Fig. 8

Type 4 postembryonic development of Pycnogonida. a Newly hatched protonymphon larva 1 of Phoxichilidium femoratum, ventral view (modified from [65]). b-f Sequence of larval and postlarval instars of Anoplodactylus eroticus, endoparasitic in the hydrozoan Pennaria disticha. SEM (b, d-f) and brightfield (c) micrographs (modified from [86]). Reproduced with permission of Amy Maxmen. b Newly hatched protonymphon larva 1, dorsal view, note modified filamentous terminal articles of palpal and ovigeral larval limbs (arrows). Arrowheads mark gland processes of palpal and ovigeral larval limbs. c Postembryonic instar 2 (=modified protonymphon larva 2), dorsal view. Note significant reduction of palpal and ovigeral larval limbs. c Instar with primordia of walking leg pairs 1 and 2, lateral view. d Slightly later than (c), ventrolateral view. Note distinct limb buds of walking leg pairs 1–3 and lack of walking leg 4 primordia. e Old postlarval instar, shortly before molt and emergence from the hydranth, dorsal view. Note elongate anlagen of walking leg pairs 1–3 and tiny limb bud of walking leg 4. g Hydranth of live Pennaria disticha, infested by A. eroticus (Original: Amy Maxmen). g A. eroticus old postlarval instar (compare to (f)) protruding from ruptured hydrant of P. disticha. (Original: Amy Maxmen). Note orange color of the midgut diverticula extending into the walking legs