Genomic resource development for the South African scallop, Pecten sulcicostatus

Thesis (MSc)--Stellenbosch University, 2016.ENGLISH ABSTRACT: Although South Africa boasts a rich biodiversity, many South African species, especially marine species, remain uncharacterised. Many of these species show great potential for commercial use, in particular for the aquaculture of endemic species for high-value, specialised markets. Only once these species have been identified and genetically characterised can the feasibility of aquaculture be evaluated. ‘Scallop’ refers to species of marine bivalve molluscs in the family Pectinidae, although it may also refer to species in other closely related families within the superfamily Pectinoidea. There are 29 scallop species in the waters surrounding South Africa, and of these, Pecten sulcicostatus has been identified as a candidate species for aquaculture. Non-destructive sampling is necessary for studies on genetic fitness and population structure to not be hindered by the death of the study individuals. DNA extraction methods using non-destructive sample tissue have not been developed for scallops, therefore this study compared the use of various tissue types in DNA extraction, allowing for the development of an effective non-destructive DNA extraction method for P. sulcicostatus using tentacle tissue and mucus swabs. This study also allowed for the development of an effective DNA extraction method for use on dried or degraded tissue, which will, in turn, allow for the use of opportunistic and historic samples in future studies on P. sulcicostatus. Despite the potential commercial value of P. sulcicostatus, no genetic resources are available for this endemic species. The development of genetic markers will assist in future studies on the genetic composition of this species as well as the genetic constitution of P. sulcicostatus populations along the South African coast – factors which are important for the formulation of effective genetic management strategies. This study therefore aimed to develop genetic markers for P. sulcicostatus and to conduct preliminary analyses using these markers to demonstrate their usefulness for future studies, which will assist in the establishment of a sustainable aquaculture industry. This study allowed for the optimisation of a fragment of the 16S rRNA gene which was successfully used to determine intra- and interspecific genetic diversity and shed light on the evolutionary relationship of five Pecten species. A set of 10 microsatellite markers was developed for P. sulcicostatus using cross-species amplification from Pecten maximus, a sister species to P. sulcicostatus, with a success rate of 50%. The set of microsatellite markers was successfully applied to generate genetic diversity data, which, in future studies, could be used to evaluate the extent of intra- and interpopulation genetic partitioning and variation. This study also provided the first reduced genome sequences for P. sulcicostatus, with over 7.3 million reads. The use of two bioinformatic approaches aided in the identification of 55 putative microsatellite markers as well as 2 530 putative SNPs. Although currently limited, this study marks the first step towards providing genetic information to assist in the development of genetic management strategies within the context of establishing a sustainable aquaculture industry for this endemic species. The genetic resources developed in this study could be used in various downstream applications such as genetic diversity assessment, population structure inference, linkage studies as well as marker assisted selection. In future, the microsatellite markers and SNPs developed in this study could also be continuously used to monitor genetic diversity as the species is subjected to aquaculture.AFRIKAANSE OPSOMMING: Ten spyte van ‘n ryk biodiversiteit, is baie Suid-Afrikaanse spesies, veral mariene spesies, steeds ongekarakteriseerd. Baie van hierdie spesies het groot potensiaal vir kommersiële gebruik, veral die akwakultuur van endemiese spesies vir hoë-waarde, gespesialiseerde markte. Slegs nadat hierdie spesies geïdentifiseer is en geneties gekarakteriseerd is, kan die volhoubaarheid van akwakultuur geëvalueer word. 'Kammossel' verwys na spesies van marine tweekleppigediere in die familie Pectinidae, alhoewel dit ook na spesies in ander naby verwante families binne die superfamilie Pectinoidea kan verwys. Daar is 29 kammossel spesies in die waters rondom Suid-Afrika. Van die 29 Suid-Afrikaanse kammossel spesies, is Pecten sulcicostatus geïdentifiseer as 'n kandidaat vir akwakultuur. Nie-vernietigende monsterneming is nodig vir studies van genetiese fiksheid en populasie struktuur sodat die dood van individue nie dié studies verhinder nie. Die gebruik van nie-vernietegende monster weefsel in DNS ekstraksie is nog nie vir kammossels ontwikkel nie, dus vergelyk hierdie studie die gebruik van verskillende tipes weefsel in DNS ekstraksie, om ‘n nie-vernietigende DNS ekstraksie metode vir P. sulcicostatus te ontwikkeling met behulp van tentakel weefsel en slym deppers. Hierdie studie het ook 'n DNS ekstraksie metode ontwikkel vir gebruik op droë of afgebreekte weefsel, wat gebruik kan word vir opportunistiese en historiese monsters in toekomstige studies op P. sulcicostatus. Ten spyte van die feit dat P. sulcicostatus geïdentifiseer is as 'n potensiële akwakultuur spesies, is daar geen genetiese hulpbronne beskikbaar vir hierdie spesie nie. Die ontwikkeling van genetiese merkers vir hierdie endemiese spesies sal bydra tot toekomstige studies op die genetiese samestelling van hierdie spesie, asook die genetiese samestelling van P. sulcicostatus populasies rondom die Suid-Afrikaanse kus – belangrike faktore vir die formulering van effektiewe genetiese bestuur strategieë. Die doelwit van hierdie studie was dus om genetiese merkers vir P. sulcicostatus te ontwikkel en om voorlopige bevestiging van hierdie merkers uit te voer om hul nut te bewys vir toekomstige studies wat sal help met die vestiging van 'n volhoubare akwakultuurbedryf. Hierdie studie het 'n fragment van die 16S rRNA geen geoptimiseer wat gebruik is om intra- en interspesifieke genetiese diversiteit te bepaal en die evolusionêre verwantskappe van vyf Pecten spesies te bestudeer. 'n Stel van 10 mikrosatelliet merkers is ontwikkel vir P. sulcicostatus deur die gebruik van kruis-spesies amplifisering vanaf Pecten maximus, 'n suster spesies van P. sulcicostatus, met 'n suksessyfer van 50%. Die mikrosatelliet merker stel is gebruik om genetiese diversiteit data daar te stel, wat in toekomstige studies gebruik kan word om intra- en interpopulasie genetiese verskille/differensiasie en variasie te evalueer. Hierdie studie het ook die eerste verkleinde genoom volgorde bepaling vir P. sulcicostatus gedoen, met meer as 7.3 miljoen lesings. Twee bioinformatiese tegnieke het ‘n totaal van 55 vermeende mikrosatelliet merkers asook 2 530 vermeende enkel nukleotied polimorfisme (ENP) in hierdie studie geidentifiseer. Alhoewel tans beperk, is hierdie studie die eerste stap in die verskaffing van genetiese inligting vir die ontwikkeling van genetiese bestuur strategieë binne die konteks van die totstandkoming van 'n volhoubare akwakultuurbedryf vir hierdie endemiese spesie. Die genetiese hulpbronne wat in hierdie studie ontwikkel is, kan in verskeie toekomstige studies gebruik word vir genetiese diversiteit assessering, populasiestruktuur inferensie, koppeling studies asook merkerbemiddelde seleksie. Die mikrosatelliet merkers en ENP kan ook voortdurend gebruik word om genetiese diversiteit te monitor as die spesie onderworpe is aan akwakultuur