Morphometric characteristics of the oocytes of the mussel Dreissena polymorpha (Pallas, 1771) in the Dubrava Reservoir

master's thesis

• Title: Morfometrijske značajke oocita školjkaša Dreissena polymorpha (Pallas, 1771) u akumulaciji Dubrava
• Author: Nikolina Konjuh
• Mentor: Jasna Lajtner (mentor)
• Committee member: Jasna Lajtner (predsjednik povjerenstva)
• Committee member: Ines Radanović (član povjerenstva)
• Committee member: Draginja Mrvoš-Sermek (član povjerenstva)
• Committee member: Iva Juranović Cindrić (član povjerenstva)
• Granter: University of Zagreb; Faculty of Science; (Department of Biology); Zagreb
• Defense date and country: 2017-03-15, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Biology

Abstract

Slatkovodni školjkaš Dreissena polymorpha jedna je od najdominantnijih invazivnih vrsta u rijekama i jezerima Europe koja se u Hrvatskoj počela širiti tijekom 1980-tih godina. Kako bi se nadopunile spoznaje o reproduktivnim značajkama ove vrste u akumulacijskom jezeru hidroelektrane Dubrava analizirane su ženke uzorkovane u akumulaciji od ožujka do kolovoza 2000. god. Ciljevi ovog rada su bili istražiti sezonske cikluse rasta oocita i njihovih jezgri, usporediti razvojne stadije gonada s ustanovljenim veličinama oocita i usporediti dobivene podatke s rezultatima prijašnjih istraživanja u Hrvatskoj. Razvojni stadij gonada i rast oocita analiziran je na tkivu visceralne vreće, koje je tehnikom parafinskih blokova izrezano na debljinu 10 μm i obojano hemalaun-eozinom. Rezultati pokazuju da su analizirane ženke u ožujku bile u stadiju gametogeneze, mrijest je trajao od travnja do lipnja, nakon čega su u srpnju zabilježeni stadiji nakon mriještenja te u kolovozu stadiji mirovanja, uz znakove početka gametogeneze. Primjenom morfometrijskog programa Zen2Lite ukupno je izmjereno 5190 oocita i njihovih jezgri. Najveće prosječne vrijednosti promjera oocita i njihovih jezgri (35,32 μm; 23,02 μm) ustanovljene su u lipnju (u gonadnom stadiju pred mriještenje), dok su najmanje prosječne vrijednosti (10,34 μm; 6,62 μm) utvrđene u stadiju mirovanja, u kolovozu. Zabilježene su statistički značajne razlike u promjeru oocita i njihovih jezgri kako između istraživanih mjeseci tako i s obzirom na ustanovljene gonadne stadije (p < 0,001). Utvrđene reproduktivne značajke ove vrste ne razlikuju se značajno od dosadašnjih istraživanja u rijeci Dravi i akumulaciji Dubrava, dok se manje razlike u odnosu na akumulaciju Čakovec mogu objasniti okolišnim čimbenicima, prvenstveno temperaturom vode.

Abstract (english)

Freshwater mussel Dreissena polymorpha is one of the most dominant invasive species in the rivers and lakes of Europe, which began to spread in Croatia in the 1980s. To complement the knowledge about reproductive characteristics of this species in the accumulation lake of Dubrava Hydroelectric Power Plant, we analysed females sampled in the reservoir from March to August 2000. The objectives of the study were to investigate the seasonal patterns of oocyte growth and growth of their nuclei, compare the gonad developmental stages with recorded sizes of oocytes and to associate the obtained data with the results from previous research in Croatia. The development stage of gonads and the growth of oocytes were analysed on visceral mass tissue, processed for paraffin blocks technique, cut to a thickness of 10 μm and stained with hemalaun-eosin. The results show that females sampled in March are at the stage of gametogenesis, spawning lasts from April to June, in July females are in the post spawning stage, and in August animals are in resting stage, with the signs of new gametogenesis. In total, we measured 5190 oocytes and their nuclei, by using morphometric program Zen2Lite. The highest average value of the oocytes diameter and of their nuclei (35.32 μm; 23.02 μm) was recorded in June (the gonadal stage before spawning), while the lowest average value (10.34 μm; 6.62 μm) was noted for the resting stage in August. Statistically significant differences in the diameter of oocytes and their nuclei were recorded among the studied months and also among established gonadal stages (p < 0.001). Identified reproductive characteristics of this species are not significantly different from previous studies in the Drava River and reservoir Dubrava, while minor differences in relation to the accumulation of Čakovec can be explained by environmental factors, primarily water temperature.

• Keywords: Bivalvia; reproduktivni ciklus; gonadni stadiji
• Keywords (english): Bivalvia; reproductive cycle; gonad stages
• Language: croatian
• URN:NBN: urn:nbn:hr:217:093561
• Study programme: Title: Biologija i kemija; smjerovi: nastavnički; Study programme type: sveučilišni; Study level: integrirani preddiplomski i diplomski; Academic / professional title: magistar/magistra edukacije biologije i kemije (magistar/magistra edukacije biologije i kemije)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2017-05-25 07:43:24