Strip tongue

Strip tongue
	Microchirus variegatus ; top right - top view, left - view from below; below - dwarf tongue ( Buglossidium luteum )
Systematics
	Carangaria
Order :	Carangiformes
Partial order :	Flatfish (Pleuronectoideo)
Family :	Sole (Soleidae)
Genre :	Microchirus
Type :	Strip tongue
Scientific name
	Microchirus variegatus
	( Donovan , 1808)

The striped tongue ( Microchirus variegatus , English: Thickback sole, French: Sole panachée), also called variable sole , is a small, benthic fish from the family of sole (Soleidae) and the order of flatfish (Pleuronectiformes).

General

M. variegatus was first described in 1808 by the British-Irish zoologist and illustrator Edward Donovan , as Pleuronectes variegatus . Some authors add the name of the subgenus to the name: Microchirus (Microchirus) variegatus , this variant is allowed as an alternative according to the nomenclature rules. There are a number of synonyms whose use is no longer scientifically recognized today: Monochirus lingula (Costa, 1847–48), Monochirus variegatus (Donovan, 1808), Pleuronectes fasciatus (Nardo, 1824), Pleuronectes mangili (Risso, 1810) , Pleuronectes microchirus (Delaroche, 1809) and Solea variegata (Donovan, 1808).

features

As with all species of the order of the flatfish, the body of M. variegatus is highly flattened laterally in the adult stage and both eyes are on the same side of the body. The body is therefore asymmetrical and has a blind side (side of the body without eyes) and a top side (side of the body with eyes). As with almost all sole, the eyes of M. variegatus are found on the right side of the body. In contrast to the upper side, the pectoral fin ( pectoralis ) is only rudimentary on the blind side and is supported by two or three fin rays.

The striped tongue, which is one of the smaller species of the sole family, is usually 12 to 15 cm tall and in the older age groups, between 10 and 13 years of age, reaches a size of up to 20 cm. As with all species of the genus Microchirus , both the dorsal fin ( dorsalis ) and the anal fin ( analis ) are not connected to the base of the tail. This is an important distinguishing feature for morphologically very similar solenette ( Buglossidium luteum represents), the tail ( caudal ) is connected by a thin membrane with the dorsal and anal fins.

The basic color of the fish varies from gray-brown to reddish. Characteristic of this species are brown, irregular bars on the upper side of the fish, which spread as dark spots, especially on the dorsal and anal fin. They serve as a distinguishing feature to other species of the genus Microchirus .

During the breeding period, the females have large, orange to red ovaries, which can be easily recognized by the light blind side of the fish. This makes it easier to differentiate between the two genders, who otherwise look very similar.

Geographical occurrence and habitat

The distribution area of M. variegatus extends in the eastern Atlantic from the north of the British Isles to the south, in the Bay of Biscay , to the Iberian Peninsula . M. variegatus is also native to the entire Mediterranean region , including the Adriatic . The strip tongue can also be found along the Madeira archipelago .

The species prefers soft soils of fine sand and muddy sediments. M. variegatus is mainly found on the outer continental shelf between 50 and 150 m depth and to a lesser extent over the continental slope to a depth of 400 m.

nutrition

M. variegatus feeds on carnivores ( carnivores ) and has a great variety in its food intake. As food components, inter alia, are sessile and freely movable polychaetes ( polychaetes ), Amphipoda ( flea crabs ), small mollusks , Decapoda ( decapods ), Echinodermata and Foraminiferen .

The main food components change in different regions due to the different quantities of the respective food groups. To set polychaete the main food component of M. variegatus is in Irish waters while strips tongues in French waters mainly on crustaceans ( Crustacea feed).

Reproduction

In M. variegatus is sexually separated with external fertilization. The spawning period extends mainly over the spring months, although regional differences can occur. The spawning period in the French part of the Atlantic extends from March to mid-July, while the spawning period in Irish waters does not begin until May, but extends into August and thus further into summer.

Females reach sexual maturity at around three years of age. By this time they have already reached a body length of approximately 9 cm. Males, on the other hand, only reach sexual maturity at around four years of age, which can be explained by the generally somewhat slower growth of the males. They reach an approximate body length of 8.2 cm at the onset of sexual maturity.

The spawning release takes place “offshore” on the outer continental shelf and on the continental slope at great depths. The spawning depth is related to the maximum depth of the respective body of water. Spawning takes place on the French Biscay between 100 and 200 m depth, while in the English Channel it takes place in shallower waters.

Ripe eggs are released in several successive “waves”, the exact periodicity of which is still unknown for many members of the Soleidae family , including M. variegatus . Spawned eggs are smooth, spherical and do not stick. They are 1.12 to 1.42 mm in size.

development

The development of the fertilized eggs takes place floating in the pelagic area of the sea. As soon as the larvae hatch, they float in the water as zooplankton (animal plankton). Juveniles of M. variegatus settle “offshore” in “open-sea nurseries”. "Open-sea nurseries" are areas of the open sea that provide the juveniles with plenty of food and thus serve them as a kind of "nursery" in which they can grow up and reach the adult stage.

