Leptocephalus
A leptocephalus (meaning "slim head"
Fishes with a leptocephalus larval stage include the most familiar eels such as the
The fishes of the other four traditional orders of elopomorph fishes that have this type of larvae are more diverse in their body forms and include the
Description
Leptocephali (singular leptocephalus) all have laterally compressed bodies
They also lack
Leptocephali differ from most
Leptocephali appear to feed on tiny particles floating freely in the ocean, which are often referred to as marine snow. Leptocephali larvae live primarily in the upper 100 metres (330 ft) of the ocean at night,[5] and often a little deeper during the day. Leptocephali are present worldwide in the oceans from southern temperate to tropical latitudes, where adult eels and their close relatives live. American eels, European eels, conger eels, and some oceanic species spawn and are found in the Sargasso Sea.[8]
Leptocephalus brevirostris was declared as a biological species in 1856, but was later found to be the larva of
Development
The eggs of eels in the order Anguilliformes are quite large compared to those of many other fishes. They are about 1–4 millimetres (1,000–4,000 μm; 39–157 thou) in diameter. Once the larvae are newly hatched, the yolk extends posteriorly. Some larvae hatch with features of the head more developed than others. The preleptocephalus stage is the period immediately after the larvae hatch. During this stage, the larvae do not yet feed externally. These larvae typically have poorly developed eyes and few or no teeth.[5]
The leptocephalus stage of the larvae begins after the nutrients from the yolk have been absorbed and the eyes and teeth are formed. At this point, the larvae usually have long forward-facing pointy teeth. As the larvae grow larger, the teeth will be replaced by shorter teeth and will increase in number. The maximum size larvae reach varies from about 5–10 centimetres (2–4 in) but can be as large as 30 centimetres (12 in) or more depending on the species. After the leptocephali have reached their maximum size, they enter their glass eel stage. Their laterally compressed bodies tend to become more rounded in this stage. The head also thickens, the olfactory organ enlarges, and their teeth are lost.[5]
Leptocephali differ from other fish larvae in their development. In other teleosts (those without leptocephali), the egg hatches and then the larvae get nutrients from a yolk sac. Following this, external feeding begins once the yolk sac has depleted. The larvae begin to increase in size and develop into a juvenile fish once external feeding begins. In those fish with a leptocephalus stage; however, after hatching and obtaining nutrients from the yolk, the larvae do not begin external feeding. This is peculiar because the larvae still continue to grow in size. From this information, it is concluded that one of the biggest and most basic differences in the developmental cycles of teleosts without leptocephali and teleosts with leptocephali is the food source that the larvae use.[10]
Leptocephali are poorly understood, partly because they are very fragile and eat particulate material instead of zooplankton, and their good swimming ability lets them avoid most standard-sized plankton nets used by marine biologists. A video recording of a naturally swimming leptocephalus filmed at night off the island of Hawaii shows an example of their swimming behavior.[11]
Visual system
Two facts are known regarding the visual system of the leptocephali. The first is that they have a rod-dominated visual system.[12] The second is that the Synaphobranchidae (a specific family of leptocephali) have telescopic eyes, meaning a tubular eye with a sphere-shaped lens on the top occurs.[5]
Aquaculture
Some progress has been made to grow the leptocephali of the
Leptocephali are rarely used as food, except in some parts of Japan. The leptocephali of the common Japanese conger,
See also
References
- ^ "Leptocephalus | Definition of leptocephalus by Merriam-Webster". www.merriam-webster.com. Merriam-Webster Online Dictionary. Retrieved 2015-11-27.
- ^ a b Inuoe, Jun, M. Miya, et al. “Mitogenomic evidence for the monophyly of elopomorph fishes (Teleostei) and the evolutionary origin of the leptocephalus larva.” Molecular Phylogenetics and Evolution 32 (2004): 274-286. Web. 2 Nov. 2012.
- ^ a b Meyer-Rochow, Victor Benno (1974). "Leptocephali and other transparent fish larvae from the South-Eastern Atlantic Ocean". Zoologischer Anzeiger. 192: 240–251.
- ^ Castle, Peter H.J. (1973). "A giant notacanthiform Leptocephalus from the Chatham Islands, New Zealand". Records of the Dominion Museum of New Zealand. 8: 121–124.
- ^ a b c d e f g Miller, Michael J. “Ecology of Anguilliform Leptocephali: Remarkable Transparent Fish Larvae of the Ocean Surface Layer.” Aqua-BioScience Monographs 2 (2009): 1-94. Web. 2 Nov. 2012.
- ^ Fahay, Michael (1983-07-01). "Guide to the Early Stages of Marine Fishes occurring in the Western North Atlantic Ocean, Cape Hatteras to the Southern Scotian Shelf." Journal of Northwest Atlantic Fishery Science 4 (1983): 46-61, 1 July 1983. Retrieved on 2012-11-02 from http://journal.nafo.int/Volumes/Articles/ID/14/Guide-to-the-Early-Stages-of-Marine-Fishes-occurring-in-the-Western-North-Atlantic-Ocean-Cape-Hatteras-to-the-Southern-Scotian-Shelf.
- ISSN 1432-1793.
- ISSN 0022-1112.
- ^ "WoRMS - World Register of Marine Species - Leptocephalus brevirostris Kaup, 1856". marinespecies.org. Retrieved 2015-11-27.
- ^ Pfeiler, Edward (1986). "Towards and Explanation of the Developmental Strategy in Leptocephalus Larvae of Marine Teleost Fishes." Environmental Biology of Fishes 15 (1986): 3-13. Retrieved on 2012-11-02 from Web.
- ^ "Ophichthid leptocephalus off Kona, Hawaii - Australian Museum". australianmuseum.net.au. Retrieved 2015-11-27.
- ^ Taylor, Scott Michael, Ellis Loew, and Michael Grace (2011). “A rod-dominated visual system in leptocephalus larvae of elopomorph fishes (Elopomorpha: Teleostei).” Environmental Biology of Fishes 92 (2011): 513-523. Retrieved on 2012-11-02 from Web.
- ISSN 0447-5763. Retrieved 2019-01-27.
- ^ Bird, Winifred. "In Japan, Captive Breeding May Help Save the Wild Eel". Yale Environment 360. Yale School of the Environment. Retrieved 28 April 2021.
- ^ Says, Gigibeyon (2009-01-15). "Japanese Seasonal Fish: Noresore/Conger Eel Whitebait". SHIZUOKA GOURMET. Archived from the original on 3 July 2018. Retrieved 2019-01-27.