Surface morphology of taste buds in catfish barbels

Summary External taste buds abound on barbels of the adult catfish Corydoras arcuatus. When examined by scanning electron microscopy, they are visualized as a series of punctate, conical elevations projecting from the general surface epithelium. All taste buds were found to be of one type. Both their external and internal surface features could be clearly elucidated on intact barbels and in barbels fractured transversely at various positions along their length. An extensive nerve terminal network penetrates the base of each taste bud. Two populations of elongated cells bearing prominent microvilli project through the central pore at the tip of each bud. One set of microvilli is thicker, longer and more club-shaped than its counterpart. While both are randomly distributed within each central pore, the small, short microvilli appear to outnumber the larger ones. A third population of cells, devoid of any apical microvilli, was also seen in some of the taste buds examined internally. These cells do not project to the external surface and are interpreted as basal cells described in previous light and transmission electron microscope studies of taste buds in other vertebrate species. The functional significance of some of these morphological findings is discussed.Supported by grants from the Medical Research Council of Canada and the Muscular Dystrophy Association of CanadaThe excellent technical assistance of Mr. F.T. McConnell is gratefully acknowledged     

Fine structure of taste buds in the barbel of the catfish,Ictalurus punctatus

Summary Taste buds occur in the epithelium of the catfish barbel along its entire length. Two major cell types, light and dark cells, occupy the upper two-thirds of the taste bud. A third cell type, the basal cell, lies on the basal lamina and is essentially separated from the light and dark cells by a plexus of unmyelinated nerve fibers. The dark cells have branching processes, both apically and basally whereas the light cells have a single apical process and many basal processes. The apical processes of dark cells contain secretory granules, while the apical processes of light cells contain an abundant agranular endoplasmic reticulum. Light cell nuclei contain bundles of 10 nm filaments, often arranged in the shape of a cup or ring, but nucleoli are rarely seen. It is suggested that this morphology indicates a low degree of RNA synthesis by light cells. The basal cells contain large numbers of vesicles, about 60 nm in diameter, which are sometimes seen in clumps in relation to an adjacent nerve fiber in a configuration resembling a synapse. Curiously, although basal cells present a large surface to the basal lamina, there are no hemidesmosomes. This suggests that the basal cell does not originate from the epidermis.Supported by grant#NS-06181 from the National Institute of Neurological Diseases and Stroke, U.S. Public Health Service     

Changes in the cell population of taste buds during degeneration and regeneration of their sensory innervation

Summary Taste buds of rabbit foliate papillae were observed in control, after denervation and during reinnervation by the glossopharyngeal nerve. In control, taste bud cells could be divided into three groups according to their shapes and staining characteristics. Most of the cells were identified as either dark (corresponding to gustatory) or light (corresponding to supporting) cells. However, some cells were encountered which could not readily be placed in either group; they have been termed intermediate cells. Nine to twelve hours after axotomy, wandering cells were observed in many of the taste buds. Thereafter taste buds gradually decreased in size and disappeared, for the most part, by the 14th postoperative day. It was found that dark cells disappeared first, then at a later stage the light cells also disappeared. During reinnervation, dark cells were first to appear about 40 days after the operation and light cells were not seen till about 9 days later.From the observations, it is concluded that the dark cells of the taste bud differentiate from epithelial cells under the influence of nerves and mature into light cells through intermediate cells.     

Proteomics of buccal cavity mucus in female tilapia fish (Oreochromis spp.): a comparison between parental and non-parental fish

