Morphological and cytological ontogenesis of the ampullae of Lorenzini and lateral line canals in the Oman shark,Iago omanensis Norman 1939 (Triakidae), from the Gulf of Aqaba, Red Sea

摘要: The Oman shark, Iago omanensis, is a small, placental viviparous species encountered in great numbers the deeper waters of Gulf Aqaba, Red Sea. It reproduces year-round, providing an opportunity to study ontogenesis organ systems at various stages development. This examines morphological and cytological development mechanoreceptive lateral line (LL) system electrosensory Ampullae Lorenzini. Female I. omanensis were collected bimonthly from Aqaba depths 300–800 m sacrificed with overdose MS222. Their uteri dissected embryos separated fixed for light electron microscopy. A total 260 varying dimensions studied. The first primordia neuroectodermal LL neuromasts are seen 18 mm TL. These then sink into dermis, ripen, develop tubuli that join form canal systems, especially developed on head. In contrast, Lorenzini start out as groups embryonic cells situated subdermally. 24–26 TL initially they tubuli. With growth, ampullar alveoli gradually widen their ends sensory epithelium. elongate, bringing sites over rostrum head, where capsules formed. presynaptic attached afferent neural extensions forming rami which extend, adult sharks, dorsal nucleus medulla. preterm juveniles 150–160 TL, fully cytologically. The results this support hypothesis separate modalities structural similarity due origin neuroectoderm. dichotomy evolution occurred very early ancestry ecomorphological adaptation different functions. Anat. Rec. 252:532–545, 1998. © 1998 Wiley-Liss, Inc.