The mechanism of olfactory organ ventilation in Periophthalmus barbarus (Gobiidae, Oxudercinae)

Periophthalmus barbarus Linnaeus, 1766 has many adaptations for amphibious life as a consequence of tidal zone occupation. One of them is the ability to keep a little amount of water and air in mouth while on land or in hypoxic water, correlated with closing a gill lid for gas exchange improvement. It causes that mechanisms of olfactory organ ventilation described in other species of actinopterygians (compression of accessory nasal sac(s) by the skull and jaw elements while mouth and gill lid moving) are not in operation. There is a specific mechanism of olfactory organ ventilation independent on jaw and skull elements movements. Compression of accessory nasal sacs is possible by a0 contraction and it is a movement effect on bones combined by ligaments. This process can be observed on P. barbarus as lifting the rostral part of the head.     

Periophthalmus spilotus, a new species of mudskipper from Sumatra (Gobiidae: Oxudercinae)

A new species of mudskipper,Periophthalmus spilotus, is described on the basis of 16 specimens from Sumatra, Indonesia. It differs from other species ofPeriophthalmus by the following combination of characters: pelvic fins totally united into rounded disk; first dorsal fin high, greyish, no spots on fin nor elongate spines; second dorsal fin typically with 14 total elements; anal fin typically with either 14 or 15 total elements; length of anal-fin base 21.8–29.0% SL; and length of second dorsal-fin base 22.5–26.7% SL. This species is most similar to, and probably most closely related to,P. chrysospilos.     

Development of the olfactory organ in the rainbow fish Nematocentris maccullochi (Atheriniformes,Melanotaeniidae)

Summary The development of the olfactory organ in the rainbow fish, Nematocentris maccullochi, was studied using scanning and transmission electron microscopy; it was compared with the developmental process in other teleosts, especially in the closely related atherinids and cyprinodonts. The formation of the nares parallels that in atherinids, salmonids, cyprinids and heterosomats, but differs from that found in cyprinodonts. Another ontogenetic feature in which the olfactory organs of the rainbow fish and also of atherinids differ from those of cyprinodonts, is the occurrence of transitory kinociliary cells which disappear during the postlarval period. The divergent evolutionary pathways are discussed with reference to experimental investigations. During development, ciliated and microvillous receptor cell types occur. At the primary larval stage ciliated receptor neurons are exclusively present. At a later stage the microvillous type develops and becomes equal in frequency. Thus, the microvillous receptor represents a separate type of olfactory neuron and is not a progenitor of the ciliated receptor cell.This work was supported by the Deutsche ForschungsgemeinschaftThe authors would like to acknowledge Prof. G. Hartmann (Hamburg) and Prof. V. Storch (Kiel) for use of the SEM, Prof. K. Seifert (Neumünster) for valuable discussion. For skillful technical assistance we are indebted to Miss C. Heim, Mrs. K. Hoffmann, and Mr. H.P. Dreyer     

Firing properties of accessory olfactory bulb mitral/tufted cells in response to urine delivered to the vomeronasal organ of gray short-tailed opossums

In comparison with many mammals, there is limited knowledge of the role of pheromones in conspecific communication in the gray short-tailed opossum. Here we report that mitral/tufted (M/T) cells of the accessory olfactory bulb (AOB) of male opossums responded to female urine but not to male urine with two distinct patterns: excitation followed by inhibition or inhibition. Either pattern could be mimicked by application of guanosine 5'-O-3-thiotriphosphate and blocked by guanosine 5'-O-2-thiodiphosphate, indicating that the response of neurons in this pathway is through a G-protein-coupled receptor mechanism. In addition, the inhibitor of phospholipase C (PLC), U73122, significantly blocked urine-induced responses. Male and female urine were ineffective as stimuli for M/T cells in the AOB of female opossums. These results indicate that urine of diestrous females contains a pheromone that directly stimulates vomeronasal neurons through activation of PLC by G-protein-coupled receptor mechanisms and that the response to urine is sexually dimorphic.     

