Mud sepia

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Mud sepia
Sepia elegans.jpg

Mud Sepia ( Sepia elegans )

Systematics
Trunk : Molluscs (mollusca)
Class : Cephalopods (cephalopoda)
Order : Sepioloida
Family : Sepiidae
Genre : sepia
Type : Mud sepia
Scientific name
Sepia elegans
Blainville , 1827

The mud sepia or small sepia ( Sepia elegans ) is a cephalopod from the family Sepiidae that occurs in the Mediterranean and Eastern Atlantic . This small species is the smallest member of the Sepiidae family in the Mediterranean.

Systematics

Based on genetic comparisons between the mud sepia , the thorn sepia and the common squid , it was found that the first two species are more closely related than the latter. Therefore, the introduction of a new subgenus was proposed, after which Sepia elegans should now be called Rhombosepion elegans .

Anatomy and appearance

The mud sepia reaches a coat length of 72 mm (males) or 89 mm (females). The coat is more than twice as long as it is wide. They reach a weight of 50–60 g. With the same coat length, the females are heavier than the males. This makes the mud sepia the smallest representative of the Sepiidae in the Mediterranean . The mantle is laterally provided with a fin hem, the flaps of which, however, are not connected to one another at the rear end of the mantle. At the front end of the coat it tapers triangularly and protrudes over the head of the animal. Dorsally within the mantle lies the so-called Schulp , the calcareous inner shell of the cuttlefish . This is elongated straight and tapers towards the front and rear ends. Viewed from the side, it is convex in shape. The ventral side is turned in and the dorsal side is convex. At the rear end the outer limbs of the Schulps form two curved wings which lead ventrally. A small keel is located dorsally at the rear end.

In addition to the size, male and female animals differ on the basis of other anatomical features. The mud sepia has ten limbs, organized in a circle around the mouth. Two of these are transformed into tentacles. At the distal end of the tentacles are the oval clubs. Only the inside of these clubs is fitted with suction cups on the catch tentacles. These are used to catch prey and are larger in females compared to body length than in males. Compared to the arms, the tentacles' suction cups are different in size. At the proximal end there are three to four greatly enlarged suction cups. Dorsally on the flattened surface that supports the suction cup, there are slightly enlarged suction cups, which, however, are smaller than the central suction cups on the non- hectocotylated arms of the male.

Counting the arm pairs begins with the two dorsal arms. In the males, the suction cups of the first three pairs of arms are arranged in rows of four, except for the ten rows at the tip of the arm. There are two suction cups per row. In the fourth pair of arms, only the few rows (two to four) at the top have suction cups in rows of two, the remaining rows each have four suction cups. The hectocotylus (the male reproductive organ) is found at the tip of the third left arm. On the other arms, the size of the suction cups decreases as the distance from the head increases. On the hectocotyl-bearing arm, the nine to eleven middle rows of suction cups are reduced, the suction cups near the head and at the end of the arm are normally shaped.

The position of the suckers in the females differs from that of the males. Arms one to three have five rows close to the body, each with two suction cups, while the fourth pair of arms has only two to four rows. The rows further away from the body each have four suction cups.

Ventrally, on the left and right, there are six longitudinal grooves, the two in front being considerably shorter than the others. Near the middle of the body, the females have an unpaired sperm library on the underside of the abdomen.

The mantle is pale but covered dorsally with purple-black chromatophores. The density of the chromatophores on the head is lower. The grooves described above are white.

There is a risk of confusion with the Dornsepie ( Sepia orbignayana ). Important distinguishing features are the lack of a thorn on the Schulp of S. elegans and the number of suction cups on the tentacles (over 100 in S. orbingnayana ). The species differs from small individuals of Sepia officinalis by its reddish brown color.   

Distribution area and habitat

The mud sepia lives sublittoral to a depth of 500 meters. The greatest population density is found at about 150 meters depth. There they inhabit muddy ground. The young are benthic from the moment they hatch . Although it is a marine species, the mud sepia is tolerant of changes in the salinity of the water. The species was found in the brackish water of the Marmara Sea and in the estuary of river mouths. In some areas, the mud sepia migrates depending on the seasons. In spring and summer, individuals rise from deeper waters to depths of 40–70 m.

The species occurs in the entire Mediterranean and in the Eastern Atlantic from 50 ° N. The species is found around the British Isles , west of Scotland, Ireland and the English Channel .

