Pen shells

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Pen shells
Different pen shells, from left to right: Pinna muricata, Atrina fragilis, Atrina vexillum and Pinna bicolor

Different pen shells, from left to right: Pinna muricata , Atrina fragilis , Atrina vexillum and Pinna bicolor

Systematics
Class : Mussels (Bivalvia)
Subclass : Pteriomorphia
Order : Ostreida
Superfamily : Pinnoidea
Family : Pen shells
Scientific name
Pinnidae
Leach , 1819

The pen shells (Pinnidae) are a shell - Family from the order of Ostreida . Currently (2013) 55 (possibly 57) recent species are included in the family. In addition to this number, there are at least twice as many fossil species. The noble pen shell ( Pinna nobilis ) is the largest European shell with a length of up to 1.2 meters and is also one of the largest shell species worldwide. The Pinnidae family is the only family in the superfamily Pinnoidea .

features

The large to very large cases are fan-shaped, triangular or paddle-shaped and can be over a meter long (largest specimen found: 120 centimeters). They are mostly equally hinged, with a few species the housing is slightly twisted and unevenly hinged. The housing is stuck with the front end (below) in the sediment, the rear end (above) protrudes from the sediment; the housing usually gapes here. However, it is flexible to a certain extent during life and can still be completely closed by pulling the sphincter muscles. They are mostly compressed laterally, i. H. the housing is flat, diamond-shaped or lenticular. The small inconspicuous vertebrae sit at the front (lower) end. At the ventral margin near the front end (below, in the sediment) there is another gaping gap; here the byssus comes out. The lock has no teeth. The ligament is very long, extends up to two thirds of the length of the dorsal margin, and lies in a groove (sub-internal).

The shell is comparatively thin and fragile and consists of the mineral shell and the thick, organic periostracum . The mineral shell is made up of an outer, calcitic prism layer and an inner, aragonitic mother-of-pearl layer . The latter is limited to the front third or to the front two thirds of the inside of the flap. The surface is provided with ribs, or sharp scales arranged in rows or scales and spines open to the rear, or also approximately smooth with more or less distinct growth stripes.

The anterior sphincter sits near the anterior end (below) and is relatively small, while the posterior sphincter is very large and usually sits more or less in the middle.

Geographical distribution, way of life and habitat

The recent representatives of the pen mussels live in temperate, subtropical and tropical seas. They stick their front end first in soft soils between scree, water plants or stony corals ; they are sessile animals . They anchor themselves with byssus threads in the sediment or a solid particle (stone, casing) in the sediment. The rear (upper) end usually protrudes one or two thirds out of the sediment (most species of the genus Pinna ), or the rear (upper) end is almost flush with the sediment surface (most species of the genus Atrina ). The pen mussels feed on plankton, which they filter from the water. Most species range from the shallow subtidal to a depth of about 100 m. Some types such as B. Atrina fragilis live in much greater water depths (approx. 150 to 600 meters).

Reproduction and life cycle

The pen shells are protandric hermaphrodites , but usually of separate sexes. True hermaphrodites, d. H. Specimens in which male and female genital organs are present at the same time are rare. The animals can also change sex during their lifetime. Several times a year male and female animals release their sex products into the open water, where fertilization occurs. For some species, however, it is also discussed whether the eggs are not retained in the shell space and fertilization occurs there. Only when the larvae are able to swim are they released into the open water. Female animals produce up to 725,000 eggs. The trochophora larva develops from the fertilized egg within one to two days , which quickly develops into the plankton-eating Veliger larva. After a few days, this forms a first, initially organic housing, the Prodissoconch. After one to several week (s), the larva changes over to bottom life and, through a metamorphosis, forms the juvenile mussel, which can already attach to the subsoil and "grow into" the seabed. The animals grow very quickly in the first three to four years. In the case of the noble pen shell, increases of ten centimeters and more were found per year. With the onset of sexual maturity, growth slows down.

Most species do not live to be more than ten years old: the Mediterranean pen shell ( Pinna nobilis ) is the longest-lived and largest pen shell species. It can be up to 25 years old and over a meter long.

Taxonomy

This taxon of the family group was established by William Elford Leach in 1819 in the correct spelling Pinnidae according to today's nomenclature rules. The superfamily Pinnoidea is monotypical, i. H. contains only the family Pinnidae. The Pinnoidea / Pinnidae are currently (2016) placed in the order Ostreida .

The recent pen mussels are divided into three genera by MolluscaBase . In 2013, Peter Schultz and Markus Huber compiled 55 species (+ two still uncertain species). The exact number of fossil species is not known, as a complete list is not yet available.

