The Bacterial Flora of the Gut Contents and Environment of Larval Lampreys

Rogers, P. A., Glenn, A. R., Potter, I. C. 1980. The bacterial flora of the gut contents and environment of larval lampreys. (School of Environmental and Life Sciences, Murdoch University, Australia.) — Acta zool. (Stockh.) 61(1): 23–27. The microbial flora of the contents of the intestine of larval lampreys, as well as of the water and substrate in the ammocoetes' habitat, have been cultured on Trypticase Soy Agar. The bacteria have been separated into taxonomic groups, using the scheme of Cowan and Steele (1974) and the API 20E system. The microbial flora of the gut contents of larval lampreys closely parallels that found in the environment in which the ammocoetes live. Bacillus, Aeromonas and Aeromonas-like organisms were by far the most abundant bacteria identified, followed by Pseudomonas and members of the Enterobacteriaceae. The only anaerobic components of the bacterial flora in the gut contents and the environment were Clostridium and a relatively uncommon and unidentified Gram-negative organism. Estimates of abundance of the microflora indicated that the concentration of bacteria was much greater in both the gut contents and the substrate than in the water overlying the animals' burrow.     

Studies on the Erythrocytes of Larval and Adult Lampreys (Lampetra fluviatilis)

The erythrocytes of larval and adult Lampetra fluviatilis were examined in suspensions of whole blood, solutions of various ionic strengths, scanning electron photomicrographs and air dried smears. Although a wide range of shapes were observed in hyper- and hypotonic solutions, the cells in whole blood and isotonic solutions were predominantly biconcave with an eccentric nucleus. The biconcave shape was also seen in scanning electron photomicrographs of erythrocytes fixed with glutaraldehyde in lamprey Ringer. The mean diameter of larval and adult cells in whole blood suspensions was 11.2 and 11.6 μm respectively. Although in air dried smears the areas of the larval and adult erythrocytes were virtually identical, the erythrocyte nuclear area was markedly higher in ammocoetes with only a small amount of overlap between the values obtained for the two stages in the life cycle.     

Temporal Patterns of Larval Fish Occurrence in a Large Subtropical River

Knowledge of temporal patterns of larval fish occurrence is limited in south China, despite its ecological importance. This research examines the annual and seasonal patterns of fish larval presence in the large subtropical Pearl River. Data is based on samples collected every two days, from 2006 to 2013. In total, 45 taxa representing 13 families and eight orders were sampled. The dominant larval family was Cyprinidae, accounting for 27 taxa. Squaliobarbus curriculus was the most abundant species, followed by Megalobrama terminalis, Xenocypris davidi, Cirrhinus molitorella, Hemiculter leuscisculus and Squalidus argentatus. Fish larvae abundances varied significantly throughout the seasons (multivariate analyses: Cluster, SIMPROF and ANOSIM). The greatest numbers occurred between May and September, peaking from June through August, which corresponds to the reproductive season. In this study, redundancy analysis was used to describe the relationship between fish larval abundance and associated environmental factors. Mean water temperature, river discharge, atmospheric pressure, maximum temperature and precipitation play important roles in larval occurrence patterns. According to seasonal variations, fish larvae occurrence is mainly affected by water temperature. It was also noted that the occurrence of Salanx reevesii and Cyprinus carpio larvae is associated with higher dissolved oxygen (DO) concentrations, higher atmospheric pressure and lower water temperatures which occur in the spring. On the other hand, M. terminalis, X. davidi, and C. molitorella are associated with high precipitation, high river discharge, low atmospheric pressure and low DO concentrations which featured during the summer months. S. curriculus also peaks in the summer and is associated with peak water temperatures and minimum NH₃–N concentrations. Rhinogobius giurinus occur when higher atmospheric pressure, lower precipitation and lower river discharges occur in the autumn. Dominant fish species stagger their spawning period to avoid intraspecific competition for food resources during early life stages; a coexistence strategy to some extent. This research outlines the environmental requirements for successful spawning for different fish species. Understanding processes such as those outlined in this research paper is the basis of conservation of fish community diversity which is a critical resource to a successful sustainable fishery in the Pearl River.     

