The Localization of Organically Bound Iodine in the Endostyle of Amphioxus

Abstract

An account is given of some features of the organization of the endostyle of Amphioxus, with particular reference to the distribution of sites of mucus secretion as indicated by positive responses to tests for acid mucopolysaccharides. Autoradiography shows that the centre of distribution of organically-bound iodine is associated with the tips of the mucus-secreting cells of zone 5, and not with the glandular tracts. Mucus secretion also occurs elsewhere in the endostyle (although not in the dorsal glandular tracts), but as it is not associated with any accumulation of bound iodine it is concluded that the binding in zone 5 is a specialized property of the cells of that particular zone. The results are discussed in the light of recent work on the protochordates and the ammocoete larva, and it is concluded that in Amphioxus, as in the Tunicata, there is reason for supposing that the iodination process is a biochemical specialization and that its product must therefore be of some physiological significance to the organism. Attention is also drawn to the evolutionary interest of the association of iodine-binding with a mucin rather than with a glycoprotein.

Ciona intestinalis peroxinectin is a novel component of the peroxidase–cyclooxygenase gene superfamily upregulated by LPS

“…The morphogenesis of this gland, that originates from the embryonic pharyngeal epithelium, supports the homology. In addition, endostyle incorporates iodine (Barrington, 1957(Barrington, , 1958Salvatore, 1969), and the expression of homolog thyroidspecific developmental genes during endostyle development has been reported (McCauley and Bronner-Fraser, 2002; Ogasawara, 2000; Ogasawara and Satoh, 1998; Ogasawara et al, 2001; Venkatesh et al, 1999). The zones 7, 8 and 9 of the C. intestinalis endostyle have been retained the endostyle regions homologs to the vertebrate thyroid (Ogasawara and Satoh, 1998), disclose peroxidase activity (Fujita and Sawano, 1979;Kobayashi et al, 1983), and a specific TPO has been identified in the zone 7 (Ogosawara et al, 1999).…”

Particle capture mechanisms in suspension-feeding invertebrates

“…Since the early contributions of Orton (1913) and van Weel (1937), several authors have described lancelets as filter feeders (e.g. Barrington 1958, Olsson 1963, Welsch 1975, Baskin & Detmers 1976, Rähr 1982, Riisgård & Svane 1999, Ruppert et al 2000, Nielsen et al 2007). As an obligate filter feeder B. lanceolatum is straining off phytoplankton from the surrounding water.…”

“…As particles pass along the pharynx they are drawn up against the internal wall of the branchial basket and the particles become caught in the mucus filter-net. The endostyle in the ventral part of the pharynx produces the mucus filter which is transported along the branchial bars by means of frontal cilia to the dorsal groove where the filters of 2 sides with the captured particles are rolled together and transported posteriorly to the oesophagus (Barrington 1958, Olsson 1963, Welsch 1975, Baskin & Detmers 1976, Flood 1981, Rähr 1982. Riisgård & Svane (1999) further described and characterized Branchiostoma lanceolatum as a true filter feeder, and simultaneously measured clearance rates of differently sized particles showed that particles ≥4 µm are retained by the mucus filternets with 100% efficiency (see also Ruppert et al 2000).…”

Upregulated transcription of phenoloxidase genes in the pharynx and endostyle of Ciona intestinalis in response to LPS

“…A trough-shaped structure (endostyle) is the first trait of the digestive system, it is a glandular ciliated groove that lays along the ventral wall of the pharynx, it extends to the esophagus, and produces the mucus for suspension feeding. It has been histologically divided in eight functional units called ''zones'' numbered bilaterally from midventral to dorsolateral (Barrington, 1957(Barrington, , 1958Fujita and Sawano, 1979;Fujita and Namba, 1971;Thorpe et al, 1972;Ogasawara and Satoh, 1998). In C. intestinalis, a long zone 9, consisting of low epithelial cells, further extends outside the endostyle furrow.…”