A seminal study of the dynamics of a mudskipper (Periophthalmus papilio) population in the Cross River,Nigeria

A seminal study was conducted in which the population dynamics (growth, mortality and recruitment) of the mudskipper (Periophthalmus papilio) in the Cross River, Nigeria, was elucidated for the first time using length frequency data and the ELEFAN software. The allometric relationship was: Weight=0.012(Length)^2.940, n=415, r²=0.939, P <0.0005. The seasonalized Von Bertalanffy growth parameters were L=19.39 cm, K=0.51 y^–1, C=0.3, and WP=0.4. The instantaneous total mortality coefficient Z was 2.208 y^–1 while the instantaneous natural mortality coefficient was 1.341 y^–1. The instantaneous fishing mortality coefficient of 0.867 y^–1 yielded the expectedly low exploitation rate E of 0.393. Our estimate shows that the species could reach an average maximum life span of about 6 years in the Cross River system. These results are used in quantitative elucidation of the state of exploitation of the population and will serve as input for the proper and scientific management of the fish resource.Alfred Wegener Institute Contribution nr. 1090.     

Topographical relation between the olfactory bulb and the olfactory tract in tench (Tinca tinca L)

Electrical activity was recorded from single cells in the olfactorybulb when electrically stimulating the medial and lateral olfactorytract and when stimulating the olfactory epithelium with aminoacids. Bulbar units excited by stimulation of the medial olfactorytract were found in the medial and middle parts of the bulb.Neurones in the dorso-lateral part of the bulb were excitedby stimulation of lateral tract. Units inhibited by stimulationof the lateral or medial olfactory tracts had a reversed distributionwith the majority found in the medial or lateral parts of thebulb respectively. The chemicals tested induced changes in thedischarge of units mainly situated in the lateral part of thebulb.     

Fine structure of the pineal organ in the troglobytic fish,Typhlichthyes subterraneous (Pisces: Amblyopsidae)

Summary The pineal organ of the blind, cave-dwelling fish, Typhlichthyes subterraneous, was examined with both light and electron microscopes. Like the eyes, the pineal in this troglobytic species was found to be regressed. Two cell types, photoreceptor and supportive cells, were described in the pineal epithelium. Although ganglion cells were not identified, small, unmyelinated nerve fibers were present. The photoreceptor cells had degenerated outer segments. Accordingly, it was suggested that the pineal in this species is not likely to function in photoreception. However, the presence of well developed Golgi bodies, clear and dense-cored vesicles, variable amounts of rough endoplasmic reticulum and glycogen particles indicated that both cell types are metabolically active and may play a role in secretion.     

Ontogeny of the electric organ discharge and the electric organ in the weakly electric pulse fish Brachyhypopomus pinnicaudatus (Hypopomidae, Gymnotiformes)

I recorded the electric organ discharges (EODs) of 331 immature Brachyhypopomus pinnicaudatus 6–88 mm long. Larvae produced head-positive pulses 1.3 ms long at 7 mm (6 days) and added a second, small head-negative phase at 12 mm. Both phases shortened duration and increased amplitude during growth. Relative to the whole EOD, the negative phase increased duration until 22 mm and amplitude until 37 mm. Fish above 37 mm produced a “symmetric” EOD like that of adult females. I stained cleared fish with Sudan black, or fluorescently labeled serial sections with anti-desmin (electric organ) or anti-myosin (muscle). From day 6 onward, a single electric organ was found at the ventral margin of the hypaxial muscle. Electrocytes were initially cylindrical, overlapping, and stalk-less, but later shortened along the rostrocaudal axis, separated into rows, and formed caudal stalks. This differentiation started in the posterior electric organ in 12-mm fish and was complete in the anterior region of fish with “symmetric” EODs. The lack of a distinct “larval” electric organ in this pulse-type species weakens the hypothesis that all gymnotiforms develop both a temporary (larval) and a permanent (adult) electric organ. Accepted: 1 March 1997     

