Development of lateral line organs in leptocephali of the freshwater eel Anguilla japonica (Teleostei, Anguilliformes)

Abstract

A study of the ontogeny of the lateral line system in leptocephali of the Japanese eel Anguilla japonica reveals the existence of three morphologically different types of lateral line organs. Type I is a novel sensory organ with hair cells bearing a single kinocilium, lacking stereocilia, distributed mainly on the head of larvae, and morphologically different from typical superficial neuromasts of the lateral line system. Its developmental sequence suggests that it may be a presumptive canal neuromast. Type II is an ordinary superficial neuromast, common in other teleost larvae, which includes presumptive canal neuromasts that first appear on the trunk and accessory superficial neuromasts that later appear on the head and trunk. Type III is a very unusual neuromast located just behind the orbit, close to the otic vesicle, with radially oriented hair cells, suggesting that these serve as multiple axes of sensitivity for mechanical stimuli. The behavior of larval eels suggests that the radially oriented neuromasts may act as the sole mechanosensory organ until the ordinary superficial neuromasts develop. The finding that larval eels possess a well-developed mechanosensory system suggests the possibility that they are also capable of perceiving weak environmental mechanical stimuli, like other teleost larvae.

Ecology of Anguilliform Leptocephali: Remarkable Transparent Fish Larvae of the Ocean Surface Layer

“…Some eel larvae appear to be born in a morphologically very undeveloped state with almost no development of the features of the head, as has been observed in species hatched in the laboratory, such as A. japonica (Fig. 5;Okamura et al 2002), Muraenesox cinereus , and Conger myriaster . Other species though, such as ophichthids may hatch at a more developed state with the eyes and some early teeth already formed (Leiby 1979a(Leiby , 1989.…”

“…Okamura et al (2002) used SEM to examine the development of mechanoreceptor cells in newly hatched larvae of A. japonica that were obtained from artificially matured and spawned eels. Those larvae had three types of these sensory cells distributed on various parts of their body at different developmental stages (Fig.…”

Feeding on protists and particulates by the leptocephali of the worm eels <i>Myrophis</i> spp. (Teleostei: Anguilliformes: Ophichthidae), and the potential energy contribution of large aloricate protozoa

“…The leptocephali examined here were from the same collections as other larval fishes examined from the northern Gulf of Mexico; consequently, the availability of ciliates as food for leptocephali was the same. Leptocephali are fully capable of sensing (Hulet, 1978;Okamura et al, 2002;Døving and Kasumyan, 2008) and capturing (Pfeiler, 1989) protozoa, including aloricate ciliates. Ciliates are likely to be easy prey for leptocephali in the ocean and they are eaten readily by other larval fishes (Figueiredo et al, 2007).…”

Responses of hatchlingXenopustadpoles to water currents: first function of lateral line receptors without cupulae

“…There have also been studies using scanning electron microscopy and other methods to define the development of lateral line neuromasts and their receptive hair cells in the axolotl (Northcutt et al, 1994), the flounder (Otsuka, 2003) and the eel (Okamura et al, 2002). However, there have been few studies on the development of lateral-line neuromast function (Blaxter, 1987).…”