Haplognathia filum, Sterrer, 1966

Haplognathia filum View in CoL

SLIR, TyrTLIR, FLIR, and Syn1LIR nervous structures as well as DAPI-stained cell nuclei are visualized with CLSM. The nervous system is generally similar to that of H. gubbarnorum ; however as the animal is very thin and slender, most of the nervous structures are more densely packed in the medio-lateral axis and are elongated in the antero-posterior axis (Figs. 11e, 12e, f). Yet, there are some structures not observed (either absent or damaged) in H. gubbarnorum . Six longitudinal rostral nerves (1 × drn, 2 × dln, 2 × lrn, 1 × vrn, Figs. 11e, 12e, f) show strong TyrTLI reactivity and innervate the asymmetrical spiral organs ( so, Figs. 11e, 12e), laterally located pompom ciliated organs ( pcr, Figs. 11e, 12e, f), and apical rostral anterior cells ( rac, Figs. 11e, 12e) of presumably sensory function. In the posterior part of the animal, the lateral nerve cords ( lc, Figs. 11f, 12d) are connected by a posterior SLIR and TyrTLIR commissure ( pc, Figs. 11f, 12d), related to the posterior ganglia ( pg, Figs. 11f, 12d), as well as by a terminal tail commissure ( tc, Figs. 11f, 12d). In addition to the Syn1LIR structures described for H. gubbarnorum, Syn 1LI reactivity was detected in the midventral nerve cord ( mvc, Fig. 12h), the middorsal longitudinal neurite bundle ( mdn, Fig. 12h), and in nerves connecting the stomatogastric nervous system with the ventro-posterior part of the neuropil ( sgn, Fig. 12i).