Myoanatomy of Barentsia discreta (Busk, 1886) (Kamptozoa: Coloniales)

The anatomy of the muscular system of Barentsia discreta (Kamptozoa) was studied by confocal laser scanning and transmission electron microscopy. The calyx musculature, muscles associated with the digestive tract, atrial ring muscles, and tentacle muscles are described. The structure of the muscular bulbus located in the upper part of the stalk and the muscle base of the stalk were examined. The middle part of the stalk and the stolon lack musculature. The structure of the star-cell complex lying at the boundary of the stalk and calyx was examined in detail. Emschermann's (1969) opinion was confirmed that the star-cell complex performs the function of a heart, providing the transport of substances from the calyx to the stalk and stolon. The general plan of the muscle arrangement is similar in all Kamptozoa; it consists of central muscles of the calyx, atrial ring muscles, tentacle muscles, and muscles associated with the digestive tract. Oral, lateral, and aboral muscles extending from the stalk into the calyx, which were described for solitary forms, are lacking in the calyx of colonial B. discreta. The calyx of B. discreta is separated from the stalk by a septum, through which muscles do not penetrate from the stalk.