鱼类嗅觉系统和性信息素受体的研究进展

鱼类嗅觉系统包括外部嗅觉器官、嗅神经和嗅球三个部分.嗅觉器官也称为嗅囊,由嗅上皮和髓质组成.气味物质的化学信息主要由嗅上皮上随机分布的嗅觉感受神经元感知,通过嗅神经将嗅觉信息传递到嗅球,嗅球在空间上有不同的功能分区,嗅觉信息经过嗅球各分区整合后分别传入端脑,发挥其生理功能.性信息素在鱼类生殖过程中的作用是通过嗅觉系统来完成的,其中嗅觉感受神经元上的性信息素受体起着重要作用.鱼类性信息素受体的研究主要从两个方面入手,一是从低浓度特异的性信息素引起嗅觉器官电生理反应或行为反应入手,寻找特异的性信息素受体;二是参照哺乳动物嗅觉受体的研究结果,从嗅觉受体基因遗传保守性入手,研究鱼类性信息素受体的结构与功能.     

鳜嗅囊组织结构与早期发育北大核心CSCD

本研究采用组织切片和免疫组织化学方法以及扫描电镜和透射电镜观察并描述了鳜(Siniperca chuatsi)嗅囊组织结构特征和早期发育过程。结果显示,鳜具有2对鼻孔,前后鼻孔紧密相连,具有皮瓣。嗅囊位于嗅腔内,由16~20个初级嗅板构成,为G型嗅囊,初级嗅板通过褶皱产生次级嗅板。嗅板远端边缘为非感觉区,感觉区主要位于嗅板中端和近端。嗅上皮细胞可分为6类,即纤毛非感觉细胞、纤毛感觉细胞、微绒毛感觉细胞、支持细胞、基细胞和黏液细胞。从仔鱼到幼鱼阶段,1~7日龄仔鱼嗅基板较薄,表面有纤毛,10日龄嗅窝内陷并形成嗅腔,26日龄稚鱼形成第1对初级嗅板,55日龄幼鱼形成8对初级嗅板。55日龄前,鳜嗅囊发育较迟缓,初级嗅板侧向平行排列,尚未形成次级嗅板。     

鲻鱼嗅囊组织形态结构观察及功能探讨

实验用鱼为全长35.5~40.0 cm的野生鲻(Mugil cephalus),采用石蜡切片以及透射电镜技术对鲻的嗅囊以及嗅板细胞进行观察。结果表明:鲻的嗅觉器官由左右两个呈扁平椭球形嗅囊构成,分别由前后两个鼻孔与外界相通。嗅囊长径与眼径之比为0.80,长径与短径之比为2.09。嗅囊的嗅轴左右两边分别有垂直于嗅轴并向上倾斜排列整齐的18~25个披针形嗅板,只有初级嗅板未见次级嗅板。嗅板由中央髓和两侧的嗅上皮两部分构成,中央髓由疏松的结缔组织和毛细血管组成。嗅上皮又分为感觉区和非感觉区,感觉区位于嗅板的内侧,具有发达纤毛,呈连续分布状态,非感觉区位于嗅板边缘,细胞纤毛较少。通过光镜和电镜的综合研究结果显示嗅上皮细胞大致可分为5类:基细胞、支持细胞、纤毛非感觉细胞、纤毛感觉细胞和柱状细胞。文章讨论了鲻的感官活动类型。     

4种两栖爬行动物嗅器和犁鼻器的显微结构比较

用光镜观察了4种两栖爬行动物嗅器和犁鼻器的组织结构.结果显示,北方山溪鲵(Batrachuperus tibetanus)鼻囊内开始分化出犁鼻器,犁鼻器位于嗅器的腹外侧,但犁鼻器还不发达;隆肛蛙(Feirana quadranus)犁鼻器与嗅器虽然共同位于鼻囊内,但犁鼻器较为发达且其周围有发达的犁鼻腺,犁鼻器通过一细小管道与嗅器相通;秦岭蝮(Gloydius qinlingensis)和菜花烙铁头(Trimeresurus jerdonii)犁鼻腔与鼻腔已经完全分离形成两个独立的囊,而且鼻腔又进一步分化为嗅部与呼吸部.说明犁鼻器从有尾两栖动物开始出现,至无尾两栖类开始分化,到蛇类高度发达且成为一个独立器官.犁鼻器的形成是脊椎动物适应陆地生活的直接结果,是四足动物的特征之一.     

