Report of Epibiont Diatom P. pacificum on the Cyclopoid Copepod D. affinis from the Southwestern Shelf Waters of India (Eastern Arabian Sea)

Pseudohimantidium pacificum, an epizoic diatom has been reported from different parts of the global oceans, however, has not been reported from the shelf waters of India. This symbiotic association of P. pacificum with a specific copepod species (Ditrichocorycaeus affinis) was repeatedly noticed from the shelf waters of the Arabian Sea during the winter monsoon from three locations in the South East Arabian Sea. Our study suggests towards host specificity of P. pacificum and additionally reveals their preference towards male hosts which is consistent with the earlier reports from other regions. Most importantly, this report extends the range of geographic distribution of the epibiont and this is the third report on this epibiont from the Indian Ocean region. It also suggests that epibiosis in marine zooplankton is much frequent phenomenon that has the potential to play an important role in the marine zooplankton population dynamics.