The septal organ of the rat during postnatal development

The septal organ of Masera (SO) is a small, isolated patch of olfactory epithelium, located in the ventral part of the nasal septum. We investigated in this systematic study the postnatal development of the SO in histological sections of rats at various ages from the day of birth (P1) to P666. The SO-area increases to a maximum at P66-P105, just as the animals reach sexual maturity, and decreases thereafter, significantly however only in males, indicating a limited neurogenetic capacity for regeneration. In contrast, the main olfactory epithelium area continues to expand beyond P300. The modified respiratory epithelium ('zwischen epithelium') separating the SO and the main olfactory epithelium contains a few olfactory neurons up to age P66. Its length increases postnatally so that the SO becomes more ventral to the OE. Although the position of the SO relative to other anatomical landmarks changes with development it is consistently located just posterior to the opening of the nasopalatine duct (NPAL). Thus, a possible function of the SO is in sensing chemicals in fluids entering the mouth by licking and then delivered to the nasal cavity via the NPAL; therefore the SO may be involved in social/sexual behavior as is the vomeronasal organ (VNO). We suggest that the SO is a separate accessory olfactory organ with properties somewhat different from both OE and VNO and may exist only in species where the NPAL does not open into the VNO.     

Histological Architecture of the Nasal Region in Rana chensinensis

The nasal region of Rana chensinensis is divided into the nasal capsules and nasal cavities. In this study, we investigated the adult histological structure of the nasal capsules and nasal cavities in the frog R. chensinensis under the microscope. We found that an eminentia olfactoria is present in this frog and the presence of the eminentia olfactoria may be connected to a terrestrial life style. The double staining method using alcian blue and alizarin red showed that the septomaxilla, the most important bone associated with the olfactory capsules, is an intramembranous bone in R. chensinensis. The opening of the nasolacrimal duct showed a close proximity to the apertura nasalis externa. The presence of the nasolacrimal duct in the olfactory region may be an adaptation to a terrestrial environment. The function of the vomeronasal and olfactory organs is discussed in the paper.     

棕色田鼠与沼泽田鼠犁鼻器和副嗅球的组织结构

用组织学方法研究了棕色田鼠(Microtus mandarinus)、沼泽田鼠(M．fastis)副嗅球和犁鼻器的结构及其在两种鼠间的差异，以此探讨两种田鼠的进化机制与适应功能。两种田鼠的犁鼻器位于鼻腔前端鼻中隔基部的两侧，呈管状结构；沿着犁鼻器的长轴犁鼻管呈现不同的形态学特征，犁鼻管直接开口于鼻腔，从前向后沿着长轴旋转，中间管壁(犁鼻粘膜)变成底部，侧面管壁(假覆层上皮)变成犁鼻管顶壁，最终犁鼻管变小成为一个腺体的分支，不同部位具有不同的组织学特征。通过选取中间相似部位对两种田鼠进行比较研究，发现棕色田鼠犁鼻粘膜比沼泽田鼠厚，而其长度却短于沼泽田鼠。棕色田鼠副嗅球颗粒细胞带宽和僧帽细胞带宽均大于沼泽田鼠，而带长却小于沼泽田鼠。相关分析发现，犁鼻器和副嗅球形态有一定的对应关系，这可能和两个结构之间存在着神经投射有关。棕色田鼠幼体的犁鼻粘膜、神经细胞核、假覆层上皮、血管面积均小于成体[动物学报49(2)：248—255，2003]。     

Asterropteryx atripes, a new gobiid fish from the Western Pacific Ocean (Perciformes: Gobioidei)

