Do male reproductive characteristics change seasonally in Littorina saxatilis?
This is a suggestion for a Degree Project for Bachelor's and Master's levels at the Department of Marine Av性爱s. Degree projects at the Department of Marine Av性爱s are done independently and must be written and assessed individually.
Subject: Marine Biology
Suitable level and length: Bachelor (15 hp)
Suitable time period: Project can be performed all year round
Location: 罢箩盲谤苍枚
Main supervisor: Becky Cramer
Background
Despite decades of research on the snail Littorina saxatilis, a very basic aspect of their biology remains unknown: does breeding happen year-round, or is it seasonally restricted? Unlike many close relatives, L. saxatilis males do not shed their penis for the winter, and at least some females have brood in their brood pouches all year鈥攂oth pieces of evidence suggesting year-round breeding.
However, pointing towards seasonal breeding, we recently observed testicular regression; there are seasonal patterns in the number of offspring female carry; and females can store sperm and fertilize eggs with these stored sperm for an extended period of time. It is therefore not clear whether L. saxatilis males produce sperm and copulations occur year-round.
Project description
In this project, you will analyze testis development, male sperm stores, and sperm morphology from samples collected across the year (including some samples you collect directly). This project will support an on-going project examining testes transcriptomes in L. saxatilis.
Problem
To understand whether and how male reproductive characteristics change seasonally in L. saxatilis.
Method
Snails will be collected at various time points through the year (most likely I will do most of the collecting before your project starts, and you will collect a few final time points). Each snail will be dissected, and images will be taken of the testes and seminal vesicles in a standardized way that enables measurements of the size of these organs.
Sperm will also be imaged for analysis of the proportion of morphologically normal sperm and for measurement of normal sperm length. Your primary tasks will be to collect new samples at several time points during the project period, and to analyze images from the whole time series.
Skills learned
- Microdissection with dissecting scope
- Microscopy
- Taking quantitative measurements from images
- Evaluating sperm morphological normality
- Statistical analysis and random-effects design
- Visualizing patterns in data
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Main supervisor Becky Cramer
Email: becky.cramer@gu.se
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