DISTRIBUTION OF THECAMOEBIANS (TESTATE AMOEBAE) IN SMALL LAKES AND PONDS, BARBADOS, WEST INDIES

Abstract

Thecamoebian faunas identified from 15 small permanent and ephemeral lakes and ponds on Barbados, West Indies, are characterized by low numbers of individuals and low species diversities (Shannon-Wiener Diversity Index = 0–1.4). Four lakes and ponds were found to contain no thecamoebians. The faunas were dominated by Centropyxis aculeata , with lesser numbers of Arcella vulgaris , Cucurbitella tricuspis , Centropyxis constricta and Cyclopyxis kahli . Very low numbers of the small idiosomic species Euglypha rotunda and an undifferentiated Corythion-Trinema type were also reported; the first records from a tropical region. Centropyxid-dominated faunas have been reported from other tropical areas and may indicate stressed environmental conditions. Additional important ecological controls on these faunas include substrate characteristics, the nature of bankside and aquatic vegetation and water depth. Land use characteristics do not appear to have a significant influence on faunal distribution, although the soil indicator thecamoebian species C. kahli seems to have been introduced into at least one pond through erosion from adjacent fields. Significant numbers of the salt marsh foraminiferid Jadammina macrescens , and lesser numbers of Polysaccammina ipohalina and Miliammina fusca , were found in one coastal pond, with a few specimens of J. macrescens found in another. The presence of this unusual, nonmarine foraminiferal fauna may relate to the intrusion of salt water into local ground waters, or possibly the introduction of sea salt from the prevailing Atlantic winds. Foraminiferal and thecamoebian colonization into the ponds may have been avian mediated.