Tapeworm Reproduction: Proglottids, Hermaphroditism & Egg Release

Cestodes (tapeworms) are hermaphroditic; each mature proglottid contains complete male and female reproductive systems.

Proglottid Anatomy

• Male: Testes (numerous), vas deferens, cirrus (copulatory organ).
• Female: Ovary (bilobed), oviduct, ootype, Mehlis' gland (shell formation), uterus (egg storage), vagina.

Reproductive Process

1. Self-fertilization (common) or cross-fertilization between proglottids/worms.
2. Zygotes → embryonate in uterus → gravid proglottid fills with thousands of eggs.
3. Gravid proglottids detach (apolysis) → passed in feces.
4. Eggs released in environment → ingested by intermediate host (cattle, pigs, fish) → oncosphere hatches → cysticercus develops.

Human Infection

• Taenia saginata (beef), T. solium (pork): Human = definitive host.
• T. solium eggs → human = intermediate host → cysticercosis (neurocysticercosis if CNS).
• Diphyllobothrium (fish): Human = definitive host; B12 deficiency possible.