 A new gobiid fish, Asterropteryx atripes, is described on the basis of eight specimens from Iriomote-jima Island, Ryukyu Islands, and El Nido, Philippines. It differs from its congeners by having the following combination of characters: 3rd spine of first dorsal fin long, filamentous, distal tip usually over end of 2nd dorsal fin base when appressed in both sexes; pelvic fins almost separated, innermost (=5th) segmented rays connected by rudimentary low membrane between bases, and no frenum; 4–7 short spines on posterior margin of preopercle (the uppermost spine usually just behind the cephalic sensory canal pore N); eye large, 32.3–35.8% of head length; enlarged haemal arches on 1st two caudal vertebrae; a distinct black band from posterior margin of eye to caudal fin base (indistinct in dark-phase individuals); black pelvic fin (vivid in dark-phase individuals); numerous minute bright blue spots on head and body in life; no distinct dark spots on head and body; iris entirely reddish-brown or dusky (bright white ventrally in pale-phase individuals) when alive or fresh, and entirely black in preservation, without white transverse bar on middorsal surface; hovering habit. The new species appears to be most closely related with the other only known hovering species, A. striata; the latter is readily distinguished from the former in having no long, filamentous dorsal spine; semitranslucent pelvic fin; and a series of small black spots along dorsal fin base and dorsal edge of caudal peduncle. Asterropteryx contains two distinct groups, and the monophyly of the genus is open to question. Received: March 19, 2000 / Revised: February 25, 2002 / Accepted: April 25, 2002     

Deviant anatomy of the olfactory system of the Malagasy frog Mantidactylus betsileanus (Anura: Mantellidae)

Frogs of the family Mantellidae are endemic to Madagascar and the Comoran island of Mayotte. Like many other animals in this biogeographical region, they have passed through millions of years of isolated evolution which led to ecological, physiological and anatomical specialization. The present study compares the intranasal anatomy of a mantellid, the Malagasy Common Marsh Frog (Mantidactylus betsileanus Boulenger, 1882) with that of the Malaysian Green Flying Frog (Rhacophorus reinwardtii Schlegel, 1840), a representative of the sister group of mantellids (the family Rhacophoridae). Histological examination revealed that the structure of the nasal cavities of M. betsileanus strongly deviates from the usual nasal morphology of anurans. In the typical condition, to which also R. reinwardtii conforms, the two parts of the nasal cavity (main chamber and accessory chambers), containing two different chemosensory systems (main olfactory organ and vomeronasal organ respectively), are connected by a slit-like longitudinal opening. In M. betsileanus, this elongated opening is almost completely reduced. Therefore, main chamber and accessory nasal chambers are markedly separated anatomically, leading to an enhanced spatial segregation of the two different organs of smell. Whether these anatomical alterations correspond to a more significant role of vomeronasal perception and might be related to the presence of characteristic pheromone-producing femoral glands in mantellid frogs requires further study.     

Salmonid olfactory system-specific protein (N24) exhibits glutathione S-transferase class pi-like structure

A salmonid olfactory system-specific protein (N24) that has been identified in lacustrine sockeye salmon (Oncorhynchus nerka) was characterized by biochemical and molecular biological techniques. N24 is a homodimer, and the intact molecular mass is estimated as approximately 43.3 kDa by gel filtration. Furthermore, N24 was located only in the cytosolic fraction of the olfactory tissues as determined by subcellular fractionation. cDNA encoding the lacustrine sockeye salmon N24 was isolated and sequenced. This cDNA contained a coding region encoding 216 amino acid residues and the molecular mass of this protein is calculated to be 242,224.77. The protein and nucleotide sequencing demonstrates the existence of a remarkable homology between N24 and glutathione S-transferase (GST; EC 2.5.1.18) class pi enzymes. Northern analysis showed that N24 mRNA with a length of 950 bases is expressed in lacustrine sockeye salmon olfactory epithelium. Olfactory receptor cells showed strong hybridization signals for N24 mRNA in the olfactory epithelium. N24 demonstrated glutathione binding activity in affinity-purified GST column experiments. The present study describes for the first time cDNA cloning of GST in fish olfactory epithelium.     

