Hypnea

Abstract: Morphology and molecular phylogeny of a red algal species, Hypnea flexicaulis that is recently described from Japan, were investigated based on 23 collections from Korea (21), Taiwan (1), and the Philippines (1). Hypnea flexicaulis has percurrent axes with flexuous, antler-like branches which have wide branching angles, and abaxially curved ultimate branchlets. In order to study DNA divergence and phylogenetic relationships of the species, we determined plastid rbcL and mitochondrial cox1 sequences from the 23 collections. All 21 specimens from five different locations in Korea were almost identical to H. flexicaulis from Japan in rbcL sequences. Although there was a difference of three to five base pairs (bp) between samples from Korea and the Philippines or between the Philippines and Taiwan, Bayesian analyses of the rbcL data showed that all specimens from Korea, Japan, the Philippines, and Taiwan were strongly monophyletic. However, it is interesting that specimens from the Philippines differed by 31-34 base pairs in mitochondrial cox1 gene from those of materials from Korea and Taiwan, which differed by one to seven bp in rbcL between them. Although H. boergesenii is different from H. flexicaulis in having many antler-like branchlets, both appeared as sisters in all analyses of the rbcL data. This is the first report of H. flexicaulis from Korea based on morphology, rbcL, and cox1 gene sequences.

Abstract: The principal genera of plants consumed by green turtles in Torres Strait were Hypnea, Laurencia, Vadalia, Sargassum and Thalassia. Although some selectivity for soft red algae was detected, no evidence was found to support the theory that turtles feed on algae only when seagrasses are unavailable, but nor do algae appear to confer a nutritional advantage on those animals than eat them. Geographical variation in green turtle diets appears to be determined by the relative availability of seagrass and algae and the structure of the local herbivore community.

Abstract: The natural food spectrums of the different size groups of abalone, Haliotis asinina L., from Tawi-Tawi, southern Philippines, were determined by analysis of gut contents. Laboratory experiments were conducted to determine the feeding and defecation patterns and functional response of the abalone to varying food density under ambient water conditions. Like other tropical haliotids, H. astinina prefers red algae to brown algal species. Eighteen algal species, 72.2% of which are red algae (Rhodophyta), were observed in the gut contents of all size groups of abalone: Laurencia, Hypnea, Amphiroa and Coelothrix are the most frequent food species. Hypnea and Laurencia are also the most abundant food items of H. asinina. A chi-square test indicated that frequency of occurrence (%) of most algal food species in the gut samples is independent of the size of the animal. About 84% of all algal species were observed in the gut contents of small abalone. Haliotis asinina (mean shell length +/- SD = 3.48 +/- 0.05 cm) showed a distinct nocturnal feeding periodicity and remained cryptic during daylight hours. Feeding activity was intense from 1800 to 0200 h, but it slowed down a few hours before sunrise, resulting in about 11 h of feeding time within a 24-h cycle. Defecation occurred during the feeding period in proportion to the amount of food consumed and faecal production during the night was significantly higher than during the daylight hours. The total daily faecal output was 1.26 mg dry weight abalone-1. The experiments showed that H. asinina (mean shell length +/- SD = 3.55 +/-0.02 cm) consumed more food when food density increased in linear proportion to food abundance. However, food consumption levelled off at a food density equivalent to 35% of body weight.