Assessment of within-population genetic structure in <Emphasis Type="Italic">Quercus crispula</Emphasis> and <Emphasis Type="Italic">Q. dentata</Emphasis> by amplified fragment length polymorphism analysis

The spatial genetic structure was assessed by amplified fragment length polymorphism (AFLP) technique for Quercus crispula Blume (37 individuals) and Q.dentata Thunberg (54 individuals) growing along a 550-m transect in Ishikari, Hokkaido, northern Japan. The simple Mantel test revealed significant negative correlation between genetic similarity and geographic distance in Q.dentata and negative but insignificant correlation in Q.crispula. Spatial autocorrelation analysis revealed that Mantels r generally decreased from positive to negative values with the increase of spatial distance in both oak species with significant deviation from zero for the 50–100-m (positive) and 250–300-m classes (negative) in Q.dentata. Thus, significant spatial genetic structure was revealed at least in Q.dentata     

Spatial and temporal variations in insect-infested acorn fall in a <Emphasis Type="Italic">Quercus liaotungensis</Emphasis> forest in North China

Three plots with different aspects and slope characteristics were surveyed in 1999 and 2000 to clarify the spatial and temporal variations in insect-infested acorn fall patterns in a Quercus liaotungensis Koidz. forest in the Dongling Mountain region, North China. There was a significant difference in the proportion of infested acorns in the three plots in a low crop year, but not in a mast year. Within oakwoods on the southeast-facing slope, the insect infestation rate on the upper slope was significantly higher than on the lower slope, but not in the northwest-facing plot. Infestation rate in the low crop year in all three plots was significantly higher than infestation in the mast year. Most of the early fallen acorns had a higher proportion of insect infestation, and in the mast year it was much more obvious than in the low crop year. The proportion of infested acorns in seed bank along the topographic gradient showed a similar decreasing trend with acorn fall time, but the proportion on the upper slope was the highest and the proportion on the lower slope was the lowest. Larval emergence from acorns commenced just after acorns fell from the trees and lasted for 40–50days, with peak emergence occurring from 24 to 32days after acorn rain began. We conclude that insect-infested acorn distribution in Q.liaotungensis shows spatial and temporal heterogeneity, and an early drop of infested acorns can be a short-term defensive strategy against insect infestation.     

Host plant suitability of a recently naturalized thistle Cirsium vulgare (Asteraceae) for a phytophagous ladybird beetle,Epilachna pustulosa (Coleoptera: Coccinellidae)

The phytophagous ladybird beetle, Epilachna pustulosa Kôno occurs mainly on the thistle Cirsium kamtschaticum Ledeb. In recent years, we have confirmed feeding and oviposition by E.pustulosa, and some degree of larval development of this beetle, on a naturalized congeneric thistle, Cirsium vulgare (Savi) Tenore. In this study, we assessed the host suitability of C.vulgare for E.pustulosa, using larval rearing and simple food choice tests, by comparing the performance on, and preference for, their legitimate host C.kamtschaticum. All experiments were initiated in July, when the utilization of C.vulgare by E.pustulosa became obvious. For larval performance, E.pustulosa showed a lower eclosion rate, shorter developmental duration and smaller body size when reared on C.vulgare than on C.kamtschaticum. Cirsium vulgare appeared to be a less adequate larval food than C.kamtschaticum. Adult feeding preference was altered seasonally; females preferred C.kamtschaticum to C.vulgare in a food choice test conducted in early July, whereas they showed the opposite preference in tests conducted in mid and late July. The utilization of C.vulgare by E.pustulosa appeared to be induced by qualitative deterioration of C.kamtschaticum leaves in July, which resulted in increased dispersion of adult beetles.     