Rapid growth can be observed in M. variegatus up to the age of seven or eight . After the age of eight, the growth of the fish slows down until there is hardly any evidence of growth from the age of ten or eleven. The oldest individuals caught so far were between 16 (males) and 17 (females) years old. From investigations of the otoliths (ear stones) one deduces an increased growth between the months of May and August. This period roughly represents the spawning period of the animals examined in Irish waters.

Larval development

In contrast to other species of the Soleidae family, the life cycle of M. variegatus takes place entirely in "offshore" locations, which means that the individuals do not normally reach coastal areas during any of the ontogenetic developmental stages. So far it can only be assumed why the hatched larvae of M. variegatus remain in “offshore” locations.

One of these assumptions is related to the missing swim bladder of the larvae of M. variegatus . Although most flatfish no longer have a swim bladder in the adult stage, it is larval in many species, but is regressed again in the course of ontogeny. The larvae of M. variegatus are the only members of the Soleidae family that do not have this characteristic. The functions of the swim bladder during the behavioral development of larvae are so far poorly understood. However, it is believed that in addition to its hydrostatic function, the swim bladder also serves to sense hydrostatic pressure fluctuations associated with the tides. In the case of the sole ( Solea solea ), an increase in sensitivity to pressure fluctuations in the tidal amplitude has already been determined. A selective tidal transport of larvae to the coast could also be demonstrated using models. The missing swim bladder of the larvae of M. variegatus could therefore be one reason why the larvae of the striped tongue, in contrast to other sole species (e.g. Solea solea ), cannot be transported to the coast by the tides and can thus " Offshore ”locations.

Another reason could be the amplification of the sensory perception of M. variegatus , which is associated with the metamorphosis of the larvae. This change enables the larvae to recognize their prey at low lighting levels and at the same time to better perceive changes in environmental factors. Larvae that have settled on the shelf are thus able to feed on small, epibenthic prey. This is believed to have contributed to the fact that the larvae reduced swimming and remained in offshore locations.

The subject of another assumption are changes in the otoliths (small auditory stones), which indicate the change to the lateral swimming orientation in freshly "settled" flatfish. In contrast to other sole species (e.g. Solea solea ), these changes in M. variegatus are not initiated towards the end, but rather at the beginning of the metamorphosis . This confirms the assumption that the larvae of M. variegatus turn to benthic life at an early stage and increases the likelihood of settlement in “offshore” locations.

Parasites

M. variegatus serves as a host organism for a number of parasites. In addition to Lomasoma stephanskii , a parasitic intestinal worm, Apocreadium galaicus , a suction worm (trematode) from the class of flatworms (platelet worms), is a common parasite of the striped tongue . It occurs mainly in the intestine of M. variegatus , but also occasionally in the stomach of the animals. The main infection time with A. galaicus is between November and January, while the infection between May and June is only very slightly or not at all detectable. As little is known about the life cycle of A. galaicus so far , it is assumed that the low infection rate between May and June is related to the missing intermediate host of the parasite in the diet of M. variegatus during this period. If the adults of A. galaicus die in M. variegatus , i.e. in their final host, the infection rate is zero. From July, the infection rate of sole increases again, which is probably due to the ingestion of larvae that cause reinfection.

meaning

Like many other flatfish, the striped tongue is edible and is therefore a commercially important fish in fishing.

The IUCN Red List of the IUCN classifies "not at risk" the strip tongue as (least concern) one. However, the population trend is unknown.

literature

P. Louisy: Marine fish. Western Europe Mediterranean. Eugen Ulmer Verlag, Stuttgart 2002, ISBN 3-8001-3844-1 .

Web links

Commons : Microchirus variegatus - collection of images, videos and audio files

Microchirus variegatus on Fishbase.org (English)