Mouthbrooding is an elaborate form of parental care displayed by many teleost species. While the direct benefits of mouthbrooding such as protection and transportation of offsprings are known, it is unclear if mouthbrooding offers additional benefits to embryos during incubation. In addition, mouthbrooding could incur negative costs on parental fish, due to limited feeding opportunities. Parental tilapia fish (Oreochromis spp.) display an elaborated form of parental care by incubating newly hatched embryos in oral buccal cavity until the complete adsorption of yolk sac. In order to understand the functional aspects of mouthbrooding, we undertake a proteomics approach to compare oral mucus sampled from mouthbrooders and non-mouthbrooders, respectively. Majority of the identified proteins have also been previously identified in other biological fluids or mucus-rich organs in different organisms. We also showed the upregulation of 22 proteins and down regulation of 3 proteins in mucus collected from mouthbrooders. Anterior gradient protein, hemoglobin beta-A chain and alpha-2 globin levels were lower in mouthbrooder samples. Mouthbrooder oral mucus collectively showed increase levels of proteins related to cytoskeletal properties, glycolytic pathway and mediation of oxidative stress. Overall the findings suggest cellular stress response, probably to support production of mucus during mouthbrooding phase.     

Herbivory in the tilapia Oreochromis niloticus: a comparison of feeding rates on phytoplankton and periphyton

A quantitative comparison of the grazing behaviour of young Oreochromis niloticus feeding on the planktonic cyanobacterium Microcystis aeruginosa and a periphytic community dominated by the cyanobacterium Oscillatoria sp., determined that biomass ingestion rates of fish filter-feeding on planktonic cyanobacteria were significantly lower than those surface-grazing on periphyton. Comparisons of published laboratory data on filter-feeding with field data on algal ingestion rates suggest that filter-feeding may be a relatively unimportant method of ingesting algae.     

Essence of keratin in lips and associated structures of a freshwater fish Puntius sophore in relation to its feeding ecology: Histochemistry and scanning electron microscope investigation

Morphological specializations in the lips and associated structures of Puntius sophore were examined by scanning electron microscopy and histochemically. The upper lip (UL), in P. sophore, is associated with the horny upper jaw sheath (HUJS) on its ventral side and with the rostral cap (RC) on its dorsal side through a thin and extensive fold of skin (FSUR). The lower lip (LL) is greatly enlarged, conspicuous and associated with horny lower jaw sheath (HLJS) on the dorsal side and ventrally continues with ventral head skin (VHS). On the lateral sides there is a thin and extensive fold of skin (FSLS) between the lower lip and VHS. In contrast to the mucogenic epithelia of the UL, LL, the RC and fold of skins, the horny jaw sheaths are keratinized in nature and surface epithelial cells are characteristically modified into unculi. The UL and the LL are equipped with epithelial cells (EC), mucous cells (MC) and taste buds (TB) while in addition to these cells club cells (CC) are also present in the RC. Keratin found in unculi is an extremely strong protein which is tough and insoluble, they form the hard but un-mineralized structures. Keratin in unculi could be regarded as an adaptation for browsing or scraping food materials from the substrate as the fish grubs about the bottom. The elaboration of mucus is considered to lubricate the surface and protect the epithelia from abrasions. Taste buds are associated to locate and select palatable food and to trigger a ‘pick-up’ reflex.     

Electron Microscopy and Spectroscopical Studies on the Coloured Patches on the Wing of a Butterfly,Graphium sarpedon (Lepidoptera: Papillionidae) With Reference to Their Photobiological and Electrical Properties

The surface ultra-structural features of the coloured patches on the wing of a butterfly Graphium sarpedon have been studied with the help of scanning electron microscopy. Comparisons have been made between the dark brown area and the light green patches of the wing. A diffraction grating pattern with 15 lines per μm² with a uniform spacing of about 1 μm is present in the light green patches. A slightly coarser grating is present on the dark brown area, which constitutes the major portion of the wing. Sensilla chaetica was found on both the light green and dark brown area. A special type of sensilla trichodea with a big socket and some elongated projections were localized only on the light green patches. This region of the wing also contains some spherical structures with a diameter of 0.5 to 0.6 μm. The infra-red spectroscopy has revealed some differences in the nature and position of the peaks in the low-energy region in the dark brown area and the light green patches. The atomic absorption spectroscopy also shows qualitative as well as quantitative differences in the inorganic set up of the two regions. The electron spin resonance spectroscopy reveals the presence of a peak in the dark brown region only, indicating the presence of free radical in it. The differences observed in the ultra-structural and spectroscopical features, and also in the inorganic components of the two regions, are discussed in relation to their physical and physiological properties.     

