Studies on the respiratory pigments of three species of serpulid polychaetes at different stages in the life cycle

Abstract

Abstract Histochemical, histological and spectroscopic methods have been used to study the origins, distribution, spectral properties and functions ofthe blood pigments in various developmental stages of three closely related species of serpulid polychaetes. Histochemical reactions for the pigments, chlorocruorins in Spirorbis corallinae and S. spirorbis and haemoglobin in Janua pagensueheri, appear first in the unfertilised eggs as these mature in the ovary and body cavity. They occur initially around the animal pole but during cleavage and development of the free-swimming non-feeding larval stages are found increasingly in the endoderm. They become especially concentrated in the anterior walls ofthe differentiating stomach and granules giving these thermostable reactions are subsequently present at this site throughout life. The granules appear to be precursors ofthe soluble circulating blood pigments and it is concluded that the anterior stomach is a major haemopoietic organ. During the brief free-swimming phase the larvae develop prominent calcium-secreting glands in the peristomium, rich in acid and alkaline phosphatases, which at metamorphosis become the adult tube-forming glands. In the larval, settlement and early tube-building stages the glands contain large amounts of chlorocruorin or haemoglobin, identified spectroscopically as well as histochemically, but these disappear as the adult vascular system develops with its own pigmentladen plasma. Presence of the respiratory pigments throughout embryogenesis is probably linked to the brooding of the embryos in the adult tube (S. corallinae and S. spirorbis) or operculum (J. pagensuekeri) and their temporary occurrence in the tube-forming glands before development of the blood system equally has obvious functional significance. The pigments have well defined absorption bands in the visible spectrum whose peaks are in the range recorded for other serpulids; they react reversibly with oxygen and have a strong affinity for carbon monoxide. Treatment with CO causes clear shifts in absorption peaks but is not apparently harmful, treated worms continuing to feed, grow and reproduce. The shifts persist unchanged for at least 14 days but then progressively disappear; normal values, and reactivity with oxygen, are fully restored within a further 7 days.