Mercuric chloride induced toxicity responses in the olfactory epithelium of Labeo rohita (HAMILTON): a light and electron microscopy study

Bioaccumulation of mercury and histomorphological changes in the olfactory epithelium of Labeo rohita were investigated after exposing the fish to two sublethal concentrations of HgCl₂ (66 and 132 μg/L) for 15 and 30 days. Mercury deposition increased in the tissue significantly (p < 0.05) with dose- and duration-dependent manner. Severe damage to the olfactory epithelium was evident. When fish exposed to 66 μg/L for 15 days, the histology of olfactory epithelium exhibited that mucous cell proliferation was upregulated and cell size was significantly increased from the control. Similar trends were found in 30 days exposure in both treated groups. Histology showed that mercury induced degeneration of columnar sensory cells, supporting cells and ciliated non-sensory cells and induced basal cell proliferation. Basal cell hyperplasia led to form intraepithelial proliferative lesion, thickening of epithelium, basal lamina disruption and cyst formation. Scanning electron microscopy revealed that mercury exposure at 66 μg/L caused clumping and loss of cilia, erosion in microridges on the supporting cells and proliferation of mucous cell opening. Complete degeneration of ciliated cells and cyst formation was observed in the fish when exposed to 132 μg/L HgCl₂. This result suggests that prolonged exposure to mercury might cause irreversible damage to the olfactory epithelium and impair the olfactory function of fish.     

褶纹冠蚌鳃的组织学和扫描电镜观察

利用光镜和扫描电镜研究了雌性褶纹冠蚌外瓣鳃的组织学和形态。结果表明，雌性褶纹冠蚌具一对外瓣鳃，每个外瓣鳃都由内，外二鳃小瓣构成，每片鳃小瓣又由许多纵行排列的鳃丝组成，鳃丝表面具前纤毛，前侧纤毛和侧纤毛，其壁主要由角质层，上皮和基膜组成，内含几丁质棒，鳃腺和血管。相邻鳃丝之间由丝间隔相连，鳃小瓣内的空腔被瓣间隔分隔成许多鳃水管。丝间隔和瓣间隔的壁主要由单层柱状上皮和基膜组成，其内均有血管分布，在繁殖期间瓣间隔形态发生变化，将鳃水管分隔成许多小室，形成胚胎发育的卵化室。     

Largemouth bass predators reduce growth,feeding and movement in juvenile channel catfish

Fine ML, Mayo MS, Newton SH, Sismour EN. Largemouth bass predators reduce growth, feeding and movement in juvenile channel catfish. Ecology of Freshwater Fish 2011: 20: 114–119. © 2010 John Wiley & Sons A/S Abstract – Animals utilise sensory cues to make decisions that will decrease their vulnerability to predation. With a well‐developed olfactory system and taste buds located inside the mouth and on the external body surface, catfishes are excellent subjects to investigate nonconsumptive predator effects. Juvenile channel catfish Ictalurus punctatus are often eaten by largemouth bass Micropterus salmoides, and we tested the hypothesis that largemouth bass fed catfish would adversely affect foraging and growth in channel catfish. Groups of catfish were placed in tanks partitioned by a mesh screen: experimental tanks had a largemouth bass on the other half of the tank, and control tanks had an empty chamber. Experimental catfish exhibited a long‐term decrease in spontaneous motion, feeding and growth. Feeding catfish to the bass caused the experimental catfish to freeze after a multi‐second latency suggesting transport of an alarm cue. Thus, there were long‐term effects from the continuous presence of the bass and additional short‐term cues from the bass consuming a catfish.     

CYP1A1 immunolocalization in the olfactory organ of rainbow trout and its possible induction by β-naphthoflavone: analysis in adults and embryos around hatching

Cytochrome P4501A1 (CYP1A1) isoform, which is known as being of major toxicological significance, has been well-studied in the mammalian olfactory mucosa. Only few studies have dealt with this biotransformation system in the fish olfactory organ which is particularly vulnerable to waterborne xenobiotics since sensory neurons are in direct contact with the aquatic environment. The present immunocytochemical study describes the cellular and subcellular distributions of CYP1A1 in the olfactory organ of rainbow trout in both adults and embryos around hatching. The enzyme inducibility in response to a 4-day exposure to waterborne -naphthoflavone (0.1 mg l^–1), a model inducer of CYP1A1, was also examined. In untreated adult fish, CYP1A1 was almost exclusively expressed in the nonsensory epithelium which covers the edges and the tip of the lamellae. Both goblet and ciliated nonsensory cells appeared immunoreactive. In -naphthoflavone-treated fish, in addition to a strong labeling in the nonsensory epithelium, ciliated nonsensory cells in the olfactory epithelium appeared well-labeled. Four days before hatching, only a few cells were weakly stained in the placodal epithelium of some embryos. By 7 days post-hatching, the enzyme expression was increased in the olfactory pit and it was restricted to ciliated nonsensory cells. No evident CYP1A1 induction was detected in either embryos or alevins. Results suggest the presence of a two-line CYP1A1 biotransformation system in the adult fish olfactory organ: a basal level of enzyme expression insured by the nonsensory epithelium and an additional line in which the sensory epithelium is activated in response to CYP1A1 inducers. This system might take place during development in parallel with the onset of the nonsensory epithelium.     

