Fig. 8

Myoanatomy of the lophophoral system of Asajirella gelatinosa stained for f-actin and against acetylated-α-tubulin, visualised as volume renderings. A Oral view of a polypide, retracted into the tentacle sheath. The tentacle sheath consists of longitudinal muscles with proximal bifurcations. The dense circular musculature of the foregut is followed by the less dense arrangement in the cardia. Several muscle bundles of the retractor muscle insert at various areas of the digestive tract. B Oral view of the lophophore showing prominent muscle bases of the oral tentacles and abfrontal muscles ascending into the tentacles. C, D Distal view on the lophophoral arms showing the prominent lophophore arm muscles becoming slender along the oral- anal axis as tentacle muscles branch off. At their origin a pair of retractor muscle inserts. Abfrontal (C) and frontal (D) muscles of the tentacle associated with the lophophore arm muscles. E Anal view of the oral tentacles showing the large bases of the abfrontal tentacle muscles including several median bands. In contrast to the former, the frontal muscles lack prominent bases. Both tentacle muscles ascent as inverted ‘v’ muscles. Interdigitating with the tentacle muscles, radial nerves branch off a circumoral nerve ring while mediofrontal nerves are located next to the frontal tentacle muscles. afm abfrontal tentacle muscle, afmb abfrontal tentacle muscle base, ca cardia, cae caecum, con circumoral nerve ring, em epistome musculature, fm frontal muscle, int intestine, inv inverted ‘v’ muscle, l lophophore, la lophophore arm, lam lophophoral arm musculature, phm pharynx musculature, rm retractor muscle, rn radial nerve, tsm tentacle sheath musculature