Optimal feeding strategy of the temperate herbivorous fish Aplodactylus punctatus: the effects of food availability on digestive and reproductive patterns

In this study we examined differences in feeding behevior of populations of the marine temperate herbivorous fish Aplodactylus punctatus, in three different localities off the Chilean coast, which differ qualitatively and quantitatively in food availability. We test whether food selection follows optimal foraging strategics, whether there is any modification of the fishes' digestive tracts in relation to their diets, and whether differences in diet quality affect the allocation of energy into reproduction and maintenance in these populations. Samples of this fish and of the understore algal assemblages were taken seasonally from May 1989 to February 1990. For each population we analyzed dietary composition, weight of the digestive tract and of the food content, the condition factor (K), and the gonadosomatic index (GSI). Our results showed that the diet observed in the three populations closely resembled the differences in macro-algal abundance and composition among the three localities studied. Local differences in diet quality were inversely related to the amount of food consumption and size of the digestive tract, suggesting that under differential conditions of food availability A. punctatus is able to compensate for variations in food quality through a flexibility in its digestive strategies. The nutritional status (K) of individuals, and their reproductive pattern (GSI) were directly related to diet quality. These results indicate that although A. punctatus is able to adjust its digestive processes to different algal food regimes, the digestive modifications observed in food-poor environments are not sufficient to compensate for the lack of food and allow fish to reach the nutritional status and reproductive output reached in a food-rich environment. This study represents the first natural experiment demonstrating a direct relationship among food availability, feeding patterns, digestive processes, and reproductive effort.     

The structure of the buccal cavity and pharynx in relation to the method of feeding of Reighardia sternae Diesing 1864 (Pentastomida)

The buccal complex of the haematophagous pentastomid Reighardia sternae has been described. It consists of a buccal capsule containing a prominent oral papilla communicating with a heavily chitinized pharynx which is crescentic in cross section. The chitinous skeleton of the buccal apparatus provides a framework for the attachment of various muscle systems, the contractions of which have been related to the mode of operation of the oral papilla and pharnyx during the feeding process. Particular emphasis was placed on the possible function of the oral papilla in the initial rupture of a blood capillary, and on the pumping action of the pharynx during the ingestion of the liberated blood.     

尼罗罗非鱼Orexin前体基因的克隆、组织分布及其在摄食调控中的表达

该文采用RT-PCR和cDNA末端快速扩增技术(rapid-amplification of cDNA ends,RACE)的方法,从尼罗罗非鱼(Oreochromis niloticus)下丘脑总RNA中获得了尼罗罗非鱼Orexin前体基因的cDNA全长序列。该cDNA全长648bp,其中开放阅读框的长423bp,编码Orexin前体蛋白为140个氨基酸,包括37个氨基酸的信号肽、43个氨基酸的Orexin-A、28个氨基酸的Orexin-B和末尾32个氨基酸组成的功能不详的多肽。采用Real-time PCR技术对尼罗罗非鱼Orexin前体基因的组织表达模式以及在摄食前后、饥饿和再投喂状态下的表达量变化进行了研究。结果显示,在脑部和外周等18个组织中都检测到了Orexin前体基因的表达,其中在下丘脑中表达量最高;在摄食前后,尼罗罗非鱼Orexin前体基因的表达量显著低于在摄食状态中;饥饿2、4、6和8d后,Orexin前体基因在下丘脑中的表达量与正常投喂组相比均显著升高,饥饿4d再投喂后,表达量又恢复至正常水平。这些结果表明,Orexin在尼罗罗非鱼摄食中可能有着重要的调节作用。     

Structures and movements of the buccal and pharyngeal jaws in relation to feeding in Diplodus sargus

