniusculus (Dana, 1852), is native to north-western North America inhabiting lakes, streams and rivers (Lowery & Holdich, 1988) as well as saline waters (Henry & Wheatly, 1988;Holdich et al., 1997). It is also tolerant to environmental extremes such as temperature and various pollutants (Firkins, 1993). Pacifastacus leniusculus is similar in many ways to Astacus astacus (Linnaeus, 1758) and consequently has proved popular alternative since the decline of the latter species due to the introduction crayfish plague into many Europe catchments (Holdich, 1999). The signal crayfish is identified by its red colour, and large robust chela including a white to turquoise patch on the claw gives this crayfish its common name. This North American crayfish has been introduced into many European watersheds.The narrow-clawed crayfish, Astacus leptodactylus (Eschscoltz, 1823) is a native of Turkey and near East Europe.It occupies a similar niche to that of P. leniusculus. However, in addition to streams, rivers, lakes, and ponds, it also inhabits swamps. Thus, it is sometimes called the swamp crayfish (Cherkashina, 1975;Köksal 1988, Harlioglu & Harlioglu, 2004. Astacus leptodactylus is commercially exploited either as imports or from introduced populations distributed widely across Europe, exception of the Iberian Peninsula and Nordic countries (Harlioglu & Holdich, 2001;Holdich 2002;Skurdal & Taugbol, 2002). This species is identified by its long claws (mainly typical for males) and is commonly named the narrow-clawed or Turkish crayfish (Harlioglu, 1996).Pacificastacus leniusculus and A. leptodactylus have become popular experimental animals. The Turkish crayfish has been subjected to bi...