Biotransformation enzyme activities in the olfactory organ of rainbow trout (Oncorhynchus mykiss). Immunocytochemical localization of cytochrome P4501A1 and its induction by β-naphthoflavone

Olfaction is a crucial function in most fish species, but little is known about biotransformation enzymes in the olfactory organ. This study demonstrates that biotransformation enzymes usually found in the rainbow trout liver, are present in the olfactory organ as well. While microsomal cytochrome P450 reductase, p-nitrophenol hydroxylase and cytosolic glutathioneS-transferase presented similar levels in both the olfactory organ and the liver, microsomal 7-ethoxyresorufinO-deethylase (EROD), 7-ethoxycoumarinO-deethylase, and 7-pentoxyresorufinO-deethylase were much lower in the olfactory organ (77-, 35-, 200-times respectively). Furthermore, microsomes from the olfactory organ were able to perform testosterone hydroxylation only in the 16α-position while testosterone was hydroxylated in the 16β-position by liver microsomes. Using polyclonal antibodies raised against perch cytochrome P4501A1, the immunoreactive protein was shown to be strongly expressed in various cellular types forming the nonsensory epithelium. Some immunostaining was also reported in the nonsensory cellular elements constituting the sensory epithelium, while olfactory receptor cells failed to show cytochrome P4501A1-immunoreactivity. Finally, the exposure of rainbow trout to waterborne β-naphthoflavone (0.1 μg ml⁻¹) for 2 or 4 days resulted in a higher induction of EROD activity in the olfactory organ compared to the liver. The presence of biotransformation enzymes in the olfactory organ of rainbow trout addresses the question of their involvement in the detoxication/toxication of pollutants as well as in the olfactory function.     

扁玉螺鳃的形态学研究

用光镜和扫描电镜观察了扁玉螺鳃的组织学和表面结构,鳃叶上皮由５个区带的细胞组成,即前纤毛柱状细胞,立方细胞,侧纤毛柱状细胞,后纤毛柱状细胞及呼吸上皮。侧纤毛是产生呼吸水流的动力来源,呼吸上皮细胞表面凹凸不平,其组织学和表面结构有助于进行气体交换。     

中国蛤蜊鳃的光镜与扫描电镜观察

用光镜和扫描电镜观察了中国蛤蜊鳃的组织学和表面结构。所有鳃丝的组织结构均相同。鳃丝上皮按结构与功能可区分为4个区带：前纤毛柱状细胞区、侧纤毛柱状细胞区、粘液细胞区和扁平细胞区。前纤毛和侧纤毛分别与食物的运送和呼吸水流的产生有关。扁平细胞为呼吸上皮，其结构有助于气体交换。相邻鳃丝通过成排的、含有血管的丝间连接连系。     

Gyrodactylus salmonis infection impairs the olfactory system of rainbow trout

Monogenean worms are ectoparasites that are known to be infectious to a wide variety of fish. Few species of monogenean parasites have been reported in the olfactory chamber of fish in current peer‐reviewed literature. However, the impacts of these parasites on the olfactory system are not well understood. In this study, the effects of Gyrodactylus salmonis on the olfactory system structure and performance were investigated in rainbow trout (Oncorhynchus mykiss). The olfactory performance of the infected fish was examined using an electro‐olfactography (EOG) technique, while the ultrastructure of the olfactory rosette was studied using scanning electron microscopy (SEM) and light microscopy (LM). The infected rainbow trout displayed reduced responses to two standard olfactory cues (L‐alanine and TCA). The SEM micrographs revealed that many regions of the olfactory epithelium in the infected fish were heavily pitted and the LM examination of the olfactory epithelium showed local proliferation of mucous cells in the sensory regions as compared to the control group. The results of this study demonstrated that G. salmonis causes physical damage to the olfactory system of fish that lead to olfactory impairment.     

