TIBETODUS,A NEW PYCNODONT FISH FROM CHANGTU

A complete series of vomerine teeth of pycnodontoidea has been foundfrom the vicinity of Changtu(Sikang).It represents the first record of vertebrateremains in the Tibetan highlands.Order PycnodontoideaFamily CyrodontidaeGenus Tibetodus,new genusDiagnosis as given for the type species Tibetodus gyrodoidesSpecies Tibetodus gyrodoides,new species.Material:A vomer with the teeth nearly complete.Field No.C.3340.     

Heterophylly in Ranunculus flabellaris: The Effect of Abscisic Acid on Leaf Anatomy

Ranunculus flabellaris Raf., the yellow water crowfoot, exhibitsstriking heterophylly between submerged and terrestrial leaves.Leaves produced under water are highly divided with numerousnarrow lobes and deep sinuses, whereas terrestrial leaves havefew broad lobes and shallow sinuses. When plants are submergedin a 25 µM solution of ABA, the typical transition fromterrestrial to submerged leaves is completely suppressed and,instead, terrestrial-like leaves are produced. Image analysistechniques show that, in addition to this modification of leafmorphology, leaves produced under ABA treatment possess surfaceand internal features characteristic of terrestrial leaf anatomy.This study provides evidence that the environmental factorsthat influence the morphological and anatomical expression ofheterophylly may act through endogenous ABA. Ranunculus flabellaris, yellow water crowfoot, ABA, heterophylly, leaf anatomy     

Water Relations and Cell Wall Elasticity Quantities in Phaseolus vulgaris Leaves

The investigations were designed to test osmotic adjustment,cell wall bulk elastic modulus and stomatal behaviour duringand after water stress and rewatering in the primary and firsttrifoliolate leaf of Phaseolus vulgaris. Leaf water relationsquantities fully recovered after rewatering within a few hours;diffusion resistance to vapour flow, however, required 6 h.Leaf growth recovery was considerably delayed. Osmotic adjustmentwas absent during water stress in both the primary and the firsttrifoliolate leaf. The bulk elastic modulus (_v), however, waslower for the primary leaf (higher elasticity) than for thetrifoliolate leaves. These two types of leaves differed in theirdrought resistance in that the primary leaf exhibited wiltingat the end of the stress period (7 d) while the trifoliolateleaf remained relatively turgid. The bulk elastic modulus ofthe cell wall changed almost proportionally with the turgorpressure (_p). The structure coefficient (), an indicator forthe intensity of change of the bulk elastic modulus with turgorwas higher for the primary than for the first trifoliolate leaf.The leaf diffusion resistance (r), below the turgor loss point,changed proportionally with the solute potential with very similarregression lines for the relation of (r) versus RWC ¹. The datasuggest that greater drought resistance of the first trifoliolateleaf is related to a decreased bulk elastic modulus, but notto osmotic adjustment nor to differences in stomatal resistanceduring water stress. Key words: Phaseolus vulguris, Water stress, Recovery, Cell wall elasticity     

Relationships between stream macroinvertebrates and environmental variables at multiple spatial scales

1. Aquatic communities are structured by multiple forces, and identifying the driving factors over multispatial scales is an important research issue. The East Asian monsoon region is globally one of the richest environments in terms of biodiversity, and is undergoing rapid human development, yet the river ecosystems in this region have not been well studied. We applied a hierarchical framework to incorporate regional and local environmental effects on stream macroinvertebrate communities in this region. The knowledge gained is expected to improve the understanding of the importance of spatial scale on regional and local diversity in the East Asian monsoon region. 2. A national data set of benthic macroinvertebrates and environmental variables (geographical, land‐use, hydrological, substratum and physicochemical elements) in Korean rivers was used to determine the habitat preferences of macroinvertebrates. 3. Latitude, proportion of forest coverage, riffle habitat, silt substratum and temperature were the most important determinants for the ordinations of macroinvertebrate communities in each category evaluated by canonical correspondence analysis (CCA). The optimal habitats for stream macroinvertebrates are not the same for all species, and overall community metrics and abundance of sensitive species tended to be lower in open agricultural and urban streams than in forested streams. The sensitivity of mayflies and stoneflies to anthropogenic disturbances implicated them as good indicators to assess the effects of urban and agricultural activities. 4. A partial CCA was used to evaluate the relative importance of macrohabitat and microhabitat variables on community composition at three spatial scales (whole country, the large Han River basin and two small sub‐basins in the lowlands and highlands). The majority of community variation (17–22% for each environmental element) was explained by macrohabitat variables at the regional spatial scale. In contrast, large proportions (15–18%) were explained by microhabitat variables at the local spatial scale. 5. Our findings indicate that the relative importance of habitat scales should be determined by geographical size and that comprehensive understanding of multispatial scale patterns can be important for implementing sound biodiversity conservation programmes.     

The effect of host resistance on the metabolic rate of engorged females of Rhipicephalus evertsi evertsi

Abstract. This study investigated the effect of acquired resistance in guinea-pigs on the metabolic rate of adult females of the tick Rhipicephalus evertsi evertsi. Guinea-pigs were subjected to three successive infestations of ticks and the rate of CO₂ production (Vco₂) measured in first and third infestation engorged females. Ticks which fed on resistant hosts showed a 52% decrease in mass compared to ticks that fed on naive animals. Reduction in mass was accompanied by a decrease in Vco₂ (mlh^-1) per tick but an increase in mass specific Vco₂ (mlg^_1h^_1). However, both groups shared a single allometric relationship between body mass and metabolic rate (Vco₂). We suggest that the differences in size rather than any factor directly relating to the mechanism of acquired resistance account for the differences in metabolic rate between ticks fed on naive and resistant guinea-pigs.     

The optics of tsetse fly eyes in relation to their behaviour and ecology

Abstract The visual acuity of two species of tsetse flies, Glossina morsitans morsitans Westw. and Glossina pallidipes Aust., was investigated. Male G. morsitans eyes have an acute zone in the forward region, with large hexagonal lenses (mean minimum diameter, D=33, SE±0.7 μm), relatively small interommatidial angle (Δ(φ=1.08^o) and angular receptive field of individual ommatidia (Δp) of not less than 1.14^o. A narrow band of square lenses, with intermediate diameter and Δφ, merges with smaller hexagonal lenses in the periphery (24±0.7 μm), with relatively large interommatidial angle (Δφ=3.7^o) and small angular receptive field (Δp = c. 1.6^o). G.pallidipes eyes are similar, except that the lenses in the acute zone are larger than those of G.morsitans , in proportion to their larger body size. Female eyes are not significantly different from male eyes, except that they have a narrower region of binocular overlap (maximum for males = 24^o, for females = 18^o). The eye parameter (p=DΔφ) in the acute zone of male G.morsitans = 0.62, and in the peripheral zone = 1.56. These relatively high values are consistent with fast flight, visual detection of drift due to low wind speeds, mating chases and discrimination of cryptic host animals at high light intensities. The extended region of binocular overlap in males may serve as an early warning system of the approach of potential females. From our estimates, tsetse flies ought to be able to detect small objects against the sky c. 30 min before sunrise and after sunset, and to use their peripheral vision perhaps 15 min earlier and later than this.