Table 1 Summary of the defining characters of early post-embryonic stages in S. maritima: embryoid stages (Proembryoid I to Foetus) and first free living juvenile stage (adolescens I) (ec: embryonic cuticle)

Ecdysis ec

Proembryoid I

Sharp angle between anterior and posterior trunk anterior half much larger, with ventral side concave

Limbless

terminal trunk undifferentiated, barely developed

Ventral (slightly anterior), 14 unclear antennomeres, depressed

Ecdysis e1 and e2

Proembryoid II and III

Angle between anterior and posterior trunk anterior half slightly larger, with ventral side flat

Limb buds just appearing

terminal trunk undifferentiated, extended

Ventral orthogonal, 14 antennomeres slightly elongated

Ecdysis e3

Peripatoid

Uniform circular section of trunk along AP axis

Limb buds extended but barely, if not, segmented

single genital segment defined (single segmental furrow present)

Ventral forward more than 90 degrees from the main head/trunk axis, 14 well defined antennomeres

Ecdysis e4

Foetus

Trunk slightly dorsoventrally depressed

Limbs segmented, although less developed than the rest of the legs

subdivision in segments, but number and shape unclear because not clearly defined

Elongated and divaricated further, extending forward, almost on the trunk plane

Appearance of setae, maxillipeds/forcipules tanned and multisegmented

Adolescens I

Trunk dorsoventrally depressed

Legs fully differentiated but distinguished from the rest of the legs

differentiated with several sclerites in two genital segments and terminal anal valves

Tanned in stripes, rich in setae and sensilla

Well developed and abundant setae, tanning in particular of head and forcipular segment