The schulp of the mud sepia is sometimes found on beaches on the North Sea coast , but no live animals have been found so far. It is believed that the current made these remains into the North Sea. To the south, the distribution area on the west coast of Africa extends up to 15 ° S.

nutrition

As a cephalopod, the mud sepia feeds carnivorously . Their rapid growth requires a high rate of metabolism , which is why they have a high energy requirement. Main food source are different species of crustaceans and the bony fish , more rarely also polychaete captured. In contrast to other cuttlefish (e.g. Sepia officinalis ), no indications have been found that S. elegans changes its diet depending on its body size.

The elongated tentacles play an important role in preying on food. The prey is likely to be captured by means of a tentacle shot, as has been observed with the common squid. Other hunting methods that are widespread among the cuttlefish (e.g. jumping for prey) have not yet been observed in S. elegans .

The club at the distal end of the tentacles is used to prey on food. Since this is longer in the females of the species than in the males, it is possible for the females to catch more and larger prey. This could explain the faster growth of the females.

Reproduction and life cycle

When reaching sexual maturity , the male's coat length is on average 41 mm, that of the females 42 mm. However, the smallest sexually mature specimens observed were 20 mm (males) and 32 mm (females) long. Accordingly, males reach sexual maturity earlier than females.

In the ovaries of females, eggs can be found in three different stages of maturity. There are between 2 and 25 mature eggs in the fallopian tube. The ovulation is described as asynchronous, wherein mature eggs accumulate in the fallopian tube. The males store an average of 370 spermatophores in the so-called Needham 's sac ( “needham's sac” ). These are between 3.9 and 5.5 mm long, their length increases with the height of the corresponding male.

The brownish colored, smooth, and gelatinous eggs measure between 4.2 and 4.6 mm in diameter. They are attached to solid substrate in areas with muddy ground by the females. The eggs are covered with mucus from the nidamental gland as they are deposited. Egg clumps with 12-25 eggs are formed. Popular places for these egg clumps are sea ​​fans and clam shells. Freshly hatched cuttlefish are on average 5.5 mm long (mantle length: 3.3 mm) and weigh 11.5 mg. A planktonic stage as a paralarve does not take place.

Juvenile and sexually mature individuals can be found throughout the year. This leads to the conclusion that there are no fixed spawning times for S. elegans . Rather, S. elegans spawn continuously throughout the year. However, the water temperature during spawning is between 13 ° and 18 ° C. The young animals reach sexual maturity after about a year. Their mantle length increases by around 2.8 mm (males) or 3.0 mm per month. However, the growth and size of S. elegans are dependent on their environment. For example, adults are larger in the western Mediterranean than in the eastern. This could be due to the lower food supply and the higher temperatures in the eastern Mediterranean. Sepia elegans is 12-18 months old.

Fisheries and endangerment

The mud sepia is usually not fished specifically, but is caught as bycatch in the trawl fishery. In the Mediterranean area, mud sepia is sold along with other small species of sepia. In Turkey, the squid is thrown back into the water with other bycatches, and the survival rate is likely to be low.

In some areas, the mud sepia suffers from overfishing , such as the Strait of Sicily , where it is intensely fished. There is no information on total population size.

The acidification of the seas leads to a densification of the Schulps in Sepia. It is believed that this negatively affects the control of lift. By feeding on benthic prey, the mud sepia is more heavily contaminated with cadmium than other cephalopods. The species is believed to have an efficient detoxification mechanism.

Symbionts and parasites

In the accessory nidamental glands of the females, there are symbiotic bacteria such as various strains of Roseobacter . The role of these bacteria in the mud sepia is not known. Larval stages of the copepod Pennella varians can be found on the gills . Also aggregata sp . from the group of the Apicomplexa was found in S. elegans .

Predators

So far only a few predators of the mud sepia have been detected. Remains of the species have been found in the stomachs of common golden mackerel ( Coryphaena hippurus ), bottlenose dolphins ( Tursiops truncatus ) and hake ( Merluccius merluccius ). Other predators of the mud sepia are other cephalopods such as the common squid ( Loligo vulgaris ) and the thorn sepia as well as representatives of the cartilaginous fish such as the small spotted dogfish ( Scyliorhinus canicula ), the striped eagle ray ( Pteromylaeus bovinus ), the marble electric ray ( Torpedo marmorata ) Crayfish ( Raja clavata ). Bone fish such as Johns fish ( Zeus faber ) and the great amber mackerel ( Seriola dumerili ) are also known to prey on mud sepia. Eating sludge sepia is believed to be a possible pathway for the heavy metal cadmium to pass through the food chain.

