First record on the development of the larva of the basally branching nemertean species Carinina ochracea (Palaeonemertea)

Table 1 Timetable of developmental stages of Carinia ochracea reached by most of the larvae observed at 18 °C counted after artificial fertilization

Time after fertilization (figure reference)	Structures observed in developmental stage
20-hpf (Fig. 1a)	Hatching, onset of gastrulation
1-dpf (Figs. 1b, 2a, 3a)	Gastrulation completed, frontal epidermal invaginations formed, formation of midgut cilia
2-dpf (Figs. 2b, 3b)	formation of apical tuft of elongated cilia, mouth opening begins to move frontally
3-dpf (Figs. 1c, 2c, 3c)	Larva begins to elongate, mouth opening more frontal, midgut lumen with cilia visibly enlarged, muscular contractions observable, neurites of central nervous system detectable, nephridia detectable, pigmented eye begins to form ventro-laterally
4-dpf (Fig. 2d)	pigmented eye enlarged, frontal epidermal invaginations more posterior and less deep
5-dpf (Figs. 2e, 3d)	Further elongation of larva, becomes more slender, pigmented eye further enlarged and closer to ventral midline, frontal epidermal invaginations less deep
7-dpf (Figs. 2f, 3e)	Further elongati on of larva, pigmented eye further enlarged and situated almost on the ventral midline, midgut visibly empty,
10-dpf (Fig. 1d)	No further progress in development, considerable fraction of larvae degenerate because of starvation, no settlement observed

Note that the times change considerably between and within one batch of larvae (hpf hours after fertilization, dpf days after fertilization)

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