Food composition of Clarias gariepinus (= C. lazera) (Cypriniformes,Clariidae) in Lake Kinneret (Israel)

The feeding behaviour of the freshwater piscivore, Clarias gariepinus (C. lazera) (C & V 1840) was studied over two periods: 1973–1975 and 1981–1982, in Lake Kinneret (Israel). The total number of fish analysed was 264 and their sizes (SL) and weights varied between 238 and 830 mm (146 to 5728 g). More than fifty species of plants and animals from the plankton, benthos and nekton of Lake Kinneret were identified in the intestines of C. gariepinus. Preyed fish were the most abundant food component (81%) and constituted the highest biomass, with Mirogrex terraesanctae representing the majority (although other species were also found). The potential impact of piscivory in the Kinneret ecosystem is considered.     

Directional fixation of mutations in vertebrate evolution

Summary We have made pairwise comparisons between the coding sequences of 21 genes from coldblooded vertebrates and 41 homologous sequences from warm-blooded vertebrates. In the case of 12 genes, GC levels were higher, especially in third codon positions, in warm-blooded vertebrates compared to cold-blooded vertebrates. Six genes showed no remarkable difference in GC level and three showed a lower level. In the first case, higher GC levels appear to be due to a directional fixation of mutations, presumably under the influence of body temperature (see Bernardi and Bernardi 1986b). These GC-richer genes of warm-blooded vertebrates were located, in all cases studied, in isochores higher in GC than those comprising the homologous genes of cold-blooded vertebrates. In the third case, increases appear to be due to a limited formation of GC-rich isochores which took place in some cold-blooded vertebrates after the divergence of warm-blooded vertebrates. The directional changes in the GC content of coding sequences and the evolutionary conservation of both increased and unchanged GC levels are in keeping with the existence of compositional constraints on the genome.     

Short and plump physique of Mexican-American children

Mexican-American children are shorter but relatively heavier than non-Hispanic whites and blacks. The objectives of this paper are to assess the extent to which this "short and plump" physique occurs in data collected in two national surveys (HANES I and II); to determine variations by age, sex, and socioeconomic status; and to investigate the anthropometric characteristics that may account for the overweight. Three groups, defined on the basis of reported ancestry and observed race, are studied: Mexican-Americans (MEXAME), non-Hispanic Whites, (EURAME), and blacks (BLACK). Short stature was clearly associated with the poverty index (PI) in all three groups. MEXAMEs with a PI greater than 1.6 were similar in stature to EURAMEs at the same income level at ages 1-11 years but not at 12-17 years. On the other hand, MEXAMEs were shorter than BLACKs at all ages and income levels. The body mass index (kg/cm2) and poverty were unrelated. With respect to the anthropometric characteristics examined that are related to the body mass index, MEXAMEs and EURAMEs were similar in sitting height as a proportion of total height, arm muscle and fat areas, and triceps skinfold but different in the following ways: MEXAMEs had narrower elbow but broader bitrochanteric breadths and larger chest circumferences and subscapular skinfolds. Greater upper body dimensions and fatfolds seem to best describe the physique of MEXAMEs. However, in multiple regressions, these anthropometric characteristics failed to account fully for the greater relative weight of MEXAMEs as compared to EURAMEs.     

Freeze-fracture study of the lateral-line canal organ of the Japanese sea eel,Lincozymba nystromi

Summary Specializations of apical surfaces of hair cells, supporting cells and marginal cells in the lateral-line canal organ of Japanese sea eel, Lincozymba nystromi, were examined with a freeze-fracture technique. Apical surfaces of hair cells have a lower density of intramembrane particles (IMP) than those of the surrounding supporting cells. Density of IMP on the streocilia is almost the same as that on the apical surface of hair cells. Junctions between hair and supporting cells were tighter than those between two supporting cells; those between supporting and marginal cells were tighter than those between hair and supporting cells, and those between two marginal cells were the tightest in the lateral-line canal organ.     