版纳鱼螈幼体和成体皮肤的结构

采用光镜和扫描电镜,对我国特有的珍稀濒危两栖动物版纳鱼螈Ichthyophis bannanicus幼体和成体的皮肤进行形态学和组织学观察.版纳鱼螈幼体和成体的皮肤均可分为表皮、真皮疏松层和真皮致密层;皮肤中含有粘液腺和颗粒腺;在不同发育阶段或同一个体的不同部位,其皮肤的各种组成成分在结构和厚度上存在着差异:成体和幼体都是头部的表皮最厚,尾部的最薄;幼体表皮各层细胞分化不明显,几无角化现象,成体表皮的各层细胞分化明显,表层细胞明显角化;成体躯干部皮肤最厚,头部最薄,幼体则是头部皮肤最厚,尾部最薄;幼体和成体的头部皮肤都分布有大量的粘液腺,颗粒腺分布较少;幼体的躯干部皮肤则主要分布着大量颗粒腺,尾部只有颗粒腺,未见粘液腺;成体躯干部和尾部皮肤均分布有大量的颗粒腺和粘液腺.     

Iron Levels Change in Larval Heliothis virescens Tissues Following Baculovirus Infection

Inductively coupled plasma mass spectrometry and (59)Fe radiotracers were used to investigate changes in levels of Fe in the tissues of 4th instar Heliothis virescens larvae following infection with Helicoverpa zea single nucleopolyhedrovirus (HzSNPV) or with Autographa californica multiple nucleopolyhedrovirus. Baculovirus infection led to significant changes in hemolymph Fe levels late in infection. (24)Na radiotracer ingested by 4th instar larvae was rapidly cleared to nearly undetectable levels 6 h post-ingestion. In contrast, (59)Fe radiotracer fed to 4th instar larvae declined within the first few hours of ingestion and then remained constant at approximately 60% of the initial tracer activity. While Fe radiotracer levels among larval tissues changed, whole insect tracer levels did not decline from 6 to 60 h post-ingestion. Tissues from HzSNPV larvae had higher radiotracer levels in the hemolymph and midgut 36 and 60 h post-infection. The protein-bound/free ratio of (59)Fe was significantly higher in baculovirus infected hemolymph than in uninfected hemolymph at 60 h post-infection, indicating that Fe released from damaged cells is protein-bound. In both studies, hemolymph Fe levels were higher in HzSNPV infected larvae. This first study of tissue Fe levels during viral infection of an insect clearly demonstrates that Fe homeostasis is substantially disrupted.     

Fine Structure of Cellular Inclusions in Measles Virus Infections

Cells which are infected with measles virus have been known for some time to contain inclusion material that is distinguishable from normal cellular components by application of traditional staining methods and observation in the light microscope. The fine structure of the inclusion material contained in HeLa cells infected with Edmonston strain of measles virus has been examined in the electron microscope. Two steps have been found necessary in this study: (1) the recognition by phase-contrast microscopy of the living cell of bodies that are defined as inclusion material when the cells are classically stained; and (2) the recognition in the electron microscope of inclusion-body material that had previously been identified in the living cell. The fine structure of the nuclear and cytoplasmic inclusion material in osmium-treated cells was found to consist mainly of randomly arrayed filaments of low electron density. Dense, highly ordered arrays of filaments were found near the center of the nuclear inclusions, sometimes as a two-dimensional, nearly orthogonal arrangement. If the size of the measles virus is taken to be around 100 mµ in diameter, the strands seen in the inclusions cannot be fully formed virus.     

花背蟾蜍蝌蚪皮肤的结构与发育

为研究花背蟾蜍(Bufo raddei)蝌蚪在变态发育期皮肤的显微结构特点,选取G19、G22、G26、G36、G41、G43和G46共7个发育期蝌蚪的连续石蜡切片及成体的背部皮肤切片,采用H.E和AB-PAS染色方法,观察了皮肤各层结构的发育时序并进行了相应的测量.结果表明,在G19、G22和G26蝌蚪表皮均为1层细胞;G36蝌蚪皮肤细胞形态和层数在背腹部出现了显著的区别;在G41基本完成了表皮2层细胞的构建;G43期完成完整的真皮构建,其中分布有毛细血管和2种皮肤腺.G46皮肤在厚度、腺体和毛细血管分布等方面表现出了明显的区域性差异,并与成体皮肤结构有明显的差别,显示出蝌蚪在发育过程中皮肤结构的变化与其生存环境之间紧密的关联性.     