顶鼻康吉鳗嗅囊形态的光镜与扫描电镜观察

用光学显微镜和扫描电镜观察了5尾不同体长顶鼻康吉鳗标本嗅囊的形态结构。结果表明：顶鼻康吉鳗嗅囊近卵圆型;嗅囊长径与眼径的比值为1．3～1．6;单个嗅囊的嗅板数为82～122片;嗅板厚度约100μm;嗅板垂直对称地排列于嗅轴两侧,不同部位的嗅板大小和形状不一致;嗅板从嗅轴向两侧分出,至嗅囊腔顶部几乎相互接触;嗅板远离嗅轴端和向嗅囊腔一侧游离,其余部分与嗅囊膜相连;嗅板向嗅囊腔的游离缘分布有许多嗅孔;未观察到次级嗅板,但在嗅板的表面具有脊状隆起和凹陷;嗅板表面密被纤毛,包括非感觉纤毛、感觉纤毛和微绒毛,嗅板远离嗅轴的端部还观察到一种大型的杆状纤毛。嗅板表面存在大量纤毛表明,顶鼻康吉鳗嗅囊的水动力机制应属纤毛摆动型（isosmates）。     

多斑岭鳅嗅觉器官表面超微结构及其形态适应

多斑岭鳅(Oreonectes polystigmus)是营洞穴生活的鱼类,嗅觉器官在其生活中发挥了重要作用。本文对保藏于中国科学院动物研究所鱼类标本馆的4尾多斑岭鳅标本进行解剖,利用扫描电镜观察多斑岭鳅嗅囊上皮超微结构,以期了解嗅觉器官适应洞穴黑暗环境而产生的形态适应。多斑岭鳅的嗅囊呈椭圆型,嗅囊长径平均为2.27 mm,嗅囊长径与眼径比平均为1.36,揭示其为"嗅觉"鱼类。其嗅轴为直线型,嗅囊腔内对称紧密排列2排嗅板,嗅板数为22~24个。单个嗅板呈卜状亚型,舌状突起较发达。观察发现,非感觉纤毛连续广布在嗅板各个部位,但在嗅板近嗅轴处较少,此处裸露的表皮多褶皱,其上分布很多细微小孔。感觉纤毛主要分布于非感觉纤毛分布较稀疏的地方。上皮表面微绒毛多,一般在非感觉纤毛下,前后两端嗅板上的微绒毛数量相对较少。多斑岭鳅嗅囊水动力机制应属嗅上皮纤毛运动机制。嗅孔分布不均,中间嗅板上的嗅孔较嗅轴前、后分布的嗅板为多,同一嗅板上近嗅轴处的嗅孔最多。由于纤毛分布不均,嗅上皮可分为裸露区和非裸露区,一般裸露区和非裸露区边界清晰,嗅轴上非感觉纤毛和微绒毛主要分布在非裸露区的凹槽里。嗅轴和嗅板近嗅轴处裸露区面积较大,嗅轴裸露区上皮被一系列的连续的微脊切割成多边形,多边形内具有许多隆起与小孔。嗅轴处正是嗅囊中水流回流的区域,为感受水中气味的重要位置,推测与洞穴生活的习性有密切关系。多斑岭鳅嗅囊形态属于G型,这类鱼类其嗅觉功能在鱼类生命活动中发挥了重要作用。同近缘的地表种相比,多斑岭鳅具有较多的嗅板数目、较多数量感觉纤毛和微绒毛,且其嗅囊长径与眼球径比值大于1,这些都揭示了其为"嗅觉"鱼类,表现出了对洞穴黑暗环境的适应。     

谈谈动物的鼻和嗅觉

一提到嗅觉,人们自然会联想到这是鼻子的功能。不同动物的鼻子着生位置和形状亦有所不同。猴类的鼻子一般位于颜面部的前下方,与人鼻很相似;地下穴居动物如鼹鼠的鼻是口、鼻愈合呈一长圆筒状;水生动物鳄类、鲸类、鱼类的鼻,一般位于头顶或前上方,鳄类鼻部还有瓣膜,当身体没入水中时,就用瓣膜封闭鼻孔。长鼻猴和大象都有一个特别长而下垂的鼻;金丝猴的鼻小而朝天,故称“仰天鼻”;旧大陆猴的鼻孔间距离较窄,鼻孔向下长;鲫鱼的鼻是两个皱折囊形成有小孔……。鼻一般具有呼吸、防护、嗅觉等功能,然而鱼的鼻不与口腔相通,没有呼吸作用,只有十分灵…     

