Timing of the maturation transition in haddock Melanogrammus aeglefinus

Abstract

The timing of maturation in haddock Melanogrammus aeglefinus was examined using changes in gonad development, follicle stimulating hormone β (FSH-β) transcript expression profile, growth and condition of 1 year old females held under a common environment between the summer and winter solstices. The circumnuclear ring, cortical alveolus and vitellogenic oocyte stages were first observed in August, October and November, respectively. FSH-β transcript levels did not change significantly until September but increased markedly thereafter in maturing fish. A combined analysis of the mean oocyte diameter of the leading cohort, histological staging and FSH-β transcript profile provided evidence of a commitment to maturation by October or November. Contrary to that previously proposed for gadoid species, histological analysis of field-caught immature M. aeglefinus during the spawning season indicated that cortical alveolar, rather than circumnuclear ring, stage oocytes provided definitive evidence of maturation. A decrease in relative liver size following the summer solstice suggested a possible link between energy status and maturation.

Implications of a warming North Sea for the growth of haddock Melanogrammus aeglefinus

“…Such year classes which mature younger and smaller may consequently be smaller at older ages (Taylor & Stefánsson, 1999). Recent experiments carried on North Sea M. aeglefinus revealed that the decision to mature occurs between June and August and is possibly linked to the energy status of the fish (Tobin et al , 2010). Thus, providing that the faster growth of young individuals is associated with a better energy status, this could imply that M. aeglefinus at high temperature would mature in the current year rather than delaying maturity for the next year.…”

Effects of ambient oxygen and size-selective mortality on growth and maturation in guppies

“…At the completion stage, there are several layers of spermagonial cysts, sperm cells and developed testicular ducts with enzyme activity, and spermatozeugmata (sperm bundles) are present (Schreibman et al ., 1982; Koya et al ., 2003). We consider the initiation of maturation to be a good representation of male maturation ‘decision’ in guppies; it is the time when they commit to maturation, reflecting more accurately the factors that affect maturation than the final maturation stage (Tobin et al ., 2010; Harney et al ., 2012; Diaz Pauli and Heino, 2013). Therefore, in the present study we assessed the effect of oxygen and size selection on the initiation of maturation, from now on referred to as maturation.…”

How to Measure Maturation: A Comparison of Probabilistic Methods Used to Test for Genotypic Variation and Plasticity in the Decision to Mature

“…3, S1, S2) and feature age integration (Table 1). This finding highlights the importance of using traits at the beginning of maturation rather than the end (Tobin et al 2010). Approaches such as measuring changes in hormone titers or patterns of gene expression may allow more accurate estimation of when the maturation process begins.…”

“…Any of these maturation "indicators" can be used to model PMRNs. We would expect those based on IM-1 to most accurately describe the role of age and size in initiating maturation (Davidowitz and Nijhout 2004;Wright 2007;Tobin et al 2010), but those based on IM-3 may be useful in understanding the trade-off between growth and reproduction. PMRNs based on all three maturation indicators were investigated, to describe how effects of age and size changed over the course of the maturation process.…”

“…There is also increasing awareness of the importance of underlying ontogenetic processes in shaping these reaction norms (Reznick 1990; Johnson and Porter 2001; Wolf et al 2001; West‐Eberhard 2003; Berner and Blanckenhorn 2007). Maturation is rarely a simple transition from juvenile to adult, but rather a process consisting of a number of co‐ordinated and potentially heritable endocrinological and neurophysiological changes, controlling the allocation of resources to growth, maintenance, and reproductive function (Bernardo 1993; Stern and Emlen 1999; Nijhout 2003). The limited studies carried out to date (Boorse and Denver 2004; Davidowitz and Nijhout 2004; Mirth and Riddiford 2007; Nijhout 2008) suggest that understanding the proximate causes of maturation is essential to explaining variation in the age and size at which individuals achieve maturity (Marshall and Browman 2007).…”