Hoarding of acorns by granivorous mice and its role in the population processes of Pasania edulis (Makino) Makino

In order to evaluate the role of granivorous mice, Apodemus speciosus Temminck and Apodemus argenteus Temminck, in the regeneration of Pasania edulis (Makino) Makino, an evergreen tree, we conducted field studies examining acorn crops, the population dynamics and hoarding behavior of mice and pre- and postdispersal acorn predation in an evergreen broad-leaved forest dominated by P.edulis in Kagoshima, southern Japan. The study was conducted from 1994 to 2000. Apodemus mice selected sound acorns and hoarded them in the soil after transporting them for distances ranging from 5.4 to 19.9m. This behavior appeared to be beneficial to the establishment of seedlings of P.edulis. However, the positive effects were negated by a high rate of recovery of the acorns hoarded by the mice. A life-table analysis of five cohorts of P.edulis indicated that postdispersal predation of acorns by Apodemus mice was a major contributor to annual variation in the number of new seedlings. A considerable number of acorns germinated only in years with a good acorn crop and a low level of resident mice. These results suggest that Apodemus mice are serious acorn predators rather than important dispersers. After germination, acorns were attacked by the acorn borer at a high rate. From these results, we can conclude that acorn production probably makes a smaller contribution to the regeneration of P.edulis than coppice shoot production at the study site.     

Larval development and food habits of the marbled parrotfish, <Emphasis Type="Italic">Leptoscarus vaigiensis</Emphasis>, associated with drifting algae

The larval development and food habits of the marbled parrotfish, Leptoscarus vaigiensis (Scaridae) associated with drifting algae were studied. In this study, 628 L. vaigiensis of various developmental stages ranging from postflexion larvae (9.4mm in standard length, SL) to adults (192.0mmSL) were sampled from drifting algae at two fishing ports in Nakagusuku Bay of Okinawa Island. In 3969 fish comprising 65 taxa in 34 families of Teleostei collected with drifting algae, L. vaigiensis occupied 15.8% of samples and occurred generally throughout the whole year. A large number of L. vaigiensis were collected from July to October accompanied by an occurrence of drifting algae composed of Sargassum spp. Larvae and early juveniles ranging from 11.1 to 14.9mmSL appeared sporadically throughout the year, and postflexion larvae 11mmSL occurred from July to November. Their food shifted from planktonic copepods in postflexion larvae and juveniles ranging from 10.0 to 14.9mmSL to seaweed in the juveniles ranging from 15.0 to 24.9mmSL. Furthermore, adults and young over 25mmSL fed almost exclusively on seaweed, with Sargassum spp. constituting the drifting algae. These facts indicate that drifting algae may have a role concerning food and habitat, and may act as a nursery for L. vaigiensis.     

Predispersal predation by rodents to beechnuts (Fagus crenata Blume)

The rodents predation intensity and discrimination ability toward the predispersal beechnuts (Fagus crenata) were investigated using a tree tower in a beech forest, central Japan in 1999 and 2000. In this stand, using seed traps, the densities of fallen viable nuts were 35.1m^–2 in 1999 and 8.4m^–2 in 2000. The vertebrate-damaged nuts had fallen 5.6 and 2.2m^–2 in 1999 and 2000, respectively. Yet, the crop of viable nuts in 1999 was not so rich as that in a mast year. In 1999, predispersal predation by rodents was recognized at 16–19m above ground through the bagging experiment. In 2000, there were no predispersal predation and yet we captured Apodemus argenteus three times and Glirulus japonicus frequently on the tree. Judging from the facts of their feeding behaviors and the tooth scars left on the cupules and nuts, Apodemus argenteus might have been more responsible for predation to the predispersal beechnuts rather than Glirulus japonicus. Apodemus argenteus population seemed to be abundant on the ground in both years. If the main agent of predispersal predator were Apodemus argenteus, their number shifted to the canopy would be much larger in 1999 than in 2000 according as the crop of viable nuts. In an additional experiment, rodents preferred intact cupules to insect-damaged cupules on the tree, suggesting that they discriminated the quality of the predispersal nuts, even in the cupule stage, through olfactory and/or visual senses. Thus, predispersal nut predation by rodents was prevalent during the limited period in autumn.     