Lethal Temperatures in Ammocoetes of Four Species of Lampreys

Abstract An investigation has been made of the resistance time and upper lethal temperature of ammocoetes of four species of lampreys provided with a substrate into which they could readily burrow. In general, ammocoetes burrowed after transfer from the acclimation to the experimental temperature baths and later came out of the substrate only in lethal temperatures. A relationship was observed between the resistance time and the time taken to emerge, with the resistance time increasing exponentially with decreasing experimental temperature. In Ichthyomyzon fossor, landlocked Petromyzon marinus, Lampetra (Lethenteron) Lamottenii and in Lampetra (Lampetra) planeri from two different times of the year, the incipient lethal levels over a two week experimental period for larvae acclimated to 15° G were respectively 30.5, 30, 29.5, 28.5 and 28° C. Values for P. marinus acclimated to 5 and 25° C were respectively 29.5 and 31° C, whereas in L. planeri they were 28 and 29° C in April/May and 27 and 29° C in July/August. Extrapolation of the results for the three acclimation temperatures yielded ultimate incipient lethal levels of 31.4° G in P. marinus and 29.2 and 29.4° C for L. planeri examined in the spring and summer respectively.     

Oral Fimbriae and Papillae in Parasitic Lampreys (Petromyzontiformes)

There are 38 species of living lampreys, 18 parasitic and 20 nonparasitic. The parasitic species feed as adults, while the nonparasitic do not. The taxonomy and systematics of the living lampreys is based primarily on dentition characters. Since the number of oral fimbriae and oral papillae have never been systematically investigated in lampreys, we compared them in 17 of the 18 parasitic lampreys to assess their usefulness as taxonomic characters. Both showed little variation with total length and sex within a species, while exhibiting greater variation between species. Parasitic species belonging to the three lamprey families could be distinguished using the number of oral fimbriae: southern hemisphere Mordaciidae (0) and Geotriidae (55–65) and northern hemisphere Petromyzontidae (81–144). However, the taxonomic usefulness of the two characters at the species level was limited. Ten out of the 17 species of parasitic lampreys were placed into four distinct groups based on their numbers of oral fimbriae, and only in two of these was the character diagnostic. Twelve out of the 17 species were placed into two distinct groups based on their numbers of oral papillae and for none of these was the character diagnostic. Blood feeders and intermediate feeders (blood + flesh) were shown to have significantly higher numbers of oral fimbriae than flesh feeders. The higher numbers of oral fimbriae in the former two types of feeders were presumed to be linked to their greater need to create a good seal for feeding purposes. Blood feeders were also shown to have significantly higher numbers of oral papillae than either intermediates or flesh feeders. The higher numbers of oral papillae in the blood feeders were presumed to be linked to their greater need to find suitable attachment sites for feeding purposes.     

The taxonomy of the Lampreys Geotria and Mordacia and their distribution in Australia

The taxonomy of the Southern Hemisphere lampreys, Qeotria and Mordacia , is reviewed. Many invalid species have been created within these genera due to a lack of knowledge of the great morphological changes that take place during development. The sequence of changes in the dentition of Mordacia is described in detail.
Geotria is now considered to be monotypic, containing only Q. australis Gray, which is found in Australia, New Zealand, and South America. Caragola is regarded as a synonym of Mordacia , and thus the exclusively South American C. lapicida becomes M. lapicida (Gray). The other Mordacia species, M. mordax (Richardson) and M. praecox Potter, are found only in Australia. All these species are anadromous and parasitic, except M. praecox , which is nonparasitic and never leaves fresh-water.
A comparison of anatomical features indicates that living lampreys (Petromyzonidae) are best separated into three subfamilies: Petromyzoninae to contain all Northern Hemisphere genera, Geotriinae for Geotria , and Mordaciinae for Mordacia.
A record of the Australian rivers in which lampreys have been found, shows that both genera are sympatric in South Australia, western Victoria, and Tasmania, and that only Qeotria is found in Western Australia, and only Mordacia in south-eastern Australia.     

