Life cycle of the marine leech ( Zeylanicobdella arugamensis) isolated from sea bass ( Lates calcarifer) under laboratory conditions

Abstract

Infestation of unidentified marine leeches in Malaysia was first reported in 1988 in grouper ( Epinephelus coioides) cultured in floating cages with a prevalence of 0.4%. Recently (2004–2006), the marine leech Zeylanicobdella arugamensis was regularly isolated from marine fish cultured in cages. In May 2006, approximately 60% of moribund sea bass fingerlings reared in cages were infected with Zeylanicobdella arugamensis, which may also serve as a vector for the bacteria, Vibrio alginolyticus. The aim of the present study was to determine the life cycle of Z. arugamensis under laboratory conditions. A total of 105 adult leeches, 4.5–14.0 mm in length, from five trial experiments were sampled and brought to the laboratory. Leeches with average size exceeding 10.00 mm could deposit cocoons after 5–8 h of isolation. Seven days were needed for the new egg inside the cocoon to develop into juvenile under 27 °C at 28 ppt. It took another 9 to 10 days for the juvenile leeches to grow to mature adults. Overall, the Z. arugamensis took 16 to 17 days to mature. In the present study, we observed that a single leech can reproduce and this self-fertilization or direct fertilization has never been reported in a piscicolid leech.