PROROCENTRUM-BELIZEANUM, PROROCENTRUM-ELEGANS, AND PROROCENTRUM-CARIBBAEUM, 3 NEW BENTHIC SPECIES (DINOPHYCEAE) FROM A MANGROVE ISLAND, TWIN-CAYS, BELIZE

Three new benthic dinoflagellate species, Prorocentrum belizeanum, Prorocentrum elegans, and Prorocentrum caribbaeum, from mangrove floating detritus are described from scanning electron micrographs. Species were identified based on shape, size, surface micromorphology, ornamentation of thecal plates, and architecture of the periflagellar area and intercalary band. Cells of P. belizeanum are round to slightly oval with a cell size of 55-60 mum long and 50-55 mum wide. Areolae are round and numerous (853-1024 per valve) and range from 0.66 to 0.83 mum in size. The periflagellar area of P. belizeanum is a broad V-shaped depression; it accommodates a flagellar and an auxiliary pore and a flared, curved apical collar. The intercalary band of P. belizeanum is horizontally striated. Prorocentrum elegans is a small species 15-20 mum long and 10-14 mum wide, with an ovate cell shape. The thecal surface is smooth. Two sizes of valve pores were recognized: large, round pores (20-22 per valve) arranged in a distinct pattern and smaller pores situated in an array along the intercalary band. The periflagellar area is V-shaped; it accommodates an uneven sized flagellar pore, an auxiliary pore, and an angled protuberant flagellar plate. The intercalary band is transversely striated. It is a bloom-forming species. Prorocentrum caribbaeum cells are heart-shaped with a rounded anterior end and a pointed posterior end. Cells range from 40 to 45 mum long and 30 to 35 mum wide. Thecal surface has two different-sized pores: large, round pores (145-203 per valve) arranged perpendicularly from the posterior margins, and small, round pores unevenly distributed on the thecal surface. The periflagellar area is ornate. It is V-shaped with a curved apical collar located next to the auxiliary pore; a smaller protuberant apical plate is adjacent to the flagellar pore. The intercalary band is transversely striated and sinuous. Cells are active swimmers.