1. Leptocephalus larvae
杨婧漪

2. Description
In Chinese柳叶形幼体 flat and transparent larva of the eel, marine eels, and other members of the superorder Elopomorpha. 1.Anguilliformes: conger, moray eel, garden eel ,family Anguillidae 2.elopomorph fishes tarpon, bonefish, spiny eel, pelican eel and deep sea species like Cyema atrum and notacanthid species in 1856: a biological species in 1758:Linnaeus, the larva of Anguilla anguilla

3. Characteristics have laterally compressed, transparent bodies（a）
body organs are small，only have a simple tube for a gut
lack red blood cells until they begin to metamorphose into the juvenile glass eel stage
when they start to look like eels
1、2 、3results in them being very transparent when they are alive
have dorsal and anal fins confluent with caudal fins, but lack pelvic fins
fang-like teeth that are present until metamorphosis
(add1)long larval periods of about 3 months to more than 1 year
(add2)mucinous pouch.
They move with typical anguilliform swimming motions and can swim forwards and backwards.

4. Development Egg: large compared to those of many other fishes.
preleptocephalus stage： do not yet feed externally， nutrients from the yolk (poorly developed eyes and few or no teeth )
Leptocephalus：(after..) eyes and teeth are formed. long forward-facing pointy teeth, As the larvae grow larger, the teeth will be replaced by shorter teeth and will increase in number.
glass eel stage: laterally compressed bodies->more rounded. Head-> thickens, olfactory organ-> enlarges, teeth ->lost
maximum size: 5–10 cm (2–4 in) but can be as large as 30 cm (12 in) or more depending on the species ……
Anadromous& catadroumous
egg-stage > leptocephalus > glasseel > elvers > yelloweel > silvereel

5. Others visual system:1.rod-dominated visual system.
2. telescopic eyes Synaphobranchidae
means a tubular eye with a sphere-shaped lens on the top occurs.
Their food source was difficult to determine because zooplankton, which are the typical food of fish larvae, were never seen in their guts. cause they grow to much larger sizes
Unagi is a popular food in Japan and East Asia, but Leptocephali are rarely used as food, except in some parts of Japan

6. The above is what I learned from Wikipedia
The above is what I learned from Wikipedia. And then here is something else I learnt from term papers, which I think it is interesting.

7. Finding
Question（a）
Leptocephali appear to feed on zooplankton(tiny particles floating free in the ocean or marine snow) was difficult to determine because they were never seen in their guts So it is still open to debate whether or not leptocephali actively ingest live food organisms and the feeding mechanism of leptocephalus larvae is still unknown,as a result of this,someone make research to make sure this point
Trypsin: in the digestive tract of immature eels (particularly the exocrine pancreas) and in the digestive tract of leptocephali by immunostaining using trypsin antibodies . Trypsin enzyme activity was highest in larval segments.(Charli Kruse, 20 June 1996)
There were distinctive differences between the species of leptocephali, which declare that it is characteristic of cells of the exocrine pancreas. (Charli Kruse, 20 June 1996)

9. Results
So Their experiments showed, in addition to consuming energy-rich reserves (Walter, 1910) accumulated in the preleptocephalic stage, larvae have the biochemical pathways necessary to digest nutrients. Chemoreception was shown to be critical to elicit the feeding response. Feeding by S flex posture from a distance might be of some significance for the early larvae to catch movable food. (Xu Fang Liang,30 December 2002) This is related to previous problems, though it didn’t compietely solve the problem.

10. Reference
[1] [2] Charli Kruse, Beate Strehlow, Holger Schmidt, Peter K. Müller, Presence of trypsin in distinctive body segments of leptocephalus larvae of Anguilliformes Research article Aquaculture, Volume 142, Issues 3–4, 20 June 1996, Pages [3] Xufang Liang, Jun Xie, Qiuong Wang.,Benedikte H Pedersen. Feeding mechanism and nutritional strategy of Japanese eel larva [J]. Acta acta.,2002(06):

11. Fin
Thanks for watching