Alpheus saxidomus new species, a rock boring snapping shrimp from the Pacific coast of, Costa Rica, with notes on Alpheus simus Guérin-Méneville, 1856

Recently, Professor Dr. Rudolf Fischer, Institut für Geologie und Paläontologie, Philipps-Universität, Marburg, F. R. Germany, submitted for identification some material of an Alpheid shrimp, which was found to be responsible for a considerable erosion of part of a rocky shore on the Pacific coast of Costa Rica. The species proved to be new to science, while also the rock-boring activities seem hitherto to be unknown for the Alpheidae, or, for that matter, for Decapod Crustacea as a whole. The new species proves to be closely related to Alpheus simus Guérin-Méneville from the Caribbean area, but it shows minor, but evidently constant differences. It is a great pleasure to thank Professor Fischer for his kindness in allowing me to study this material and for the permission to cite here his observations on these interesting shrimps. The material is preserved in the collection of the Rijksmuseum van Natuurlijke Historie, Leiden. Some notes on Alpheus simus are added, as there proves to be a confusion about its nomenclatural and taxonomic status. Alpheus saxidomus new species Playa Tamarindo, Nicoya Peninsula, Pacific coast of Costa Rica, about 10°19'N 85°53'W; boring in basaltic rock in the surf zone; October 1978; R. Fischer. — 11 specimens (7 ovigerous females). Holotype is the largest ovigerous female ( RMNH Crust. no. D. 32108) ; the other specimens are paratypes (RMNH Crust. no. D. 32109). Size. — The carapace length of the specimens varies between 4 and 7 mm, of the ovigerous females it is 6 to 7 mm. The rather numerous eggs are 0.8 to 1.0 mm in diameter, those in which the young are practically ready for hatching measure 1.1 to 1.6 mm.