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Pipefish

Pipefishes or pipe-fishes (Syngnathinae) are a subfamily of small fishes, which, together with the seahorses, form the family Syngnathidae.

Physical Description[edit]

Pipefish look like straight-bodied seahorses with tiny mouths. The name is derived from the peculiar form of their snout, which is like a long tube, ending in a narrow and small mouth which opens upwards and is toothless. The body and tail are long, thin, and snake-like. They have a highly modified skeleton formed into armored plating. This dermal skeleton has several longitudinal ridges, so that a vertical section through the body looks angular, not round or oval as in the majority of other fishes.[1]

A dorsal fin is always present, and is the principal (in some species, the only) organ of locomotion. The ventral fins are constantly absent, and the other fins may or may not be developed. The gill openings are extremely small and placed near the upper posterior angle of the gill cover.[1]

Many are very weak swimmers in open water, moving slowly by means of rapid movements of the dorsal fin. Some species of pipefish have tails that are prehensile, as in seahorses. The majority of pipefishes have some form of a caudal fin (unlike seahorses), which can be used for locomotion.[1] See fish anatomy for fin descriptions. There are species of pipefish with more developed caudal fins, such as the group collectively known as flagtail pipefish, which are quite strong swimmers.[citation needed]

Habitat and distribution[edit]

Most pipefish are marine dwellers; only a few are freshwater species. Pipefishes are abundant on coasts of the tropical and temperate zones. Most species of pipefish are usually 35–40 cm in length and generally inhabit sheltered areas in coral reefs, seagrass beds. There are approximately 200 species of pipefish.[citation needed]

Reproduction and parental care[edit]

Male pipefish (Syngnathus acus) with sub-caudal pouch.

Pipefishes, like their seahorse relatives, leave most of the parenting duties to the male. The male pipefish provides all of the postzygotic care for its offspring, supplying them with nutrients and oxygen through a placenta-like connection. It broods the offspring either on distinct region of its body or in a brood pouch. Brood pouches vary significantly among different species of pipefish, but all contain a small opening through which female eggs can be deposited. The location of the brood pouch can be along the entire underside of the pipefish or just at the base of the tail, as with seahorses.[2] Pipefish in the genus ‘’Syngnathus’’ have a brood pouch with a ventral seam that can completely cover all of their eggs when sealed. In males without these pouches, eggs adhere to a strip of soft skin on the ventral surface of their bodies that does not contain any exterior covering.[3]

Courtship between male and female pipefish involves lengthy and complicated shows of display. For example, in the ‘’Syngnathus typhle’’ species, copulation is always preceded by a ritualized dance by both sexes. The dance involves wriggling and shaking motions that are very conspicuous, especially in comparison to the specie’s otherwise extremely secretive lifestyle. Under the threat of the presence of a predator, pipefish are more reluctant to perform their dances. In addition, when risk of predation is high, they copulate less frequently, dance less per copulation, and females transfer more eggs per copulation. Although the S. thyphle males normally prefer to mate with larger females, they mate randomly when potentially threatened by predators.[4]

During pipefish copulation, which signifies the termination of the courtship dance, the female transfers her eggs through a small ovipositor into the male brood pouch or onto the special patch of skin on the male’s ventral body surface. While the eggs are being transferred, the mating pair rises through the water until copulation is complete. At this point, the male assumes an S-shaped posture and fertilizes the eggs, all the while descending back down the water column.[5] Males possessing brood pouches release their sperm released directly into them; the pouches are then vigorously shaken. The ventral seams are not opened until weeks later when the male pipefish give birth.[3]

There is a physical limit to the number of eggs and that a male pipefish can carry, and males are therefore considered to be the limiting sex. Females can often produce more eggs than males can accommodate inside their brood pouches, resulting in more eggs existing within the population than can be cared for. Other factors that may restrict female reproductive success include male pregnancy length as well as energy investment in progeny.[6] Because the pipefish embryos develop within the male, feeding off of its nutrients, male pipefish invest more energy than females in each zygote that reaches maturity. Additionally, they invest more energy per unit time than females throughout each breeding season.[7] As a result, according to various research studies, some males may consume their embryos rather than continuing to rear them under situations in which their bodies are exhausted of resources, in order to regain energy. Pregnant male pipefish can absorb nutrients from their broods, in a manner very similar to filial cannibalism that is found in many other families of fish. The smallest eggs in a brood of various egg sizes usual have lower survival rates than larger ones. The difference is due to the larger eggs being competitively superior and more likely to develop into mature adults. In other instances, some pipefishes may decide to consume the embryos of mates that seem less fit or desirable, as each male generally copulates with more than one female.[5]

Young are born free-swimming with relatively little or no yolk sac, and begin feeding immediately. From the time they hatch they are independent of their parents, who at that time may choose to view them as food. Some fry have short larval stages and live as plankton for a short while. Others are fully developed but miniature versions of their parents, assuming the same behaviors as their parents immediately.

Pair bonding varies wildly between different species of pipefish. While some are monogamous or seasonally monogamous, others are not.

Sub-caudal pouch of Syngnathus acus, with the young ready to leave the pouch. One side of the membrane of the pouch is pushed aside to admit of a view of its interior.

Many species exhibit polyandry, a breeding system in which one female mates with two or more males. This tends to occur with greater frequency in internal brooding species of pipefishes than with external brooding species. Polyandrous species are also more likely to have females with complex sexual signals such as ornaments.[8]

Genera[edit]

Notes[edit]

  1. ^ a b c Chisholm, 1911, p. 634.
  2. ^ Wilson AB, Ahnesjö I, Vincent AC, Meyer A (June 2003). "The dynamics of male brooding, mating patterns, and sex roles in pipefishes and seahorses (family Syngnathidae)". Evolution 57 (6): 1374–86. PMID 12894945. 
  3. ^ a b A. G. Jones, J. C. Avise (2001). "Mating Systems and Sexual Selection in Male-Pregnant Pipefishes and Seahorses: Insights from Microsatellite -Based Studies of Maternity". The Journal of Heredity. Retrieved 2013-09-15. 
  4. ^ Anders Berglund (July 1993). "Risky sex: male pipefishes mate at random in the presence of a predator". Animal Behavior. Retrieved 2013-09-15. 
  5. ^ a b Sagebakken (2012). Parental care and brood reduction in a pipefish. Goteborg. ISBN 978-91-628-8532-8. 
  6. ^ Anders Berglund, Gunilla Rosenqvist, Ingrid Svensson (1989). "Reproductive Success of Females Limited by Males in Two Pipefish Species". The American Naturalist. Retrieved 2013-09-15. 
  7. ^ Anders Berglund, Gunilla Rosenqvist, Ingrid Svensson (1986-03-26). "Reversed sex roles and parental energy investment in zygotes of two pipefish (Syngnathidae) species". Marine Ecology-Progress Series. Retrieved 2013-09-15. 
  8. ^ Rosenqvist G, Berglund A (2011). "Sexual signals and mating patterns in Syngnathidae.". J Fish Biol 78 (6): 1647–61. doi:10.1111/j.1095-8649.2011.02972.x. PMID 21651521. 
  9. ^ http://marinespecies.org/aphia.php?p=taxdetails&id=154405 accessed 19 July 2011

References[edit]

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