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Identifying genetic variation in candidate genes for heat stress and association thereof with growth performance in dusky kob (Argyrosomus japonicus)
Thesis (MSc)--Stellenbosch University, 2026.
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| Format: | Thesis |
| Language: | English |
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Stellenbosch : Stellenbosch University
2026
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| _version_ | 1867613912603557888 |
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| access_status_str | Open Access |
| author | Linder, Stephanie Jane |
| author2 | Rhode, Clint |
| author_browse | Linder, Stephanie Jane Rhode, Clint |
| author_facet | Rhode, Clint Linder, Stephanie Jane |
| author_sort | Linder, Stephanie Jane |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MSc)--Stellenbosch University, 2026. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/136285 |
| institution | Stellenbosch University (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:43:40.919Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2026 |
| publishDateRange | 2026 |
| publishDateSort | 2026 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/136285 Identifying genetic variation in candidate genes for heat stress and association thereof with growth performance in dusky kob (Argyrosomus japonicus) Linder, Stephanie Jane Rhode, Clint Stellenbosch University. Faculty of AgriSciences. Dept. of Genetics. Thesis (MSc)--Stellenbosch University, 2026. Linder, S. J. 2026. Identifying genetic variation in candidate genes for heat stress and association thereof with growth performance in dusky kob (Argyrosomus japonicus). Unpublished masters thesis. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/6d72b986-7987-4a89-8bb9-504da48ce12d Sciaenidae is a globally distributed and economically important finfish family, with dusky kob (Argyrosomus japonicus) being the species of interest in South Africa. Unfortunately, the wild populations have collapsed due to decades of overexploitation by commercial and recreational fisheries. Therefore, a shift towards aquaculture has been initiated to meet the market demands for this fish. However, dusky kob has a long generational time and late onset of sexual maturation, thereby making phenotypic selection strategies, which are commonly used by aquaculture facilities, suboptimal. The incorporation of molecular markers into breeding schemes by means of marker assisted selection will be beneficial. In fact, this way one can not only select for fish that grow faster, but also include other traits of interest, such as heat tolerance. This is of particular interest given the current state of climate change, and the association of heat stress and growth performance. As temperature increases, so does growth, but only up to a point. Once the threshold temperature is reached, growth is hindered following the induction of heat stress. Furthermore, since many genes involved in regulating heat stress are conserved, there is concern about whether the rate of climate change may exceed that of species adaptation to it. Therefore, the aims of this study were as follows: firstly, to briefly assess and compare the macroevolution of six candidate heat stress genes to the species' 'neutral' evolution (modelled using full mitochondrial genome data from 18 different finfish species, with about half of them being from the family Sciaenidae). Secondly, from a microevolutionary perspective, the study aimed to identify SNPs in these candidate heat stress genes, and the association thereof with differential growth performance in commercial dusky kob, by means of a case-control analysis. The results show that the Chinese and South African dusky kob diverge from each other in proteins HSP90b, PDE9a and IGFBP2a. In proteins PDE9a, KMD6a, LDHA, and to an extent, COL12a1, two Sciaenidae species from different temperature habitats (Sciaenops ocellatus and Larimichthys crocea) converge with each other. Across all six protein trees, the species from the family Sciaenidae cluster together in a monophyletic clade, distinct from the others species examined, supporting the suggestion that Sciaenidae may belong to their own phylogenetic order. Lastly, all of the candidate heat stress genes were found to be under significant purifying selection, thus warranting further investigation into the status of genetic variation within individual species and populations to assess the potential for acclimation and facilitation of adaptation to climate change, so that appropriate management, adaptive and conservation strategies can be developed where required. The results from the analyses involving only South African dusky kob revealed eight SNPs across candidate genes igfbp2a, hsp90b and kdm6a, and three haplotypes of igfbp2a that were significantly associated with differential growth performance. Breeding schemes may incorporate these data with marker assisted selection to allow for selection of broodstock individuals early in their developmental stages and subsequent improved gains in the offspring generations. Masters 2026-04-30T17:05:04Z 2026-04-30T17:05:04Z 2026-03 Thesis https://scholar.sun.ac.za/handle/10019.1/136285 en Stellenbosch University 105 pages application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Linder, Stephanie Jane Identifying genetic variation in candidate genes for heat stress and association thereof with growth performance in dusky kob (Argyrosomus japonicus) |
| title | Identifying genetic variation in candidate genes for heat stress and association thereof with growth performance in dusky kob (Argyrosomus japonicus) |
| title_full | Identifying genetic variation in candidate genes for heat stress and association thereof with growth performance in dusky kob (Argyrosomus japonicus) |
| title_fullStr | Identifying genetic variation in candidate genes for heat stress and association thereof with growth performance in dusky kob (Argyrosomus japonicus) |
| title_full_unstemmed | Identifying genetic variation in candidate genes for heat stress and association thereof with growth performance in dusky kob (Argyrosomus japonicus) |
| title_short | Identifying genetic variation in candidate genes for heat stress and association thereof with growth performance in dusky kob (Argyrosomus japonicus) |
| title_sort | identifying genetic variation in candidate genes for heat stress and association thereof with growth performance in dusky kob argyrosomus japonicus |
| url | https://scholar.sun.ac.za/handle/10019.1/136285 |
| work_keys_str_mv | AT linderstephaniejane identifyinggeneticvariationincandidategenesforheatstressandassociationthereofwithgrowthperformanceinduskykobargyrosomusjaponicus |