Sonic/Vocal Motor Pathways in Squirrelfish (Teleostei, Holocentridae)

Abstract

Similar to many teleost fish, squirrelfish (family Holocentridae) produce vocalizations by the contraction of muscles that lead to vibration of the swimbladder. We used biotinylated compounds to identify the position and extent of vocal motor neurons in comparison to additional motor neuron groups, namely those of red and white dorsal epaxial muscle and opercular muscle that are located adjacent to or near the sonic muscle. The sonic motor nucleus (SMN) was located in the caudal medulla and rostral spinal cord in a ventrolateral position with dendrites extending dorsally in a dense bundle along the lateral edge of the medulla and axons exiting via ventral occipital nerve roots. Transneuronal transport of biocytin identified premotor neurons within the SMN and in the medially adjacent reticular formation that projected to the contralateral SMN and more rostrally to the octavolateralis efferent nucleus and nucleus praeeminentialis, suggesting interactions between vocal and octavolateralis systems as seen in other teleosts. Motor neurons innervating the red and white dorsal muscle formed a loose aggregate in the dorsal motor column, adjacent to the medial longitudinal fasciculus, sending fibers bilaterally throughout the spinal cord with axons exiting via ventral spinal nerve roots. Opercular motor neurons were located within the facial motor nucleus. The anatomical characteristics of the SMN of squirrelfish, a representative member of the order Beryciformes, are similar to those of representative members of the closely related order Scorpaeniformes, but diverge from the SMN of more distantly related orders of paracanthopterygiian and ostariophysan teleosts. These results therefore suggest a possible homology among the SMNs of acanthopterygiian fishes.

Sound production and mechanism in Heniochus chrysostomus (Chaetodontidae)

“…Generally speaking, these paired muscles insert on the swimbladder or a neighbouring structure, which attaches to the swimbladder via ligaments. Extrinsic muscles are found in different taxa, including the Ophidiiformes (Howes, 1992), Holocentridae (Carlson and Bass, 2000) and Sciaenidae (Ono and Poss, 1982;Sprague, 2000). Classically, swimbladder sound production in many fish is evoked as a forced response by the contraction of specialized sonic or drumming muscles (Ladich and Fine, 2006).…”

Sonic Motor Pathways in Piranhas with a Reassessment of Phylogenetic Patterns of Sonic Mechanisms among Teleosts

“…Neuroanatomical studies have identifi ed two major patterns of organization for sonic motor neurons [for review, see Ladich and Bass, 1998;Carlson and Bass, 2000]. One pattern exhibits motor neurons positioned close to the midline, near the fourth ventricle and central canal in the caudal medulla and rostral spinal cord.…”

“…This includes the mormyrid Brienomyrus [Bass, 1985], batrachoidiforms [see Bass and Baker, 1991], siluriforms [pimelodid, ariid, mochokid and doradid catfi shes; Ladich and Fine, 1994;Bass, 1996, 1998]. A second pattern showing sonic motor neurons that have a similar rostralcaudal extent within the ventral motor column has been identifi ed among scorpaeniforms [scorpaenids, triglids and cottids;Bass, 1985;Finger and Kalil, 1985;Bass and Baker, 1991;Ladich and Bass, 1998;Yoshimoto et al, 1999], beryciforms [holocentrids; Carlson and Bass, 2000] and perciforms [osphronemids; Ladich and Fine, 1992]. Pimelodid catfi sh have both a midline population of motor neurons associated with a sonic swim bladder mechanism and a ventrolateral population associated with a pectoral spine mechanism [Ladich and Fine, 1994].…”

Sound production mechanism in carapid fish: first example with a slow sonic muscle

“…Generally speaking, these paired muscles insert on the swimbladder or a neighbouring structure, which attaches to the swimbladder via ligaments. Extrinisc muscles are found in different taxa including the Ophidiiformes (Howes, 1992), Holocentridae (Carlson and Bass, 2000) and Sciaenidae (Ono and Poss, 1982;Connaughton et al, 1997;Sprague, 2000).…”