‘Limatik’ Encounters – 5

Is it a boy or a girl? How does one know whether a leech is male or female? How to they reproduce?

Readers and listeners unavoidably ask this kind of questions for nearly all organisms where I had been interviewed. This is understandable because of our upbringing, often religion-based and expectedly human-centered. Within that human-oriented way of thinking or curiosity, however, there is that possibility of concern as to how each organism, whether plant, animal, fungi or microbe is able to perpetuate its kind – its species.

Nobody has really ventured into the study of the reproductive biology of our local land leeches. However, based on the known general biology of leeches, they are classified as protandric hermaphrodites. Hence, when you see a leech, you don’t ask whether it is a boy or a girl, a he or a she. There is no real Adam nor real Eve in the world of leeches, no straight male nor straight female.

Hermaphrodites, according to google and Wikipedia, are organisms that have complete or partial reproductive organs, such that each individual has the capacity to produce gametes normally associated with both male and female sexes. In the case of leeches, they are sequential hermaphrodites, i.e., they produce eggs and sperm at different stages of their life. Specifically, being protandric hermaphrodites means that the direction of change is from male to female. The male reproductive organs, the testes, mature first, and then, the female organs, the ovaries, later with the interval depending probably on the species and whether the prevailing environmental conditions are favorable for the survival of offspring.

The limatik species as members of the terrestrial subgroup of leeches probably also lack a penis and the sperm is passed from one individual to another by injecting a spermatophore or sperm capsule into the integument, under the epidermis. During mating, the leeches intertwine and grasp each other with their suckers. A spermatophore is pushed by one through the integument of the other, much like a hypodermic syringe punctures through skin and injects substances, usually into the clitellar region. The sperm is liberated and passes to the ovisacs, either through the channels of the body cavity (coelom) or interstitially through specialist “target tissue” pathways.

A few hours to a few days after copulation, the small, relatively yolkless eggs are laid. In most species, an albumin-filled cocoon is secreted by the clitellum and receives one or more eggs as it passes over the female gonopore (or genital pore). In the case of terrestrial leeches, these egg cocoons are deposited under a stone or buried in damp soil, or a pile of leaf litter. Our local limatiks probably have an annual or perhaps, at most, a biannual life cycle. One politician compared human beings that do not conform with is biblical dichotomy of things as “worse than animals,” even saying “it’s common sense.” Obviously, people like him haven’t read nor have been informed about leeches. Or maybe, to put it bluntly, leeches, like all other organisms, were not designed and manufactured by one super engineer or manufacturer.

This image showing a pair of mating tiger leeches, is from Mongabay (mongabay.com) with the following details: Image ID: borneo_3594 | Date photographed: 2008-May-01; PhotographerRhett A. Butler CountryMalaysia Location: Sabah. Thanks very much Mongabay/Rhett A. Butler

They are products of evolution by natural selection.

3 thoughts on “‘Limatik’ Encounters – 5

  1. Hi Jun,
    How about these 2 hypotheses about their adaptations just by inferring from the info on life history you shared with us?
    1. To have reproductive success, multiple cohorts should exists in their populations (more than one mating period to produce individuals of different ages; this is to assure there exists males & females at the same time).
    2. I will guess that the trigger to transform from male to female is increase in resource availability. It still seems more expensive to do your job as a reproductive female, making egg & hosting the fertilization process, than producing sperm.
    What do you think? Testable naman di ba?


    1. Hello Marissa! I’ve actually been thinking about Hypothesis 2, especially that we have observed them to be more abundant during the rainy months when there are more abundant land leeches. That was the first paragraph of ‘Limatik’ Encounters – 2. To me, both hypotheses are testable, but maybe it’s relatively easier to test the second compared to the first hypothesis. I wish some of our ecology students could be coaxed into doing thesis work on them. Thanks very much for your comment.


  2. Thank you Sir Lit for all these information about leeches. Keep safe always and continue to inspire us your avid fans in biological world

    Best regards!

    On Mon, Sep 7, 2020, 8:00 AM Better LIT than never, wrote:

    > Jun Lit posted: ” Is it a boy or a girl? How does one know whether a leech > is male or female? How to they reproduce? Readers and listeners unavoidably > ask this kind of questions for nearly all organisms where I had been > interviewed. This is understandable because of o” >


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