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Title: Intersexuality and endocrine disruption in the amphipod Echinogammarus marinus : from genes to physiology
Author: Yang, Gongda
ISNI:       0000 0004 2737 6788
Awarding Body: University of Aberdeen
Current Institution: University of the Highlands and Islands
Date of Award: 2013
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The intertidal amphipod (Echinogammarus marinus LEACH) exhibits several forms intersexuality and has been considered an ideal model to study reproductive endocrine disruption in Crustacea. This study aimed to investigate both the physiology and transcriptome in intersex E. marinus with the objective of better understanding their reproductive biology and aid the development of biomarkers of de-masculinisation in Crustacea. E. marinus populations from three Scottish (Thurso, Inverkeithing and Loch Fleet) and two English sites (Portsmouth Harbour and Langstone Harbour) were assessed for intersexuality prevalence, sperm counts or microsporidian infection rate. Increased incidence of intersexes and reduced sperm counts were revealed in amphipods from industrial impacted sites. The microsporidian species infecting E. marinus were identified for the first time, and Dictyocoela duebenum and Dictyocoela berillonum were found to be dominant in Inverkeithing and Portsmouth Harbour E. marinus populations, respectively. Microsporidian has been reported as a potential factor inducing intersexes in amphipods. In this study, microsporidian infection was revealed to significantly associate with external intersex males, but not with internal intersex males. A cross-species cDNA microarray was used to characterise the gene expressions of three male phenotypes (normal males, internal and external intersex males), and PCA analysis clearly differentiates the three groups into three separate patches. The de novo transcriptome sequencing was carried out on E. marinus gonadal tissue, by employing Roche 454 pyrosequencing producing one of the largest cDNA libraries for a crustacean species. A total of 12,645 gonadal contigs were assembled from 213,212 sequencing reads, and 1206, 1745 and 782 contigs were found to be male-, female- and intersex-specific genes, respectively. A large number of strongly male and female sex biased gene sequences have been identified and annotated by GO terms which will provide a powerful resource for future studies into the reproductive biology of crustaceans.
Supervisor: Boyd, Kenneth Sponsor: Natural Environment Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Amphipoda