Seagrass epiphytes

Epiphytes are those organisms which grow upon plants. In aquatic environments macrophytes are usually rapidly colonized by microorganisms such as bacteria and micro-algae, and later by larger algae and invertebrates unless the macrophytes have chemical or physical mechanisms for excluding these organisms. Much of the literature on seagrass epiphytes is concerned with taxonomy (e.g. Humm, 1964; Marsh, 1973; May et al., 1978; Harlin, 1980; Pansini and Pronzato, 1985), and shows that seagrasses are colonized by a diverse range of algae and sessile invertebrates such as hydroids, bryozoans and sponges. In this paper we shall not provide further lists of epiphytic organisms, but rather will consider the distribution of the epiphytic organisms on individual seagrasses, between different seagrass species, and at different localities. We shall also discuss the mechanisms of colonization and recruitment, and the role of these epiphytic organisms in the ecology of seagrass communities

The oral fimbriae of the lamprey Geotria australis

The frond-like fimbriae surrounding the oral disc of the lamprey, Geotria australis, have been examined in living specimens, and by using histological, histochemical and ultra-structural techniques. Approximately 57 fimbriae are present in this species, with those at the posterior end of the disc being significantly larger than those in the anterior and lateral regions. The terminal finger-like projections of the fimbriae possess a stratified epithelium composed solely of a series of rows of mucous-producing cells. Tests have shown that the mucus of the epithelial cells contains large amounts of N-acetyl neuraminic acid. Since the adjacent fimbriae are closely apposed when the lamprey is using its oral disc for suction, it is suggested that their flexible shape, mucous secretions and production of an increased surface area for attachment, help to provide a more efficient seal. Since fimbriae are present in all lampreys except those species belonging to the Mordaciidae, it is postulated that their absence in this latter family can be related to known differences in the behaviour of their adult stages

The subcutaneous attachment of the monogenean Heterobothrium elongatum (Diclidophoridae) in the gills of Torquigener pleurogramma (Pisces: Tetraodontidae)

The subcutaneous attachment of the monogenean Heterobothrium elongatum (Diclidophoridae) in the gills of Torquigener pleurogramma (Pisces: Tetraodontidae). International Journal for Parasitology 20: 769-777. Heterobothrium elongatum predominantly occurred on the most anterior pair of gill arches of infected pufferfish, Torquigener pleurogramma. Juvenile and immature stages attached to gill lamellae and were concentrated on the ventral regions of the anterior pair of gill arches. Following penetration of subcutaneous tissues, young adult worms formed a subcutaneous channel either directly above or below the transverse septum, a tissue layer connecting the bases of adjacent gill rays. Large, sexually mature worms extended for most or all of the length of the gill arch where they filled the area normally occupied by the longitudinal lymphatic vessel (branchial vein) or lay adjacent to the efferent branchial and colateral arteries. Subcutaneous attachment by the parasite induced a marked inflammatory reaction in the host. During growth, the mid-region of the parasite became markedly elongate and formed a stalk connecting the haptor lying in the dorsal region of the gill and the body which emerged from the lower margin of the gill where penetration began

The development of an artificial, Amphibolis-like seagrass of complex morphology and preliminary data on its colonization by epiphytes

A method is described for the construction of artificial seagrass plants whose stems and terminal leaf clusters resemble those of Amphibolis spp. In preliminary trials, the artificial seagrasses were deployed and withstood at least 40 days immersion in a shallow, subtidal Amphibolis meadow on a moderate energy coastline in south-western Australia. In trials conducted between August (winter) and April (autumn), the artificial seagrasses became colonized with numerous algae and invertebrates that were present as epiphytes on living Amphibolis within the same meadow. Recruitment of epiphytes was usually rapid, and a number of species became fertile within the trial period. The artificial seagrasses described in this study represent a valuable tool for the assessment of epiphyte recruitment and growth on seagrasses that possess perennial stems and branches, and transient leaves within terminal clusters

The presence of helminths in a Southern Hemisphere lamprey (Geotria australis Gray), with a discussion of the significance of feeding mechanisms in lampreys in relation to the acquisition of parasites

This paper reports for the first time the presence of helminths in the gut and coelomic cavity of Southern Hemisphere lampreys. Moreover, the records of Pelichnobothrium and Hepatoxylon in the lamprey Geotria australis are also the first records of these helminth genera in any species of lamprey. A consideration of the literature on the parasites and feeding mechanisms of lampreys provides good evidence that those parasites which are found in adult lampreys but typically utilize arthropod intermediate hosts are obtained via the food ingested by the lamprey's host fish