Fig. 1 in The architecture of the physid musculature of Physa acuta Draparnaud, 1805 (Gastropoda: Physidae)

Fig. 1. (A) Dorsal view of P. acuta with all visceral structures removed to show the broad insertion of the physid muscle s.s. (Pm) in the columellar muscle (Cm) in the snail foot. The Cm has two pedal horns that run anteriorly towards the head while the thicker posterior part runs a short distance towards the tail. The anterior horns start as thick bundles but taper as they near the head. (B) Dorsal view of P. acuta with its visceral hump removed to show the Pm and its five branches numbered Pm1–5. Pm1 runs anteriorly from the origin to the neck and head, Pm2 across the neck to the left hand side of the head, Pm3 and Pm4 descend to the left side of the body and Pm5 wraps around the Cm before passing anteriorly, also to the left hand side of the body. The columellar muscle was not drawn but is located inside the loop made by Pm5. (C) Dorsolateral view of P. acuta with the skin and visceral hump removed. The branches of the Pm are seen coming from right to left over the anterior part of body, intertwining as they do so with Cm fibres that run from the middle to the anterior part of the body. Pm fibres are overlain by Cm fibres. (D) Lateral view of P. acuta showing the location of Pm branches 2–5 within the snail body where they overlie each other. Pm1 is obscured. The fan muscle (Pf) radiates posteriorly from its origin on the physid muscle s.s. (Pm) to a diffuse insertion beneath the mantle.