Morphological study of two species of shrimp Palaemon adspersus Rathke 1837 and Palaemon elegans Rathke 1837 from the Caspian Sea.

The Caspian Sea has only two species of shrimp, the scientific names of which are Palaemon adspersus Rathke 1837 and Palaemon elegans Rathke 1837. These two species have entered the Caspian Sea from the Black Sea. In the present study, the morphological characteristics of two shrimp species, P. adspersus and P. elegans, were comparatively studied. The samples were collected from Anzali port area by 500 μ mesh size Landing net, then transferred to the marine biology laboratory in 70% ethanol for preservation and later studies. Different parts of the body as well as mouthparts were studied and examined by a stereomicroscope. Based on many photographs schematic images were drawn. The results showed that the most important morphological features used to distinguish two species from each other, the differences are in rostrum (number of teeth), telson (number of setae and the size of terminal spines), maxilla 1 (lower lacinia), mandibule (palps and dental appendages of molar and incisor), which can be used as keys to identify two species.Keywords: Morphology, Mouthparts, Shrimp, Caspian Sea