Immunocytochemical and electron-microscopic investigations of the pineal organ in adult agamid lizards,Uromastix hardwicki

Summary Lacertilian species display a remarkable diversity in the organization of the neural apparatus of their pineal organ (epiphysis cerebri). The occurrence of immunoreactive S-antigen and opsin was investigated in the retina and pineal organ of adult lizards, Uromastix hardwicki. In this species, numerous retinal photoreceptors displayed S-antigen-like immunoreactivity, whereas only very few pinealocytes were labeled. Immunoreactive opsin was found neither in retinal photoreceptors nor in pinealocytes. Electron microscopy showed that all pinealocytes of Uromastix hardwicki resemble modified pineal photoreceptors. A peculiar observation is the existence of a previously undescribed membrane system in the inner segments of these cells. It is evidently derived from the rough endoplasmic reticulum but consists of smooth membranes. The modified pineal photoreceptor cells of Uromastix hardwicki were never seen to establish synaptic contacts with somata or dendrites of intrapineal neurons, which are extremely rare. Vesiclecrowned ribbons are prominent in the basal processes of the receptor cells, facing the basal lamina or establishing receptor-receptor and receptor-interstitial type synaptoid contacts. Dense-core granules (60–250 nm in diameter) speak in favor of a secretory activity of the pinealocytes. Attention is drawn to the existence of receptor-receptor and receptor-interstitial cell contacts indicating intramural cellular relationships that deserve further study.Supported by the Deutsche Forschungsgemeinschaft (Ko 758/31) and the Deutscher Akademischer Austauschdienst (Senior DAAD Research Fellowship to M.A.H.)     

Immunocytochemical markers revealing retinal and pineal but not hypothalamic photoreceptor systems in the Japanese quail

Summary The retinal proteins opsin,-transducin, S-antigen and interstitial retinol-binding protein (IRBP) are essential for the processes of vision. By use of immunocyto-chemistry we have employed antibodies directed against these photoreceptor proteins in an attempt to identify the photoreceptor systems (retina, pineal and deep brain) of the Japanese quail. Opsin immunostaining was identified within many outer (basal portion) and inner segments of retinal photoreceptor cells and limited numbers of photoreceptor perikarya. Opsin immunostaining was also demonstrated in limited numbers of pinealocytes with all parts of these cells being immunoreactive. These results differ from previous observations. In contrast to the results obtained with the antibody against opsin, S-antigen and-transducin immunostaining was seen throughout the entire outer segments and many photoreceptor perikarya of the retina. In the pineal organ immunostaining was seen in numerous pinealocytes in all follicles. These results conform to previous findings in birds. In addition, IRBP has been demonstrated for the first time in the avian retina and pineal organ. These findings underline the structural and functional similarities between the retina and pineal organ and provide additional support for a photoreceptive role of the avian pineal. No specific staining was detected in any other region of the brain in the Japanese quail; the hypothalamic photoreceptors of birds remain unidentified.     

Ultrastructural immunocytochemical study of the massa caudalis of the subcommissural organ-Reissner's fiber complex in lamprey larvae (Geotria australis): Evidence for a terminal vascular route of secretory material

Summary The massa caudalis of the subcommissural organ-Reissner's fiber complex of lamprey larvae (Geotria australis) was studied immunocytochemically at the ultrastructural level by use of the immunoperoxidase-silver methenamine procedure. An antiserum raised against bovine Reissner's fiber was utilized as primary antibody.The caudalmost portion of the central canal and its ampulla caudalis communicate, via wide intercellular spaces in their dorsal wall, with large cavities or lacunae. In addition, distinct openings in the dorsal wall of the ampulla establish an open communication between the latter and the lacunae. The lacunae are lined by slender processes of cells of unknown nature. No junctional complexes can be observed between these cells, which lack a basal lamina. The lacunae communicate with structures resembling blood capillaries, however, they are devoid of a basal lamina. These peculiar vessels, in turn, are in direct communication with characteristic blood capillaries.Reissner's fiber (RF) and its massa caudalis are strongly immunoreactive with the antiserum used. The wide intercellular spaces in the dorsal wall of the central canal and the ampulla, as well as the lumina of the (i) lacunae, (ii) modified vessels and (iii) blood capillaries are filled with a flocculent, strongly immunoreactive material. No immunoreactive material was found outside these structures. Thus, the blood capillaries appear to represent the only final target of RF-material arriving at the ampulla caudalis.Supported by Grant I 38259 from the Stiftung Volkswagenwerk, Federal Republic of Germany, Grant S-85-39 from the Dirección de Investigaciones, Universidad Austral de Chile, and Grant 6027 from Fondo Nacional de Desarrollo Científico y Tecnológico, Chile. The authors express their gratitude to Mrs. Elizabeth Santibáñez and Mr. Julio Lamilla for providing the lamprey larvae and to Mr. Humberto Molina for preparing the three-dimensional drawing     

Water use efficiency and carbon isotope composition of plants in a cold desert environment