鱼类嗅觉器官的构造与功能

鱼类的嗅觉器官是其重要的化学感受器之一,由鼻孔、鼻腔和位于鼻腔内的嗅囊构成,鱼类嗅觉器官的进化与发展也经历了一个由低级到高级、由简单到复杂的过程。鱼类的嗅觉器官在鱼类的生活中,诸如摄食、御敌、生殖和集群等行为上发挥着重要的作用。     

从内鼻孔的发育和进化看四足类的起源

陆生脊椎动物头部具有两对鼻孔。一对外鼻孔,位于头部前背面,另一对是内鼻孔。内鼻孔作为脊椎动物由水上陆进化的关键结构之一,其发生和进化在近一个半世纪的时间内一直是科学家们争论的热点。内鼻孔是陆生脊椎动物的鼻囊与口腔之间的开口,是呼吸空气的必经之道,其开口位置在口腔上腭部,在前颌骨、上颌骨、锄骨和腭骨之间。Romer探讨了为     

秦岭蝮嗅觉系统和犁鼻系统的显微结构观察

用光镜观察了秦岭蝮Gloydius qinlingensis嗅觉系统和犁鼻系统的组织结构.结果显示秦岭蝮嗅觉系统主要包括嗅器和嗅球,犁鼻系统主要包括犁鼻器和副嗅球,并且嗅器和犁鼻器已经完全分离形成两个独立的囊,犁鼻器位于嗅器的内侧.嗅器粘膜上皮进一步分化为嗅上皮和呼吸上皮,背侧嗅上皮下的固有层内有丰富的Bowmans腺,腹侧呼吸上皮内有大量的杯状细胞,其固有层未见有Bowmans腺.鼻腔的中段出现了发达的犁鼻器,犁鼻上皮明显比嗅上皮厚,其固有层内未见有犁鼻腺,在犁鼻腔内还有蘑菇体.     

Anatomy,histology, and histochemistry of the olfactory organ of the Korean shuttles mudskipper Periophthalmus modestus

The Korean shuttles mudskipper Periophthalmus modestus has paired olfactory organs on its snout, consisting of anterior and posterior nostrils, a single olfactory canal with sensory and nonsensory epithelia, and a single accessory nasal sac. Its sensory epithelium consists of numerous islets forming a pseudostratified layer and contains various cells: olfactory receptor neurons, supporting cells, basal cells, lymphatic cells (LCs), and axon bundles. The sensory epithelium is a stratified squamous layer comprising stratified epithelial cells, mucous cells (MCs) with glycogen, flattened cells (FCs), LCs, and unidentified cells. Specific structures are as follows: (a) a tubular anterior nostril projecting outward, (b) a slit posterior nostril, (c) an elongated olfactory canal, (d) an ethmoidal accessory nasal sac, (e) axon bundles found only in the basal layer of the sensory epithelium, (f) FCs only at the top of the nonsensory epithelium, and (g) glycogen-containing MCs. Such structures seem to be unique in that they have not been observed in most teleost fishes spending their whole life in water.     

Thoracic pressure and nasal patency

Maximum nasal flow rate in the right and left nostrils was simultaneously determined during expiration with the help of two flowmeters in 10 healthy subjects in different postures and in two patients, one with Horner's syndrome and the other with facial palsy. It was found that pressure on the hemithorax from any surface (i.e., lateral, anterior, posterior, or superior) leads to reduced patency of the ipsilateral nostril but increased patency of the nostril on the opposite site. In the patient with Horner's syndrome, the nostril on the affected side remained blocked even on compression of the opposite hemithorax, and in the one with facial nerve palsy, the nostril on the affected side remained patent despite compression of the hemithorax on that side. The findings suggest that compression of hemithorax leads to changes in the congestion of the nasal mucosa that may be mediated through autonomic nerves.     

