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Figure 1 | BMC Biology

Figure 1

From: Magnetic resonance imaging (MRI) has failed to distinguish between smaller gut regions and larger haemal sinuses in sea urchins (Echinodermata: Echinoidea)

Figure 1

Siphonal grooves versus siphons in sea urchins. (A) Gross anatomical dissection of Diadema setosum seen from the oral side after removal of the jaw apparatus (photograph by Gregory W. Rouse). Conspicuous gut regions are the esophagus (es) and stomach (st), which makes a clockwise circuit of the body from approximately 6 o'clock to 5 o'clock. The siphonal groove (indicated by arrows) and the inner marginal sinus (indicated by arrowheads) of the haemal system accompany the stomach throughout its course. (B, C) Cross sections of the inner marginal sinus (ims), siphonal groove (sg), and part of the stomach (st) of two diadematid species: (B) Diadema setosum and (C) Diadema antillarum. (D) Cross section of the inner marginal sinus (ims), siphon (si), and part of the stomach (st) of a non-diadematid sea urchin, Arbacia incisa. In all the cross sections, the inner marginal sinus contains a clot of haemal fluid.

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BMC Biology

ISSN: 1741-7007

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