Abstract
The muscular system of the dwarf ectoparasitic male of Scolelepis laonicola (Tzetlin, 1985) was reconstructed by Falloidin-TRITC technique and confocal scanning microscopy. The anterior part of the male penetrates the female. All four main longitudinal muscle strands of the male’s body enter the female; they are twisted about 90°. Oblique muscle fibers form a pear-shaped structure; they are very similar to the peristomial muscles in Prionospio cirrifera Wirèn. The well-developed musculature of the virtually immobile parasitic male of S. laonicola indicates good swimming abilities of juvenile males at the presettlement stage of the free-living larva.