Morphology of the sense organs of anchovy Engraulis japonicus

ABSTRACT:   The morphology of the lateral line system, the inner ear, the olfactory epithelium and the taste bud of the wild adult anchovy Engraulis japonicus was examined by photo microscopy and scanning electron microscopy. Hematoxylin solution was injected into the lateral line canals to show the arrangement of the lateral line system. The lateral line system has well-developed supraorbital, infraorbital and preoperculomandibular canals on the head, dense canal branches on the operculum, lateral line canals on the trunk, and no free neuromasts. The inner ear comprises three semicircular canals and three otholithic end organs: the sacculus, the lagena and the utriculus. The olfactory organs and taste buds were examined by scanning electron microscopy. The paired olfactory organs on the snout have rosettes of lamellae, whose sensory epithelium consists of receptor cells of both the ciliated and microvillous type. The taste buds are distributed only inside the mouth, and mostly between the teeth of the upper and lower jaws, and between the gill teeth on the gill rakers. Well-developed lateral lines on the head are advantageous for schooling, and the taste buds in the mouth and on the gill rakers are advantageous for filter-feeding on plankton.     

大黄鱼消化道器官显微与亚显微结构

采用电镜和光镜技术研究大黄鱼消化道的组织结构。大黄鱼舌粘膜上皮为复层扁平上皮，其中含有杯状细胞和味蕾，舌腹面固有膜有浆液性腺泡；食道粘膜上皮为复层扁平上皮，表层扁平细胞下有粘液细胞。胃粘膜上皮为单层柱状，细胞游离端含有大量成熟粘液原颗粒，核周有不同成熟阶段的粘原颗粒，细胞器位于核周及下方，贲门和盲囊部胃小凹处有粘液腺，固有膜含大量胃腺，幽门部没有胃腺；胃腺细胞为矮锥形，细胞内含微管泡系和酶原颗粒，是一种典型的泌酸胃酶细胞。前肠、中肠和后肠粘膜上皮均为单层柱状上皮，其中有许多杯状细胞，肠上皮有密集的微绒毛，侧面有连接复合体，胞内各种细胞器均较丰富。大黄鱼消化道组织结构的特点与消化、吸收作用密切相关。     

Interactions between novel water,thyroxine and olfactory imprinting in underyearling coho salmon,Oncorhynchus kisutch (Walbaum)

Experimental evidence suggests that olfactory imprinting by salmon occurs during a sensitive period associated with surges in plasma thyroxine (T4) levels during smolting. Life-history studies, however, suggest that imprinting may occur prior to smolting. A possible resolution of this paradox may lie in the finding that exposure of coho salmon, Oncorhynchus kisutch (Walbaum) smolts to novel water sources induced transient increases in plasma T4 levels. If novel water-induced T4 surges occur prior to smolting and T4 surges are required for olfactory imprinting, juvenile salmon experiencing novel water sources as they move through their watershed may learn olfactory waypoints (e.g. stream confluences). To test this hypothesis, we exposed subyearling coho salmon, Oncorhynchus kisutch (Walbaum), to novel odours or water sources at distinct developmental stages. Subyearlings did not demonstrate dramatic increases in plasma T4 levels during smolting and exposure to novel water sources also had no effect on basal T4 levels. Previous studies have indicated that such coho smolts successfully imprint to similar exposure paradigms and home accurately. These results suggest that surges in plasma T4 levels during smolting may not be necessary for olfactory imprinting and accurate homing.     

Detection of thyroid hormone receptors in the olfactory system and brain of wild masu salmon,Oncorhynchus masou (Brevoort), during smolting by in vitro autoradiography

Thyroid hormone regulates a number of physiological functions during smolting in salmonids. However, the target sites and roles of thyroid hormone in the central nervous system (CNS) are not known in detail. We detected thyroid hormone-specific binding sites (i.e. thyroid hormone receptors) in the olfactory epithelium and the brain (the olfactory bulb, the telencephalon, the mid-brain and the cerebellum) of wild masu salmon, Oncor- hynchus masou (Brevoort), during smolting by means of in vitro autoradiography with frozen sections. A saturation experiment with the brain indicated the presence of a single class of binding sites of high affinity. T3-specific binding was detected in the olfactory epithelium and in all regions of the brain except the olfactory bulb. The T3-specific binding value in the olfactory epithelium was higher than in all other regions of the brain. This binding value in the olfactory epithelium increased at the full-smolt stage. The presence of thyroid hormone receptors in various regions of the CNS suggests that thyroid hormone plays an important role in the functional change in the brain and the olfactory epithelium during smolting.     

