BETA-KAPPA-CARRAGEENANS AS EVIDENCE FOR CONTINUED SEPARATION OF THE FAMILIES DICRANEMATACEAE AND SARCODIACEAE (GIGARTINALES, RHODOPHYTA)

The Dicranemataceae consists Of five species in four genera of macrosc opic red algae endemic to the southern half of Australia plus a single species from southern Japan. Investigations of the nonfibrillar wall components of five of the six species show that all are composed mainl y of hybrid (or mixed) beta (beta)/kappa (kappa)-type carrageenans. De tailed studies of Tylotus obtusatus (Sonder)J. Agardh show that it pro duces the largest dry-weight percentage of beta-carrageenan yet record ed. Monosaccharide composition, total sulfate content, sulfation Patte rn revealed by infrared and C-13-nuclear magnetic resonance spectrosco py, and a positive specific optical rotation ([alpha]D +54-degrees) ar e indicative of a low-sulfate-containing carrageenan with gelling prop erties similar to those of agar and furcellaran. Beta-carrageenan is r ecorded in only five other red algal species belonging to relatively u nrelated families, and we conclude that its uniform occurrence in the highly specialized family Dicranemataceae has phylogenetic significanc e. Chemical and anatomical examination of the genus Sarcodia, which pr oduces lambda-type carrageenan in both its gametophytic and tetrasporo phytic phases, suggests that, despite the recent proposal to incorpora te the Dicranemataceae into the Sarcodiaceae, the two families should continue to be separated.