Differentiation of Alona Costata Sars From Two Related Species (Cladocera, Chydoridae) 1)

Abstract

DIFFERENTIATION OF ALONA COSTATA SARS FROM TWO RELATED SPECIES (CLADOCERA, CHYDORIDAE) 1) BY DAVID G. FREY Department of Zoology, Indiana University, Bloomington, Indiana, U.S.A. The three species of Alona considered in this study - A. co.rtata Sars, 1862, A. rustic Scott, 1895, and A. bicolor sp. nov. - are closely related morphologi- calty. They are the only known species of the genus with transversely elongated lateral pores on the head. These are readily visible in intact specimens and hence of great value in immediately assigning a specimen to this group of species. Dif- ferences in head-pore topology of subfossil material