Did you know that fish has hermaphrodites?
本文同时提供以下语言的翻译:中文
Introduction
The research on fish hermaphroditism and fish degeneration is a topic that few people pay attention to. The current research results are likely to be modified or corrected,
and we hope that scholars can make breakthroughs in this field.
In the class teleost, sex change is very common.Many fish are androgynous and have pairs of gonads.That is to say,
They either have only one pair of ovaries or one pair of testicles.But the way most fish reproduce through ivf allows them to change their sex, known as bisexual dimorphism.
Fish secrete hormones that turn undeveloped glands into ovaries, or testes.
A good example is the red snapper, a school of one male and dozens of females.The male is in the lead, leading the pack in feeding, protecting the species and mating.
Once the males die, the largest of the remaining females develop into males and continue to lead the pack.This process is called denaturation.
Hermaphroditism
But studies of more than 3,000 fish samples in the past have confirmed that all of them are unisexual – they change sex, but do not become hermaphrodites.
But in the Woods Hole lab study, an exception was discovered: a possible hermaphroditism was found in striped kilopas, members of the Carp family.
Before we get into the details, let’s take a look at some of the secondary sexual characteristics that fish have between the sexes.
Although different species of fish have different elements to distinguish sex, there are mainly the following directions:
bodily form：
Different fish have different conditions,
Among mature individuals, some species have larger males, such as the red eaglefish mentioned above.In some cases, the female is larger than the male, such as the striped killifish.
Pattern, color:
Generally speaking, males and females have different patterns, or colors, and males are more brightly colored than females.
In the striped killifish, the two sexes had completely different body color patterns;Males consist of distinct transverse bands that extend from the back of the head to near the base of the caudal fin;
The female’s body, on the other hand, consists mainly of distinct longitudinal stripes, perfect at the front and fused with the male’s cross stripes at the back.
PS: The cross stripe pattern is the original pattern of the species, and all immature fish, regardless of sex, are born with this pattern.
Behavior:
During the spawning season, the behavior of the striped killifish male is in sharp contrast to that of the female.The former are energetic and aggressive and often follow females in order to lay eggs with them.
The discovery of a special case
On June 3, 1907, researchers at Woods Hole Oceanographic Institution took a large male swish for sperm testing, but they extruded eggs from the individual.
The problem is that this individual has clearly male characteristics (clear male stripes), but the outer fallopian tubes of the spawning female, and the dorsal fin is not dark.
The individual was kept alone in a special tank, and studies showed that the eggs of the male striped killifish had low fertility.At this point, another female of similar size was placed in the tank.
Probably because all the eggs had been expelled, the killifish became emaciated.
He also appeared bossy and began to take on more masculine features.
The fish was closely watched during the last week of July.On some occasions, it exhibits a distinctly masculine behavior.It circles the female, making repeated movements that appear to be a faint attempt to lay eggs.
Can’t be sure at this point, but in other ways, it’s a courtship male behavior.
On the last day of July, the experimenters were forced to leave the lab, and the killifish was killed and carefully preserved in formalin.Examination of the gonads preserved in formalin revealed that it was a compound gland, containing about 5% of testicular tissue, slightly immature and embedded in a mass of immature and obsolete ovarian tissue.
Testicular tissue appears as a tiny mass, mainly near the posterior end of the gland.Although testicular structure is evident, these small masses show atypical structure than normal testis, are less dense, and are interspersed with connective tissue.
The color, size, and appearance of the entire gland are the same as that of a well-preserved testis, unlike the yellow seasons of a normal ovary after spawning.
The picture shows a drawing of the Hermaphrodite striped killifish
Conclusion
- An interesting aspect of this discussion is that because the ta tissue does not appear to show sexual dimorphism, the testicular tissue is located behind the ovarian tissue and to some extent overlapses with the latter.This condition of the gonads is reminiscent of the compound glands mentioned earlier.
- Increased understanding of secondary sexual characteristics of secretions: in this case, the presence of relatively small amounts of imperfect testicular tissue has a negative effect on individuals (mainly females), inhibiting the transition of juveniles to female color patterns;The positive effect of this individual at the end of the spawning season is to approximate the colour and behaviour of the male.
- In all cases of the series of hermaphroditism described in the available literature, hermaphroditism occurred during successive seasons.In less than a month the proto-female changes were evident.This situation is clearly anomalous.
**Citation
- On a Hermaphrodite Example of the Herring(Clupa Harengus). Ann, Mag. Nat.Hist.(7), Vol.9, pp 195-196
- Newman, H. H. “A Significant Case of Hermaphroditism in Fish.” Biological Bulletin, vol. 15, no. 5, Marine Biological Laboratory, 1908, pp. 207–14.
Did you know that fish has hermaphrodites?
