Round-tailed macropod

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Round-tailed macropod
Macropodus ocellatus.png

Round-tailed macropod ( Macropodus ocellatus )

Systematics
Order : Climbing fish species (Anabantiformes)
Subordination : Labyrinth fish (Anabantoidei)
Family : Osphronemidae
Subfamily : Macropodusinae
Genre : Paradise fish ( Macropodus )
Type : Round-tailed macropod
Scientific name
Macropodus ocellatus
Cantor , 1842

The round-tailed macropod ( Macropodus ocellatus , Syn . : Macropodus chinensis ) is a small freshwater fish from the suborder of the labyrinth fish . The fish are found in China between the Pearl River and the Amur , on Taiwan and in the western and southern flatlands of Korea . The round-tailed macropod was introduced by humans to the Japanese main island of Honshu , to Shikoku and possibly also to the Russian Amur region.

description

The round-tailed macropod is a maximum of 8 cm long and thus remains smaller than the macropod ( Macropodus opercularis ) or the black macropod ( Macropodus spechti ). Furthermore, it differs from the two aforementioned types by the smaller head width, which makes the head appear more pointed. The rounded caudal fin is characteristic of the species, while the tail of the other macropods is deeply forked. In older males of the round-tailed macropod, it takes on an elongated-oval shape. The pelvic fins of the fish are very short when caught in the wild, but they can lengthen considerably when bred from aquariums. As with other macropods, the ends of the dorsal and anal fin are long, and in the males they are very long. Overall, males are significantly larger, usually darker in color than the females, and develop a high, arched neck with age.

The round-tailed macropod has a gray-yellow basic color. The eponymous eye-spot ( Latin : "ocellatus"), which is greenish or bluish, is located on the gill cover . During the breeding season, the throat, abdomen and the middle trunk area of ​​the adult males and more aggressive females become dark brown, slate gray or black and can be iridescent bluish with a certain incidence of light from the side. The unpaired fins have bluish-white seams; the membranes of the dorsal and anal fin show light blue stripes and the caudal fin light blue dots. As a frightening color, the round-tailed macropod shows a herringbone-like stripe pattern on the sides of the body.

habitat

Round-tailed macropods inhabit stagnant and slow-flowing waters, especially in lowlands. These include flooded rice fields with water levels of only 10 to 20 cm, as well as residual water pools. The large area of ​​distribution, especially in the north-south direction, extends from the cold-temperate zone in North Korea and Manchuria to the southern Chinese subtropics, although its main distribution area is in the temperate zones down to the Yangtze. In the northern part of its range, cold winters with air temperatures of −20 ° C are not uncommon. The fish survive the winter under a thick ice cover with water temperatures around 4 ° C. The German ichthyologist Hans-Joachim Paepke was able to examine round-tailed macropods in their natural habitat in North Korea in 1990. Among other things, he found the fish in a small pond in the catchment area of ​​the Taedong-gang . The sparse bank vegetation consisted mainly of common beach ledges ( Bolboschoenus maritimus ). The Japanese water nut ( Trapa japonica ), the rough horn leaf ( Ceratophyllum demersum ) and the curly pondweed ( Potamogeton crispus ) grew in the open water . In addition to the round-tailed macropods, the silver crucian carp ( Carassius auratus ), the gudgeon ( Gobio gobio cynocephalus ), the blue-banded harlequin ( Pseudorasbora parva ) and the large, piscivorous carp fish Chanodichthys erythropterus were found in the pond.

Studies of the habitat of the round-tailed macropod in the catchment areas of the Hai He River and on the island of Chongming Dao at the mouth of the Yangtze River are many decades older . The round-tailed macropod lived in Hai He together with the half- beaked species Hyporhamphus intermedius , the spiny eel Sinobdella sinensis , the goby-like Rhinogobius davidi and Micropercops swinhonis and the bitterling species Rhodeus sinensis . On the island of Chongming Dao, round-tailed macropods lived in the many small rivers and ditches that run through the island and which were made up of rough horn leaf ( Ceratophyllum demersum ) and spiky thousand leaf ( Myriophyllum spicatum ). Accompanying fish were the grass carp ( Ctenopharyngodon idella ), the bitterling species Rhodeus ocellatus and the piscivorous carp fish Culter alburnus and Hemiculter leucisculus . The Chinese woolly crab ( Eriocheir sinensis ) was also found here .