Conversion of food waste into hydrogen by thermophilic acidogenesis

Conversion of food waste into hydrogen by thermophilic acidogenesis was investigated as a function of organic loading rate (OLR), hydraulic retention time (HRT) and pH in a continuous stirred tank reactor. In order to identify hydrogen-producing microorganisms, denaturing gradient gel electrophoresis (DGGE) of the polymerase chain reaction (PCR) – amplified V3 region of 16S rDNA analysis was conducted at each tested pH. The conversion of food waste into hydrogen was strongly influenced by the operational conditions. The hydrogen production was increased as OLR increased up to 8gVSl^-1d^-1, but drastically decreased at 10gVSl^-1d^-1. The yield of hydrogen was decreased from 2.2 to 1.0mol-H₂/mol-hexose consumed as HRT decreased from 5 to 2days. More carbohydrates in the food waste were decomposed at longer HRT, 76–90%, at HRT of 2–5days. The hydrogen production peaked at pH 5.5±0.1 and significantly decreased at pH 5.0±0.1. The biogas produced was composed of hydrogen and carbon dioxide, but no methane was detected at all tested conditions. The hydrogen contents in the gas produced were more than 55% (v/v) and not sensitive to all tested conditions. The optimum operational condition for continuous hydrogen production from the food waste was obtained at 8gVSl^-1d^-1, 5 days HRT and pH 5.5±0.1 where the hydrogen production rate, content, yield and the efficiency of carbohydrate decomposition were 1.0l H₂/l-d, 60.5% (v/v), 2.2mol-H₂/mol-hexose consumed and 90%, respectively. The hydrogen production was related with the concentration of total organic acids (TOA) which was strongly dependent on that of butyrate indicating that the reaction was mainly butyrate fermentation. The hydrogen-producing microorganism of Thermoanaerobacterium thermosaccharolyticum that involved in acetate/butyrate fermentation, was detected with strong intensity at all tested pHs by denaturing gradient gel electrophoresis (DGGE) of the polymerase chain reaction (PCR) – amplified V3 region of 16S rDNA analysis and sensitive to the tested pHs. The experimental results indicated that effective hydrogen production from the food waste could be obtained continuously by thermophilic acidogenesis at proper operational condition.     

Life Cycle of the Tick Haemaphysalis Leporis-palustris (Acari: Ixodidae) Under Laboratory Conditions

The life cycles of two separate populations (colonies A and B) of the rabbit tick, Haemaphysalis leporis-palustris, were studied under laboratory conditions. Domestic New Zealand rabbits, Oryctolagus cuniculus, and wild rabbits, Sylvilagus brasiliensis, were used as hosts for ticks from colony B and only O. cuniculus rabbits were used as hosts for ticks from colony A. Developmental periods were observed in an incubator at 27±1°C and RH 90±5%. Larvae from colonies A and B fed for 8.0±3.7 days and 8.5±1.3 days, respectively, on O. cuniculus. On S. brasiliensis larvae from colony B fed for 7.2±1.3 days. Nymphs from colony A fed for 8.1±1.4 days on O. cuniculus and nymphs from colony B fed for 8.1±1.0 days on S. brasiliensis. Only one engorged nymph from colony B was recovered from O. cuniculus. Females from colony A fed for 20.9±5.9 days on O. cuniculus and females from colony B fed for 18.6±2.4 days on O. cuniculus and 18.7±3.7 days on S. brasiliensis. Engorged larvae from colony A required 13.7±3.7 days to molt while engorged larvae from colony B required 11.8±3.0 and 11.5±1.8 days to molt, after having fed on O. cuniculus and S. brasiliensis, respectively. Engorged nymphs from colonies A and B required 16.3±1.9 days and 14.7±1.4 days to molt, respectively. Engorged females from colonies A and B required 4–7 and 3–5 days, respectively, to start oviposition. Mean egg incubation periods lasted for 33–34 days. For ticks from colony B, host species accounted for significant differences (p<0.05) in larval and nymphal feeding periods, oviposition weights and CEIs. Significant differences (p<0.05) between the two colonies when ticks fed on O. cuniculus were observed for larval and nymphal feeding and premolt periods, engorged female and oviposition weights and conversion efficiency indexes (CEI). S. brasiliensis were always a more suitable host for H. leporis-palustris than O. cuniculus. Significantly more larvae and nymphs engorged and molted when fed on S. brasiliensis (p<0.001). Females fed S. brasiliensis were more successful to lay fertile eggs and showed the highest engorged and egg mass weights, and the highest CEIs. Data of H. leporis-palustris fed on wild rabbits (one of its natural host species) are reported for the first time.     

