Fig. 2 H. itoi, nauplius 1 in Naupliar development of Facetotecta (Crustacea: Thecostraca) and the nature of the first nauplius instar in the Crustacea - pro et contra the Hexanauplia concept

Fig. 2 H. itoi, nauplius 1, ventral side (SEM) a General view (cuticular folder with putative rudiments of frontal filaments from 'C' in rectangle area). b Labrum. c Putative rudiments of frontal filaments. d Right naupliar limbs, segments of exopods numbered in Arabic, segments of endopods numbered in Roman. e Posterior part, 5 transverse cuticular rows or combs of denticles corresponding to ventral cuticular ridges of hindbody in subsequent instars indicated by arrowheads. Abbreviations: a1 - antennules; a2 - antennae; ba - basis; co - coxa; dcs - dorsocaudal spine; ff? - putative rudiments of frontal filaments; fs - furcal spines; hb - hindbody; lb - labrum; md - mandible. Scale bars in μm