Evaluation of antibacterial activity and innate immune components in skin mucus of Indian major carp,Cirrhinus mrigala

The present work has been undertaken to analyse the antibacterial activity and innate immune components in the skin mucus of Indian major carp, Cirrhinus mrigala. Skin mucus was extracted separately in triple‐distilled water (TDW), 3% acetic acid (3% AA) or 0.1% trifluoroacetic acid (1% TFA). All mucus extracts exhibited different spectrum of the antibacterial activity against different groups of pathogenic bacteria. Protein profiling by polyacrylamide gel electrophoresis revealed a series of protein bands in the TDW extract, four major protein bands in the AA extract and two protein bands in the TFA extract. Tandem mass spectrometry analysis of distinct protein bands identified potential innate immune factors – histone H2A, histone H3, histone H4, haemoglobin, cofilin and nucleoside diphosphate kinase in the TDW extract, and ubiquitin and histone H2B isoforms in acidic extracts of skin mucus of C. mrigala. The presence of these innate immune molecules suggests that skin mucus play an important role in the protection of the fish against microbial invasion.     

Prevalence,intensity and pathology of the nasal parasite Nasicola hogansi in Atlantic bluefin tuna (Thunnus thynnus)

Ectoparasitic flatworms of Nasicola (Monogenoidea: Capsalidae), which infect nasal epithelium of true tunas (Thunnus spp.), are not well studied, nor have their impacts on the host's olfactory organ been evaluated. Infections of Nasicola hogansi on Atlantic bluefin tuna, Thunnus thynnus, were investigated with emphasis on the relationship between infection prevalence, abundance and mean intensity with bluefin tuna size, sex, body condition and capture month, as well as histopathological effects. Commercially caught Atlantic bluefin tuna (n = 161, 185–305 cm curved fork length) from the Gulf of Maine were sampled during June through August 2009 for infections by N. hogansi. A total of 247 specimens of N. hogansi were collected, with a prevalence of 45.3%, mean abundance of 1.57 (CI: 1.21–2.03) and mean intensity of 3.45 (CI: 2.91–4.22). Neither fish sex nor landing month had a significant effect on parasite parameters. Larger and better-conditioned Atlantic bluefin tuna had a higher mean intensity of infection. Pathology associated with infection by N. hogansi included extensive necrosis, sloughing of the nasal epithelium and associated inflammation of underlying connective tissues. Further epidemiological and pathological study of this host–parasite system is warranted since impaired olfaction, if present, could adversely affect spawning and migration of this top ocean predator.     

GnRH systems in masu salmon and barfin flounder

Multiple forms of the gonadotropin-releasing hormone (GnRH) exist in teleost fish. A salmonid fish, masu salmon Oncorhynchus masou has salmon GnRH (sGnRH) and chicken GnRH-II (cGnRH-II). sGnRH neurons were scattered from the olfactory nerve through the ventral telencephalon (VT) and the preoptic area (POA). sGnRH but not cGnRH-II was detected in the pituitary. sGnRH mRNA levels in the VT and the POA increased during gonadal maturation, suggesting that sGnRH neurons in these areas are involved in gonadal maturation. sGnRH neurons were first detected in a cluster near the olfactory epithelium 40 days after fertilization. sGnRH neurons were not detected in the brain by the olfactory epithelia lesion, suggesting that sGnRH neurons are derived from the olfactory epithelium. A pleuronectiform fish, barfin flounder Verasper moseri has sGnRH, cGnRH-II and seabream GnRH (sbGnRH). sGnRH and cGnRH-II-immunoreactive fibers were observed throughout the brain, but not in the pituitary. sbGnRH neurons were located in the POA and sent fibers to the pituitary, indicating that sbGnRH is involved in GTH secretion. Judging from the location of neuronal somata and their projections, it is indicated that three GnRH systems exist in the barfin flounder; the TN-, the MT- and the POA-GnRH system. However, in masu salmon, clear anatomical identification of the TN- and the POA-GnRH system is difficult, because the GnRH neurons located in the ventral forebrain are consecutive and the GnRH form produced in these neurons is the same (sGnRH). Thus, it is suggested in masu salmon that sGnRH neurons are derived from the olfactory epithelium, migrate into the brain and play different roles according to the location in the brain.     

