Anatomy of finfish and shellfish

Unit 13- Mollusca

13.3.10. Reproductive System
The sexes are separate. There is a single gland lying ventrally in the apical region of the visceral mass, and opening directly into the coelom by a slit. A single gonoduct runs on the left from the coelom to the mantle cavity and opens near the funnel. The male reproductive system includes a testis, a vas deferens, a spermatophoric sac containing sperm packets or spermatophores, and a copulatory organ or penis. The female reproductive system comprises of an ovary, an oviduct, an ovi-ducal gland, and a part of nidamental glands, which produce a jelly in which the eggs are embedded.
During breeding season, the male squid displays a courtship behaviour which was known and described by Aristotle over 2,000 years ago. He transfers the spermatophores by the specialized tip (heterocotylus) of the third right arm to the mantle cavity or within the seminal recepte on the buccal membrane of the female, where the tip of the arm becomes detached and remains free.

Fig. 7- Loligo Male reproductive system Fig. 7- A Female squid laying egg

The fertilized eggs are deposited in masses, usually found attached to rocks below the tide mark. The eggs are large, with much yolk, and are laid in elongate gelatinous capsules. Owing to the shape of egg masses, they have been known for centuries as "dead man's fingers". Cleavage is meroblastic and the young hatch, within 2-3 weeks, as miniature adults able to swim and feed at once.