Red sea squirt
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Red Sea Squirt ( Halocynthia papillosa ) |
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| Halocynthia papillosa | ||||||||||||
| Linnæus , 1767 |
The Red sea squirt or Red Kännchenseescheide ( Halocynthia papillosa ) is in the Mediterranean occurring ascidian (sea squirt) and is among the tunicates (tunicates). H. papillosa was first described in 1767 by the Swedish naturalist Carl von Linné .
Systematics
The red sea squirt H. papillosa belongs to the Pyuridae family and thus to the Stolidobranchia group . The Stolidobranchia are counted among the ascidia and these in turn belong to the taxon of the tunicata (tunicates). The tunicates are the chordates expected, specifically to the Urochordaten. Thus H. papillosa belongs to the Deuterostomians (Neumünder).
With around 2000 known species, ascidia belong to the tunicata class with the most diverse forms.
Species identification
H. papillosa has an undivided hermaphrodite gland on each side, the dorsal salts that are present are separated and the two- to four-lobed siphons are clearly separated. These in turn are surrounded by brownish bristles. These features, together with the orange to coral-red papillary coat, make H. papillosa an easily recognizable species of ascidia.
Occurrence
Halocynthia papillosa occurs in the entire Mediterranean area and is thus the most common ascidia species found in benthos , which can be found on the stony and rocky subsoil of the littoral. It is also common on sandy subsoil in the sublittoral and also in Posidonia sea grass meadows. It can be found on the Spanish and French coasts, as well as in the Adriatic Sea . H. papillosa is endemic and lives as a solitary ascidia preferentially near the coast and in shallower zones. In the depths of 20 - 50 m it reaches the greatest abundance and individual size. This is due to the fact that at these depths there is a uniform ocean current and thus it is easier for filter feeders to eat , which is accompanied by better growth. The lowest known occurrence of H. papillosa to date is 58 m. It is particularly common on crevices or rocky overhangs. Since H. papillosa is a very stress-sensitive species, it is more likely to be found in areas that are less frequented by humans.
morphology
The body has a bag-like to bulbous structure, which is lined inside by a gill intestine. Individual individuals can reach a size of up to 15 cm. The food particles filtered out of the surrounding water are transported via slime bands into the gill intestine, which makes up most of the interior. More precisely, the ingestion of food takes place in that water enters the sea squirt through the ingestion opening and the water with the food particles is moved further inside by cilia . The food particles stick to the mucus-secreting endostyle , which is located ventrally on the gill intestine, and are transported to the gill intestine for digestion. The water exits the ascidia via the egestion opening. The water flow is unidirectional. Like all tunicates, H. papillosa has a blind-ended blood vessel system. In order to be able to supply the entire body with sufficient oxygen, the pumping direction of the heart is reversed at regular intervals.
The coat of H. papillosa , the tunica, which gives the tunicata its name, serves as mechanical protection, which is epidermal in origin. The special feature here is that the tunica of Ascidians addition to proteins and cellulose contains. Cellulose normally only occurs in plant cells, where it serves to stabilize the cell wall. Sea squirts are the only animals that have this plant substance. The tunica is the most striking thing about H. papillosa , because it is colored bright red due to the embedded α- and β- carotenoids , hence the German name “Rote Seescheide”. In addition to the carotenoids, there are also cynthiaxanthin and astaxanthin in the coat.
The musculature of H. papillosa is greatly reduced and only occurs in the swimming tail of the larva and in the inflow and outflow opening of the adult animal. The nervous system is rudimentary with only one ganglion , but this one ganglion is capable of complete regeneration. H. papillosa has ciliary sensory cells, statocysts and, in the larval form, pigment cup-o-cells as sense organs . An excretory organ is not necessary, since the waste products produced during digestion, such as ammonium ions, are released directly into the environment via the gill intestine.
growth
The main growth of H. papillosa takes place in summer, which is extremely unusual in comparison to other ascidia species, as their growth phase occurs in the winter months. In the winter months there is more food available, in summer the water is more oligotrophic and therefore contains fewer nutrients that are available to the organisms. In contrast to other species, H. papillosa has no estivation ; on the contrary, H. papillosa has the highest growth rate in summer .
Reproduction
Halocynthia papillosa is a hermaphroditic organism, so there are both female and male sex cells in an individual. In order to avoid self-fertilization, the ovaries ripen first and then the testis . An individual reproduces only once a year, ovarian growth occurs from March to September, and growth of the testis from July to September. The highest reproduction rate is therefore at the end of summer. The gametes are released directly into the surrounding sea water. If fertilization occurs, a pelagic larva develops, which swims around between 12 and 24 hours until it settles in a suitable place and undergoes a metamorphosis . During the metamorphosis from pelagic animal to sessile active filter feeder, the notochord, tail and sensory organs are broken down. The gill gut and peribranchial space, on the other hand, are expanded. The water temperature can be seen as the main regulating factor in reproduction.
nutrition
As a microphagous active suspension eater, H. papillosa feeds on microorganisms between 0.6 and 70 μm in size. These include heterotrophic bacteria, phytoplankton , ciliates and prokaryotes . H. papillosa is characterized by a very heterogeneous diet, which is sometimes due to the fact that it is not a selective filter feeder. Food is taken in by the fact that water is pumped through the filter structures and the food particles are separated from the water with the help of the slime bands. The filtration rate depends mainly on the water temperature, the feed concentration, the individual size and the oxygen content in the water. An optimal filtration takes place at 23 ° C. Ascidia are able to filter continuously for 24 hours.
