PALAEMON (PRAWN) -REPRODUCTIVE SYSTEM
Palaemon is a unisexual animal. Male and Female animals shows many morphological differences.
|
S.No. |
Male |
Female |
|
1 |
The second pair of chelate legs are longer and stronger. |
The second pair of chelate legs are smaller and thin, |
|
2 |
The thoracic legs are closely arranged. |
The thoracic legs are less closely arranged. |
|
3 |
Second pair of pleopod has appendix masculina. |
Absent. |
|
4 |
The male genital openings are present on the arthroidal membrane of the last pair or walking legs. |
The female genital openings are on the coxa of the third pair of walking legs. |
|
5 |
The male prawn is bigger when compared with female prawn of the same age. |
The female prawn is smaller than the male of same age. |
Male reproductive system:
The male prawn has a well-developed male reproductive system, it has the following parts.
a) Testis: They are two in number. They are long and narrow. They are present on the posterior half of the hepato-pancreas and beneath the pericardial sinus and heart. Anteriorly they extend up to the renal sac and posteriorly they run upto the first abdominal segment. In between the two testes a gap is present in the middle. Through this gap cardio-pyloric strand passes.
Each testis is composed of a many lobules and which are connected by connective tissue. The lobule is fined by germinal epithelium.
b) Vasa deferentia: From each testis a vas deferens arises, k is a long narrow duct. It coils near the hepato-pancreas. It runs vertically downwards.
c) Seminal vesicle: The lower part of the vas deferens is expanded. It is club shaped and muscular. It is called seminal vesicle. It stores the spermato-phores.
d) Male genital openings : The seminal vesicles open out through male genital pores. These openings are situated on the arthrodial membranes of the last pair of walking legs. Each opening is guarded by a small flap.
B. Female reproductive system:
It contains a pair of ovaries and a pair of oviducts.
a) Ovaries: These are present on the posterior half of the hepatopan-creas below the pericardial sinus and heart. They extend anteriorly up to the renal sac and posteriorly up to the first abdominal segment. In a mature female, the ovaries are sickle shaped and lie side by side, with a big gap between them in the middle. Cardiopybric strand passes through it. In the breeding season the ovaries enlarge and may extend into the first abdominal segment. Each ovary has a large number of ova surrounded by a membrane. The ova are in the different stages of development in the ovary.
b) Oviducts: These are slender and curved tubes. They have a wide proximal end. Each oviduct starts from the middle of the outer border of the ovary. It runs vertically downwards.
c) Female genital aperture: The oviducts open out through female genital opening. They are present on the coxa of the third pair of walking legs.
Copulation and fertilization: During copulation the male deposits the spermatophores near the female genital openings of the female. Near the female genital opening ova are present attached to the pleopods. Fertilization is external
Development: In Palaemon the devebpment is direct. The larval stage is absent. The eggs hatch and give small prawns which undergo many moultings before becoming adults.