The Lateral Line System of Hagfishes (Craniata: Myxinoidea)

Braun, Christopher B.; Northcutt, R. Glenn

doi:10.1111/j.1463-6395.1997.tb01010.x

Cited by 53 publications

(46 citation statements)

References 78 publications

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“…Taste buds occur in all vertebrates, but they are lacking in hagfishes [Lindström, 1949;Georgieva et al, 1979;Braun and Northcutt, 1997]. Hagfishes do, however, possess two classes of chemosensory cells: solitary chemosensory cells (SCC) and Schreiner organs.…”

Section: Phyletic Variation In the Distribution Of Taste Budsmentioning

confidence: 99%

“…1A) that are scattered over the surface of the skin of most anamniotes and innervated by either cranial or spinal nerves [Whitear, 1922;Finger, 1997]. In hagfishes, SCC's are primarily restricted to the oropharynx and the tips of the barbels surrounding the mouth [Braun and Northcutt, 1997]. In contrast, the Schreiner organs, which are superficially similar to taste buds but apparently comprise a single class of sensory cells similar to SCC's, occur in large numbers within the oropharynx and over the entire external surface (180,000+ organs) of the body in hagfishes.…”

Section: Phyletic Variation In the Distribution Of Taste Budsmentioning

confidence: 99%

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Taste Buds: Development and Evolution

Northcutt¹

2004

Brain Behav Evol

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The gustatory system in vertebrates comprises peripheral receptors (taste buds), innervated by three cranial nerves (VII, IX, and X), and a series of central neural centers and pathways. All vertebrates, with the exception of hagfishes, have taste buds. These receptors vary morphologically in different vertebrates but usually consist of at least four types of cells (dark, light, basal, and stem cells). An out-group analysis indicates that taste buds were restricted to the oropharynx, primitively, and that external taste buds, distributed over the head and, in some cases, even the trunk, evolved a number of times independently. The sensory neurons of the cranial nerves that innervate taste buds are believed to arise from epibranchial placodes, which are induced by pharyngeal endoderm, but it has never been demonstrated experimentally that these sensory neurons do, in fact, arise from these placodes. Although many details of the development of the innervation of taste buds are still unknown, it is now clear that taste buds are induced from either ecto- or endodermal epithelia, rather than arising from either placodes or neural crest. At present, there are two developmental models of taste bud induction: The neural induction model claims that peripheral nerve fibers induce taste buds, whereas the early specification model claims that oropharyngeal epithelium is specified by or during gastrulation and that taste buds arise from cell-cell interactions within the specified epithelium. There is now substantial evidence that the early specification model best describes the induction of taste buds.

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Section: Phyletic Variation In the Distribution Of Taste Budsmentioning

confidence: 99%

Section: Phyletic Variation In the Distribution Of Taste Budsmentioning

confidence: 99%

Taste Buds: Development and Evolution

Northcutt¹

2004

Brain Behav Evol

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“…A further difference between non-neopterygians and neopterygians is the fact that most non-neopterygian ampullary organs are innervated by the preotic lateral line nerves [except in lampreys and lungfishes; Northcutt, 1986;Braun and Northcutt, 1997], whereas neopterygian ampullary organs (except in gymnotids) are innervated by both pre-and postotic lateral line nerves [Northcutt 1997]. …”

Section: Ampullary Organsmentioning

confidence: 99%

“…However, due to the patterns seen during early development, hagfishes are considered to have a lateral line system, albeit in a reduced state [Braun and Northcutt, 1997]. Lampreys have a more classic lateral line system, with a few exceptions: their neuromasts lack cupulae; and their electroreceptors are not ampullary organs, rather they are intra-epidermal organs [not unlike those found in placoderms) [Northcutt, 1996;Braun and Northcutt, 1997]. Finally, Latimeria ampullary organs appear to come only from the anterodorsal placode [Northcutt, 1997].…”

