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Figure 7 | Frontiers in Zoology

Figure 7

From: Myoanatomy and serotonergic nervous system of the ctenostome Hislopia malayensis: evolutionary trends in bodyplan patterning of ectoprocta

Figure 7

Schematic representation of apertural areas of retracted ectoproct zooids with associated muscles. The distal zooidal part points upwards. Epidermal layers are drawn in continuous lines and coelomic epithelia dashed. Tentacles are displayed in dark grey and the diaphragm in orange. (a + b) Apertural muscles in phylactolaemates consist of sparse vestibular dilatators and duplicature bands that either insert at the diaphragm (b) or at the tentacle sheath (a). (c) Cyclostomes possess bundles of vestibular dilatators that extend from the distal bodywall to the diaphragm. Comparable to the duplicature bands, cyclostomes possess an attachment organ built by peritoneal strands. (d - h) Ctenostomes. (d) Paludicelloidean ctenostomes as Paludicella show homologs of phylactolaemate duplicature bands, parieto-vaginal bands, and prominent vestibular dilatators, which are subdivided into the proximal parieto-diaphragmatic muscles and the distal parieto-vestibular muscles. (e + f) Ctenostomes forming elongated peristomes/stolons usually lack parieto-vaginal bands and show a strong separation of parieto-diaphragmatic and distal parieto-vestibular musculature. Alcyonidioideans (g) possess parieto-vaginal bands, whereas hislopioideans (h) lack them. The vestibular dilatators consist of a single portion in hislopioideans. In Alcyonidioideans they are separated into parieto-diaphragmatic and distal vestibular musculature. (i) Cheilostomes possess parieto-vaginal bands and parieto-diaphragmatic musculature as found in ctenostomes. The aperture in cheilostomes is closed by the opercular occlusors - most likely modified distal vestibular muscles. Abbreviations: a - atrium, ao - attachment organ, db - duplicature bands, dvm - distal vestibular muscles, ms - membranous sac, oocl - operculum occlusors, op - operculum, pdm - parieto-diaphragmatic muscles, pvb - parieto-vaginal bands, sph - sphincter, v - vestibulum, vd - vestibular dilatators.

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