Sniffing longer rather than stronger to maintain olfactory detection threshold

Air flow-rate is usually higher in one nostril in comparison to the other. Also, within bounds, higher nasal flow-rate improves odorant detection. It follows from the above that odorant detection should be better in the nostril with higher flow-rate in comparison to the nostril with lower flow-rate. Paradoxically, previous research has shown that odorant detection thresholds are equal for the high and low flow-rate nostrils. Here we resolve this apparent paradox by showing that when detecting through the nostril with lower air flow-rate, humans sniffed longer than when detecting through the nostril with higher air flow-rate, thus equalizing performance between the nostrils. When this compensatory mechanism was blocked, a pronounced advantage in odorant detection was seen for the nostril with higher air flow-rate over the nostril with lower air flow-rate. Finally, we show that normal birhinal sniff duration may enable only one nostril to reach optimal threshold. This finding implies that during each sniff, each nostril conveys to the brain a slightly different image of the olfactory world. It remains to be shown how the brain combines these images into a single olfactory percept.     

Functional morphology of the nasal region of a hammerhead shark

We describe several novel morphological features in the nasal region of the hammerhead shark Sphyrna tudes. Unlike the open, rounded incurrent nostril of non-hammerhead shark species, the incurrent nostril of S. tudes is a thin keyhole-like aperture. We discovered a groove running anterior and parallel to the incurrent nostril. This groove, dubbed the minor nasal groove to distinguish it from the larger, previously described, (major) nasal groove, is common to all eight hammerhead species. Using life-sized plastic models generated at 200 μm resolution from an X-ray scan, we also investigated flow in the nasal region. Even modest oncoming flow speeds stimulate extensive, but not complete, circulation within the model olfactory chamber, with flow passing through the two main olfactory channels. Flow crossed from one channel to another via a gap in the olfactory array, sometimes guided by the interlamellar channels. Major and minor nasal grooves, as well as directing flow into the olfactory chamber, can, in conjunction with the nasal bridge separating incurrent and excurrent nostrils, limit flow passing into the olfactory chamber, possibly to protect the delicate nasal structures. This is the first simulation of internal flow within the olfactory chamber of a shark.     

HRP uptake by olfactory and vomeronasal receptor neurons: use as an indicator of incomplete lesions and relevance for non-volatile chemoreception

The transport of HRP (horseradish peroxidase) from the nasalcavity to the brain by intact olfactory receptor axons was usedto investigate the effectiveness of methods commonly used inbehavioral studies for deafferenting nasal chemoreceptor systems.The HRP experiments demonstrated that routine intranasal lavagewith zinc sulfate solution fails to destroy all olfactory receptorneurons in hamsters, in spite of the distinct behavioral deficitthat this treatment can cause in the male hamster. The intracranialdeafferentation of the accessory olfactory bulb by surgicalsection of the vomeronasal nerves was generally effective butthere was much incidental damage to main olfactory nerves thatwould probably not be detected without the HRP tracer. The distribution pattern of HRP molecules introduced into themammalian nasal cavity, as shown by the uptake of HRP by nasalchemoreceptors and its transport to the brain, was also usedto identify potential pathways for non-volatile stimulus moleculeswithin the nose. HRP reaction product was reliably detectedin the glomeruli of the main olfactory bulb after HRP was depositedat the nostril, demonstrating that nonvolatile materials, oncethey have entered the nasal cavity, can reach the main olfactoryreceptor neurons in the posterior nasal epithelium. Significantamounts of HRP reaction product were never observed in the accessoryolfactory bulbunlessa large dose of epinephrine had been givento activate the vomeronasal organ pumping mechanism, which drawssubstances into the vomeronasal organ lumen. Thus, it seemsthat stimulus access to vomeronasal receptor neurons is controlledindependently of access to main olfactory receptor neurons.     

A novel population of neuronal cells expressing the olfactory marker protein (OMP) in the anterior/dorsal region of the nasal cavity

The olfactory marker protein (OMP) is expressed in mature chemosensory neurons in the nasal neuroepithelium. Here, we report the identification of a novel population of OMP-expressing neurons located bilaterally in the anterior/dorsal region of each nasal cavity at the septum. These cells are clearly separated from the regio olfactoria, harboring the olfactory sensory neurons. During mouse development, the arrangement of the anterior OMP-cells undergoes considerable change. They appear at about stage E13 and are localized in the nasal epithelium during early stages; by epithelial budding, ganglion-shaped clusters are formed in the mesenchyme during the perinatal phase, and a filiform layer directly underneath the nasal epithelium is established in adults. The anterior OMP-cells extend long axonal processes which form bundles and project towards the brain. The data suggest that the newly discovered group of OMP-cells in the anterior region of the nasal cavity may serve a distinct sensory function.     

