Echinobase Image ID: 183964

Figure 1. Anatomy of the starfish Asterias rubens. (A) Aboral view of a specimen of A. rubens; the white line indicates the approximate position of the section shown in (C). (B) Oral view of a specimen of A. rubens; the white line indicates the approximate position of the section shown in (D). (C) Trichrome-stained transverse section of an arm from a specimen of A. rubens. The body wall comprises ossicles (which appear white here) that are surrounded and interlinked by collagenous tissue (stained blue). The body wall has several types of appendages, which include spines and papulae. The body wall is lined internally by a coelomic epithelium, which is underlain along its midline aborally by a longitudinally orientated muscle known as the apical muscle. Linked to the aboral body wall by mesenteries are digestive organs known as pyloric caeca. The oral side of the body wall comprises ambulacral and adambulacral ossicles and two rows of tube feet, which are linked to bulb-shaped ampullae located internal to the body wall. The V-shaped radial nerve cord runs between the two rows of paired tube feet; lateral to the outer rows of tube feet are the marginal nerves. (D) Trichrome-stained transverse section of the central disk region, which is largely filled by the highly folded cardiac stomach. The cardiac stomach is linked orally to a short esophagus, which in this preparation is everted through the oral opening (mouth) that is surrounded by a peristomial membrane. Lateral to the peristomial membrane is the cirumoral nerve ring. Aboral to the cardiac stomach is the smaller pyloric stomach, which is linked via pyloric ducts to the pyloric caeca located in the arms [see (C)]. Aboral to the pyloric stomach is a short rectum (not seen here), which has associated rectal caeca. Abbreviations: ado, adambulacral ossicle; am, apical muscle; ao, ambulacral ossicle; ce, coelomic epithelium; co, carinal ossicle; conr, circumoral nerve ring; cs, cardiac stomach; es, esophagus; lsm, longitudinal supra-ambulacral muscle; me, mesentery; mn, marginal nerve; mo, marginal ossicle; pa, papula; pc, pyloric caeca; pd, pyloric duct; pm, peristomial membrane; ps, pyloric stomach; rc, rectal caeca; ro, reticular ossicle; sp, spine; tf, tube foot; tsm, transverse supra-ambulacral muscles. Scale bars: (A,B) = 1 cm; (C,D) = 210 µm. Image published in: Tian S et al. (2017) Image downloaded from an Open Access article in PubMed Central. Copyright © 2017 Tian, Egertová and Elphick. Larger Image Printer Friendly View

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