Fishelson L, Baranes A
Department of Zoology, Tel Aviv University, Ramat Aviv, Israel.
Anat Rec. 1997 Nov;249(3):409-21. doi: 10.1002/(SICI)1097-0185(199711)249:3<409::AID-AR13>3.0.CO;2-S.
Sharks (Selachi) are among the largest predators in deep and shallow seas, feeding on live and dead prey. Olfaction is one of the central senses by which they forage, especially at night and in deep water. The organs responsible for this function are the olfactory rosettes, which are situated in their nares. This study follows the ontogenesis and cytological development of the olfactory rosettes of the Oman shark, Iago omanensis, found in the Gulf of Aqaba, Red Sea, at depths of 150-1500 m.
The sharks were collected bimonthly by means of a specially designed vertical standing net and sacrificed by an overdose of MS222. The olfactory rosettes were extracted from the adults and embryos, then fixed and prepared for EM and LM studies.
Iago is a placental, matrotrophic species with a maximal dimension of 800 mm TL (total length). It reproduces all year round, giving birth to a maximum of four (occasionally five) young of 170-180 mm TL. In newborn and adult fish the nasal olfactory organs are as described for other sharks, composed of olfactory lamellae with secondary folds. The number of lamellae increases during embryogenesis up to a maximum of 28-32 in adults. The primary nasal placodes first appear in larvae of 10-14 mm on the dorso-lateral part of the head and then become gradually displaced to the ventral position, typical for adults. Ontogenesis of the nasal rosettes is characterized by a gradual development of the lamellae and their secondary folds, with a concomitant ripening of the sensory elements (ciliated, microvillar, and rod-like bearing cells), as well as glandular and supporting cells and cells containing kinocilia that agitate the nasal water flow.
The released young possess functional olfactory organs and developed neural transmission across the olfactory bulb and tract, to the olfactory lobes in the brain, enabling them to forage from birth. Presented data show the occurrence in I. omanensis of two types of ciliated and microvillar cells. Ciliated and rod-bearing sensory neurons are described for the first time in sharks.
鲨鱼（板鳃亚纲）是深海和浅海中最大的食肉动物之一，以活的和死的猎物为食。嗅觉是它们觅食的主要感官之一，尤其是在夜间和深水中。负责这一功能的器官是位于鼻孔内的嗅叶。本研究追踪了在红海亚喀巴湾150 - 1500米深处发现的阿曼鲨（Iago omanensis）嗅叶的个体发生和细胞学发育。
每隔两个月通过专门设计的垂直立网收集鲨鱼，并用过量的MS222使其安乐死。从成年鲨鱼和胚胎中提取嗅叶，然后固定并准备用于电子显微镜（EM）和光镜（LM）研究。
阿曼鲨是一种胎生、母性营养型物种，最大全长为800毫米。它全年繁殖，最多可产下四（偶尔五）条全长170 - 180毫米的幼鲨。在新生和成年鱼类中，鼻嗅觉器官与其他鲨鱼的描述相同，由带有次级褶皱的嗅板组成。嗅板的数量在胚胎发育过程中增加，成年时最多可达28 - 32个。初级鼻基板首先出现在头部背外侧10 - 14毫米的幼体中，然后逐渐移至腹侧位置，这是成年鲨鱼的典型位置。嗅叶的个体发生特点是嗅板及其次级褶皱逐渐发育，同时感觉元件（纤毛、微绒毛和杆状承载细胞）、腺细胞、支持细胞以及含有动纤毛的细胞成熟，动纤毛可搅动鼻内水流。
出生的幼鲨拥有功能性嗅觉器官，并在嗅球和嗅束之间以及到大脑嗅叶之间建立了发达的神经传递，使它们从出生就能觅食。现有数据表明阿曼鲨存在两种类型的纤毛细胞和微绒毛细胞。首次在鲨鱼中描述了纤毛和杆状感觉神经元。
