Biology Reference
In-Depth Information
Figure 3.
Various types of leptocephali. (a) tenpounder,
Elops hawaiensis
(33.5 mm in total
length, TL); (b) bonefi sh,
Albula vulpes
(61.5 mm in TL); (c) halosaur, Halosauridae sp. (280 mm
in TL); (d) giant mottled eel,
Anguilla marmorata
(42.0 mm in TL); (e) fl at-nosed xenocongrid
eel,
Chilorhinus platyrhynchus
(48.0 mm in TL); (f) congrid eel,
Ariosoma
sp. (101.0 mm in TL);
(g) bobtail snipe eels, Cyematidae sp. (21.0 mm in TL). Myomeres are partially drawn except
for (d). All illustrations were copied from 'An Atlas of the Early Stage Fishes in Japan' with
permission. Original fi gures were drawn by Dr. Mochioka (a, b, c, d and f), Dr. Tabeta (e),
and Dr. Kanegae (g).
transparent gelatinous matrix is accumulated under the skin. Leptocephali
lack most of the ossifi ed skeletal elements, including a vertebral column
and thus the body is supported by the gelatinous matrix. The head is small
in relation to the body size and the body height is relatively deep, although
this latter feature varies among species. The maximum body length of
the leptocephali of most species is much greater than the body length of
young juveniles because of shortening that occurs during metamorphosis,
although the extent of this reduction is also variable among species. At
the same time, the body shape changes from leaf-like to the juvenile style.
The shortening and transformation of the body are associated with the
breakdown of the gelatinous tissue, which occupies most of the relatively
massive trunk of leptocephali. The intestine is more or less straight and
opens at an unusually posterior position on the abdomen. Prominent
teeth are present on the upper and lower jaws and these are lost during
metamorphosis. The eyes and olfactory organs are well-developed. V- or
W-shaped myomeres are visible, and the number of myomeres is a major
characteristic used in species identifi cation.
