Population dynamics and sex-determining mechanisms in the marine amphipod, Echinogammarus marinus

摘要: Despite their huge diversity, abundance and ecological importance, very little is still known about sex determining mechanisms within Crustacea. Sex determination in crustaceans to be influenced by environmental factors, via parasitic infection genetically, however, it possible that all three can involved a single species. The gonochoristic marine amphipod Echinogammarus marinus (Leach, 1815) currently being used for the development of biomarkers measure influence contamination on crustacean differentiation pathways. To truly understand whether anthropogenic disruption an issue, critical governing process E. are fully evaluated. Therefore, aim this project was fill gaps our knowledge general population dynamics marinus, with particular focus elucidating ubiquitous amphipod. has been linked feminising parasites, date, no such studies have species (ESD) or genetic (GSD). This investigated two populations differed structure. Langstone Harbour (Southern England, UK) revealed presence (PSD). However, study shown seasonal breeding pattern, growth decline closely related parameters (temperature) parasites (trematodes) respectively. data also seasonally altered ratios, ranging from 36% 71% males. ESD recorded first time revealing photoperiod cue determination. This finding validated laboratory showed male bias broods developed long day light regimes (16h light: 8h dark) female short regime (8h 16h dark). ratios found field significant correlation each other supporting these findings. A new trematode parasite belonging Microphallidae family identified encysts brain demonstrates clear capacity behavioural changes its host. Individuals infected displayed distinct positive phototaxic negative geotaxic alterations could potentially increase susceptilbility predation. These at level gene expression suggesting modulation neuronal genes individuals. Putative serotonin receptor 1A, inebratied neurotransmitter, tryptophan hydroxylase amino acid decarboxylase like most dramatic change expression. represents record pathways amphipods. Another Invertkeithing (Scotland, high levels intersexuality. strengthened evidence PSD present 40.4 % either Paramyxea microsporidia parasites. From individuals 75% were 88.5% intersexes, presented infection. investigation explored transmission efficiency involved. Vertical Paramyxean sp. host alsoshowed highest mother eggs (96.8%). lead question microsporidian D. duebenum feminiser highlighted another candidate distortion. Despite range genomic techniques employed, attempt determine sexual did not reveal any specific regions. considering preliminary nature work, provided insight future directions. Several key exclusive identified. In addition, crucial method performed will allow investigations variation marinus. transcriptome now sequenced along models enabling greater understanding links between genome ecology. With large investment as model species, basic biological questions addressed. Consequently, thesis aid genetics effects.