Studies On Structure Of Reproductive System And Gametogenesis In Sepia Lycidas

Sepia lycidas is an important economic Cephalopods in South Sea of China. The structure ofreproductive system and gametogenesis were observed by using the methods of anatomy,histology, scanning electron microscope and transmission electron microscope. The main resultswere as follow:1. The reproductive system of S. lycidas was located at the end of coelom. The malereproductive system was consisted of nine parts, i.e.: testis, sperm duct, mucilaginous gland,ejaculatory apparatus gland, middle tunic gland, outer tunic gland, harding gland, finishing gland,and spermatophoric sac. The sperm duct could be further divided into anterior, middle (ampullae),and posterior part. The mature spermatozoon produced in the testis and transported by the spermduct, formed sperm masses in the mucilaginous and ejaculatory apparatus gland, then arranged ina new regular in the middle and outer tunic gland, and turned hard in the harding gland, andformed mature spematophores in the finishing gland. The mature spematophores stored in thespermatophoric sac, and ejuculated outside by batches in the mating seasons. The femalereproductive system was consisted of five parts, i.e.: ovary, oviduct, oviduct gland, a pair ofnidamental gland, and a pair of subaltern nidamental gland. Oogenesis is asynchronous, and theoocyte mature by batches, form a tertiary egg envelope by joint action of the oviduct gland,nidamental gland, and subaltern nidamental gland.2. The asynchronous spermiogenesis could be divided into five periods of S. lycidas, i.e.:spermatogonium, primary spermatocyte, secondary spermatocyte, spermatid, and maturespermatozoa, and the spermatid could be further divided into five stages (I~V) of division anddifferentiation. During spermiogenesis, the nucleus undergoes a process of lateral contraction andlongitudinal elongation, from a round or oval shape into an irregular spindle, and finally into aslightly curved long cylinder. The chromatin formed flocculent blocks, dense granules, fine fibers,crude fibers, and lamellae, and condensed into regions with high electron densities. Themorphology of acrosme was also changed, from a round shape to helmet-like, conical, backward“U”-like, and finally into bullet-like. The vacuole-shaped mitochondria experienced migrationand fusion, were oval with abundant cristae, and formed a mitochondrial spur that incompletelysurrounded the flagellum. The mature spermatozoa were101.28μm long, and consisted of a headand tail.3. The asynchronous oogenesis of S. lycidas could be divided into four periods, andsubdivided into ten stages according to the morphology and size of oocyte, the morphology offollicular cell, and the situation of vitellogenesis. The four periods and ten stages were: oogoniaperiod (oogonia), protoplasmic growth period (no follicular cell, single follicular epithelium, anddouble follicular epithelium), interstitial growth period (early stage of follicle penetration, middlestage of follicle penetration, and late stage of follicle penetration), and trophoplasmic growthperiod (early vitellogenesis, late vitellogenesis, and mature oocyte). 4. The duration of reproductive cycle was one year in both the male and female S. lycidas. Thedevelopment of the ovarian was earlier but lowlier than the testis. According to the morphology ofgonad, gonad somatic index (GSI), and percentage of gamete at different stage, both the ovarianand testis development could be divided into six stages, i.e.: pre-formation, formation, smallgrowth, large growth, pre-maturation, and maturation.