The NSS Bulletin - ISSN 1090-6924
Volume 41 Number 1: 11-14 - January 1979
A publication of the National Speleological Society

Variations in Body Color and Eye Pigmentation of Asellus brevicauda Forbes (Isopoda: Asellidae) in a Southern Illinois Cave System
Edward A. Lisowski

Abstract

Aquatic isopods were collected at 7 stations in and near Cave Spring Cave, Hardin Co., Illinois. Asellus brevicauda was the most common isopod species in the immediate vicinity of Cave Spring Cave and decreased in relative abundance downstream from the cave, whereas Lirceus fontinalis, which was never observed upstream from the resurgence of the cave stream, became more abundant. Asellus intermedius was ubiquitous, and Asellus stygius was found only in the cave stream and at its resurgence.

Of all the A. brevicauda collected, 37% were white, 28% were normally dark, and 35% were intermediate in integumentary pigmentation. The percentage of white forms decreased downstream from the cave, while the percentage of intermediate and dark forms were usually equal at a given station. Parasitism by acanthocephalan larvae was not a factor in the reduction or loss of body pigmentation. Reduced eye pigmentation was observed in 29% of the white A. brevicauda. The variation in body color and eye pigmentation was attributed to a change in the genetic constitution of the population.

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