Eel mother

Eel mother
Eel mother in her natural habitat
Systematics
Order : Perch-like (Perciformes) Subordination : Cottoidei Partial order : Eel mother relatives (Zoarcales) Family : Eel Nuts (Zoarcidae) Genre : Zoarces Type : Eel mother
Scientific name
Zoarces viviparus
( Linnaeus , 1758)

Eel mother (young (†))

male

The eel mother ( Zoarces viviparus ) is a small fish of the north-east Atlantic coast (in the northern foothills of the Gulf Stream , between 49 ° and 72 ° N; at temperatures of 3 to 15 ° C). It is noticeable, among other things, that it does not lay eggs, but gives birth to young that have developed after internal fertilization.

features

The eel-like demersal fish (without swim bladder) is a maximum (rarely today) 52 cm long, weighs 510 g and is 10 years old. Nowadays you can hardly find specimens larger than 35 cm. Males and females differ little; both have a genital papilla for the purpose of fertilization . Pregnant fish are of course more voluminous than males.

The skin is covered with thick mucus, the very small scales are not easy to see. The coloring is very different from person to person, but always camouflaging, with rows of dark, cloudy or ring-shaped spots - mostly (olive) brown, with a yellowish underside. The lower jaw is often lighter than the rest of the head. The dorsal, caudal and anal fins have merged - similar to the eel - to form a fringe, the rays of which can be specified as follows: 140 + 10 + 100. A notch before the transition from the dorsal to the caudal part is usually clear ( supported by a few short, harder rays - the others are quite soft). The pelvic fins are far forward (jugular, ie at the "throat"), but are narrow - they look as if they were in regression (V 3). The round pectoral fins, however, are large (P 19-21) - Zoarces C. 1829 has 101-126 (mostly 108-118) vertebrae, six Branchiostegal radii, no pyloric tubes (MacKay 1929) and (haploid) 24 or 26 chromosomes. Due to the low level of vagility , several populations (“races”) can be distinguished.

The English name eel-pout could mean "eel pout" (which is etymologically not certain; see & nbspu.): To pout means " pursing the lips, stretching out". In fact, one sometimes sees eel nuts with their upper jaws protruding pointed (fish never have lips, only - as here - jaw edges thickened in front of the teeth) - even if the mouth hardly needs to be open. The mouth, otherwise terminal, becomes subordinate. This "(insulted) lip apron" is particularly noticeable due to the light color of the skin fold, which enables it to be pushed forward. How it happens functionally and anatomically, however, does not seem to have been investigated yet. (See also Zoarces americanus !) It provides an advantage when snapping small animals from the sediment. The front part of the jaw margins is occupied by a row of strong, not quite pointed teeth, followed by smaller, pointed teeth on the side. The gill openings reach far forward. The eel mother has only one nostril on each side. The hemispherical protruding eyes are relatively small, significantly smaller than the eye sockets.

Another specialty of the eel mother is its green bones after cooking. This has led to disgust because of the suspected toxicity, so that the fish was at least considered unsavory and useless by locals. If it was previously thought that the inner coloration of the “green bone” was based on vivianite , non-toxic iron (II) phosphate, we now know that the coloration is due to biliverdin .

There are also such “green bones”. B. among garfish .

ecology

The fish lives quite hidden (e.g. under mussel shells) on rocky, stony or seaweed and seaweed coasts from the tidal zone (flood pool) to a depth of 20 (maximum 40) m. Whether it digs itself into sand or gravel, as is sometimes claimed, is still doubtful. It survives falling dry for several hours by breathing air through its gills; it can use water that is relatively low in oxygen and, in the event of oxygen depletion (through eutrophication and warming), still flee when other biotope inhabitants are already suffocating. To protect against cold water ingress, it has anti-freeze proteins in the blood plasma (which are even of interest to the food industry because they do not suppress the growth of ice crystals, but they do inhibit it).

The pollution of the North and Baltic Seas leads to numerous developmental disorders (e.g. increase in the number of males); In the garbage on the ocean floor, eel nuts also find very attractive hiding spots, e.g. B. in cans and bottles. Therefore the fish hardly causes any problems in marine aquariums and is also often used in environmental monitoring (e.g. in Holland).

