Oogenesis and spawn-formation in the pigmy lion fish Dendrochirus brachypterus (Pteroidae)

Abstract

Dendrochirus brachypterus possesses a special type of ovary in which the germinative epithelium surrounds a spongy stroma hanging in the lumen. The inner side of the ovarian wall is covered by a special type of epithelium that produces a gelatinous envelope around the gametes (spawn) during reproduction. In general, oogenesis in the lion fish resembles that of other teleosts, the characteristic difference being in the formation of ovigerous peduncles-protrusions of the spongy stroma, each of which bears a single oocyte. During oogenesis the oocytes rise above the germinal epithelium, enveloped in their follicular epithelia. The larger the oocyte the greater the length of its peduncles and the further its position from the germinal layer (Fig. 3). During this phase of development, a marked multiplication of yolk granules occurs; they increase their diameter and finally homogenize at ovulation. Under favorable thermal conditions, oogenesis continues all year round. The peduncular growth of oocytes enables the growing egg cells to move away from the egg-producing surface, thus making space available for the ovary to produce more eggs. This ability should have a survival value for these fish if we take into consideration that the most vulnerable stage in their life history is that of planktonic larvae (Fishelson, 1975).