Biogeographic and ecological implications of newly discovered populations of the stygobiont isopod crustacean Antrolana lira Bowman (Cirolanidae)

• Published in: Journal of natural history Vol. 28; no. 5; pp. 1047 - 1058
• Main Authors: Holsinger, J.R., Hubbard, D.A., Bowman, T.E.
• Format: Journal Article
• Language: English
• Published: Taylor & Francis Group 01.10.1994
• Subjects: Antrolana lira; Cirolanidae; Cretaceous; embayments; Freshwater; groundwater; isopods; karst; phreatic; stranding; subterranean; Tertiary; USA, Virginia, Shenandoah Valley; USA, Virginia
• ISSN: 0022-2933; 1464-5262
• DOI: 10.1080/00222939400770551

The recent discovery of the stygobiont isopod Antrolana lira Bowman from five new cave localities in the Shenandoah Valley of northwestern Virginia has not only resulted in a significant range extension for this rare species but has also shed new light on its origin and increased our knowledge of its habitat. Prior to 1990, A. lira was known only from two caves on the northeastern end of Cave Hill in Augusta Co., VA. To date A. lira has been found only in bodies of cave water that fluctuate in concert with vertical movements of the local water table, suggesting that this species is confined to open fissures and solution cavities in the phreatic zone. Although it is widely accepted that subterranean freshwater isopods of the predominantly marine family Cirolanidae were derived from marine ancestors by 'stranding' during regressions of marine embayments in Late Cretaceous or Tertiary times, until now this theory failed to explain the origin of A. lira. Unlike all other stygobiont cirolanids, the known distribution of A. lira was believed to be too far inland to have been affected by Cretaceous or Tertiary marine embayments in eastern North America. However, one of the new localities extends its range approximately 96 km north-northeast of Cave Hill, and therefore much closer to carbonate rocks in the northern Shenandoah Valley that conceivably were proximate or even directly exposed to one of the more extensive marine transgressions into the Potomac basin during the late Cretaceous or early to middle Tertiary.