Figure 4

Semithin cross-sections showing histological aspects of the head and nervous system of H. psammobionta. Dorsal side to the upper right. A: Snout tip with opening of anterior pedal gland pad (arrowhead). B: Nuclei surrounding mouth opening (arrowhead) dorsal of mouth pad. C, D: Anterior head and various cell types (1-3). E: Front of cerebropleural ganglion (cpg). F: Posterior end of cpg and optic ganglion. G: Portion of visceral loop. Scale bars: A-B, 100 μm; C-F, 25 μm. Abbreviations: 1, pink-staining epidermal gland; 2, vacuolated epidermal gland; 3, amorphous cell; apg, anterior pedal glands; bb, buccal bulb; cpg, cerebropleural ganglion; dg, digestive gland; es, esophagus (thin portion); ey, eye; hn, headshield nerve; ln, labiotentacular nerve; lnag, accessory ganglion of labiotentacular nerve; mu, ventral muscle; opg, optic ganglion; opn, nerves to optic ganglion; pg, pedal ganglion; pnd, dorsal pedal nerve; rhn, rhinophoral nerve (double roots); rnag, accessory ganglion of rhinophoral nerve; sgl, salivary gland; spc, spicule cells; subg, subintestinal ganglion; vl, visceral loop.