The present paper studies the possibly different feeding strategies of Diplodus sargus to crustaceans, molluscs, worms, and small fish. The buccal jaws are built strongly and bound together by numerous ligaments. The dentition is heterodont: incisors in front and molars in the middle and hind parts. The principal originality of the musculature of this species is the forward insertion of the adductores mandibulae. These are very thick and insert on both the upper and lower jaws, so that contraction of any individual muscle acts on the buccal pieces as a whole, which thus constitute a remarkable crushing device. The pharyngeal jaws are frail as in primitive perciforms: the lower ones are well separated, being bound only anteriorly, while the upper ones consist of the second and third pharyngobranchials and a posterior toothed plate. When feeding on crabs, Diplodus sargus always sucks in the prey and seizes it with the buccal jaws. Mouth opening is accompanied by extensive protrusion of the mouth, with or without neurocranial elevation. Mouth sucking and seizing movements vary little. Once seized, the prey is usually moved to the molars and crushed. The crushing movements may be fast and ample or slow. In the latter case, deformation of the prey is observable. Crushing usually results in the crab being broken into pieces. The pharyngeal jaws grip one part of the prey and shift it to the oesophagus, then seize the second part. Diplodus sargus adapts its feeding behaviour to the type of prey. A snail, for instance, is crushed by the buccal or pharyngeal teeth, the pieces of shell are ejected, and the soft parts conveyed with difficulty to the oesophagus by the pharyngeal jaws. A fish on the other hand, is sucked tail first into the mouth cavity and quickly shifted to the digestive tract by the pharyngeal bones. Behaviour toward different prey differs by the presence or absence of parts of the sequence of feeding movements (for example crushing) or by the fact that certain movements or parts of the sequence are repeated. The variability of any movement in the sequence is the same whatever the sort of prey. Crushing occurs between the buccal incisors and molars and was observed twice between the pharyngeal teeth. Usually, it seems, the latter are involved in transport only. In transport, the left and right pharyngeal jaws may perform different functions: their movements, unlike the symmetrical movements of the buccal jaws, sometimes differ.     

Magnesium content within the skeletal architecture of the coral Montastraea faveolata: locations of brucite precipitation and implications to fine-scale data fluctuations

Small portions of coral cores were analyzed using a high-resolution laser ablation inductively coupled plasma mass spectrometer (LA ICP-MS) to determine the geochemical signatures within and among specific skeletal structures in the large framework coral, Montastraea faveolata. Vertical transects were sampled along three parallel skeletal structures: endothecal (septal flank), corallite wall, and exothecal (costal flank) areas. The results demonstrate that trace element levels varied among the three structures. Magnesium (Mg) varied among adjacent structures and was most abundant within the exothecal portion of the skeleton. Scanning electron microscopy (SEM) revealed the presence of hexagonal crystals forming thick discs, pairs or doublets of individual crystals, and rosettes in several samples. High Mg within these crystals was confirmed with energy dispersive spectroscopy (EDS), infrared spectrometry, and LA ICP-MS. The chemical composition is consistent with the mineral brucite [Mg(OH₂)]. These crystals are located exclusively in the exothecal area of the skeleton, are often associated with green endolithic algae, and are commonly associated with increased Mg levels found in the adjacent corallite walls. Although scattered throughout the exothecal, the brucite crystals are concentrated within green bands where levels of Mg increase substantially relative to other portions of the skeleton. The presence and locations of high-Mg crystals may explain the fine-scale fluctuations in Mg data researchers have been questioning for years.     

Chemosensory basis of feeding and oviposition behaviour in herbivorous insects: a glance at the periphery

