Development of pigment in the echiuran worm Bonellia viridis

Abstract

An account is given of the development of green pigment in the early larval stages of the echiuran worm, Bonellia viridis. The green pigment first appears in scattered epidermal cells of the gastrula, before the development of the trochal rings. It is contained in spherical vacuoles (0.5‐1.0 μm in diameter). As the gastrula develops into the trochophore there is an increase in total pigment content, as well as an increase in number of pigment cells and size of pigment vacuoles. The increase in pigment cell number in the trochophore results from the proliferation of the pigment cells of the gastrula. The pigment content increases rapidly before the trochophores hatch but shows little relative increase after hatching whilst the trochophores remain undifferentiated. We suggest that the pigment may have a protective role in the free‐living trochophore for camouflage or chemical defence. In trochophores that undergo male differentiation the pigmentation is lost. Since the males do not lead a free‐living existence but live as commensals inside the uterus of the female camouflage or chemical defence would be unnecessary. In trochophores undergoing female differentiation there is an increase in pigment content of the preoral lobe which develops into the proboscis. Following the enlargement of the coelom, clusters of coelomic cells accumulate green pigment whilst still in the coelom and then migrate to the integument of the body wall.

Knots, spoons, and cloches: DNA barcoding unusual larval forms helps document the diversity of Neotropical marine annelids

“…com., 2019). Bonellin, the green integumentary pigment expressed by Bonellia viridis , develops during early embryonic development (Agius & Jaccarini, 1981). The pigment disappears after settlement, but, prior to that, pigment expression can be highly influenced by light exposure (Agius & Jaccarini, 1981).…”

“…Bonellin, the green integumentary pigment expressed by Bonellia viridis , develops during early embryonic development (Agius & Jaccarini, 1981). The pigment disappears after settlement, but, prior to that, pigment expression can be highly influenced by light exposure (Agius & Jaccarini, 1981). Embryos kept in high light conditions expressed less pigment, if any, and pigment expression was only partially rescued by a shift to the dark (Agius & Jaccarini, 1981).…”

“…The pigment disappears after settlement, but, prior to that, pigment expression can be highly influenced by light exposure (Agius & Jaccarini, 1981). Embryos kept in high light conditions expressed less pigment, if any, and pigment expression was only partially rescued by a shift to the dark (Agius & Jaccarini, 1981). It is therefore possible that the observed variation in pigment among our larvae was due to developmental conditions in addition to developmental stage.…”

Effects of light on pigment development in the echiuran worm, Bonellia viridis

“…BoneZZiu viridis were collected as described previously (Agius & Jaccarini, 1981). The egg strings were removed from around the body of the female directly after laying (before cleavage).…”

“…We have shown that bonellin, the integumentary pigment of B. viridis, widely documented for its toxicity, is photodynamically active (Agius, 1978;Agius, Jaccarini et al, 1979). Since the green pigment develops in the gastrula, and the trochophores acquire a deep green pigmentation before hatching (Agius & Jaccarini, 1981) we investigated the effects of illumination on pigmentation and vulnerability to light in the early developmental stages of B. viridis.…”