Gavin W. Maneveldt

A Comparison of Various Seaweed-Based Diets and Formulated Feed on Growth Rate of Abalone in a Land-Based Aquaculture System

The effects of different diets on growth in the cultured South African abalone, Haliotis midae (Linnaeus), was investigated. Growth of juvenile Haliotis midae was monitored on a commercial abalone farm over a period of 9 months in an experiment consisting of 9 treatments with 4 replicates (n = 250 individuals per replicate). The treatments were: fresh kelp (Ecklonia maxima) blades (seaweed control); Abfeed® (formulated feed control); kelp + Abfeed® dried kelp pellets; dried kelp blades; dried kelp stipes; fresh kelp with the epiphyte Carpoblepharis flaccida; a mixed diet (Gracilaria gracilis, Ulvalactuca, and kelp) and a rotational diet (abalone were fed 1 of the 9 treatments for the first week and them kelp for the next 3 weeks). Results show that abalone grow well on all fresh seaweed combinations, but grow best on a mixed diet. The likely reason for the success of the mixed diet is that the red and green seaweed was farm grown, with an increased protein content. Dried kelp in any form produced poor growth. Abalone fed on the mixed diet grew at 0.066 mm day−1 shell length and 0.074 g day−1 body weight; this corresponds to 24.09 mm shell length and 27.01 g body weight increase per annum. Abalone fed on dried kelp grew at only 0.029 mm day−1 shell length and of 0.021 g day−1 body weight. Abalone grown on Abfeed® grew at 0.049 mm day−1 shell length and 0.046 g day−1 body weight which corresponds to 17.88 mm and 16.79 g increase per annum; this is better than the dried seaweed feeds, but poorer than the fresh seaweed combinations. This study shows that seaweed diets, particularly if the diets include seaweeds grown in animal aquaculture effluent, are good substitutes for the formulated feed generally used today.

Evolutionary history of the Corallinales (Corallinophycidae, Rhodophyta) inferred from nuclear, plastidial and mitochondrial genomes

Systematics of the red algal order Corallinales has a long and convoluted history. In the present study, molecular approaches were used to assess the phylogenetic relationships based on the analyses of two datasets: a large dataset of SSU sequences including mainly sequences from GenBank; and a combined dataset including four molecular markers (two nuclear: SSU, LSU; one plastidial: psbA; and one mitochondrial: COI). Phylogenetic analyses of both datasets re-affirmed the monophyly of the Corallinales as well as the two families (Corallinaceae and Hapalidiaceae) currently recognized within the order. Three of the four subfamilies of the Corallinaceae (Corallinoideae, Lithophylloideae, Metagoniolithoideae) were also resolved as a monophyletic lineage whereas members of the Mastophoroideae were resolved as four distinct lineages. We therefore propose to restrict the Mastophoroideae to the genera Mastophora, Metamastophora, and possibly Lithoporella in the aim of rendering this subfamily monophyletic. In addition, our phylogenies resolved the genus Hydrolithon in two unrelated lineages, one containing the generitype Hydrolithon reinboldii and the second containing Hydrolithon onkodes, which used to be the generitype of the now defunct genus Porolithon. We therefore propose to resurrect the genus Porolithon for the second lineage encompassing those species with primarily monomerous thalli, and trichocyte arrangements in large pustulate horizontal rows. Moreover, our phylogenetic analyses revealed the presence of cryptic diversity in several taxa, shedding light on the need for further studies to better circumscribe species frontiers within the diverse order Corallinales, especially in the genera Mesophyllum and Neogoniolithon.

Ecological significance of deep-layer sloughing in the eulittoral zone coralline alga, Spongites yendoi (Foslie) Chamberlain (Corallinaceae, Rhodophyta) in South Africa

Abstract The crustose coralline alga Spongites yendoi (Foslie) Chamberlain (Corallinaceae, Rhodophyta) dominates the lower eulittoral zone along the South Coast of South Africa, together with the limpet Patella cochlear Born. This coralline alga was previously shown to undergo a deep-layer sloughing twice a year, as well as continuous epithallial sloughing. The hypothesis that deep-layer sloughing could perform an antifouling function was tested by determining the percentage cover of fleshy algae developing in a limpet exclusion experiment on live and killed coralline. Substantial fleshy algal cover developed in both limpet removal treatments, negating any possible antifouling function of deep-layer sloughing. A measurable decrease in the mean thickness of the coralline population was noted during periods of sloughing. A thicker crustose coralline, Leptophytum ferox (Foslie) Chamberlain & Keats, grew more slowly and was much more heavily burrowed and more weakly attached than S. yendoi . These results are consistent with a hypothesis that deep-layer sloughing contributes to the algas relatively thin thallus, thereby conferring the advantages of faster growth and stronger attachment. However, further studies are still needed to evaluate these hypotheses further.