Forest and Landscape Structure as Predictors of Capercaillie Occurrence

ABSTRACT Capercaillie (Tetrao urogallus) is a large, endangered forest grouse species with narrow habitat preferences and large spatial requirements that make it susceptible to habitat changes at different spatial scales. Our aim was to evaluate the relative power of variables relating to forest versus landscape structure in predicting capercaillie occurrence at different spatial scales. We investigated capercaillie-habitat relationships at the scales of forest stand and forest-stand mosaic in 2 Swiss regions. We assessed forest structure from aerial photographs in 52 study plots each 5 km². We classified plots into one of 3 categories denoting the observed local population trend (stable, declining, extinct), and we compared forest structure between categories. At the stand scale, we used presence-absence data for grid cells within the plots to build predictive habitat models based on logistic regression. At this scale, habitat models that included only variables relating to forest structure explained the occurrence of capercaillie only in part, whereas variables selected by the models differed between regions. Including variables relating to landscape features improved the models significantly. At the scale of stand mosaic, variables describing forest structure (e.g., mean canopy cover, proportion of open forest, and proportion of multistoried forest) differed between plot categories. We conclude that small-scale forest structure has limited power to predict capercaillie occurrence at the stand scale, but that it explains well at the scale of the stand mosaic. Including variables for landscape structure improves predictions at the forest-stand scale. Habitat models built with data from one region cannot be expected to predict the species occurrence in other regions well. Thus, multiscale approaches are necessary to better understand species-habitat relationships. Our results can help regional authorities and forest-management planners to identify areas where suitable habitat for capercaillie is not available in the required proportion and, thus, where management actions are needed to improve habitat suitability.     

On the Occurrence and Structure of Choanocyte-like Cells in Some Echinoderms

Choanocyte-like cells with a collar of regularly arranged cylindrical microvilli around the base of the flagellum were observed in the ciliary bands of the Brachiolaria larva of Asterias rubens. The ambulacral ampullae and coelomic epithelia of adult Asterias and coelomic epithelia of Mesothuria contain similar cells with radial lamellae instead of cylindrical microvilli. Other similar but more modified types of cells, in which the inner edges of the radiating lamellae could be recognized as longitudinal ridges in the wall of a cylindrical flagellar pit, were found in ambulacral ampullae of Porania and in coelomic epithelia of Stichopus. Distinct indications of phagocytosis were seen in most of these cells. The present report together with previously published data lend support to the idea, that the choanocyte is a fundamental cell type in metazoans, probably derived phylogenetically from some flagellate ancestor.     

Heart Ratios at Different Stages in the Life Cycle of Lampreys

Heart ratios (heart weight/body weight. ×100) have been obtained for freshly killed and preserved (10% formalin) specimens of the lampreys Petromyzon marinus, Lampetra fluviatilis and L. planeri. Values for comparable stages were significantly higher in the preserved material, probably as a result of retention and fixation of blood in the heart chambers. The regression slope for the logarithmic relationship between heart and body weights was close to one in all stages of the three species investigated. A marked increase was observed in the heart ratio during metamorphosis, apparently attributable to an increase in the number and density of myocardial fibres. Heart ratios in the lamprey were generally higher than for most other fishes, with values of 0.1 and 0.3 being obtained for example in the case of freshly killed ammocoete and sexually mature adult stages of L. fluviatilis.     

Iron based oxypnictides: Structure and properties

Metals, alloys and metal oxides have been investigated over several decades for their interesting electronic properties including superconductivity. However the pnictides (multinary compounds containing at least one pnictogen) have not been so popular for their superconducting properties. That has changed recently (2008) after the discovery of superconductivity at 26 K in fluoride-doped LaO_0.9F_0.1FeAs by Kamihara et al. [1] which has created a huge excitement in the field of superconductivity and pnictides. Since then a large number of pnictogen based superconductors were discovered. This article summarizes the structure and properties of the parent compounds, LnOFePn (Ln = La, Ce and Pr; Pn = P and As). Effect of Fe-Pn hybridization on structural distortion, electronic and magnetic properties of LnOFePn is examined.     

