{"id":{"repo_id":"nus","oai_identifier":"oai:scholarbank.nus.edu.sg:10635/156064"},"canonical_url":"https://search.dev.ndltd.org/etd/nus/oai:scholarbank.nus.edu.sg:10635/156064","repository":{"repo_id":"nus","name":"National University of Singapore","base_url":"https://scholarbank.nus.edu.sg/oai/request"},"display":{"title":"UNCOVERING THE EVOLUTION AND DEVELOPMENT OF A NOVEL ABDOMINAL APPENDAGE IN BLACK SCAVENGER FLIES (SEPSIDAE: DIPTERA)","abstract":"I explore the evolution and development of a novelty in sepsid flies where males have recently evolved an elaborate brush-like appendage on the fourth abdominal segment that varies in shape and size across the family. A comparative analysis showed that male sepsids pay for more ornate 4th sternite brushes by reducing their body size and extending pupal development. I then trace the evolution of the 4th sternite brush, using a phylogenomic analysis, and show that it evolved once, was lost multiple times and reacquired in at least two species. Next, I use an optimized CRISPR/Cas9 gene editing system to test the role of candidate genes in its development in two species with morphologically distinct sternite brushes: Themira biloba and Perochaeta dikowi. I find that doublesex and abdominal-A have been co-opted into the GRN underlying 4th sternite brush development in both species. In T. biloba, extradenticle and Distal-less are additionally co-opted while there was no evidence for the involvement of Distal-less in P. dikowi, suggesting that its role in the GRN was either lost in P.dikowi or gained in T.biloba. Surprisingly, I also demonstrate a potentially unique function of doublesex and Distal-less in patterning the adult abdominal epidermis in T. biloba.","abstract_html":"I explore the evolution and development of a novelty in sepsid flies where males have recently evolved an elaborate brush-like appendage on the fourth abdominal segment that varies in shape and size across the family. A comparative analysis showed that male sepsids pay for more ornate 4th sternite brushes by reducing their body size and extending pupal development. I then trace the evolution of the 4th sternite brush, using a phylogenomic analysis, and show that it evolved once, was lost multiple times and reacquired in at least two species. Next, I use an optimized CRISPR/Cas9 gene editing system to test the role of candidate genes in its development in two species with morphologically distinct sternite brushes: Themira biloba and Perochaeta dikowi. I find that doublesex and abdominal-A have been co-opted into the GRN underlying 4th sternite brush development in both species. In T. biloba, extradenticle and Distal-less are additionally co-opted while there was no evidence for the involvement of Distal-less in P. dikowi, suggesting that its role in the GRN was either lost in P.dikowi or gained in T.biloba. Surprisingly, I also demonstrate a potentially unique function of doublesex and Distal-less in patterning the adult abdominal epidermis in T. biloba.","abstract_has_math":false,"creators":["GOWRI D/O RAJARATNAM"],"institution":null,"degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2019,"date_issued":"2019-01-24","date_published":"2019-01-24","updated_at":"2026-07-24T03:32:56Z","subjects":["evolution, development, novelty, Diptera, CRISPR/Cas9, phylogenomics"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":null,"outbound_label":null,"outbound_source":null},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:creator","label":"Author","values":["GOWRI D/O RAJARATNAM"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.issued","label":"Date","values":["2019-01-24"]},{"key":"dc:relation.isreferencedby","label":"Dc Relation Isreferencedby","values":["https://scholarbank.nus.edu.sg/handle/10635/156064"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["evolution, development, novelty, Diptera, CRISPR/Cas9, phylogenomics"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["https://scholarbank.nus.edu.sg/bitstreams/9278028b-23af-4b4c-b996-8402a512c798/download"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["I explore the evolution and development of a novelty in sepsid flies where males have recently evolved an elaborate brush-like appendage on the fourth abdominal segment that varies in shape and size across the family. A comparative analysis showed that male sepsids pay for more ornate 4th sternite brushes by reducing their body size and extending pupal development. I then trace the evolution of the 4th sternite brush, using a phylogenomic analysis, and show that it evolved once, was lost multiple times and reacquired in at least two species. Next, I use an optimized CRISPR/Cas9 gene editing system to test the role of candidate genes in its development in two species with morphologically distinct sternite brushes: Themira biloba and Perochaeta dikowi. I find that doublesex and abdominal-A have been co-opted into the GRN underlying 4th sternite brush development in both species. In T. biloba, extradenticle and Distal-less are additionally co-opted while there was no evidence for the involvement of Distal-less in P. dikowi, suggesting that its role in the GRN was either lost in P.dikowi or gained in T.biloba. Surprisingly, I also demonstrate a potentially unique function of doublesex and Distal-less in patterning the adult abdominal epidermis in T. biloba."]},{"key":"dc:format.checksum.md5","label":"Dc Format Checksum Md5","values":["b3bcb35be81347139d7d964f4851f823","3e9f532604f7f2cff897a330042693d0"]},{"key":"dc:title","label":"Title","values":["UNCOVERING THE EVOLUTION AND DEVELOPMENT OF A NOVEL ABDOMINAL APPENDAGE IN BLACK SCAVENGER FLIES (SEPSIDAE: DIPTERA)"]}]}],"canonical_facts":{"dc:creator":["GOWRI D/O RAJARATNAM"],"dc:date.issued":["2019-01-24"],"dc:description.abstract":["I explore the evolution and development of a novelty in sepsid flies where males have recently evolved an elaborate brush-like appendage on the fourth abdominal segment that varies in shape and size across the family. A comparative analysis showed that male sepsids pay for more ornate 4th sternite brushes by reducing their body size and extending pupal development. I then trace the evolution of the 4th sternite brush, using a phylogenomic analysis, and show that it evolved once, was lost multiple times and reacquired in at least two species. Next, I use an optimized CRISPR/Cas9 gene editing system to test the role of candidate genes in its development in two species with morphologically distinct sternite brushes: Themira biloba and Perochaeta dikowi. I find that doublesex and abdominal-A have been co-opted into the GRN underlying 4th sternite brush development in both species. In T. biloba, extradenticle and Distal-less are additionally co-opted while there was no evidence for the involvement of Distal-less in P. dikowi, suggesting that its role in the GRN was either lost in P.dikowi or gained in T.biloba. Surprisingly, I also demonstrate a potentially unique function of doublesex and Distal-less in patterning the adult abdominal epidermis in T. biloba."],"dc:format.checksum.md5":["b3bcb35be81347139d7d964f4851f823","3e9f532604f7f2cff897a330042693d0"],"dc:identifier.uri":["https://scholarbank.nus.edu.sg/bitstreams/9278028b-23af-4b4c-b996-8402a512c798/download"],"dc:relation.isreferencedby":["https://scholarbank.nus.edu.sg/handle/10635/156064"],"dc:subject":["evolution, development, novelty, Diptera, CRISPR/Cas9, phylogenomics"],"dc:title":["UNCOVERING THE EVOLUTION AND DEVELOPMENT OF A NOVEL ABDOMINAL APPENDAGE IN BLACK SCAVENGER FLIES (SEPSIDAE: DIPTERA)"],"dc:type":["Thesis"]},"updated_at":"2026-07-24T03:32:56Z"}