The pigmentary system of planaria

Abstract

The pigmentary system of the planaria, Dugesia gonocephala s.l. (Platyhelminthes, Turbellaria, Tricladida), consists of granules contained in chromatophore cells distributed in the parenchyma tissue. The administration of MSH release-inhibiting Factor (M.I.F.) leads to an easily observable general decolouration of the animal due to the migration of the pigment granules towards the deeper-lying cell nucleus. In planarians bisected transversely through the pharyngeal region, the decolouration occurs only in the cephalic segment, and the caudal segment remains dark. When, however, the decapitated caudal segment regenerates a head region, a decolouration response occurs when exposed to M.I.F. The significance of these results is discussed, and an hypothesis on the hormonal regulation of the pigmentary system is proposed.

Forkhead containing transcription factor Albino controls tetrapyrrole-based body pigmentation in planarian

“…The difference between body color pigmentation and eyespot pigmentation indicates the presence of two separate pigment systems for eyespot and body pigments. Applying the modified transmission electron microscopy (TEM) protocol [ 35 ], we confirmed that planarian pigment granules lay between circular and longitudinal muscle cells just beneath the basal lamina ( Supplementary Figure S1B ), in line with the previous publications [ 34–37 ]. Unlike the vital organs of planarian, the body color took more than a fortnight to recover post amputation ( Supplementary Figure S1C ).…”

“…This porphyrin-like pigment was further localized in epidermal rhabdites [ 33 ], suggesting that the tetrapyrrole-like pigment is responsible for planarian body color. Recently, body pigment cells have been observed by using electron microscopy in D. gonocephala , D. ryukyuensis and Schmidtea mediterranea , whereas chromatograph results suggested that a tryptophan-based pigment ommochrome is responsible for the body color [ 34–37 ]. However, molecular or functional validations shall be carried out to confirm these findings and, more importantly, how this process is regulated remains unclear.…”