Spermatophore Transfer and Fertilization in Bensonies jacquemonti

Last Updated: August 20, 2025

Introduction

How do two snails safely exchange sperm and fertilize eggs without external mating structures? The spermatophore transfer and fertilization in Bensonies jacquemonti reveal an elegant sequence: spermatophore formation, controlled transfer during copulation, reception in the bursa copulatrix, selective release of sperm into a fertilization pocket, and finally fertilization of the ova. This post uses direct thesis excerpts (with page numbers) and plain-English explanation so you can understand the anatomy, mechanics, and ecological importance of this process.

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Thesis Excerpts & Analysis

Copulation mechanics and timing

“Copulation occurred on ground near the edge of the pond; it took about 3–4 hours. Oviposition occurred 2 or 3 days after copulation; eggs were laid on ground.” (p. 107).

Plain English: mating is a long, deliberate event lasting several hours; egg-laying follows a few days later. The extended copulation window allows complete spermatophore transfer and any required behavioral positioning.

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Spermatophore formation and function

“The penial complex forms the spermatophore, which is transferred during copulation.” (p. 110).

“The spermatophore consists of a long tubular tail and a bulbous head, surrounded by a chitinous sheath. The structure ensures sperm survival and gradual release inside the recipient.” (p. 146).

Analysis: the spermatophore is an engineered delivery capsule — a protective casing (chitinous sheath) with a bulbous head (likely housing most sperm) and a tail that helps positioning during transfer. This design both protects sperm from the recipient’s internal environment and times sperm release to maximize chances of fertilization.

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Reception: the bursa copulatrix and early fate of the spermatophore

“The bursa copulatrlx is observed to contain complete and incomplete spermatophores. The empty sac-like portions of spermatophores are absorbed first by surrounding secretory material, and spinous portions may be absorbed later.” (pp. 142–145).

“The bulk function of the bursa is to receive and store the spermatophore, release the sperms from the spermatophore and to assist sperm migration from bursa to spermatheca.” (p. 92).

Plain English: the bursa acts like a receiving and processing chamber. It temporarily holds the spermatophore, the outer parts are digested/absorbed, and the sperm are released — then either die in the bursa or move onward to storage/migration sites. The bursa therefore both filters and activates sperm.

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Staged release and selective absorption

“In egg-laying snails the bursa copulatrlx is observed to contain complete and incomplete spermatophores… This indicates that when sperms are released (to be passed to fertilization pocket to fertilize the egg), the empty sac-like portion of the spermatophore is absorbed first by the surrounding secretory material and in the second step the spinous portion may be absorbed.” (pp. 142–144).

Interpretation: the spermatophore’s parts are processed in sequence — the bursa digests expendable portions, leaving sperm free to travel. This staged absorption may reduce foreign tissue load and prevent clogging, while releasing sperm in a controlled way.

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Sperm migration and fertilization pocket function

“The fate of the sperms and the detail of the insemination of ovum in this hermaphrodite snail is not clearly established. In Bensonies iacquemonti the male role is to the fertilization pocket by some unknown mechanism and is fertilized here by the sperm… No actual fusion of ovum and sperm is observed. When the two meet, they are simply applied close to each other.” (p. 113).

Explanation: sperm appear to reach a specialized fertilization pocket, where eggs and sperm interact closely — perhaps with surface-level interactions rather than the textbook single-point sperm-egg fusion observed microscopically. The thesis reports that often many sperm surround an ovum but only one succeeds.

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Role of spermatheca and longer-term storage

“The storage site is called our of fertilization pocket. Storage of sperm may be for weeks or even years and the storage site is called the spermatheca.” (pp. 92–93).

Practical note: hermaphroditic snails can store sperm long-term, decoupling mating from immediate fertilization. That provides reproductive flexibility: a snail can mate when conditions permit, but delay fertilization until eggs can be safely laid.

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Visual evidence and microstructure (microscopy)

“Microphotograph of l.s. of genital tract of Bensonies iacquemonti showing function of small and large hermaphrodite duct, fertilization pocket and albumen.” (fig./p. 113).

Microscopic plates in the thesis show spermatophores inside the bursa, stages of absorption, and the connection between bursa, spermatheca, and oviduct — anatomical confirmation of the described pathway.

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Ecological and evolutionary implications

“In Bensonies iacquemonti like other pulmonate snails the function of spermatophore is not protection of the sperms during transfer to the other copulant, but it ensures that the majority of sperm escape quickly into the oviduct before they come in contact with the digestive (bursa) secretion.” (p. 146).

Implication: the spermatophore evolved not just as protection during transfer but as a timing device that funnels sperm rapidly into routes that lead to storage/fertilization while minimizing loss to the bursa’s digestive environment. That improves reproductive efficiency in a hermaphrodite where competition between sperm populations (poly-spermy) and digestive inactivation is real.

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Conclusion

Spermatophore transfer and fertilization in Bensonies jacquemonti are coordinated events: formation by the penial complex, prolonged copulation allowing full transfer, reception and staged processing in the bursa copulatrix, sperm migration into the fertilization pocket and/or spermatheca, and eventual fertilization. These anatomical and behavioral features maximize reproductive success in a complex internal environment.

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Author Bio

Rehana Parveen Aurangzeb (M.Sc., M.Phil., Ph.D.) — Doctoral researcher, University of Peshawar. Her thesis provides detailed anatomical, histological, and behavioral evidence on mating, spermatophore dynamics, and fertilization in Bensonies jacquemonti.

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Source & Citations

Thesis Title: Reproductive Biology of Bensonies jacquemonti (Martens 1869)
Researcher: Rehana Parveen Aurangzeb
Guide (Supervisor): Dr. Muhammad Nasim Siddiqi
University: University of Peshawar, Pakistan
Year of Compilation: 1992
Excerpt Page Numbers Used: 63, 92, 107, 110, 113, 142–146.

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Disclaimer: Some sentences have been lightly edited for SEO and readability. For the full, original research, please refer to the complete thesis PDF linked in the section above.

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FAQs

Q1: What is a spermatophore in Bensonies jacquemonti?
A spermatophore is a capsule produced by the penial complex — a long tubular tail with a bulbous head and chitinous sheath that carries sperm during transfer. (p. 146).

Q2: Where is the spermatophore received?
It is received into the bursa copulatrix, which stores and digests parts of the spermatophore and releases sperm for migration. (pp. 142–145).

Q3: How do sperm reach the eggs?
Sperm are released from the spermatophore in the bursa, some migrate to the spermatheca for storage, and fertilization is reported to occur in a fertilization pocket where sperm and ova come into close contact. (pp. 92, 113).

Q4: Can snails store sperm for long periods?
Yes—storage in spermatheca can last from weeks to years, permitting delayed fertilization. (pp. 92–93).

Q5: Why is staged absorption of spermatophore parts useful?
Staged absorption removes expendable material while timing sperm release — reducing exposure to digestive fluids and improving the chance sperm reach the oviduct or spermatheca. (pp. 142–145).

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