Department of Botany and Zoology

Permanent URI for this community

https://scholar.sun.ac.za/handle/10019.1/219

Browse

Browsing Department of Botany and Zoology by Subject "Abalone -- Diseases and pests"

Now showing 1 - 1 of 1
  • Thumbnail Image
    Item
    A systematic review of the so-called cosmopolitan polydorid Polydora hoplura Claparede, 1869 (Polychaeta: Spionidae) on the South African coast.
    (Stellenbosch : Stellenbosch University, 2014-12) Van Niekerk, Sandy Eve; Simon, Carol; Matthee, Conrad; Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology.
    ENGLISH ABSTRACT: Introduction: Polydora hoplura is considered a cosmopolitan or alien species on the South African coast and is an important pest affecting farmed abalone and oysters in the region. The first description of P. hoplura by Day (1954) on the South African coast is not comprehensive, and the documentation provides no relevant species-specific morphological information. Regional sampling conducted for the present study revealed that P. hoplura varied intraspecifically and consisted of at least four distinct morphotypes that may potentially represent different species that may warrant redescription. By combining traditional taxonomic methods with molecular techniques, the following questions were addressed: 1) Do the morphotypes of P. hoplura represent a single species on the South African coast? and 2) Are the South African representatives of P. hoplura conspecific to those collected globally? In addition, the study included a literature review with the aim to provide a brief history of the species to assess its cosmopolitanism. Materials and methods: Newly sampled specimens used in the morphological observations were compared with specimens from private collections and museum material. Traditional taxonomic characteristics were used to distinguish the four morphotypes, and these included morphological features, pigmentation patterns, aspects of reproduction and habitat preference. A cluster analysis was performed to assess the validity of the morphotypes. Furthermore, these morphotypes were also tested for potential genetic differentiation using both mitochondrial (Cytochrome b) and nuclear (28S) gene fragments. To gain preliminary insights into the level of global geographic genetic variation, South African specimens used in the molecular analysis were compared to a few specimens collected in New Zealand. Results: Genetic data obtained from mitochondrial DNA and nuclear DNA failed to differentiate the four morphotypes, suggesting that P. hoplura represented a single morphologically polymorphic species on the South African coast. Morphology: Morphotypes 1–3 were recognised as adult forms of the species, while morphotype 4 represented the first record of a juvenile form of the species. Pigmentation patterns: Morphotype 1 was characterised by the presence of dark pigmentation in the anterior region and morphotypes 2 and 3 by the absence of pigmentation. Morphotype 4 had distinct pigmentation that resembled that of late-stage larvae. Aspects of reproduction: P. hoplura is poecilogenous, producing both planktotrophic and adelphophagic larvae. Late-stage adelphophagic larvae are morphologically similar to larvae at the same stage from a previous study conducted by Wilson (1928). Habitat preferences: The cluster analysis and genetic investigation both showed that the species was not strictly host specific since individuals collected from abalone, oysters, scallops and sand showed genetic ‘panmixia’. Conclusions: Different P. hoplura morphotypes collected along the South African coastline represent the same gene pool when compared at the molecular level. Furthermore, the South African specimens are molecularly similar to specimens collected in New Zealand. The cosmopolitanism of the species could not be fully assessed as specimens from the Northern Hemisphere, particularly from the type locality, were not included in the study. It is concluded that the species has been introduced into South Africa, in accordance with a previous study (Mead et al., 2011).