Section: Variation In Patternsmentioning

confidence: 99%

“…These receptors are not directly comparable to the hair cells of neuromasts for several reasons: because there are no stereocilia, the individual receptors are not polarized; there is no apparent orientation of sensory cells; and there is no evidence of a unified cupula. However, due to the patterns seen during early development, hagfishes are considered to have a lateral line system, albeit in a reduced state [Braun and Northcutt, 1997]. Lampreys have a more classic lateral line system, with a few exceptions: their neuromasts lack cupulae; and their electroreceptors are not ampullary organs, rather they are intra-epidermal organs [not unlike those found in placoderms) [Northcutt, 1996;Braun and Northcutt, 1997].…”

Section: Variation In Patternsmentioning

confidence: 99%

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Lateral Line Receptors: Where Do They Come from Developmentally and Where Is Our Research Going?

Gibbs

2004

Brain Behav Evol

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The lateral line system is composed of both mechanoreceptors, which exhibit little variation in structure between taxonomic groups, and electroreceptors, which exhibit considerably more variation. Cathodally sensitive ampullary electroreceptors are the primitive condition and are found in agnathans, chondrichthyans, and most osteichthyans. Aquatic amphibians also have ampullary electroreceptors for at least part of their life cycle. The more recently evolved anodally sensitive ampullary electroreceptors and tuberous electroreceptors are only found in four groups of teleost fishes. The basic ontogenetic unit of lateral line development is the dorsolateral placode. Primitively, there are six pairs of placodes, which pass through sequential stages of development into lateral line receptors. There is no question about the origin of primitive mechanoreceptors or electroreceptors, however, we do not have a good understanding of the origin of teleost mechanoreceptors and their ampullary or tuberous electroreceptors; do they come exclusively from dorsolateral placodes or from neural crest or even general ectoderm? A second intriguing lateral line question is how certain teleost fish groups evolved tuberous electroreceptors. Electroreception appears to have re-evolved at least twice in teleosts after being lost during the neopterygian radiation. It has been suggested that the development of tuberous electroreceptors might be due to changes in placodal patterning or a change in the general ectoderm that placodes arise from. Unfortunately, our understanding of lateral line origins in fishes is very sketchy, and, if we are to answer such an evolutionary question, we first need more complete information about lateral line development in a variety of fishes, which can then be combined with gene expression data to better interpret lateral line receptor development.

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Schreiner organs: A new craniate chemosensory modality in hagfishes

Braun

1998

J. Comp. Neurol.

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An extensive system of sensory organs resembling taste buds was previously known in the skin of hagfishes. These sensory organs, called here Schreiner organs, are found throughout the epidermis of both Eptatretus stoutii and Myxine glutinosa. They are found also at high densities in the prenasal sinus, nasopharyngeal duct, and pharynx, and at lower densities in the oral and velar chambers. Schreiner organs are multicellular aggregates composed of acetylated tubulin-immunoreactive receptor cells and nonimmunoreactive cells. A considerable range of variation was found in Schreiner organ morphology, but discrete classes of organs could not be recognized. Schreiner organs are innervated by all sensory trigeminal rami, the glossopharyngeal/vagal nerve, and cutaneous rami of spinal nerves, but not by the facial nerve. The central projections of these rami form a continuous tract in the trigeminal sensory zone and the dorsolateral funiculus of the spinal cord. Some Schreiner organs may be represented in the nucleus of the solitary tract, but this structure is certainly not the primary recipient zone of Schreiner organ afferents. In light of these systemic differences between vertebrate taste systems and the Schreiner organ system of hagfishes, it is concluded that Schreiner organs are not homologous to taste buds. This sensory modality of hagfishes has no direct homolog in vertebrates and appears to be a specialization of hagfishes, perhaps derived from the primitive somatosensory system of the earliest craniates.

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The Lateral Line System of Hagfishes (Craniata: Myxinoidea)

Cited by 53 publications

References 78 publications

Taste Buds: Development and Evolution

Taste Buds: Development and Evolution

Lateral Line Receptors: Where Do They Come from Developmentally and Where Is Our Research Going?

Schreiner organs: A new craniate chemosensory modality in hagfishes

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