SummaryControl of reproductive development in crustaceans requires neuropeptides, ecdysone and methyl farnesoate (MF). A major source of neuropeptides is the X-organ-sinus gland (XO-SG) complex located in the eyestalk ganglia of crustaceans. The other regulatory factors (either peptides or neuromodulators) are produced in the brain and thoracic ganglia (TG). Two other regulatory non-peptide compounds, the steroid ecdysone and the sesquiterpene MF, are produced by the Y-organs and the mandibular organs, respectively. In the current review, I have tried to recapitulate recent studies on the role of gonadal regulatory factors in regulating crustacean reproduction.Key words: crustaceans, reproduction, gonads, X-organ-sinus gland, peptides.
THE JOURNAL OF EXPERIMENTAL BIOLOGY4 crustaceans, the testis contains 10-15 lobes each composed of many seminiferous tubules, whose shape changes according to the stage of spermatogenesis. Spermatogenesis starts in the undifferentiated seminiferous tubules (proacini) at the top of each lobe. Meiotic activity occurs in the acini that develop proacini somewhat proximally from the top of each lobe. In this stage, the lobules contain mostly primary spermatocytes. Differentiation of secondary spermatocytes and spermatids takes place in the seminiferous tubules, which lie in the center of each lobe. All these seminiferous tubules are filled with spermatocytes and spermatids surrounded by a layer of otheocytes of mesodermal origin. The hormonal control of spermatogenesis is not completely understood in crustaceans. There is information on MF as a reproductive hormone in males.
The female reproductive systemThe reproductive system of female crustaceans consists of the paired ovaries, oviducts, gonophores and an external sperm reception area. The ovarian lobes are connected by a central bridge of ovarian tissue (Fig.1D). The ovarian lobes are symmetrically arranged and lie in the cephalothorax on the top of the stomach and hepatopancreas (HP). An oviduct arises laterally from each ovary at a point just beside the position of the heart. It extends ventrally and opens through a gonophore in the abdomen. In sexually receptive females, each pore is equipped with a large tuft of long setae, which apparently serve as a tube for the passage of ova. In the fully mature state, the shapes of ovarian limbs can be distinguished only with difficulty as the ovary fills the thoracic region of the body cavity completely.In the majority of female Malacostraca, oogonial proliferation and ovarian differentiation take place when the ovary is translucent to opaque white (previtellogenic ovary). During vitellogenesis the color of the ovary changes from pale yellow (vitellogenic stage I) to orange (vitellogenic stage II) and it then becomes brown (vitellogenic stage III) to dark brown prior to spawning. Maturation of the ovary also includes an increase in the size of the ovary as the oocytes proliferate and increase in diameter, due to yolk deposition.
Role of neuropeptides in reproductionThe hormonal control o...