Individual evidence

↑ Edward Donovan: The natural history of British fishes, including scientific and general descriptions of the most interesting species and an extensive selection of accurately finished colored plates. Volume 1, London 1802-1808. (digitized online)
↑ PJP Whitehead, M.-L. Bauchot, J.-C. Hureau, J. Nielsen, E. Tortonese (Eds.): Fishes of the North-eastern Atlantic and the Mediterranean. Volume III, UNESCO, Paris 1986.
↑ W. Fischer, M.-L. Bauchot, M. Schneider: Fiches FAO d'Identification des Espèces pour les Besoins de la Pêche (Révision 1). Méditerranée et Mer Noire. Zone de Pêche 37. Volume II: Vertébrés. Commission des Communautés Europèennes et FAO, Rome 1987, pp. 1325-1329.
↑ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j P. A. King, JM Fives: Littoral and Benthic Investigations on the West Coast of Ireland: XXIII. A Contribution to the Biology of the Thick-Back Sole Microchirus variegatus (Donovan, 1808) in the Galway Bay Area. In: Proceedings of the Royal Irish Academy. Section B: Biological, Geological, and Chemical Science. Volume 90B, 1990, pp. 23-31.
↑ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ R. Amara, JC. Poulard, F. Lagardère, Y. Désaunay: Comparison between the life cycles of two Soleidae, the common sole, Solea solea, and the thickback sole, Microchirus variegatus, in the Bay of Biscay (France). In: Environmental Biology of Fishes. Volume 53, No. 2, 1998, pp. 193-209.
↑ ^a ^b ^c P. Louisy: Marine fish. Western Europe Mediterranean. Stuttgart 2002, p. 349.
↑ ^a ^b E. Massutí, JA Reina-Hervás, D. Lloris, L. Gil de Sola: First record of Solea (Microchirus) boscanion (Osteichthyes: Soleidae) in the Mediterranean Sea, with data on other sympatric soleid species. In: Journal of the Marine Biological Association of the United Kingdom. Volume 82, No. 5, 2002, pp. 907-911.
↑ ^a ^b ^c F. Álvarez, R. Iglesias, AI Paramá, J. Leiro, M. Sanmartín: Abdominal macroparasites of commercially important flatfishes (Teleostei: Scophthalmidae, Pleuronectidae, Soleidae) in northwest Spain (ICES IXa). In: Aquaculture. Volume 213, No. 1-4, 2002, pp. 31-53.
↑ ^a ^b ^c ^d C. Déniel: La Reproduction des Poissons Plats (Téléostéens - Pleuronectiformes) en Baie de Douarnenez. II. - Cycles sexuels et Fécondité des Soleidae: Solea vulgaris vulgaris, Solea lascaris, Buglossidium luteum et Microchirus variegatus. In: Cahiers de Biologie Marine. No. 25, 1981, pp. 257-285.
↑ ML Sanmartín, F. Alvarez, P. Quinteiro, E. Paniagua: Apocreadium galaicus sp. n. (Digenea: Apocreadiidae), a Parasite of the Thickback Sole Microchirus variegatus (Soleidae, Osteichthyes) from nw Spain. In: Parasite. No. 2, 1995, pp. 211-216.

[1] Edward Donovan: The natural history of British fishes, including scientific and general descriptions of the most interesting species and an extensive selection of accurately finished colored plates. Volume 1, London 1802-1808. (digitized online)

[Whitehead-2] PJP Whitehead, M.-L. Bauchot, J.-C. Hureau, J. Nielsen, E. Tortonese (Eds.): Fishes of the North-eastern Atlantic and the Mediterranean. Volume III, UNESCO, Paris 1986.

[Fischer-3] W. Fischer, M.-L. Bauchot, M. Schneider: Fiches FAO d'Identification des Espèces pour les Besoins de la Pêche (Révision 1). Méditerranée et Mer Noire. Zone de Pêche 37. Volume II: Vertébrés. Commission des Communautés Europèennes et FAO, Rome 1987, pp. 1325-1329.

[King-4] ↑ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j P. A. King, JM Fives: Littoral and Benthic Investigations on the West Coast of Ireland: XXIII. A Contribution to the Biology of the Thick-Back Sole Microchirus variegatus (Donovan, 1808) in the Galway Bay Area. In: Proceedings of the Royal Irish Academy. Section B: Biological, Geological, and Chemical Science. Volume 90B, 1990, pp. 23-31.

[Amara-5] ↑ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ R. Amara, JC. Poulard, F. Lagardère, Y. Désaunay: Comparison between the life cycles of two Soleidae, the common sole, Solea solea, and the thickback sole, Microchirus variegatus, in the Bay of Biscay (France). In: Environmental Biology of Fishes. Volume 53, No. 2, 1998, pp. 193-209.

[Louisy-6] P. Louisy: Marine fish. Western Europe Mediterranean. Stuttgart 2002, p. 349.

[Massutí-7] E. Massutí, JA Reina-Hervás, D. Lloris, L. Gil de Sola: First record of Solea (Microchirus) boscanion (Osteichthyes: Soleidae) in the Mediterranean Sea, with data on other sympatric soleid species. In: Journal of the Marine Biological Association of the United Kingdom. Volume 82, No. 5, 2002, pp. 907-911.

[Álvarez-8] F. Álvarez, R. Iglesias, AI Paramá, J. Leiro, M. Sanmartín: Abdominal macroparasites of commercially important flatfishes (Teleostei: Scophthalmidae, Pleuronectidae, Soleidae) in northwest Spain (ICES IXa). In: Aquaculture. Volume 213, No. 1-4, 2002, pp. 31-53.

[Déniel-9] C. Déniel: La Reproduction des Poissons Plats (Téléostéens - Pleuronectiformes) en Baie de Douarnenez. II. - Cycles sexuels et Fécondité des Soleidae: Solea vulgaris vulgaris, Solea lascaris, Buglossidium luteum et Microchirus variegatus. In: Cahiers de Biologie Marine. No. 25, 1981, pp. 257-285.

[Sanmartín-10] ML Sanmartín, F. Alvarez, P. Quinteiro, E. Paniagua: Apocreadium galaicus sp. n. (Digenea: Apocreadiidae), a Parasite of the Thickback Sole Microchirus variegatus (Soleidae, Osteichthyes) from nw Spain. In: Parasite. No. 2, 1995, pp. 211-216.