Schultz & Huber (2013) subdivide the genus Pinna into the sub-genera Pinna (Pinna) , Pinna (Abyssopinna) Schultz & Huber, 2013, Pinna (Cyrtopinna) Mörch, 1853, Pinna (Exitopinna) Iredale, 1939, Pinna (Quantulopinna) Iredale, 1939, Pinna (Subitopinna) Iredale, 1939 and Pinna (Streptopinna) Martens, 1880; in addition there is the fossil subgenus Pinna (Plesiopinna) Amano, 1956 and possibly Pinna (Sulcatopinna) Hyatt, 1892. The genus Atrina is divided into the three subgenus Atrina (Atrina) , Atrina (Australopinna) Schultz & Huber, 2013 and Atrina (Servatrina) Iredale, 1939 divided.

Phylogeny

In 2014 a first study on the phylogeny of pen shells based on molecular genetic studies was published. According to this, the genus Atrina is monophyletic, while Streptopinna was located within the genus Pinna . The authors therefore devalued Streptopinna as a subgenus of Pinna .

use

In the past, the noble pen shell, native to the Mediterranean, was caught and eaten with special fishing irons. Today it is protected and fishing is prohibited. The fine, silk-like byssus threads (shell silk) were used to make high-quality clothing or even pictures. The manufacture and processing of shell silk was given up at the end of the 19th century. In Japan, however , the species Atrina pectinata and Atrina kinoshitai are still often offered as seafood at fish markets.

Species protection

Pen mussels are quite common in tropical seas, but the noble pen mussel ( Pinna nobilis ) that lives in the Mediterranean has become rare due to overfishing and water pollution. That is why it is protected throughout the European Union and, according to the Federal Nature Conservation Act, may no longer be imported into Germany.

supporting documents

literature

  • Michael Amler, Rudolf Fischer, Nicole Rogalla: mussels . Haeckel library, Volume 5. Enke Verlag, Stuttgart 2000, ISBN 3-13-118391-8 .
  • S. Peter Dance, Rudo von Cosel (arrangement of the German edition): The great book of sea shells. 304 p., Verlag Eugen Ulmer, Stuttgart, 1977 ISBN 3-8001-7000-0 (p. 229)
  • Rudolf Kilias: Lexicon marine mussels and snails. 2nd edition, Verlag Eugen Ulmer, Stuttgart 1997 ISBN 3-8001-7332-8 (p. 252)
  • Gert Lindner: Mussels and snails of the world's oceans . 5th, revised. and exp. Ed., 319 p., New edition, Munich a. a., BLV, 1999 ISBN 3-405-15438-3 .
  • Raymond Cecil Moore (Ed.): Treatise on invertebrate paleontology. Mollusca, 6, Bivalvia 1. XXXVIII, 489 pp., New York, 1969 (pp. N283).
  • Fritz Nordsieck : The European sea shells (Bivalvia). From the Arctic Ocean to Cape Verde, the Mediterranean Sea and the Black Sea. 256 p., Gustav Fischer Verlag, Stuttgart 1969 (p. 41)
  • Guido Poppe and Yoshihiro Goto: European Seashells Volume 2 (Scaphopoda, Bivalvia, Cephalopoda) . 221 p., Verlag Christa Hemmen, Wiesbaden 1993 (2000 unc. Reprint), ISBN 3-925919-10-4 (p. 55)

On-line

Individual evidence

  1. ↑ a b Peter Schultz, Markus Huber: Revision of the worldwide Recent Pinnidae and some remarks on fossil European Pinnidae. Acta Conchyliorum, 13: 164 S., Hackenheim, ConchBooks, 2013
  2. ↑ D. Zavodnik, M. Hrs-Brenko, M. Legac: Synopsis on the fan shell. Pinna nobilis L. in the eastern Adriatic Sea. In: CF Boudouresque, M. Avon, V. Gravez, (Eds.): Les Espèces Marines à Protéger en Méditerraneé , pp. 169–178, GIS Posidonie publications, Marseille 1991.
  3. ^ Nico AJM Sommerdijk, Maggie Cusack: Biomineralization: Crystals competing for space. Nature Materials, 13: 1078-1079, 2014 doi: 10.1038 / nmat4147
  4. ^ William Elford Leach: Descriptions des nouvelles espèces d'Animaux découvertes par le vaisseau Isabelle dans un voyage au pôle boréal. Journal de Physique, de Chimie, d'Histoire Naturelle et des Arts, 88: 462–467, Paris 1819 Online at www.biodiversitylibrary.org (p. 466)
  5. ↑ MolluscaBase: Pinnidae Leach, 1819
  6. ↑ Gérard Paul Deshayes: Trichite, Trichites. Dictionnaire classique d'Histoire naturelle. Tome TZ., P. 353/4, Paris, 1830.
  7. ↑ Sarah Lemer, Barbara Buge, Amanda Bemis, Gonzalo Giribet: First molecular phylogeny of the circumtropical bivalve family Pinnidae (Mollusca, Bivalvia): Evidence for high levels of cryptic species diversity. Molecular Phylogenetics and Evolution, 75: 11-23, 2014 doi: 10.1016 / j.ympev.2014.02.008

Web links

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