Dynamics of de novo vitellogenesis in fish with indeterminate fecundity: an application of oocyte packing density theory to European anchovy, Engraulis encrasicolus

Abstract

De novo vitellogenesis is common among teleosts; however, its dynamics and the timing of batch recruitment are poorly understood. In this study, we combine a suite of methods and theories in fish reproductive biology (oocyte packing density, stereology, ovarian allometry, oocyte size frequencies and postovulatory follicle [POF] ageing) to reconstruct the steps and timing of batch recruitment in European anchovy. Using general linear modelling to standardize oocyte numbers, we demonstrate that the fractions of primary growth, cortical alveoli and vitellogenic oocytes in the ovary are relatively stable in females with migratory nucleus oocytes (MN) or with POFs 1 and 2 days old (POF-1 and POF-2), but they change abruptly at hydration. These results imply that batch recruitment in European anchovy occurs in pulses of very short duration (less than a day). The standing crop of vitellogenic oocytes in MN, POF-1 and POF-2 females equals the number of eggs contained in two mature batches.

Energy acquisition and allocation to egg production in relation to fish reproductive strategies

“…; Schismenou et al . ). Moreover, in many of these same species, a remaining portion of vitellogenic oocytes is resorbed at the end of the spawning season (Kjesbu and Witthames ).…”

Simulating anchovy’s full life cycle in the northern Aegean Sea (eastern Mediterranean): A coupled hydro-biogeochemical–IBM model

“…For European anchovy, this inter-spawning interval has been estimated to be about 3 days (e.g. Schismenou et al, 2012;Uriarte et al, 2012). Hence, the value of S = 0.33, used in the present study is consistent with existing knowledge on species' spawning rhythm.…”

“…(1) According to the findings of Hunter and Leong (1981) for the northern anchovy (Engraulis mordax) and Schismenou et al (2012) for the Mediterranean anchovy (E. encrasicolus), recruitment of successive vitellogenic batches during the spawning period occurs in pulses and the number of vitellogenic oocytes in the ovaries of actively spawning fish equals two times the batch fecundity (number of eggs produced per spawning event). After their recruitment, the oocytes of a new vitellogenic batch grow continuously and need about two times the inter-spawning interval (number of days between two successive spawning events) to complete their development.…”

Reproductive strategies of the marine fishes from the southwest Atlantic Ocean: an application of histological and image processing techniques

“…Although the number of batches that will be recruited from Vtg3 to hydration was not estimated here, these results indicate that the oocyte recruitment occurs in pulses. According to Schismenou et al (2012), the recruitment of oocytes from one to another pulse is activated by hydration of the spawning batch in fishes with indeterminate fecundity. Thus, both spawning capable females of S. brasiliensis and S. rastrifer have one potential batch (Vtg3) within the ovaries to supply the subsequent pulse/batch (hydration) after each event of spawning.…”

“…The ovaries containing the most development stages such as germinal vesicle migration and hydrated oocytes were not analysed in this study due to their shrinkage in the histological sections, which could affect the final result overestimating the stereological variables, e.g. the volume fraction, as observed by Schismenou et al (2012) and Saber et al (2014). The descriptions of each oocyte stage are detailed in Table Oocyte production and recruitment pattern of two congeneric species | 168 Table 2.…”