Seahorses (Hippocampus hippocampus) in the aquarium tank of the former Helgoland Aquarium, photo: E. Hensel
The seahorse has always enjoyed great popularity. And not least because it is fundamentally different from all other fish. Most noticeable is the external appearance, which is more reminiscent of a horse than a fish. In Greek mythology, these animals were represented as riding or draft animals of various sea gods.In spite of all this, the question of whether this creature is actually a fish can be answered with an unequivocal “yes”. It has gills and fins not only hold on to algae and seaweed but also to each other.
This urge for social interaction is sometimes so great that the animals, which are connected to one another in a cluster, do not give up this contact even when feeding. It can then happen that they try to swim after a prey in different directions, but because of their tangled grasping organs they do not have to move and watch their food quickly search the distance after the failed feeding attack. And otherwise the short-nosed seahorses Hippocampus hippocampusare not exactly the fastest. More leisurely they go on their forays through the cylindrical acrylic glass tank in the aquarium. They spend most of their time clinging to algae, floating in the water, in a vertical or horizontal position.
It is very easy to distinguish between males and females: only the males have a brood pouch. This is located on the front of the abdomen, where a clear furrow marks its opening. The females lay their eggs with a laying arm in this brood pouch, and this is where the eggs are fertilized. After about three weeks, the young hatch from the male brood pouch. This type of reproduction is unique in the fish kingdom.One of the peculiarities of the seahorses is that they have a bone armor that gives the seahorse’s body its shape and stabilizes it. The shape of the animals deviates so much from the typical fish shape that many viewers were reminded of a land mammal with hooves, as already described.
Fascinating marine animal: the seahorse (Hippocampus hippocampus) Photo: E. Hensel
But the special mechanism of the seahorse’s ingestion of food sometimes arouses first astonishment and then delight at the acoustic event associated with it. Because contrary to their otherwise rather sluggish appearance, and when they have stayed close enough “on the heels” of their prey, they suck it in in a flash through a negative pressure created by the oral cavity. This results in a clicking sound that can be heard even outside of the tank. The food – mostly hover shrimp or brine shrimp – must not be too big, otherwise it will get stuck in the seahorse’s rather narrow mouth. Live food is particularly attractive.
Residents of the North Sea island of Helgoland reported that many seahorses were washed up on the beach. The southeastern North Sea with the German Bight does not actually belong to the typical range of seahorses. However, it is entirely conceivable that the animals will migrate from the English Channel to this part of the North Sea as a result of climate change.