Sea peacock
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Sea peacock ( Thalassoma pavo ) ♀ |
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| ( Linnaeus , 1758) |
The sea peacock ( Thalassoma pavo ) is a species of the wrasse (Labridae).
distribution
The sea peacock is native to the entire Mediterranean with the exception of the northern Adriatic and parts of the northern areas of the western basin. The sea peacock is more common in the south of the Mediterranean than in the north. In the East Atlantic it occurs in the Gulf of Guinea north of Cap Lopez and on the coasts of the Azores , Madeira , the Canary Islands , São Tomés and Annobóns . A comparison of the last one to two decades shows a shift in distribution from the subtropical area to the north, so that the sea peacock is now found in the entire north-western part of the Mediterranean.
The sea peacock prefers to stay above the rocky bedrock and in seagrass meadows, because there are plenty of hiding spots here. It occurs from shallow water areas down to depths of up to 150 m, but is mostly found in the upper 20 m. In addition to coastal waters with rocks, the sea peacock also inhabits ecosystems influenced by humans such as shipwrecks or jetties (Pollard & Alfonso 2010). In summer the males occupy vast territories on rocky coasts. In contrast to its close relative, the mermaid ( Coris julis ), the sea peacock prefers even warmer water.
features
The sea peacock is about 15 to 20 cm tall on average, the maximum size is 25 cm. He has a slim body and shows strong gender dimorphism. It has a rounded head with a terminal mouth.
The blue, ornamental pattern on the head and five bluish-green vertical stripes on the sides of the body are characteristic of its basic or initial coloration, which only the females show. The basic color of the sea peacock is bronze to golden yellow with a greenish to orange tone that varies from person to person. In addition, the sea peacock has a clearly visible black spot on the back in the middle of the dorsal fin, which is easy to see from both sides. The caudal fin is sickle-shaped, so the fin rays are elongated at both ends. In males, the outer rays of the caudal fin are even more clearly elongated as threads. The indentation of the fin is particularly easy to see in older individuals.
The youth coloring can be recognized by the green base color of the body. The black spot on the back is very noticeable and its color extends far into the dorsal fin. The edge of the caudal fin is even more rounded than that of the adult animals. The transition color of the largest females, which will shortly change sex, is characterized by the fading back spot. Only then does the rest of the body drawing change.
From a length of about 90 to 120 mm, all females change their sex without exception. The resulting males change color after changing sex. However, this is not directly related to sexual inversion. Primary males also have the initial color that the females have at the beginning. They only change their color when they are more than 130 mm long. Thus, all secondary males as well as all primary males taller than 130 mm have the splendid dress.
The coloring of the males is dominated by a broad blue-green stripe behind the head. This is the distinguishing feature to the females and juveniles, which show five green-blue horizontal stripes on the sides. The body of adult males is more massive than the physique of females and young animals and the lyre-shaped caudal fin is more indented. Older males are olive-green to green-blue in color and, in addition to the broad blue-green neck band, have another band with red-brown color just behind the pectoral fin. The head is colored with a distinctive reddish or blue pattern. Specific features of the genus Thalassoma, to which the sea peacock belongs, are eight spines in the dorsal fin, 30 scales in the lateral line and labyrinth-like, blue stripes on the head.
Way of life
The sea peacock is a busy swimmer who constantly searches its surroundings for food alone, in small or large groups. The fish eat small crustaceans , snails and mussels . To sleep they dig themselves into the sand with quick strokes of the tail fins. Sea peacocks do not care for their brood and are free spawners who swim into open water to reproduce and release their germ cells there. The eggs drift away as part of the plankton . To search for food, young fish and females often form larger groups, so-called food communities.
nutrition
The sea peacock prefers to feed on small crustaceans and molluscs such as snails and mussels. Young animals also show a behavior that is known from cleaner fish , because they clean larger fish and feed on their parasites.
Reproduction and courtship behavior
A peculiarity of the sea peacock is that it is a protogynous hermaphrodite (Pollard & Alfonso 2010). This kind of hermaphrodite goes through a protogynous sex development. This means that in the course of development there is a sex change from female to male. These males are called "super males", they have similar morphological characteristics as the mermaid.
Super males arise when groups of many females and one male leave one male out. Then one of the strongest females transforms into a new male. The gender change begins at the end of July at the earliest, but usually at the beginning to mid-August. Sea peacock females with intermediate gonades (a hybrid of female and male sex glands) were caught sporadically in July and most of the individuals were caught in mid-August. At the end of September there were no more females with intermediate gonades at all. The sex reassignment process itself only takes about three to six weeks.
