The genus Ramicrusta (Peyssonneliales, Rhodophyta) in the Caribbean Sea, including Ramicrusta bonairensis sp. nov. and Ramicrusta monensis sp. nov.
Two new species of Ramicrusta (Peysson- neliaceae, Rhodophyta), Ramicrusta bonairensis from Bonaire, The Netherlands Antilles and Puerto Rico and Ramicrusta monensis from Puerto Rico are described on the basis of both morphological and genetic criteria. Both grow closely appressed to their substrata, a characteristic that differs from their Caribbean congener, Ramicrusta tex- tilis, which forms flared or broadly fluted, expanded erect tissue, and is not closely appressed throughout. The new species also share with each other, the character, seen in microscopic sections, of appearing layered due to an abrupt decrease in cell size that occurs in the perithallus. Ramicrusta bonairensis is thicker than R. monensis, form- ing crusts up to 840 μm thick and carposporangia that measure up to 80 μm in length. Ramicrusta monensis is less thick, 585–650 μm, and produces smaller carposporangia, 40–50 μm in length. Overgrowing thalli in R. monensis are commonly observed, frequently resulting in gaps visible in transverse microscopic sections. Irregular perithallial growth may also result in hollow regions. Male gameto- phytes are reported for the first time in R. textilis and in R. monensis. Mixed reproductive phases in individual thalli, with both male gametophytic structures and tetrasporan- gial nemathecia, are also observed in R. monensis.