A systematic review of the so-called cosmopolitan polydorid Polydora hoplura Claparede, 1869 (Polychaeta: Spionidae) on the South African coast.

Van Niekerk, Sandy Eve (2014-12)

Thesis (MSc)--Stellenbosch University, 2014.

Thesis

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).

AFRIKAANSE OPSOMMING: Inleiding: Polydora hoplura word as ’n kosmopolitaans of indringerspesie aan die Suid- Afrikaanse beskou en is een van die vernaamste plae wat perlemoen- en oesterboerdery in die streek raak. Die eerste beskrywing van P. hoplura aan die Suid-Afrikaanse kus deur Day (1954) is nie omvattend nie en die dokumentasie bied geen relevante spesiespesifieke morfologiese inligting nie. Streeksgebonde monsters wat vir die huidige studie geneem is, toon aan dat P. hoplura varieer op intraspesievlak en bestaan uit minstens vier verskillende morfotipes wat potensieel verskillende spesies verteenwoordig wat moontlik herbeskrywing sou regverdig. Deur tradisionele taksonomiese metodes met molekulêre tegnieke te kombineer, is die volgende vraagstukke aangepak: 1) Verteenwoordig die morfotipes van P. hoplura ’n enkele spesie langs die Suid-Afrikaanse kus? en 2) Is die Suid-Afrikaanse verteenwoordigers van P. hoplura konspesifiek met die wat wêreldwyd versamel is? Daarbenewens sluit die studie ’n literatuuroorsig in waarmee gepoog word om ’n kort uiteensetting van die spesie se geskiedenis te bied sodat die kosmopolitanisme daarvan beoordeel kan word. Materiaal en metodologie: Eksemplare gemonster vir die doeleindes van hierdie studie is gebruik in die morfologiese waarnemings en is vergelyk met eksemplare uit privaat versamelings en museummateriaal. Tradisionele taksonomiese eienskappe is gebruik om die vier morfotipes te onderskei en dit het morfologiese kenmerke, pigmentasiepatrone, voortplantingsaspekte en habitatvoorkeur ingesluit. ’n Trosanalise is uitgevoer om die geldigheid van die morfotipes te bepaal. Verder is die morfotipes ook getoets vir moontlike genetiese differensiasie deur sowel mitochondriale (Sitokroom b) as nukliêre (28S) geenfragmente te gebruik. Om voorlopige insig te verkry in die vlakke van globale geografiese genetiese variasie, is Suid-Afrikaanse eksemplare wat in die molekulêre ontleding gebruik is, vergelyk met ’n aantal eksemplare wat in Nieu-Seeland versamel is. Resultate: Genetiese data afkomstig uit mitochondriale DNS en nukliêre DNS het nie daarin geslaag om die vier morfotipes te differensieer nie, wat aandui dat P. hoplura ’n enkele polimorfiese (morfologies gesproke) spesie aan die Suid-Afrikaanse kus verteenwoordig. Morfologie: Morfotipes 1 tot 3 word beskou as volwasse vorme van die spesie, terwyl morfotipe 4 die eerste aantekening van ’n jong vorm van die spesie verteenwoordig. Pigmentasiepatrone: Morfotipe 1 word gekenmerk deur die teenwoordigheid van donker pigmentasie aan die voorkant en morfotipes 2 en 3 deur die afwesigheid van pigmentasie. Morfotipe 4 het kenmerkende pigmentasie wat ooreenkomstig is met die van laatfaselarwes. Voortplantingsaspekte: P. hoplura is poekilogeen en produseer sowel planktotrofiese as adelfofagiese larwes. Laatfase- adelfofagiese larwes stem morfologies ooreen met larwes in dieselfde fase uit ’n vorige studie deur Wilson (1928). Habitatvoorkeur: Die trosanalise en genetiese ondersoek toon beide aan dat die spesie nie noodwendig gasheerspesifiek is nie, aangesien individue wat versamel is uit perlemoen, oesters, kammossels en sand genetiese ‘panmixia’ (lukrake paring) vertoon. Gevolgtrekkings: Verskillende P. hoplura morfotipes wat langs die Suid-Afrikaanse kus versamel is, verteenwoordig dieselfde genepoel wanneer dit op ’n molekulêre vlak vergelyk word. Daarbenewens stem die Suid-Afrikaanse eksemplare molekulêre ooreen met eksemplare wat in Nieu-Seeland versamel is. Die kosmopolitiese aard van die spesie is nie volledig geassesseer nie aangesien eksemplare uit die Noordelike Halfrond, veral dié uit die tipeligging, nie by die studie ingesluit is nie. Daar word tot die gevolgtrekking gekom dat die spesie in Suid-Afrika ingebring is, in ooreenstemming met ’n vorige studie.

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