Olfactory organ of acipenseriformes and comparison with other actinopterygians: Patterns of diversity

The position and structure of the olfactory organ and its openings vary among actinopterygians. The anterior nasal opening is a simple perforation in the skin in many extant actinopterygians (e.g., acipenseriforms, lepisosteids, and primitive Recent teleosts) and represents the primitive condition. Polypterids and Amia each exhibit a derived condition, in which the anterior nasal opening extends into a tube. The olfactory organ is relatively far away from the anterior end of the elongate rostrum in acipenseriforms, whereas the olfactory organs are closer to the anterior end of the snout in extant actinopterygians (e.g., polypterids, lepisosteids, and amiids). In adults, olfactory organs are cuplike structures in most actinopterygians, but these organs are tubelike in polypterids. Among extant actinopterygians, a nasal diverticulum is present only in polypterids. Teleosts have accessory nasal sacs, but chondrosteans, polypterids, lepisosteids, and amiids lack them. The olfactory rosette is formed by primary folds or lamellae that may be placed anterior, lateral, posterior, and/or medial to the axis of the organ. Large acipenserids have 20–32 lamellae, polyodontids have 13–18 lamellae, lepisosteids have 8–10 lamellae, and Amia may have over 100. In teleosts, the number of lamellae varies from none or a few to over 200. Secondary lamellae are present in acipenseriforms, lepisosteids, and some advanced teleosts; secondary lamellae are interpreted as independently acquired in these lineages. Secondary lamellae are absent in Amia and primitive teleosts such as Elops and Hiodon. Tertiary lamellae are present in Acipenser oxyrhynchus. The arrangement of the primary lamellae in relation to the axis of the organ results in at least 11 patterns of the olfactory rosette in actinopterygians. Lamellae that are enclosed in a tubelike sac and that have an anteromedial diverticulum are specializations of polypterids. Primary lamellae anterior, lateral, and posterior to an elongate axis are characteristic of lepisosteids. The presence of primary lamellae lateral, medial, and posterior to an elongate olfactory axis is a synapomorphy of Halecomorpha (Amia plus teleosts). The absence of secondary lamellae is a synapomorphy of Halecomorpha. © 1994 Wiley-Liss, Inc.     

Numerical modeling of turbulent and laminar airflow and odorant transport during sniffing in the human and rat nose

Human sniffing behavior usually involves bouts of short, high flow rate inhalation (>300 ml/s through each nostril) with mostly turbulent airflow. This has often been characterized as a factor enabling higher amounts of odorant to deposit onto olfactory mucosa than for laminar airflow and thereby aid in olfactory detection. Using computational fluid dynamics human nasal cavity models, however, we found essentially no difference in predicted olfactory odorant flux (g/cm2 s) for turbulent versus laminar flow for total nasal flow rates between 300 and 1000 ml/s and for odorants of quite different mucosal solubility. This lack of difference was shown to be due to the much higher resistance to lateral odorant mass transport in the mucosal nasal airway wall than in the air phase. The simulation also revealed that the increase in airflow rate during sniffing can increase odorant uptake flux to the nasal/olfactory mucosa but lower the cumulative total uptake in the olfactory region when the inspired air/odorant volume was held fixed, which is consistent with the observation that sniff duration may be more important than sniff strength for optimizing olfactory detection. In contrast, in rats, sniffing involves high-frequency bouts of both inhalation and exhalation with laminar airflow. In rat nose odorant uptake simulations, it was observed that odorant deposition was highly dependent on solubility and correlated with the locations of different types of receptors.     

中华须鳗嗅觉器官形态学观察

利用光学显微镜和扫描电镜观察了10尾不同体长中华须鳗嗅觉器官的结构.结果表明:中华须鳗嗅囊呈楔型;嗅囊膜和嗅囊腹面的透明膜共同围成嗅囊腔;嗅囊长径与眼径的平均比值为2.2倍;每侧嗅囊嗅板数变化范围在30～44之间;嗅板远轴端有一纤毛和嗅孔密集的舌状游离突;嗅板上皮纤毛密集,纤毛细胞表现为3种类型:纤毛感觉细胞、纤毛非感觉细胞和微绒毛感觉细胞;纤毛非感觉细胞和微绒毛细胞也出现在嗅囊壁.嗅板上大量的纤毛表明,中华须鳗嗅囊的水动力机制应属嗅板纤毛搅动型(isosmates).除观察到嗅囊壁表面有两种类型的微嵴外,还首次在嗅板上观察到一种呈荸荠状的杆状细胞.