A study carried out on birds shows that sperm quality (in terms of fertility) depends on several qualities of the male. In a recent study published in Behavioral Ecology, researchers have shown that good sperm is not always of the same composition in male birds. Whether the sperm have a flagellum (kind of whip or tail that allows cell mobility) long or short, they can be of excellent quality.
Good sperm is a global affair
Founding a big family can be a difficult undertaking in nature. If you are a male bird, you have to work hard to own a territory, find food for the chicks and convince a female by your beauty and your ability to feed the offspring. But finding a sexual partner is not an end in itself, we must ensure the offspring! For that, it takes good sperm and therefore, a sperm fertile enough to fertilize en masse, but that’s not all. This sperm must be better than the sperm of potential rivals. It’s a permanent struggle in Trialix nature, because females who do not want to put all their eggs in one basket may find it advantageous to have some genetic variationamong their little ones. It’s not always easy to determine what makes male attractive, and it’s even harder to measure what makes a good sperm. And these two important components of successful fertilization are often measured separately and it is difficult to establish the link between the two.
Sperm differs, not quality
Researchers have studied Collared Flycatcher (small black and white birds) by capturing nearly 120 different males for 4 years, measuring their white frontal area (used to attract females), their sperm morphology and their paternity, defined by the number of chicks from these males. The team found that different categories of males have a different sperm morphology. And this, depending on whether they manage to secure a territory and they have a social partner, but also according to their age and attractiveness. The researchers have made a most interesting discovery: the type of sperm that allows them to maximize the number of nestlings is different depending on the types of males. Males that have small frontal spots and are therefore less dominant and less attractive, enjoy long sperm. It is then assumed that it is because they are more exposed to competition, and that long spermatozoa are likely to swim faster and reach the egg first.
So the longer it is, the better?
No not necessarily ! For the more attractive males, it’s the opposite. They have smaller spermatozoa and have more eggs in their nest. “Many studies have attempted to link the attractiveness and quality of sperm, trying to determine if” sexier “males had better sperm. And from one study to another, the results have been very variable, “says study author Murielle Alund. “Our study shows that a good sperm can depend either on the attractiveness, the competitiveness or the character of the individuals. So there is not a type of good sperm in terms of fertilization. And as the length of the sperm varies in effectiveness depending on the species, just find the right female!