Individual evidence

  1. ^ A. Sanjuan, M. Pérez-Losada & A. Guerra: Genetic differentiation in three Sepia species (Mollusca: Cephalopoda) from Galician waters (north-west Iberian Peninsula). In: Marine Biology , Volume 126, Number 2, 1996, pp. 253-259, doi : 10.1007 / BF00347450 .
  2. ↑ a b c Patrizia Jereb, Uwe Piatkowski, Louise Allcock, Paola Belcari, Manuel Garcia Tasende: Biology and ecology of cephalopod species commercially exploited, Species accounts . In: Cephalopod biology and fisheries in Europe . ICES, Copenhagen, Denmark 2010, ISBN 978-87-7482-078-9 , pp. 9–29 ( uni-kiel.de [accessed April 4, 2019]).
  3. ↑ a b c d e f g h i j k l m A. Reid, P. Jereb & CFE Roper: Cuttlefishes. In: P. Jereb & CFE Roper (Eds.): Cephalopods of the World: An Annotated and Illustrated Catalog of Cephalopod Species Known to Date. Volume 1: Chambered nautiluses and sepioids (Nautilidae, Sepiidae, Sepiolidae, Sepiadariidae, Idiosepiidae and Spirulidae) , Food and Agriculture Organization of the United Nations, Rome, 2005, ISBN 92-5-105383-9 , pp. 79-80 ( digitized ).
  4. ↑ a b c d e Alp Salman: Reproductive biology of the elegant cuttlefish (Sepia elegans) in the Eastern Mediterranean. In: Turkish Journal of Fisheries and Aquatic Sciences . tape 15 , no. 2 , 2015, ISSN  1303-2712 , doi : 10.4194 / 1303-2712-v15_2_08 ( trjfas.org [PDF; accessed April 4, 2019]).
  5. ↑ a b c d Giambattista Bello: Tentacle club length and body condition in the cuttlefishes Sepia elegans Blainville, 1827 and Sepia orbignyana Férussac, 1826 (Cephalopoda: Sepiidae). In: Zoologischer Anzeiger - A Journal of Comparative Zoology , Volume 244, Numbers 3-4, 2006, ISSN 0044-5231, doi : 10.1016 / j.jcz.2005.10.001 pp. 187-192.
  6. ↑ a b c d e Jereb, Patrizia & Sobrino, Ignacio & Allcock, A & Seixas, Sonia & Lefkaditou: Sepia elegans . In: ICES (ed.): Cephalopod biology and fisheries in Europe: II. Species Accounts . 2015, ISBN 978-87-7482-155-7 , pp. 74-82 .
  7. ^ A. Guerra: Food of the cuttlefish Sepia officinalis and S. elegans in the Ria de Vigo (NW Spain) (Mollusca: Cephalopoda). In: Journal of Zoology , Volume 207, Number 4, 1985, ISSN 0952-8369, doi : 10.1111 / j.1469-7998.1985.tb04947.x , pp. 511-519, ( digitized version ).
  8. ↑ a b c d Guerra, Ángel Castro, Bernardino G .: Some aspects of the biology of Sepia elegans (Cephalopoda, Sepioidea) from the ria de Vigo, NW Spain . Université Pierre et Marie Curie, July 5, 2012 ( worldcat.org [accessed April 4, 2019]).
  9. ↑ Andrew J. Collins, Brenna A. LaBarre, Brian S. Wong Won, Monica V. Shah, Steven Heng, Momena H. Choudhury, Shahela A. Haydar, Jose Santiago & Spencer V. Nyholm: Diversity and Partitioning of Bacterial Populations within the Accessory Nidamental Gland of the Squid Euprymna scolopes. In: Applied and Environmental Microbiology , Volume 78, Number 12, 2012, ISSN 0099-2240, doi : 10.1128 / aem.07437-11 , pp. 4200-4208, ( digitized version )
  10. ↑ a b Sepia elegans: Barratt, I. & Allcock, L. March 13, 2009, accessed April 4, 2019 .
  11. ↑ a b Bustamante, Paco Caurant, Florence Fowler, Scott Miramand, Pierre: Cephalopods as a key of the transfer of cadmium to top marine predators . ( worldcat.org [accessed April 4, 2019]).
  12. ↑ Pichon, D., Grigioni, S., Favet, J., & Boucher-Rodoni, R: Symbiotic associations between Cephalopods and the Roseobacter bacteria strain . Ed .: Phuket mar. biol. Cent. Res. Bull. 2005.
  13. ↑ S. Pascual, C. Gestal, JM Estévez, H. Rodríguez, M. Soto, E. Abollo & C. Arias: Parasites in commercially-exploited cephalopods (Mollusca, Cephalopoda) in Spain: an updated perspective. In: Aquaculture , Volume 142, Number 1-2, 1996, ISSN = 0044-8486 doi : 10.1016 / 0044-8486 (96) 01254-9 , pp 1-10, ( digitized version ).