Acorn dispersal by the blue jay (Cyanocitta cristata)

Summary Blue jays transported and cached 133,000 acorns from a stand of Quercus palustris trees in Blacksburg, Virginia, representing 54% of the total mast crop. A further 20% (49,000) of the mast crop was eaten by jays at the collecting site. A large proportion of the nuts remaining beneath the collecting trees was parasitized by curculionid larvae. The number of nuts transported per caching trip ranged from 1–5 with a mean of 2.2. Mean distance between seed trees and caches was 1.1 km (range: 100 m–1.9 km). Jays appeared to choose species with small- to medium-sized nuts (Quercus palustris, Q. phellos, Q. velutina, Fagus grandifolia) and avoided the larger nuts of Q. borealis and Q. alba.Nuts were cached singly within a few meters of each other and were always covered with debris. Covering may improve germination and early growth by protecting the nut and radicle from desiccation. The vegetation structure of most suburban caching sites was analogous to open, disturbed environments in more natural landscapes. The presence of numerous Quercus seedlings in jay caching sites and the tendency for jays to cache nuts in environments conducive to germination and early growth indicate that blue jays facilitate colonization of members of the Fagaceae.     

Light utilization and competition between Echinacea purpurea, Panicum virgatum and Ratibida pinnata under greenhouse and field conditions

Competitive interactions were compared under field and greenhouse conditions for three representative tallgrass prairie species, Echinacea purpurea, Panicum virgatum and Ratibida pinnata. These were planted in monoculture and in mixtures of two species using a replacement series design with groups of four or eight plants. Competition was determined from shoot dry weight data collected during 120days in the greenhouse and after 415days in the field. Yields declined with increased density of a single species in the greenhouse from 40days onward and in the field. Relative yields were up to 100% higher in mixtures than in monocultures for all species early on in the greenhouse experiment. Later in the experiment and in the field relative yields of E.purpurea decreased in the presence of P.virgatum and R.pinnata, whereas relative yields of these two species increased in the presence of E.purpurea. There were correlations in relative yield between the field and the greenhouse experiment at 80 and 120days. In the greenhouse P.virgatum maintained higher net assimilation rates than the other species. Relative growth rates of all species were higher in monoculture and in mixtures up to 40days, after which they declined, especially for E.purpurea in mixtures. In the field, higher light intensities occurred in pure stands of E.purpurea than in mixed stands with other species. The order of competitive ability that was apparent from these field and greenhouse studies, P.virgatum=R.pinnata>E.purpurea, could be partially explained by photosynthetic rates in relation to canopy light interception.     

A Cytogenetic Study of the Leaf Beetle Genus Cyrtonus (Coleoptera, Chrysomelidae)

The chromosomes of ten species of Cyrtonus and the genome sizes of six are surveyed. Among the total of 15 chromosomally studied species, 11 have 2n=28 chromosomes and a 13+Xy_p male meioformula, three have 2n=40 and 19+Xy_p and one 2n=46 and 22+Xy_p. All but one species with 28 chromosomes show only metacentric or submetacentric chromosomes, whereas the species with 40 and 46 chromosomes display some telocentrics or subtelocentrics, that are probably derived from the former by centric fissions. However, since the number of major chromosome arms is strikingly higher in these latter species (NF=70 and 78) than in the 28-chromosome species (mostly NF=56), other chromosomal rearrangements such as pericentric inversions or heterochromatin accretions could also be involved. The genome sizes display a narrow range, from 1C=0.6–1.22pg, and they are not significantly correlated with the chromosome numbers. Some possible factors implied in the rough chromosomal evolution of Cyrtonus are discussed in relation to a few other genera of the subfamily Chrysomelinae.     

Effects of tidewater on the feeding ecology of hooded crane (<Emphasis Type="Italic">Grus monacha</Emphasis>) and conservation of their wintering habitats at Chongming Dongtan,China

