Fig. 3

Small colonies of Immergentia stephanieae in Experiment 1. a – e Development of young colony from ancestrula over 37 days. a Day 1: Early development of ancestrula after settlement of larva on Littorina littorea substrate. b Day 5: Aperture break through and first primary cystid appendage (right) apparent. c Day 34: First bud and opposite (left) primary cystid appendage. d Day 39: Bud in advanced state (lateral expansion of bud). e Day 42: Bud break through surface of substrate into a feeding zooid. f Tentacle crown of ancestrula with eight tentacles (one tentacle obscured from view). g & h Young colony. g Ancestrula with buds (one advanced and one developing) on opposite cystid appendages. h Advanced bud break through substrate and expansion of primary cystid appendage. i Borehole apertures of inaugural autozooid and advanced bud deflected in opposite directions (enantiomorphism). Advanced bud (borehole not completely open) deflected in direction opposite to preceding autozooids. j – l Two small colonies growing toward each other. j Borehole aperture of one ancestrula (anc1) covered by glossy varnish (arrow) of gastropod. Second ancestrula (anc2) growing along polychaete tube. k Expansion of cystid appendage (cy2) toward second colony and bud developed. l Breakthrough of buds into autozooids and development of new buds. Abbreviations: ab – advanced bud, anc – ancestrula, az – autozooid, b – bud, cy – cystid appendage, p – polychaete, pcy – primary cystid appendage, t – tentacle, tu – tubulets