Recent advances in our understanding of the relationship between chemosensory and behavioural responses to phytochemicals come from a number of studies on ovipositional and food selection behaviour of flies, butterflies, moths and beetles. Establishing input-output relationships has provided insight into the way in which the activity of chemoreceptors is translated into host-plant selection behaviour. This was achieved for both the qualitative contrast acceptance/rejection and for quantifiable preference hierarchies. By now it is clear that the subtlety of coding the complex phytochemical profiles offered by potential host plants relies on across-fibre patterns or ensemblefiring of taste neurons. Progress along these lines depends on unravelling processing pathways in the central nervous system, still a largely unexplored area in herbivorous insects. Increased interest can be noted for the mechanisms operating during the most peripheral events of chemoreception: the interaction of phytochemical and chemoreceptor, determining the specificity of recognition. Evidence for peripheral integration has accumulated. Deterrent receptors have an especially puzzling nature. Although such cells respond to a wide array of structurally diverse secondary plant metabolites, their sensitivity profile differs between closely related species. To what extent membrane-bound receptor molecules are involved and what degree of specificity is conferred by these, is largely unknown. Sensitivity to a certain group or class of compounds is determined by single genes in several cases. This allows for a scenario in which single gene mutations affect stimulus-receptor interactions, which might concurrently affect host-plant selection behaviour.     

Occurrence of the genus Ophicrania Kaup (Insecta: Phasmatodea) in Panay island (Philippines) and description of a new species

A distinctive new species of the phasmatodean genus Ophicrania Kaup, 1871 (Phasmatidae: Platycraninae) is described and figured from the Philippines. Ophicrania conlei n. sp. (from Mount Madja-as, on Panay island) is characterized by the bicoloured anal region of the male hind wing, divided into an inner whitish patch, and an outer brownish area. The species is also distinguished from its most similar congeners on the basis of integumental coloration, features of the antennae, thoracic nota, wings, legs, and terminalia. The present study also provides an emended diagnosis of Ophicrania, and an updated checklist of the taxa of Platycraninae recorded from the Philippine archipelago.     

Habitat distribution of the mallard in relation to vegetation structure,food, and population density

The mallard (Anas platyrhynchos Linnaeus) is a generalist feeder, breeding in a wide range of habitats, yet showing considerable between site differences in density. Variations in density and habitat use may result from inter- and intea-specific competition, habitat structure or food.We studied habitat selection of the mallard in four regions of Finland and Sweden. In each region, ten lakes were chosen ranging from oligotrophic to eutrophic. Habitat distribution of the mallard did not differ between regions despite variation in the density of the species and congenerics. Mallard density did not correlate with vegetation structure, but increased with food abundance and the number and density of congenerics although there were regional differences in mallard response.     

Responses to hypoxia of plaice,Pleuronectes platessa,and dab,Limanda limanda,in the south-east Kattegat: distribution and growth

Synopsis Plaice, Pleuronectes platessa, and dab, Limanda limanda, were sampled with a Glommen lobster trawl at 25 to 40 m depth in the SE Kattegat during spring and autumn of 1984 to 1990. During autumn, hypoxia (O₂-concentration < 3 mg I^–1) occurred in the bottom water below the halocline for four to ten weeks every year, except in 1984 when moderate hypoxia (O₂-concentration 3–5 mg 1^–1) occurred. Biomass of both species was shown to be negatively correlated with oxygen concentration during autumn. Further, a decrease in population mean total length was observed during the study period in both spring and autumn samples. Laboratory studies of growth of juvenile plaice and dab, at 15° C and 30–34%, showed that growth is reduced at 50 and 30% O₂-saturation for both species during a 20 d period. There was some adaptation to hypoxia resulting in less reduction of growth during the second half of the experiment. The frequency of fish eating was reduced in plaice at 30% O₂-saturation. Reduced mean total length of the plaice and dab population of the SE Kattegat is discussed in view of sublethal effects of oxygen deficiency.     

First data on rabbit dung as a water fertilizer in tropical fish culture and its effect on the growth of Oreochromis niloticus (Teleostei, Cichlidae)

The influence of rabbit dung on water quality, plankton occurrence and Nile tilapia growth (Oreochromis niloticus) was studied. pH and total alkalinity increased, dissolved oxygen concentration decreased but not below the critical level whilst the nitrogen parameters were not affected in a significant way. An important increase of plankton was recorded and was reflected in a decrease of transparency: the phytoplankton density was 2.7 times that of the controls. Tilapia growth rate in the manure treatments was 5.1 times that of the control group; no significant difference in survival rates was observed.