The food consists of all tangible epi benthos (including hard-shelled ones such as Mytilus ; often ingested with a lot of plant material) and detectable sediment inhabitants (e.g. also Chironomidae larvae). The eel mothers again represent important links in the trophic network for larger fish ( cod !), Seabirds ( shags , black guillemots ) and seals as well as otters and bottlenose dolphins because of their frequency . Now that the "green bones" are non-toxic she likes to fish; the fishing industry can turn them into pellets and the like. process. In contrast to Callionymus lyra , for example , Zoarces survives sorting and releasing into the sea (as "undesirable bycatch ") mostly quite well, with a mortality of around 10%.

Reproduction

The eelpout (also known in some places "Aalmöwe") (from the European long familiar bony fish the only "live-bearing" Sebastes viviparus was only much later known) .- In the genus Zoarces is Z. viviparus unique in this way (the other species guard their spawn, even in pairs). With the Teleostei , “development in the womb” is something very rare (especially in the sea - although the reason for this is not immediately obvious).

The eel mothers are usually sexually mature in the second year with a length of about 15-18 cm. The mating season usually begins around mid-August and continues in September. The (often smaller) male wraps around a female, presses his genital papilla onto "hers" and gives off his milk. In the (unpaired!) Ovary , the ripe eggs hang stalked in its lumen, which is "wrinkled". It takes about 2 to 3 weeks for them to hatch. The larvae now stick to the ovarian folds, consume their yolk sac (in about four weeks) and continue to feed on a ball-like structure that is created in sheaths (follicles) and through which the mother creates the embryos that "suck" on them. , supplied with a protein and oxygenated liquid; breathing happens z. T. with the gills. The transparent juvenile fish are released in November at the earliest, but mostly not until spring - one after the other (sometimes in two or three tranches); Their size is then, also depending on the size of the mother fish and the duration of the "pregnancy", 2.5 to 5 cm. They are very much like their parents, but behave sluggishly - perhaps to escape cannibalism (pedophagy). Brehm even writes that conspecifics huddle up to a woman in labor in order to support her - and then immediately eat the offspring. In more recent literature, however, such information can no longer be found - rather, at the time of "pregnancy" there is probably an inhibition to eat. The number of offspring per female and season is 10 to over 100, with the largest over 400.

distribution

Zoarces viviparus occurs on the coasts of the following topographical terms: English Channel, North Sea, Great Britain and Ireland, Orkney and Shetland Islands , Faroe Islands , Northern Norway, Kola Peninsula , White Sea , Baltic Sea (except for the most distant parts of the Bothnian and Finnish bosom) - i.e. also in Brackish water (like estuaries, which the fish occasionally penetrate deeper). He did not reach Iceland. As a result of global warming, it is already withdrawing significantly northwards from the canal and the Wadden Sea .

relationship

As long as one had no idea where the glass eels came from (because sexually mature eels were never found), this "descent" from the "eel mother" might have a certain plausibility, if only because of the fin fringe - eel-like fish emerged in evolution in very many taxa, also with Acanthopterygii . After all, the British pointed out a strange difference with eel-pout (maybe), because this name could also mean “eel thick head” - in contrast to the pointed head of real eels.

Later, the Zoarcidae were eagerly pushed back and forth - a condition that still persists. At first they were considered to be "slime fish" ( Blennioidei ) or "gobies". Then Wilhelm Lubosch (1929) discovered a portion in her chewing muscles that was only known from cod at the time , and now, because of a few other characteristics, they have again been classed as cod-like. Lubosch himself rejected Darwin's entire theory of descent because of such "echoes of several unrelated orders" and wanted to replace it with his "theory of ascendency". After the war, similarities to the sea ​​wolves were found again (which, however, were now moved away from the Blenniids), e.g. B. by the simple Narinen etc. Today the eel mother relatives are placed in the subordination Cottoidei of the perch- like.

Web links

Commons : Eel Mother ( Zoarces viviparus )  - Collection of images, videos and audio files

Wiktionary: Aalmutter  - explanations of meanings, word origins, synonyms, translations

• Eel mother on Fishbase.org (English)