Reproduction

Round-tailed macropods become agile at water temperatures of 15 ° C and above and get into courtship mood around 20 ° C. Both sexes become dark and the males usually begin to build a very rudimentary foam nest . The females then turn light yellow to lay their eggs. In cramped aquarium conditions, the males are initially very aggressive and also chase away females that approach too early. Under conditions that are not cramped, such as in larger ponds, a breeding pair comes together in a peaceful way long before spawning begins. Both sexes go to the spawning site together long before the actual spawning phase and greet each other with wagging, rocking movements (often referred to as "wobbling dance" in the lit.), which are shown by both sexes. Overall, the breeding pair is very peaceful under spacious conditions. Aggressions are mainly directed outward by both of them towards territorial intruders of both sexes. When both animals are finally in the mood for spawning, the female changes color to a bright to brightly shining warning yellow that is visible from afar when spawning begins. In this phase, the female is extremely and widely aggressive towards any territorial intruder, while the male concentrates almost entirely on collecting and sorting the eggs. Between the spawning phases, the female roams widely across the territory and tracks down every macropod that is in it. After a while it is ready for the next spawning release and quickly returns to the male. This is then often still concentrated on the eggs and is clearly prompted by the female to swim to the next act of spawning. The above-mentioned "wobble dance" is not limited to the initiation of the spawning act. It is shown between the couple days before the actual spawning and during spawning it is not a consistent element for initiating the next act of spawning. It is used like a general greeting element. When spawning, the male wraps around the female and turns it on its back, with its belly facing the foam nest. In a period of one to two hours there are 12 to 15 spawning processes in which a total of 200 to 300 eggs are released. Immediately after spawning, the males become lighter again. The female loses its bright warning color only slowly over the rest of the day and together with it its extremely high degree of aggression. Until the larvae hatch, it will relieve the male in defending the territory outside, while the male only defends the immediate nesting area. From now on the male will no longer tolerate the female in this narrow radius. Egg care essentially consists of stabilizing the foam nest or spawning ball with newly produced air bubbles and the occasional re-sorting of the eggs. At a temperature of 26 ° C, the larvae hatch after 28 to 38 hours. With an adhesive gland on the head, they can adhere to aquatic plants, branches or even to the skin on the water surface. After about 3.5 days they swim freely and begin to eat. The fry can grow very quickly, depending on the weather, and specimens kept in free range ponds in Europe have reproduced in their first summer.

Especially in the days before the actual spawning phase, the males often and extensively compete broadly in the form of comment fights . In addition to broad-sided imposing, pressure waves are sent out with the tail fin, the opponents are held to a fin with their mouths or are prevented from breathing by fixing each other on the mouth. All in all, these fights are exhausting, which is indicated by very frequent breathing, but otherwise remain as good as damage-free.

literature

  • Hans-Joachim Paepke: The paradise fish: genus Macropodus. (= Die Neue Brehm-Bücherei. Volume 616). Westarp Sciences, Magdeburg 1994, ISBN 3-89432-406-6 .

supporting documents

  1. ↑ a b Paepke, 1994, p. 91.
  2. ↑ a b Paepke, 1994, p. 89.
  3. ↑ a b Paepke, 1994, p. 90.
  4. ↑ Paepke, 1994, p. 93.
  5. ↑ Paepke, 1994, p. 94.
  6. ↑ Behavior at different water temperatures . erabo.de (Erich Willems), accessed on July 16, 2020 .
  7. ↑ a b Vierke 2010, section: 3. Lump formation
  8. ↑ a b Schematic representation of reproductive behavior . erabo.de (Erich Willems), accessed on July 16, 2020 .
  9. ↑ Paepke, 1994, p. 96.
  10. ↑ Paepke, 1994, p. 99.
  11. ↑ Paepke, 1994, p. 95.
  12. ↑ Video shows the comment fight in a pond . erabo.de (Erich Willems), accessed on July 16, 2020 .

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