Rhodolith-forming species of Lithophyllum (Corallinales; Rhodophyta) from Espirito Santo State, Brazil, including the description of L. depressum sp. nov.

Villas-Boas A.B., Riosmena-Rodriguez R., Amado-Filho G.M., Maneveldt G.W. and de O. Figueiredo M.A. 2009. Rhodolith-forming species of Lithophyllum (Corallinales; Rhodophyta) from Espírito Santo State, Brazil, including the description of L. depressum sp. nov. Phycologia 48: 237–248. DOI: 10.2216/08-35.1. The taxonomy of the rhodolith-forming species of Lithophyllum (Corallinales, Rhodophyta) found from Espirito Santo State, Brazil, were evaluated based on extensive subtidal sampling. A comparative analysis of the Brazilian material with recently described species lead us to conclude that three known species (Lithophyllum corallinae, L. johansenii, L. stictaeforme) and one species new to science (Lithophyllum depressum Villas-Boas, Figueiredo & Riosmena-Rodriguez) are present in the area. All four species can be distinguished primarily by their tetrasporangial conceptacle roof anatomy. This study has shown that Brazilian rhodolith beds are comparatively more diverse in number of Lithophyllum species than other areas of the world.

First report of Sporolithon ptychoides (Sporolithales, Corallinophycidae, Rhodophyta) for the Atlantic Ocean

Samples corresponding to Sporolithon ptychoides Heydrich were collected in the mesophotic zone (50 m depth) south of Espírito Santo State, Brazil. The collected material presented features characteristic of the species, namely: tetrasporangia of 75–105 × 40–55 µm grouped into sori that are raised above the surrounding vegetative thallus surface; presence of a basal layer of elongate cells in areas where the tetrasporangia develop; presence of buried tetrasporangial compartments deep in the thallus; and 3–5 cells in the tetrasporangial paraphyses. These same features said to collectively characterize S. ptychoides, were all observed in a representative specimen and the type specimen of Sporolithon dimotum (Foslie & Howe) Yamaguishi‐Tomita ex M.J Wynne. This latter species is thus conspecific with S. ptychoides and is therefore considered a heterotypic synonym thereof, as S. ptychoides has nomenclatural priority. This study expands the known geographical distribution of the species and may give insight into the origin of the species into other geographical regions.

Leptophytum foveatum Chamberlain and Keats (Rhodophyta, Corallinales) retaliates against competitive overgrowth by other encrusting algae

Abstract The encrusting coralline alga, Leptophytum foveatum, is the most abundant crustose alga in the lower eulittoral zone at Yzerfontein and other exposed sites on the West Coast of South Africa. The surface of this species is usually imbricate (appears scaly) as a result of the aparently spontaneous regeneration of margins at the surface of the thallus. The thicker, fleshy, brown crustose alga, Ralfsia verrucosa, usually overgrows the margins of the thinner L. foveatum; however, L. foveatum counteracts this overgrowth by regenerating margins at the thallus surface, and these are able to grow up and over the encroaching margin of R. verrucosa. Experiments in which these regenerated margins were removed showed that the regenerated margins are able to slow or stop the encroachment of R. verrucosa. It is suggested that the regeneration of thallus margins at the surface, away from the primary thallus margin, allows L. foveatum to maintain the advantages of being thin (e.g. more rapid lateral growth), but also gain some of the advantages of being thick (e.g. improved competitive ability).

Effects of herbivore grazing on the physiognomy of the coralline alga Spongites yendoi and on associated competitive interactions

The territorial gardening limpet Scutellastra cochlear occurs along the south and southern west coasts of South Africa, whereas one of its primary food items, the encrusting coralline alga Spongites yendoi, extends much farther north along the West Coast. A combined analysis of geographic variation in limpet grazing frequency and a limpet-manipulation experiment was used to study the interaction between the limpet and its coralline food. The coralline comprised most (c. 85%) of the limpets diet whereas fleshy algae from the limpets garden comprised c. 7%. Grazing caused the thallus of the coralline to be thin and smooth; in the absence of herbivory, or under low grazing frequencies, the crust became thick and highly protuberant. Grazing weakened the corallines interference (overgrowth) competitive ability and also reduced its fecundity. In spite of these two apparently negative impacts, the intimate herbivore–coralline association between S. cochlear and S. yendoi showed characteristics of a facultative mutualism. Grazing by S. cochlear reduces the corallines thallus thickness and consequently increased its lateral margin extension rate. Thinner forms of the coralline grew five times faster than thicker forms. An increased lateral growth results in the thinner form of the coralline being very abundant on the south and southern west coasts, occupying as much as 79% of the substratum in the lower eulittoral zone. Thinner forms of S. yendoi were also less burrowed by boring organisms and more strongly attached than thicker forms of the coralline. Grazing by S. cochlear has thus conferred the advantages of faster lateral growth (i.e. success at exploitation competition) and stronger attachment. The coralline and fleshy algae from the limpets garden were equally high in organic content on a volume basis. This suggests that the crude food value per bite in the coralline and fleshy algae is comparable. This study has shown that incompletely overlapping distributions between strongly interacting species along a broad geographical gradient is not just a significant feature of the ecology of terrestrial, but also of marine ecosystems.

