Contrasts among Calanoid Copepods from Permanent and Temporary Ponds in Arizona

Abstract

Thirty-seven plankton samples taken from Arizona ponds during October and November, 1962, contained calanoid copepods. Eighteen samples were judged to be from temporary waters, nineteen from permanent habitats. The species, in order of abundance, were Diaptomus albuquerquensis, D. siciloides, D. clavipes, D. novamexicanus, D. sanguineus and D. nudus. The first three occurred in both temporary and permanent waters; the last was present only in one permanent pond; and the other two species were restricted to temporary sites. Cephalothorax lengths for individual species were greater in tem- porary ponds than in permanent waters and, similarly, clutch sizes were greater. There was a strong correlation between female length and num- ber of eggs per clutch in D. clavipes, D. albuquerquensis and D. siciloides; the correlation was less in D. novamexicanus. Congeneric occurrence of adjacent-sized and similar-sized species is common in temporary ponds, but less so in permanent ponds. The reason for coexistence of similar- sized diaptomids, larger size, and more eggs per clutch in temporary ponds is either genetic, or the result of a better nutritional supply in ephemeral habitats. The trophic role of particles, which impart high turbidity to many temporary ponds, may be very important. In per- manent waters, predation could be a selective factor resulting in smaller individuals.