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DescriptionThe Spirorbidae, with their tightly coiled white tubes of calcium carbonate, are unmistakable. Janua pagenstecheri is one of the smaller spirorbids and is found on a variety of hard substrata and algae on rocky shores. The calcareous tube is coiled with the opening facing anti-clockwise (dextral), the coil having a diameter of up to 2 mm. Tube with three longitudinal ridges which may be lost by scour in larger individuals. There are two colour morphs of the adult. Bright orange adults occur in shallow water while pale coloured adults occur in deeper water. When the branchial crown of tentacles is everted, the brood chamber is obvious. Early embryos are brown/black but become pale later on with red eyespots.