Homologies of the adductor mandibulae muscles in Tetraodontiformes as indicated by nerve branching patterns

Abstract

Homologies of the adductor mandibulae muscles in eight families of Tetraodontiformes were hypothesized from the branching patterns of ramus mandibularis trigeminus. Insertions of the muscles to the upper or lower jaw were weak indicators of homology, migrations of the sites occurring frequently in A1, A2α, A2 , and A3. In monacanthids, tetraodontids, and diodontids, A1 tended to be split into numerous subsections, whereas in aracanids and ostraciids, A3 was highly developed, comprising three or four subsections. In tetraodontids, A2 was found to be a composite of A1 subsection and A2 . The methods of and limits to applying nerve branching patterns to muscle homology are discussed. A new naming system that reflects both muscle homologies and insertions is proposed. Materials and MethodsThe specimens examined are listed below. Triodontidae and Molidae were not examined owing to a lack of materials. Abbreviations in parentheses refer to the methods of examination: D, dissected; CS, cleared and stained. Measurements (in mm) are of standard length (SL). Muscles were observed on specimens stained by Alizarin Red-S, and cranial nerves on CS specimens prepared by the Sihler technique (Fraser and Freihofer, 1971), with the following modifications: a few crystals of thymol (mold inhibitor) were added to trypsin solution for maceration; maceration in KOH solution (0.5-1% KOH by weight) was limited to 3-7 days; Sihler's Solution II was diluted to ca. 20% with distilled water, because 100% Solution II tended to stain bone and muscle tissues, in addition to nerves. Terminology generally follows Tyler (1980) for osteology and Freihofer (1978) for neuroanatomy. In the "description" and illustrations, the names of the adductor mandibulae subdivisions follow Winterbottom (1974b). Subdivisions newly recognized (and named on the basis of their insertions) in this study are indicated by an asterisk. Aω is not illustrated in the figures, because the section so named in Tetraodontiformes does not appear to be an element of the adductor mandibulae muscles (see Discussion), although tentatively included in "Description." Material examined. Triacanthodidae: Triacanthodes anomalus, BSKU (Laboratory of Marine Biology, Faculty of Science, Kochi University) 62329 (65.7 mm, D), BSKU 64695 (5 specimens; 62.0-97.5 mm, CS); Macrorhamphosodes uradoi, BSKU 62330 (104.9 mm, D), BSKU 64696 (3; 66.7-86.1 mm, CS). Triacanthidae: Triacanthus biaculeatus, BSKU 62331 (182.8 mm, D), BSKU 64697 (4; 197.0-Ichthyological Research

The lateral line system and its innervation in the boxfish Ostracion immaculatus (Tetraodontiformes: Ostraciidae): description and comparisons with other tetraodontiform and perciform conditions

“…However, in the Upper Cretaceous Plectocretacioidea the infraorbitals and a sensory canal in the dentary (MDL) are recognizable (Tyler and Sorbini 1996), suggesting that canal neuromasts occurred in IOL and MDL primitively in tetraodontiforms. The loss of infraorbitals may be adaptive for the order, permitting a relatively "free" topographic arrangement of IOL (and innervating BR), the cheek region below the eye being variable in depth from shallow (as in T. anomalus) to very deep (as in O. immaculatus), with various development of the adductor mandibulae muscles (Winterbottom, 1974;Nakae and Sasaki, 2004). It should be noted that fossil tetraodontiforms with infraorbitals are characterized by a shallow cheek region (Tyler and Sorbini, 1996).…”

“…Regarding tetraodontiforms, little attention has been paid to the Measurements (in mm) are of standard length (SL). Bones were observed on specimens stained by Alizarin Red-S, and nerves on CS specimens prepared by the Sihler technique (Fraser and Freihofer, 1971), with modifications of Nakae and Sasaki (2004), and the Sudan Black B protocol (Filipski and Wilson, 1984). Superficial neuromasts in Ostracion immaculatus were observed by scanning electron microscopy (SEM).…”

The lateral line system and its innervation in Champsodon snyderi (Champsodontidae): distribution of approximately 1000 neuromasts

“…Bones were observed from specimens stained with alizarin red S, and nerves on cleared and stained specimens prepared by the Sihler technique (Fraser and Freihofer, 1971), with modifications of Nakae and Sasaki (2004), and the Sudan black B protocol (Filipski and Wilson, 1984). The illustrations and description given are based on about ten specimens, from which the neuromast distribution and innervation were determined, because we were unable to observe all neuromasts and lateral line nerves in a single specimen.…”

Comparative innervation of cephalic photophores of the loosejaw dragonfishes (Teleostei: Stomiiformes: Stomiidae): Evidence for parallel evolution of long‐wave bioluminescence

“…Without experimental labeling of the neurons in question, hypotheses of homology of the loosejaw SO with the SO of basal stomiiforms cannot be completely rejected. Nevertheless, if comparative neuroanatomy is to be interpreted as prima fascia evidence of primary homology (as it has in other phylogenetic studies, e.g., Thewissen and Babcock, 1991;Song and Boord, 1993;Song and Parenti, 1996;Nakae and Sasaki, 2004;Anderson, 2008), innervation of the SO of all loosejaws by fibers of the Tmd implies nonhomology of the SO of basal stomiiform taxa.…”