Jack R. Davis

Species composition and diversity of benthic macroinvertebrate populations of the Pecos River, Texas.

A 2 year study (1976-1977) of benthic macroinvertebrates of the Pecos River in western Texas was conducted. Diversity was influenced by season and year, station, and various environmental parameters. Diversity was depressed in the upper reach by high salinity and extreme physiochemical fluctuations, but increased in the lower reach due to freshwater inflow and overall improvement in water quality. Coastal saltwater organisms occurred in the upper reach. Studies on benthic macroinvertebrate organisms in Texas are in- adequate (Hendricks et al. 1969). An acute paucity of such work exists in western Texas, particularly on the Pecos River where pre- vious studies of benthic macroinvertebrates are lacking. The present study was conducted to relate seasonal and annual variation in species composition and diversity of benthic macroinvertebrates in the Pecos River to physicochemical and other ecological factors. -~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~

AQUATIC OLIGOCHAETA NEW TO NORTH AMERICA WITH SOME FURTHER RECORDS OF SPECIES FROM TEXAS

Presented herein are accounts of 12 species of Naididae and three of Tubificidae now known to occur in western Texas. Dero (D.) pectinata and Pristina americana are new to the North American fauna, having previously been reported only from neotropical regions. Nais communis, N. variabilis, Para- nais litoralis, Pristina synclites, and Monopylephorus sp. are new to Texas. Chae- togaster diastrophus, Dero (Aulophorus) furcata, Dero (D.) digitata, Pristina aequiseta, P. leidyi, Slavina appendiculata, Limnodrilus hoffmeisteri, and L. udekemianus are known from elsewhere in the state, but their presence in western Texas considerably extends their known ranges.

First Records of Cordylophora lacustris Allman, 1871 (Hydroida: Clavidae) in Texas with Morphological and Ecological Notes

Cordylophora lacustris (Coelenterata) was collected from five inland fresh-water habitats across Texas, the first records for the species in the state. Morphological variations were observed in specimens from different habitats, a phenomenon that seems correlated to seasonal growth patterns and to physicochemi- cal differences between the aqueous environments. The species is adaptable to a variety of ecological conditions and is probably more widespread than the literature indicates.