Individual evidence

1. ↑ ζωάρκης “protecting and mediating life” - thus similar to (Latin) viviparus
2. ↑ These numbers are determined partly genetically and partly due to the environment by the temperature, such as the vortex number (see below) - which was already discussed by Johannes Schmidt (1918) and Carl Hubbs (1922).
3. ↑ Viviparous eelpout - Zoarces viviparus. In: The Marine Species Identification Portal. Retrieved April 26, 2018 . 
4. ↑ Entry on pout in Wiktionary .
5. ↑ s. about image: Andreas Czerniak: Eel mother (Zoarces viviparus (Linnaeus, 1758)). (No longer available online.) In: tauchmonitor.de. Archived from the original on April 26, 2018 ; accessed on April 26, 2018 . 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.  
6. ↑ At least it is noticeable that the distal ends of the maxillary and premaxillary are not closely connected here as usual, cf. William K. Gregory: Fish skulls; a study of the evolution of natural mechanisms . Laurel, FL 1959, p. 374 ff . ( Text archive - Internet Archive ).
7. ↑ Frank Jüttner, Maike Stiesch, Waldemar Ternes: Biliverdin: the blue-green pigment in the bones of the garfish (Belone belone) and eelpout (Zoarces viviparus). In: European Food Research and Technology, magazine for food research and research. Volume 236, No. 6, 2013, pp. 943-953, doi: 10.1007 / s00217-013-1932-y .
8. ↑ cf. also HO Pörtner, R. Knust: Climate change affects marine fishes through the oxygen limitation of thermal tolerance. In: Science . Volume 315, 2007, pp. 95-97, doi: 10.1126 / science.1135471 .
9. ↑ Gisela Lannig, Ute Jacob, Thomas Brey, Rainer Knust, Hans-O. Pörtner: Are communities in polar seas losers from climate change? ( archive.org [PDF]).
10. ↑ TF Sørensen, CH Cheng, H. Ramløv: Isolation and some characterization of antifreeze protein from the european eelpout Zoarces viviparus . In: Cryoletters . tape 27 , no. 6 , 2006, p. 387-399 ( ingentaconnect.com ).
11. ↑ See also patent US6312733 : Ice crystal growth inhibiting agents from Zoarces viviparus. Published on August 14, 1997 , inventor: Alfred Jann, Rolv Lundheim. ‌
12. ^ K. Broeg, KK Lehtonen: Indices for the assessment of environmental pollution of the Baltic Sea coasts: Integrated assessment of a multi-biomarker approach . In: Marine Pollution Bulletin . tape 53 , no. 8-9 , 2006, pp. 508-522 , doi : 10.1016 / j.marpolbul.2006.02.004 .
13. ^ R. Berghahn, M. Waltemath, AD Rijnsdorp: Mortality of fish from the by-catch of shrimp vessels in the North Sea . In: Journal of Applied Ichthyology . tape 8 , no. 1-4 , 1992, pp. 293-306 , doi : 10.1111 / j.1439-0426.1992.tb00696.x .
14. ↑ maybe corruption of ~ muðer to ~ musare "Möwe"; Grimm Wb.
15. ^ KJ Götting: Reproduction and oocyte development in the eel mother (Zoarces viviparus) (Pisces, Osteichthyes) . In: Helgoland Marine Research . tape 28 , 1976, p. 71-89 , doi : 10.1007 / BF01610798 ( biomedcentral.com [PDF]).
16. ↑ Peter Vilhelm Skov, Thomas Flarup Sorensen, Hans Ramlov, John Fleng Steffensen: Vascular Arrangement and Ultrastructure of the European Eelpout Zoarces viviparus Ovary: Implications for Maternal Embryonic Exchange . In: The Anatomical Record: Advances in Integrative Anatomy and Evolutionary Biology . tape 290 , no. 12 , 2007, p. 1500-1507 , doi : 10.1002 / ar.20605 .
17. ↑ Peter Vilhelm Skov, John Fleng Steffensen, Thomas Flarup Sørensen, Klaus Qvortrup: Embryonic suckling and maternal specializations in the live-bearing teleost Zoarces viviparus . In: Journal of Experimental Marine Biology and Ecology . tape 395 , no. 1-2 , 2010, pp. 120–127 , doi : 10.1016 / j.jembe.2010.08.024 .
18. ↑ Tierl., 3rd ed., Vol. 8, p. 152
19. ^ PL van Dijk, C. Tesch, I. Hardewig, HO Portner: Physiological disturbances at critically high temperatures: a comparison between stenothermal antarctic and eurythermal temperate eelpouts (Zoarcidae) . In: Journal of Experimental Biology . tape 202 , no. 24 , 1999, pp. 3611-3621 , PMID 10574738 .
20. ↑ TC Winkler: De kwabaal-warring . In: album of nature . tape 9 , no. 1 , 1860, p. 193–208 (Dutch, natuurtijdschriften.nl - free full text).
21. ↑ "A 3 β", now called A 1 β
22. ^ Wilhelm Lubosch (1875-1938), Professor of Comparative Anatomy in Würzburg; on "polyphyly" s. Especially archive link ( Memento of the original from May 4, 2016 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. .