Summary The effects of the availabilities of water and nitrogen on water use efficiency (WUE) of plants were investigated in a sagebrush steppe. The four species studied wereArtemisia tridentata (shrub),Ceratoides lanata (suffrutescent shrub),Elymus lanceolatus (rhizomatous grass), andElymus elymoides (tussock grass). Water and nitrogen levels were manipulated in a two-by-two factorial design resulting in four treatments: control (no additions), added water, added nitrogen, and added water and nitrogen. One instantaneous and two long-term indicators of WUE were used to testa priori predictions of the ranking of WUE among treatments. The short-term indicator was the instantaneous ratio of assimilation to transpiration (A/E). The long-term measures were 1) the slope of the relationship between conductance to water vapor and maximum assimilation and 2) the carbon isotope composition (¹³C) of plant material. Additional water decreased WUE, whereas additional nitrogen increased WUE. For both A/E and ¹³C, the mean for added nitrogen alone was significantly greater than the mean for added water alone, and means for the control and added water and nitrogen fell in between. This ranking of WUE supported the hypothesis that both water and nitrogen limit plant gas exchange in this semiarid environment. The short- and long-term indicators were in agreement, providing evidence in support of theoretical models concerning the water cost of carbon assimilation.     

Interactions between developmental processes,growth, and food selection in the larvae and juveniles of Rutilus rutilus (L.) (Cyprinidae)

Summary The aim of this study was to assess the effects of developmental events, occurring in fish during the first weeks after hatching, on the quantity and quality of the ingested food and on growth. The investigation was carried out with the larvae and juveniles of Rutilus rutilus, the single cyprinid species occurring in an oligotrophic subalpine lake in Tirol, Austria. Comparison between availability of prey in the water and gut contents suggests that the selection of food by the young fish is strongly influenced by developmental processes. For example, the prevalence of indigestible phytoplankton in the gut of young larvae can be taken as a sign of the not yet fully developed sensory and locomotory capacities of the young fish (El-Fiky et al. 1987). Furthermore, quantitative and qualitative changes in the gut contents correlate strongly with changes in the form and relative length of the gut, but reflect only weakly the availability of prey in the water. In the Seefelder See population of R. rutilus the switch from a phytoplankton to a cladoceran dominated diet is accompanied by an increase in relative growth rate by nearly one order of magnitude (Wieser et al. 1988).     

Characterisation of neuropeptides of the AKH/RPCH-family from corpora cardiaca of Coleoptera

Summary Extracts of corpora cardiaca from two members of the family Tenebrionidae,Zophobas rugipes andTenebrio molitor, from one member of the Chrysomelidae,Leptinotarsa decemlineata, and from three members of the Scarabaeidae,Pachnoda marginata, P. sinuata andMelolontha hippocastani, were assayed for adipokinetic and hypertrehalosaemic activity in acceptor locusts (Locusta migratoria) and cockroaches (Periplaneta americana), respectively. All corpus cardiacum material tested, except that from the cockchafer,M. hippocastani, gave positive bioassay results. Biological activities of corpus cardiacum extracts from all species investigated can be resolved on reversed-phase high performance liquid chromatography (RP-HPLC). Gland extracts from the two tenebrionid species each show a single peak of biological activity associated with a single peak of UV absorbance having an identical retention time in both species. The two biologically active fractions from the corpora cardiaca of the potato beetle,L. decemlineata, coelute with exogenous (synthetic) hypertrehalosaemic hormones I and II of the American cockroach. The two species of the genusPachnoda contain two active compounds in their glands; compound I of each species is more abundant and elutes just ahead of the (synthetic) hypertrehalosaemic hormone of the cockroachBlaberus discoidalis. The gland material ofM. hippocastani exhibits and absorbance peak with the same retention time as the major peak from thePachnoda-species; however, this peak material does not elicit biological activity in the assays used here. After fractionation by RP-HPLC the main biologically active compounds were subjected to amino acid analyses. All factors are peptidic and contain 8 amino acid residues. The peptides from the tenebrionid species have the amino acid residues Asx₍₂₎, Glx₍₁₎, Ser₍₁₎, Pro₍₁₎, Leu₍₁₎, Phe₍₁₎ and Trp_(i), whereas the main peptide from corpora cardiaca ofP. marginata contains the residues Asx₍₂₎, Glx₍₁₎, Ser₍₁₎, Pro₍₁₎, Tyr₍₁₎, Leu₍₁₎ and Trp₍₁₎. Amino acid composition analyses of the two active fractions fromL. decemlineata reveal the residues Asx₍₂₎, Glx₍₁₎, Ser₍₁₎, Pro₍₁₎, Val₍₁₎, Phe₍₁₎ and Trp₍₁₎ for compound I and Asx₍₁₎, Glx₍₁₎, Thr₍₂₎, Pro₍₁₎, Leu₍₁₎, Phe₍₁₎ and Trp₍₁₎ for compound II.