Heydrichia cerasina sp. nov. (Sporolithales, Corallinophycidae, Rhodophyta) from the southernmost tip of Africa

Maneveldt G.W. and van der Merwe E. 2012. Heydrichia cerasina sp. nov. (Sporolithales, Corallinophycidae, Rhodophyta) from the southernmost tip of Africa. Phycologia 51: 11–21. DOI: 10.2216/11-05.1 A new species of Heydrichia (Sporolithales), Heydrichia cerasina sp. nov., is described, found only on pebbles in the low intertidal zone along a 10 km stretch of the South African south coast from Cape Agulhas to Struisbaai. The species is characterized by the following suite of features that distinguish it from the other two species of Heydrichia found in South Africa: (1) unusual cherry-red colour when freshly collected; (2) uniformly warty growth form; (3) relatively thin crust (up to 1400 µm thick); (4) tetra/bisporangial sori comprised of mostly single sporangial chambers; and (5) unbranched spermatangial structures distributed on the floor, walls, and roof of the mature male conceptacle. The species appears to be most closely related to Heydrichia homalopasta from Australia. This study has affirmed that the distribution of spermatangial structures within male chambers is a feature that cannot be used to separate Heydrichia from Sporolithon, the only other genus in Sporolithales, although features of thallus construction and tetra/bisporangia continue to distinguish the genera. A key to the southern African species from the order Sporolithales is provided.

Competitive relationships and coexistence in a guild of crustose algae in the eulittoral zone, Cape Province, South Africa

A number of crustose, fleshy and coralline algae coexist in the eulittoral zone along the south-western coast of South Africa, in spite of potentially competing for the same limiting resource, space. A number of questions concerning coexistence among crustose algae were addressed in a study conducted at Holbaaipunt, in the southwestern Cape Province. To some degree, the crustose algae occur in different zones, and this may thus reduce competition. It was shown that non-transitive networks did not exist among the crustose algae at this site, so do not contribute to the coexistence of these crustose algae. While most species occur on rock substratum, one species occurs primarily on worm tubes and compacted calcareous material, suggesting that habitat heterogeneity within zones may contribute to the coexistence of these crustose species. Differential susceptibility to, and recovery from, disturbance may also contribute to coexistence. The thinnest species in the mid-lower eulittoral zone at this site, Spongites yendoi (Foslie) Chamberlain, dominates the space in spite of its position near the bottom of the overgrowth hierarchy. This may be because its thin thallus shows faster lateral growth and less susceptibility to disturbance than its thicker competitors. Thallus thinness may be maintained by the periodic deeplayer sloughing of a surface layer, as well as by heavy grazing by Patella cochlear Born.

The Role of Encrusting Coralline Algae in the Diets of Selected Intertidal Herbivores

Kalk Bay, South Africa, has a typical south coast zonation pattern with a band of seaweed dominating the mid-eulittoral and between two molluscan-herbivore dominated upper and lower eulittoral zones. Encrusting coralline algae were very obvious features of these zones. The most abundant herbivores in the upper eulittoral were the limpet, Cymbula oculus (10.4 ± 1.6 individuals m−2; 201.65 ± 32.68 g.m−2) and the false limpet, Siphonaria capensis (97.07± 19.92 individuals m−2; 77.93 16.02 g.m−2). The territorial gardening limpet, Scutellastra cochlear, dominated the lower eulittoral zone, achieving very high densities (545.27 ± 84.35 m−2) and biomass (4630.17 ± 556.13 g.m−2), and excluded all other herbivores and most seaweeds, except for its garden alga and the encrusting coralline alga, Spongites yendoi (35.93 ± 2.26% cover). In the upper eulittoral zone, encrusting coralline algae were only present in the guts of the chiton Acanthochiton garnoti (30.5 ± 1.33%) and the limpet C. oculus (2.9 ± 0.34%). The lower eulittoral zone limpet, Scutellastra cochlear also had a large percentage of encrusting coralline algae in its gut with limpets lacking gardens having higher (45.1 ± 1.68%) proportions of coralline algae in their guts than those with gardens (25.6 ± 0.8%). Encrusting coralline algae had high organic contents, similar to those of other encrusting and turf-forming algae, but higher organic contents than foliose algae. Radula structure, grazing frequencies as a percentage of the area grazed (upper eulittoral 73.25 ± 3.60% d−1; lower eulittoral 46.0 ± 3.29% d−1), and algal organic content provided evidence to support the dietary habits of the above herbivores. The data show that many intertidal molluscs are actively consuming encrusting coralline algae and that these seaweeds should be seen as an important food source.