A man generates billions or so spermatozoa during his "active" lifetime. In the same time, a female ovary releases a strictly limited number of eggs (around 400). Despite the contrast in productivity each sex contributes exactly the same amount of genetic material to the next generation. It is an uncomfortable truth that the main biological role of males is to manufacture vast quantities of sperm to fulfill a genetic function that the other gender accomplishes much more efficiently
Nowhere is sexual imbalance seen more clearly than in the male ceratoid anglerfish, whose entire existence, 500 meters down in the sea, is geared to seeking out and serving a lady anglerfish. The first features that strike you about the male are his huge eyes for locating a mate in the dim depths of the ocean. The second are a pair of massive testicles, which occupy over half the body cavity. Yet this exotic creature is barely a miserable one or two centimeters long—compared to females ten or twenty times that length. Despite such differences, the relationship between male and female anglerfish is a model of sexual togetherness, unique in the natural world.
Love at First Sight
Once a male ceratoid anglerfish has spied a mate, using those colossal eyes, his independent existence is virtually over. The rest of his life is devoted to the single function of manufacturing sperm to satisfy the female. A male's last self-assertive act is that of grasping his partner, using pincer like “denticles" at the tips of his jaws. After the male and female come close together, their surface tissues begin to merge and eventually fuse together. Next, the two circulatory systems link up, SO that the diminutive male becomes totally permanently dependent on the female for nutrients supplied through her bloodstream.
However bizarre, the arrangement is an undoubted success. About a hundred different species of anglerfish flourish in the depths of oceans throughout the world. The explanation, it seems, is that every encounter between a male and a female of the same species, whatever their ages, is a potentially sexual affair.
Shielding Sperm from Immune System
One biological law that until very recently was thought to apply to anglerfish, Homo Sapiens, golden eagles, rattlesnakes, turtles, and all other categories of animal life on earth also concerns spermatozoa. Of several apparently immutable barriers in the body, the one that shields sperm from the immune system has been thought especially important.
The apparatus that vanquishes bacteria and other invading microbes and, incidentally often threatens to thwart organ transplantation, is normally shielded from spermatozoa and the cells that generate them. The integrity of the barrier appears to be essential to the production of sperm. In turn, this means that should the barrier be severed, the body's immune system would react to spermatozoa as foreign cells and destroy them.
In the 20th century, some intriguing work by Dr. H. Bruecker in the department of microscopic anatomy at the University of Hamburg, revealed that in at least one species, the swan (Cygnus Olor), this state of affairs is not immutable. Indeed, rupture of the barrier serves an essential purpose at one stage in the year by allowing the bird's immune system to deal with excess spermatozoa that are no longer required.
The swan has a limited breeding season, and by May or June the remaining vast numbers of spermatozoa in the bird's testes are unwanted; no more will be required until the following spring. At this stage, according to Dr. Bruecker's work, the wall is breached. Macrophages, the scavenging cells that usually engulf foreign agents such as bacteria, squeeze their way through the barrier and into the tubules that serve as the sperm factory. There they devour the leftover sperm. Then, just as quickly, they return to their routine job of monitoring the swan's bloodstream against the menace of microbial attack.
Now that we know about this ingenious divergence from what previously appeared as an absolute law of biology, we confront further puzzles. How do the scavengers know when to invade a swan's testes? And What keeps them out during the time when spermatozoa are much in demand? No One can yet answer these questions. They are part of the mysterious interconnectivity of nature. What we can be sure about is that no such novel physiology operates in the male anglerfish. Thanks to the female of the species, his copious spermatozoa are always in demand.