Morphology and structural organization of Gene''s organ in Argas walkerae

Electron microscopy revealed that Gene's organ in females of Argas walkerae Kaiser & Hoogstraal (Ixodida: Argasidae) is formed as a double-sac structure consisting of an outer epithelial and an inner cuticular sac. The latter emerges through the camerostomal aperture to the exterior in ovipositing ticks. The epithelial sac forms the corpus and the two blind-ending horns, which pass into the epithelium of the excretory duct of a gland at each side of Gene's organ and envelop the cuticular sac. Both excretory ducts open into the lumen between the epithelial and the cuticular sac. The cuticular sac is folded and consists of a fibrous endocuticula outwards towards the lumen between the epithelial and the cuticular sac and of a smooth epicuticula inwards. Parallel running grooves occur over the lateral epicuticular surface turning medially into cobble-stone pavement-like rises. Tubuli pass through the cuticular sac ending in pores on the epicuticular surface and open into the lumen between the epithelial and the cuticular sac. Muscle fibres pass through the epithelial sac at the horn tips and are inserted to the cuticular sac. In ovipositing females, the glands are fully developed and the lumen between the epithelial and the cuticular sac is filled with an amorphous mass.     

Organization of the olfactory system of the Indian major carp <Emphasis Type="Italic">Labeo rohita</Emphasis> (Ham.): A scanning and transmission electron microscopy study

Catla catla, Labeo rohita, and Cirrhinus mrigala represent important alimentary fish in India. Their reproduction/breeding depends on seasons. Fish perceive external factors-stimuli and chemical signals through the olfactory system that plays the key role in central regulation of reproduction. However, no electron microscopy data are available on organization of olfactory components of these fish. We studied organization of the olfactory organ in male L. rohita using scanning (SEM) and transmission electron microscopy (TEM). This organ consists of olfactory epithelium, a short nerve, and olfactory bulb. The olfactory organ is ovoid in shape and consists of about 47–52 lamellae in adults and about 14–20 lamellae in fingerlings. These lamellae originate from the midline raphe. By SEM, microvillar sensory and ciliated non-sensory cells were observed in the lamellae. TEM revealed microvillar receptor cell with rough endoplasmic reticulum and Golgi apparatus towards apical end. Basal cells were present at the base of receptor cell, supporting cells were located adjacent to the olfactory receptor neurons, while epithelial cells—in the nonsensory part of olfactory epithelium. Mast, blastema, and macrophage cells were also found at the basement membrane. This work is the first publication on ultrastructural organization of the olfactory system of the Indian major carp, which provides information about morphological and ultrastructural organization of the olfactory system and opens new avenues for further investigation of chemical neuroanatomy, sensory signal processing, and neural regulation of reproduction in the Indian major carp.     

The crystal structure of the olfactory marker protein at 2.3 A resolution

Olfactory marker protein (OMP) is a highly expressed and phylogenetically conserved cytoplasmic protein of unknown function found almost exclusively in mature olfactory sensory neurons. Electrophysiological studies of olfactory epithelia in OMP knock-out mice show strongly retarded recovery following odorant stimulation leading to an impaired response to pulsed odor stimulation. Although these studies show that OMP is a modulator of the olfactory signal-transduction cascade, its biochemical role is not established. In order to facilitate further studies on the molecular function of OMP, its crystal structure has been determined at 2.3 A resolution using multiwavelength anomalous diffraction experiments on selenium-labeled protein. OMP is observed to form a modified beta-clamshell structure with eight antiparallel beta-strands. While OMP has no significant sequence homology to proteins of known structure, it has a similar fold to a domain found in a variety of existing structures, including in a large family of viral capsid proteins. The surface of OMP is mostly convex and lacking obvious small molecule binding sites, suggesting that it is more likely to be involved in modulating protein-protein interaction than in interacting with small molecule ligands. Three highly conserved regions have been identified as leading candidates for protein-protein interaction sites in OMP. One of these sites represents a loop known to mediate ligand interactions in the structurally homologous EphB2 receptor ligand-binding domain. This site is partially buried in the crystal structure but fully exposed in the NMR solution structure of OMP due to a change in the orientation of an alpha-helix that projects outward from the structurally invariant beta-clamshell core. Gating of this conformational change by molecular interactions in the signal-transduction cascade could be used to control access to OMP's equivalent of the EphB2 ligand-interaction loop, thereby allowing OMP to function as a molecular switch.