斑马鱼端脑的微细形态与结构

为了深入了解斑马鱼端脑的微细形态和超微结构,采用光镜和电镜技术对斑马鱼端脑进行观察研究。斑马鱼端脑由左、右嗅球和左、右大脑半球构成。嗅球前方有一对嗅神经,后端伸出嗅茎与大脑半球联系。光镜下,嗅球组织结构从外向内依次为上皮层、神经纤维层、小细胞层和内部细胞层。大脑半球外部覆盖很薄的大脑皮,基部为纹状体,两者之间的腔隙为公共脑室。纹状体由神经核团和神经纤维构成。神经核团分布于纹状体周缘,主要有连前核、背嗅核、侧嗅核、视前核和脚内核等。神经纤维包括横行的前连合,纵行和斜行的中央嗅束和侧嗅束。电镜下,嗅球分层明显,可观察到僧帽细胞、神经胶质细胞和众多突触。大脑半球中可见神经胶质细胞、突触以及血脑屏障系统等。斑马鱼端脑形态结构与大多数硬骨鱼相似,但有个别核团存在差异。实验结果可为斑马鱼神经生物学模型的建立与应用提供有效的理论基础。     

Influence of native catfish mucus on Flavobacterium columnare growth and proteolytic activity

Flavobacterium columnare causes columnaris disease of farmed and wild freshwater fish. Skin mucus is an important factor in early stages of columnaris pathogenesis, albeit little studied. Our objectives were to (a) characterize the terminal glycosylation pattern (TGP) of catfish mucus, (b) determine the growth of F. columnare in formulated water (FW)‐containing channel catfish (Ictalurus punctatus) or hybrid catfish (Ictalurus punctatus X Ictalurus furcatus) mucus and (c) examine extracellular protease activity of two F. columnare isolates differing in virulence. The TGP of catfish mucus by lectin binding was as follows: alpha‐D‐mannose/alpha‐D‐glucose >N‐acetyl‐beta‐D‐glucosamine >N‐acetyl‐beta‐D‐glucosamine/N‐acetylneuraminic acid >N‐acetyl‐D‐galactosamine >alpha‐D‐galactose/N‐acetyl‐alpha‐D‐galactosamine >beta‐D‐galactose = alpha‐L‐fucose. Virulence studies demonstrated isolate AL‐02‐36 was highly virulent in channel catfish fry (0.1 g) with cumulative mortality of 90%‐100% versus 60% for isolate ALG‐00‐530 at equivalent doses (~3 × 10⁶ CFU/ml); a similar result was observed in larger (0.7 g) catfish. In multiple experiments, F. columnare replicated (2‐3 logs) and survived (28 days) in formulated water‐containing catfish mucus. Highly virulent isolate AL‐02‐36 possessed at least 2.5‐ to fivefold higher protease activity following growth in mucus than the less virulent ALG‐00‐530. Flavobacterium columnare utilized catfish mucus as a nutrient source and mucus presence modulated extracellular protease production.     

真鲷消化道的组织学和形态学研究

采用扫描电镜和光镜技术对真鲷的消化道进行了组织学和形态学研究。具发达颌齿的口咽腔之后，真鲷消化道由分化明显的食道、胃、小肠和直肠构成。口咽腔粘膜表面为复层上皮，其中含有怀状细胞和味蕾，表层细胞具微褶（脊）；食道粘膜也衬着复层上皮，由表层具微褶（脊）的扁平细胞、中层的怀状细胞及底部的基底细胞组成，食道粘部分区域 衬着单层柱状上皮；胃Ｖ形，粘膜表层为单层柱状上皮，贲门部和盲囊部上皮下有一厚层胃腺组织；     

Effects of urea on the molecules involved in the olfactory signal transduction: a preliminary study on Danio rerio

Among vertebrates, the physiologically uremic Chondrichthyes are the only class which are not presenting the ciliated olfactory receptor neurons in the olfactory neuroepithelium. The only sequenced genome for this class revealed only three olfactory receptor genes and the immunohistochemical detection of G protein alpha subunit typically coupled to the olfactory receptors (Gα_olf) failed in different species. Chronic renal disease can represent a cause of olfactory impairment in human. In this context, our present study focused on investigating potential effects of high urea concentration on the olfactory epithelium of vertebrates. Larvae of the teleost fish Danio rerio were exposed to urea in order to assess the effects on the olfactory signal transduction; in particular on both the olfactory receptors and the Gα_olf. The endocytosis of neutral red dye in the olfactory mucosa was detected in control and urea-exposed larvae. The amount of neutral red dye uptake was used as a marker of binding and internalization of the Gα_olf. The neutral red dye endocytosis was not affected by urea exposure, hence suggesting that the presence of the Gα_olf and their binding to the odorants are not affected by urea treatment, either. The presence and distribution of Gα_olf were investigated in the olfactory epithelium of control and urea-exposed larvae, using a commercial antibody. The immunoreactivity was increased after urea treatment, suggesting an effect of urea on the expression or degradation of this G protein alpha subunit.