Lateral line system and its innervation in Tetraodontiformes with outgroup comparisons: Descriptions and phylogenetic implications

Abstract

The lateral line system and its innervation in ten tetraodontiform families and five outgroup taxa were examined. Although some homology issues remained unresolved, tetraodontiforms were characterized by having two types (at least) of superficial neuromasts (defined by the presence or absence of supporting structures) and accessory lateral lines and neuromasts (except Molidae in which "accessory" elements were absent). The preopercular line in Tetraodontiformes was not homologous with that of typical teleosts, because the line was innervated by the opercular ramule that was newly derived from the mandibular ramus, the condition being identical to that in Lophiidae. Within Tetraodontiformes, the number of neuromasts varied between 70 and 277 in the main lines and between 0 and 52 in accessory elements. Variations were also recognized in the presence or absence of the supraorbital commissure, mandibular line, otic line, postotic line, ventral trunk line, and some lateral line nerve rami, most notably the dorsal branch of the opercular ramule, being absent in Aracanidae, Ostraciidae, Tetraodontidae, Diodontidae, and Molidae. Morphological characteristics derived from the lateral line system and its innervation provided some support for a sister relationship of tetraodontiforms with lophiiforms.

The trunk lateral line system and its innervation in Mugil cephalus (Mugilidae: Mugiliformes)

“…In M. cephalus, the fifth and sixth lateral lines are likely homologous with the middle lateral line (i.e., a typical lateral line) at the level. Because the sixth line is characterized by its course running closely parallel to the posterior ramus and is innervated by the lateral ramules as in the conventional straight lateral line (see Yamanaka et al 2010;as ''distal branches'') and in the posterior straight part of the arched lateral line (see Nakae and Sasaki 2010), the sixth lateral line is most reasonably recognized as homologous, the others being recognized here as additional.…”

Enormous gill chambers of deep‐sea coffinfishes (Lophiiformes: Chaunacidae) support unique ventilatory specialisations such as breath holding and extreme inflation

“…The lateral line system of lophiiforms, which are all ambush predators with large gill chambers (Figure ), lacks true canals and instead consists only of superficial neuromasts at the centre of open lateral line scales (Webb, ). Lophiiforms also have a unique extension of the lateral‐line system along nearly the entire length of their enormous gill chambers (Nakae & Sasaki, ), which is particularly pronounced among chaunacids (Caruso, ).…”

Taxonomy and systematics of tetraodontiform fishes: a review focusing primarily on progress in the period from 1980 to 2014

“…Yamanoue et al (2007) analyzed more species of the three groups and provided a robust phylogenetic topology that placed the Caproidei as sister to the Lophiiformes, and the two groups as a clade that is sister to the Tetraodontiformes. Nakae and Sasaki (2010) studied the lateral-line system and its innervations of nine species of tetraodontiforms (representing all families examined except for the Molidae) and a single species each from the Lophiidae, Zeidae, Caproidae, and Siganidae. Their analysis supported a close relationship of the Tetraodontiformes with the Lophiidae, but not with the Zeidae, Caproidae, or Siganidae.…”

“…Baldwin (2013) also provided a putative synapomorphy of some tetraodontiforms and lophiiforms: they are strikingly similar in having the trunk enclosed in an inflated sac covered with xanthophores. Although Nakae and Sasaki (2010), Chanet et al (2013), and Baldwin (2013) did not study many species of tetraodontiform and outgroup fishes, and the relationship between the Tetraodontiformes and Lophiiformes is now supported both by molecular and morphological characters.…”