The reproductive phase of the sea peacock can be divided into three areas. From May to the end of June the males occupy their territories and woo females. The mating phase takes place until the end of August, when the fish spawn in the open water. The males remain in their territories until mid-October. Spawning occurs either in pairs or in groups. There are four different phases in the spawning behavior of couples. In the approach phase, courtship behavior takes place in a very specific part of the territory of the dominant male, around which the male swims in elliptical laps. The courtship ritual begins when a female comes into the area. Then the male makes quick circular movements over the female and flaps back and forth with the caudal fin. In the acceptance phase, the female follows the male, who is still swimming about 1 m above her. In the subsequent ascent phase, the female moves faster and approaches the male until both swim upwards together. At first they move in a synchronized manner, but towards the end of the ascent they snap towards the surface of the water within seconds. At the end of the ascent the spawning phase begins. The animals position themselves with their genital openings in relation to one another so that the germ cells , the gametes, can be released. The female then swims back down quickly, while the male remains in the water column for some time. In the same way, spawning takes place in the group, the first phase of which is the coming together of up to 40 individuals. In the preparation phase, the fish swim confusedly; no courtship behavior is discernible. In the ascent phase, the small schools of fish swim upwards together. In the final phase, spawning occurs near the surface. In this phase, the animals try to be as close together as possible when they release the germ cells. Immediately afterwards they separate again.
Eggs and larvae
As free spawners, sea peacocks do not care for their brood. In the summer months, the fish spawn in open water (pelagic), where the germ cells are released together. The resulting eggs are planktonic. The larvae are also pelagic, which means that eggs and larvae such as plankton are widely distributed in the sea by floating in the open water with the ocean currents.
Systematics
The ornate wrasse was already in 1758 by Carl Linnaeus , the founder of biological taxonomy , in its Systema Naturae as Labrus Pavo described . The sea peacock systematically belongs to the wrasse (Labridae), which is the second largest family of sea fish. It comprises around 520 species in over 65 genera, making it one of the largest families among the reef fish. The name Labridae comes from the Latin labrus (lips), which are a distinctive feature of some species in this family. A single dorsal fin is characteristic of wrasse, with a longer hard-edged part and a shorter soft-nosed part. Within this family, the sea peacock belongs to the subfamily Julidinae (Junker Wrasse), like most wrasse. The species in this subfamily are reef dwellers.
Use and trade
The sea peacock is a popular aquarium fish because not only does it look beautiful, it is also very easy to keep. The sea peacock is caught with baited fish traps. It is only caught locally in the eastern Mediterranean and on the Macaronesian islands and mainly sold to the aquarium trade. Except for the local fishing mentioned, the sea peacock is not exposed to any major threats.
Protection status
The IUCN red list status of Thalassoma pavo is “least concern”, ie not threatened. There are no specific data on the population in the Northeast Atlantic, but since all other sea peacock populations are stable, the species is classified as not endangered.
swell
- ↑ a b c d M. Bergbauer, B. Humberg: What lives in the Mediterranean? Kosmos, Stuttgart 1999, ISBN 3-440-07733-0 .
- ↑ a b c d e f Patrick Louisy: Marine fish. Western Europe and Mediterranean. Stuttgart 2002, ISBN 3-800-13844-1 .
- ↑ a b c Rupert Riedl: Fauna and flora of the Mediterranean. 3. Edition. Hamburg 1983, ISBN 3-490-23418-9 .
- ↑ a b V. Günter, A. Kieneke, D. Muschiol, J. Nicke: Excursion Giglio 2001 ( Memento of the original from March 4, 2016 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. . Bielefeld University, project results, 2001 (accessed December 19, 2014)
- ↑ a b c Roland Kuhn (1976). Morphological and histological investigations into the sex change of Thalassoma pavo (L.), a diandric protogynous wrasse from the Mediterranean. Mainz.
- ^ Rudie H. Kuiter: Wrasse. Ulmer Verlag, Stuttgart 2002, ISBN 3-8001-3973-1 .
- ^ S. Giampietro, CN Bianchi & C. Morri: Mating behavior of the newly-established ornate wrasse Thalassoma pavo (Osteichthyes: Labridae) in the Ligurian Sea (north-western Mediterranean) . In: J. Mar. Biol. Ass. UK, 85, 2005, pp. 191-196.
- ↑ a b c Thalassoma pavo in the IUCN Red List of Threatened Species 2013.2. Posted by: Pollard, D. & Afonso, P., 2014. Retrieved December 19, 2014.
Web links
- Meerpfau on Fishbase.org (English)