Dengue Fever Occurrence and Vector Detection by Larval Survey, Ovitrap and MosquiTRAP: A Space-Time Clusters Analysis

The use of vector surveillance tools for preventing dengue disease requires fine assessment of risk, in order to improve vector control activities. Nevertheless, the thresholds between vector detection and dengue fever occurrence are currently not well established. In Belo Horizonte (Minas Gerais, Brazil), dengue has been endemic for several years. From January 2007 to June 2008, the dengue vector Aedes (Stegomyia) aegypti was monitored by ovitrap, the sticky-trap MosquiTRAP™ and larval surveys in an study area in Belo Horizonte. Using a space-time scan for clusters detection implemented in SaTScan software, the vector presence recorded by the different monitoring methods was evaluated. Clusters of vectors and dengue fever were detected. It was verified that ovitrap and MosquiTRAP vector detection methods predicted dengue occurrence better than larval survey, both spatially and temporally. MosquiTRAP and ovitrap presented similar results of space-time intersections to dengue fever clusters. Nevertheless ovitrap clusters presented longer duration periods than MosquiTRAP ones, less acuratelly signalizing the dengue risk areas, since the detection of vector clusters during most of the study period was not necessarily correlated to dengue fever occurrence. It was verified that ovitrap clusters occurred more than 200 days (values ranged from 97.0±35.35 to 283.0±168.4 days) before dengue fever clusters, whereas MosquiTRAP clusters preceded dengue fever clusters by approximately 80 days (values ranged from 65.5±58.7 to 94.0±14. 3 days), the former showing to be more temporally precise. Thus, in the present cluster analysis study MosquiTRAP presented superior results for signaling dengue transmission risks both geographically and temporally. Since early detection is crucial for planning and deploying effective preventions, MosquiTRAP showed to be a reliable tool and this method provides groundwork for the development of even more precise tools.     

Occurrence of Larval and Early Juvenile Fishes in the Surf Zone Adjacent to two Intermittently Open Estuaries, South Africa

I monitored larval and early juvenile fishes in the surf zone adjacent to two warm temperate, intermittently open estuaries in South Africa. Mugilidae (59–67%) dominated fish assemblages in the surf zones adjacent to the Van Stadens and Kabeljous estuaries. Other dominant families included the Atherinidae, Sparidae and Soleidae. The most abundant species caught during the study were the catadromous mugilid Myxus capensis, in a postflexion or early juvenile stage of development, and the sparid Rhabdosargus holubi, in a postflexion stage of development. Species displaying a degree of dependence on estuaries during the early phase of their life cycle dominated (96–98%) surf zone catches. Most fish encountered were at the postflexion stage of larval development. Larval and early juvenile fishes were more abundant during the summer and autumn months with density peaking several-fold during natural estuary opening events, particularly in the surf zone adjacent to the Kabeljous Estuary. Decreases in salinity showed a significant relationship with increases in fish density during a March opening event in the surf adjacent to the Kabeljous Estuary where catches were concentrated along a current-driven estuarine plume. Catches adjacent to the Van Stadens Estuary also increased considerably during two smaller opening events in March and November although salinity played no statistically significant role in these increased catches. Results from the surf adjacent to the Van Stadens Estuary suggested that either very small amounts of estuarine water entering the surf zone can elicit an accumulation response by estuary-dependent larval and early juvenile fishes or that an additional characteristic of estuary/river water, other than salinity per se, is aiding the cueing process.     

Structural Organization of the Blood-sinus Systems in Lampreys and Hagfish: Functional and Evolutionary Interpretations

Abstract The head and branchial regions of larval and adult lampreys and hagfish were studied histologically in serial sections. The most remarkable feature in these extant agnathans was the occurrence of large blood-sinuses. In larval lampreys, blood-sinuses are well developed in the velum, an organ that functions to introduce water and accompanying food particles from the mouth into the gill and alimentary regions. The sinuses in the velum may act to transduce the force of contraction of velar muscles to the stroke-like movement of the velum; without these sinuses muscular contractions might simply cause the velum to collapse. In adult lampreys, blood-sinuses are well developed in the peribranchial space that surrounds the branchial (gill) sac and is surrounded by the branchial pouch. It is possible that the force of contractions of the branchial-pouch muscles is transduced effectively to the branchial sac via the peribranchial blood-sinus and facilitates the expiration of water through the external gill pores. If the peribranchial sinus were absent, the muscular contraction might deform the branchial sac in an inappropriate manner. In the hagfish, the blood-sinus system is also well developed in the velum and peribranchial space, although the peribranchial sinus lies outside the muscular branchial pouch. In agnathans, the blood-sinus system may function, at least in part, as a kind of hydrostatic skeleton that transduces the force generated by muscular contraction.