Gracilaria mixta, sp. nov. and Other Western Pacific Species of the Genus (Rhodophyta: Gracilariaceae)

Abstract

Gracilaria mixta from South China is one of several terete species of Gracllaria that requires critical microscopic examination for identification. This new species demonstrates a mixture of spermatangial types that recently have been used to separate genera in the Gracilariaceae: the simple, pitlike Verrucosa type and the multicavitied Polycavernosa type arrangements. The first type is seen in the youngest branch portions, gradually changing to the second type in older parts. Both types of arrangements occasionally may be seen in the same cross section. Reexamination of male plants of the western Pacific taxa placed in Polycavernosa (= Hydropuntia) also shows both types of configurations in the same thalli. However, some species of Gracilaria with Verrucosa-type spermatangia maintain that type throughout the plants. These observations require a transfer of names from Hydropuntia (= Polycavernosa) to Gracilaria. From 16 taxa, 4 are retained in Gracilaria, 2 receive new names because of earlier homonyms, and 10 become new combinations within Gracilaria.