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.
They are products of evolution by natural selection.