Fig. 5
Light microscopy transverse histological sections of Schizocardium karankawa sp. nov. A Anterior end proboscis shows proboscis coelom filled with muscle fibers and the central portion of proboscis coelom divided via sagittal muscle plate into right and left. B Proboscis coelom with the paired tubular extensions of the cardiac vesicle, glomerulus, and stomochord or the heart–kidney–stomochord complex. C Posterior end of the heart–kidney–stomochord complex. D Neck enveloped by tissue of the anterior collar, showing the keel of the proboscis skeleton. E Collar region showing well-developed, paired peribuccal and perihaemal diverticula and the paired cornua of the proboscis skeleton. F Anterior trunk shows one of the collar canals, and the epibranchial ridge. G Six cell zones of the epibranchial ridge. H Pharyngeal region of the trunk with the primary and secondary (tongue) bars, and trunk muscles. I Pharyngeal region of the trunk with gonads. bv blood vesicles, cc collar canal, ct connective tissue, cv cardiac vesicles, clm collar longitudinal muscles, dm dorsal mesentery, ds dorsal septum, dtm dorsal trunk muscles, ebr epibranchial ridges, ep, epidermis, g glomerulus, gb gill bars, go gonads, hbr hypobranchial ridge, nc nerve cord, nfl nerve fiber layer, pbd peribuccal diverticula, pc proboscis coelom, pcm proboscis circular muscles, phd perihaemal diverticula, pl pharynx lumen, ppd peripharyngeal diverticula, s stomochord, sk skeletal keel, sc skeletal cornua, vm ventral mesentery, vtm ventral trunk muscles. Scale bars: A 450 μm; B = 1000 μm; C, D and H = 500 μm; E = 400 μm; F, I = 600 μm; G = 150 μm