Sorting food from stones: the vagal taste system in Goldfish, Carassius auratus

Abstract

The sense of taste, although a relatively undistinguished sensory modality in most mammals, is a highly developed sense in many fishes, e.g. catfish, gadids, and carps including goldfish. In these species, the amount of neural tissue devoted to this modality may approach 20% of the entire brain mass, reflecting an enormous number of taste buds scattered across the external surface of the animal as well as within the oral cavity. The primary sensory nuclei for taste form a longitudinal column of nuclei along the dorsomedial surface of the medulla. Within this column of gustatory nuclei, the sensory system is represented as a fine-grain somatotopic map, with external body parts being represented rostrally within the column, and oropharyngeal surfaces being represented caudally. Goldfish have a specialization of the oral cavity, the palatal organ, which enables them to sort food particles from particulate substrate material such as gravel. The palatal organ taste information reaches the large, vagal lobe with a complex laminar and columnar organization. This lobe also supports a radially-organized reflex system which activates the musculature of the palatal organ to effect the sorting operation. The stereotyped, laminated structure of this system in goldfish has facilitated studies of the circuitry and neurotransmitter systems underlying the goldfish's ability to sort food from stones.

Ligand-specific induction of endocytosis in taste receptor cells

“…It seems reasonable to assume that a similar division might apply also to taste buds in fish (Finger, 2005). Also, the taste receptor cells have a large, round nucleus (Finger, 2008), a characteristic feature of the cells that stained in the present study.…”

Anatomical and physiological studies of bigheaded carps demonstrate that the epibranchial organ functions as a pharyngeal taste organ

“…The precise connection between the presence of food particles and their chemicals, and EO pumping will be critical to unravel. Analogies may exist between the EO and the palatal organ, a specialized internal food recognition and sorting system in Eurasian carps including the goldfish, Carassius auratus (Finger, 2008), and common carp (Sibbing, 1982). It is interesting that taste buds and SCCs both occur on the EO, but any functional consequences of this association are unknown at present.…”

Distribution, Innervation, and Cellular Organization of Taste Buds in the Sea Catfish, <b><i>Plotosus japonicus</i></b>

“…Goldfish and related carps show complex intraoral food-sorting behaviors for selecting food particles from mud and gravel [Sibbing et al, 1986;Finger, 2008]. The palatal organs of these fish, innervated by the vagus nerve, are large and have numerous taste buds compared to other teleost species, suggesting that oropharyngeal food-sorting behavior is important for these fish [Finger, 2008].…”

“…Goldfish and related carps show complex intraoral food-sorting behaviors for selecting food particles from mud and gravel [Sibbing et al, 1986;Finger, 2008]. The palatal organs of these fish, innervated by the vagus nerve, are large and have numerous taste buds compared to other teleost species, suggesting that oropharyngeal food-sorting behavior is important for these fish [Finger, 2008]. Catfish also show extreme sensitivity to the gustatory stimuli of the extraoral organs including the barbels [Caprio, 1975], and the extraoral taste buds are especially dense in this group [Atema, 1971].…”