The histochemistry and infrastructure of the coelomocytes of species of Lumbricillus, and observations on certain other enchyfraeid genera (Oligochaeta: Annelida)

Abstract

The main coelomocyte type–the granular mucocyte–of Lumbricillus mirabilis, L. reynold‐soni and L. rivalis has inclusions consisting of a mucopolysaccharide‐protein complex with very low lipid levels. Both neutral and carboxylated acid mucopolysaccharides occur, the latter predominating in the granules of L. rivalis in which protein levels are lower than in the other two species.The Golgi‐derived granules of the mucocytes of L. mirabilis and L. reynoldsoni are electron dense when mature and are separated from each other by cytoplasm housing, generally, a single endoplasmic reticulum profile. The mucocytes arise from the peritoneum. In L. rivalis the inclusions are of finely fibrillar material typical of acid mucopolysaccharides. Studies on species of other genera show the species of littoral origin to possess mucocytes with an ultrastructure similar to that of the littoral L. mirabilis and L. reynoldsoni; those of non‐littoral origin are similar to the non‐littoral L. rivalis. The differences therefore appear to be eco‐physiological rather than taxonomic.Amoebocytic coelomocytes occur and two types are described for L. mirabilis and L. reynoldsoni. Type I is finely pseudopodous and contains numerous small, electron dense inclusions. The origin of Type I from the peritoneum is demonstrated. Type II is characterized by fewer pseudopodia and large, electron dense inclusions similar to chloragosomes. Pinocytotic vesicles occur at the cell periphery. No intermediates between Type I and II were observed, and Type II was not seen in L. rivalis. Both types occur in Enchytraeus albidus, but only Type I in Fridericia bulbosa and no amoebocytes were observed in Mesen‐chytraeus sp.