Microampullary organs of a freshwater eel‐tailed catfish, plotosus (tandanus) tandanus

Abstract

Whole body studies of Plotosus tandanus revealed that ampullary pores occur over the entire body of the fish, but are in higher concentrations in the head region. These pores give rise to a short canal (50-60 microm) produced by columnar epithelial cells bound together by tight junctions and desmosomes. At the junction of the canal and the ampulla, cuboidal epithelial cells make up the wall. The ampulla consists of layers of collagen fibers that surround flattened epithelial cells in the lateral regions and give rise to supportive cells that encase a small number of receptor cells (10-15). The ampullary wall comprises several types of cells that are adjoined via tight junctions and desmosomes between cell types. The ovoid receptor cells possess microvilli along the luminar apical area. Beneath this area, the cells are rich in mitochondria and rough endoplasmic reticulum. An unmyelinated neuron adjoins with each receptor cell opposite multiple presynaptic bodies. This form of microampulla has not been previously described within the Family Plotosidae.

The functional roles of passive electroreception in non-electric fishes

“…Canal length varies signi cantly in the electroreceptors of saltwater and freshwater vertebrates and is thought to be an adaptation for increasing sensitivity (Bennett, 1971;Szabo et al, 1972;Kalmijn, 1974;Whitehead et al, 1999Whitehead et al, , 2003. The long canals of elasmobranchs enable low frequency electric elds to be virtually unattenuated due to the high resistance of the canal walls and the low resistance of the jelly core.…”

“…The effects of habitat salinity on the structure of the ampullary organs have recently been examined in a study, which reveals that 'microampullae' occur in freshwater plotosid cat sh (Plotosus tandanus, Whitehead et al, 2003). These microampullae consist of short canals (50 ¹m) and contain low numbers (10-15) of receptor cells and appear different to the ampullary organs described for marine Plotosus anguillaris, which are characteristically de ned as resembling ampullae of Lorenzini (Obara, 1976;Zakon, 1986).…”

“…The typical ampullae in teleosts are similar but are characterised by shorter canals (e.g. 50-200 ¹m in Plotosus tandanus and Ameiurus nebulosus, in contrast to up to 20 cm long in some species of rays, Murray, 1974;Whitehead et al, 2003) and typically fewer receptor cells per ampulla (eight to 20 in the cat sh, Kryptopterus bicirrhus, in contrast to hundreds per sensory organ in the elasmobranchs; Zakon, 1986). In both groups, the structure of electroreceptors varies with habitat.…”

“…Ampullary receptors are broadly tuned to low frequency elds (<0.1-25 Hz), while tuberous receptors are tuned to higher frequency elds from 50 Hz to over 2 kHz (New, 1997). Thought to be a primitive vertebrate character, the ability to detect weak electric elds in shes has thus far been found in agnathans (lampreys but not hag shes, Bullock et al, 1983), chondrichthyans (sharks, skates, rays and chimeras, Bullock et al, 1983;Bodznick and Boord, 1986;Fields et al, 1993;New and Tricas, 1997), cladistians (bichirs, Jørgensen, 1982), chondrosteans (sturgeons and paddle sh, Teeter et al, 1980;Northcutt, 1986) and a small number of species within the osteoglossomorph (knife shes, Braford, 1982;Bullock and Northcutt, 1982;Carr and Maler, 1986;Zakon, 1988) and three orders of teleosts; mormyrids (African electric shes, Lissmann, 1958;Bell and Szabo, 1986), gymnotids (South American electric shes, Lissmann, 1958;Carr and Maler, 1986;Zakon, 1988), and siluriform (cat sh, Parker and van Heusen, 1917;Roth, 1968;Finger, 1986;Whitehead et al, 1999Whitehead et al, , 2003 groups of shes ( g. 1). Electroreception has also been found within the sister group of the actinopterygian shes, the Sarcopterygii, which comprises the dipnoan lungshes (Northcutt, 1986;Watt et al, 1999) and the actinistian coelacanth (Bemis and Hetherington, 1982).…”

Ultrastructure of the ampullary organs of Plicofollis argyropleuron (Siluriformes: Ariidae)

“…The number of receptor cells within these microampullae resemble that of freshwater species, containing only 7–20 receptor cells. For example, freshwater N. graeffei possess 8–30 receptor cells (Whitehead et al, ), Plotosus tandanus possess from 10 to 15 receptor cells (Whitehead et al, ), and the South American blind catfish, Pseudocetopsis sp. has only 1–2 receptor cells per ampulla (Andres et al, ).…”