Ecosystem service
H. papillosa is an important carbon sink (sink), as it contributes through the active filtration an important contribution to the regulation of phytoplankton and thus counteracting eutrophication of the water. Due to the frequency and widespread distribution of this species, it is a key organism, as the majority of phytoplankton regulation is carried out by H. papillosa .
Bio-indicator
The increasing diving tourism is a nuisance for the organisms living in the littoral, as divers can cause considerable damage by touching the organisms with their bodies or diving equipment. The soil substrate thrown up by divers is an equally big problem, especially for filtering organisms such as H. papillosa . The thrown up sediment can damage the mantle or get into the siphon of ascidia and thus impair food intake, which would result in poorer growth and a lower rate of reproduction. The settlement of the pelagic larva in a new area is also severely restricted by the turbulent sediment. As an extremely stress-sensitive species, H. papillosa is suitable as a bio-indicator , as the number of individuals in heavily frequented areas decreases significantly. Thus, the state of the corallogenic community can be read from the number and size of the individuals of H. papillosa . This means that an area that is too heavily frequented by divers can be protected in good time before the damage is irreversible. The attractiveness of the dive site decreases in the course of a too high frequency of use, as H. papillosa , due to the high frequency of use, grow more in hidden and protected places and are not immediately recognizable for the divers. In general, a high abundance of large H. papillosa indicates that the area is in good condition, as clean water, along with a stress-free environment, is also important for H. papillosa to thrive . An example of this is the coast of Spain: near the coast of Montgrí there are more and larger H. papillosa than near the island of Medas, about two kilometers away, as this is very popular with divers and is therefore visited more often.
attitude
The striking coloring of H. papillosa makes it a popular and perennial aquarium animal in zoological gardens. In addition to the Berlin zoo , the red sea squirt can also be admired in the Wilhelma zoological and botanical garden in Stuttgart .
literature
- ↑ a b c d e f g h i j Ibler, B. (2012). List of species and keeping of sea squirts (Ascidiacea) in Berlin. The Zoological Garden 81 (4): 175-184.
- ^ A b c d e M. Coppari, A. Gori, and S. Rossi: Size, spatial and bathymetrical distribution of the ascidian Halocynthia papillosa in Mediterranean coastal bottoms: benthic-pelagic coupling implications . In: Marine Biology . tape 161 , no. 9 , 2014, p. 2079-2095 .
- ^ G. Lecointre, H. Le Guyader: Biosystematics: all organisms at a glance; the new order in life . Springer, Heidelberg [et al.] 2006.
- ↑ a b c F. Bracher: Seescheiden (ascidia) - a new source of pharmacologically active substances . In: Pharmacy in Our Time: Science, Education and Training . tape 23 , p. 147-157 .
- ↑ a b c R. Riedl: Fauna and flora of the Mediterranean: a systematic marine guide for biologists and nature lovers . Ed .: Parey. 3. Edition. Hamburg [u. a.] 1983.
- ↑ a b c d e M. Ribes, R. Coma and JM Gili: Seasonal variation of in situ feeding rates by the temperate ascidian Halocynthia papillosa . In: Marine Ecology Progress . tape 175 , 1998, pp. 201-213 .
- ↑ a b c d e B. Luna-Perez, C. Valle, T. Vega Fernandez et al .: Halocynthia papillosa (Linnaeus, 1767) as an indicator of SCUBA diving impact . In: Ecological Indicators . tape 10 , no. 5 , 2010, p. 1017-1024 .
- ^ V. Neumann, T. Paulus and HA Baensch: Mediterranean Atlas: Fish and their habitats . Mergus, Melle 2005.
- ↑ a b A. Fiala-Médioni: Ethologie alimentaire d'invertébrés benthiques filtreurs (ascidies). II. Variations of the taux de filtration et de digestion en fonction de l'espèce . In: Marine Biology . tape 28 , no. 3 , p. 199-206 .
- ↑ M. Santic, B. Rada, A. Paladin et al .: The Influence of Some Abiotic Parameters on Growth Inclination in Ascidian Halocynthia papillosa (Linnaeus, 1767) from the Northern Adriatic Sea (Croatia) . In: Archives of Biological Sciences . tape 62 , no. 4 , p. 1007-1011 .
- ↑ K. Nishibori: Studies on the pigments of marine animals - VI. Carotenoids of some tunicates . 1958.
- ^ B. Lübbering, T. Nishikata and G. Goffinet: Initial stages of tuic morphogenesis in the ascidian Halocynthia: A fine structural study . In: Tissue and Cell . tape 24 , no. 1 , 1992, p. 121-130 .
- ↑ B. Luna-Perez, C. Valle-Perez and JL Sanchez-Lizaso: Halocynthia papillosa as SCUBA diving impact indicator: An in situ experiment . In: Journal of Experimental Marine Biology and Ecology . tape 398 , no. 1-2 , 2011, pp. 33-39 .
- ^ S. Naranjo, J. Carballo and J. Garcia-Gomez: Effects of environmental stress on ascidian populations in Algeciras Bay (southern Spain). Possible marine bioindicators. In: Marine Ecology Progress Series . tape 144 , 1996, pp. 119-131 .
- ↑ Animal population 2017, Stuttgart Zoological and Botanical Garden. (PDF) In: wilhelma.de. Retrieved January 27, 2019 .
Web links
- World Register of Marine Species, Monniot, C. (2009): Halocynthia papillosa (Linnaeus, 1767)