Dongtan (or East Tideland) on Chongming Island in China is an important wintering site of Grus monacha (hooded crane). Field observations were conducted in Dongtan in the wintering season of 2000–2001 to determine how tidal fluctuation affects the habitat use and behavior of G.monacha. Scirpus mariqueter (sea-bulrush) was the dominant species in the tidal vegetation; and its corms were the major food source for G.monacha. The corms in the outer zone (far from the dyke) were buried underground shallower than those in the inner zone (near the dyke) because of erosion by tidewater. For easy access to food, G.monacha tended to select the outer zone and the edge of tidal creeks as its foraging sites for the majority of time spent on the tideland. Regression analysis revealed that distance of the foraging sites to the dyke was correlated with tidal height. The cranes did not appear to show territorial behavior, and tended to form large-sized flocks, especially at high tide, because of the effect of the tidewater and the non-uniform distribution of food. Thus, the height of the tide is an important factor responsible for the habitat selection of G.monacha, which was also the major cause of the cranes selecting only the natural tideland at Dongtan on Chongming Island. Unfortunately, the habitats of G.monacha are limited, and even threatened, at Dongtan because the tideland is frequently reclaimed. Appropriate measures should be taken to prevent the tideland being further reclaimed, otherwise the natural wintering grounds of G.monacha will soon disappear.     

Summer forage biomass and the importance of litterfall for a high-density sika deer population

The biomass of summer forage and their contributions were surveyed to show that litterfall supported a high-density population of sika deer (Cervus nippon Temminck) in summer on Nakanoshima Island, Toya Lake, Japan. In July 1974, the grassland had the highest productivity among understory vegetations (228±55kgha^–1: mean±SE). In deciduous forests, palatable plants occupied only 0.1% of the biomass of 0.872±0.366kgha^–1, and deciduous leaves within the reach of deer (=220cm at height) produced 0.208±0.070kgha^–1. However, litterfall during this period had the highest productivity, 28.7± 5.3kgha^–1. The deer consumed litterfall (75.6% in dry weight), short grasses (17.2%), deciduous forest understory (4.1%), deciduous leaves within the reach of deer (3.0%) and conifer plantation under story (0.1%). It is suggested that the high-density deer population would be maintained by litterfall through the year instead of browsing in deciduous forests, which has been overlooked.     

(T2AG3)n Telomeric Sequence Hybridization Indicating Centric Fusion Rearrangements in the Karyotype of the Rodent Oryzomys Subflavus

Chromosome preparations of 30 specimens of Oryzomys subflavus trapped in eight Brazilian localities were C-, and G-banded and analyzed by fluorescence in situ hybridization (FISH). Two karyotypes were found, 2n=50/FN=64, at three coastal localities of the Atlantic Forest domain, and 2n=58/FN=70 at two sites located in the Cerrado biome, Brazil Central. Two fluorescence in situ hybridization (FISH) patterns of the telomeric sequence (T₂AG₃)_n were observed: in both karyotypes the probes hybridized to the telomeres of all chromosomes and also a hybridization signal in the centromeric regions of two autosome pairs was seen in the 2n=50 karyotype. These results, together with the occurrence of other diploid numbers described in the literature, suggest that O. subflavus is a complex species, bearing fusion/fission rearrangements proper to the different biomes which it inhabits.     

Early development of the self-fertilizing mangrove killifish <Emphasis Type="Italic">Rivulus marmoratus</Emphasis> reared in the laboratory

The mangrove killifish Rivulus marmoratus was reared at 25°±1°C and 17ppt salinity from 0 to 100 days after hatching (DAH), and its early development was described by examining growth and morphometric parameters, meristic characters (vertebral and fin-ray counts), bone-cartilage development, and pigmentation. Growth was isometric for preanal length, head length, snout length, body depth, pectoral-fin length, dorsal-fin length, anal-fin length, and caudal-peduncle depth. Negative allometric growth was observed in eye diameter and gape size. Meristic counts (mean±SD) for vertebrae (34.2±0.4) and dorsal- (8.6±0.5), anal- (11.4±0.5), and caudal-fin rays (30.2±0.8) were complete at 0 DAH (n=5), whereas pectoral-fin rays and pelvic-fin rays were complete by 30 DAH (14.5±0.4, n=5) and 60 DAH (4.2±0.8, n=5). Full ossification of meristic elements proceeded in the following sequence: vertebrae (by 30 DAH), caudal-, dorsal-, and anal-fin rays (by 60 DAH), pectoral-fin rays (between 60 DAH and 100 DAH), and pelvic-fin rays (by 100 DAH). Both morphological characters and meristic counts indicate that this species can be considered to be a juvenile after 9.8mm in standard length (20 DAH).     

The Effects of Hypoxia on Three Sympatric Shark Species: Physiological and Behavioral Responses

Behavioral and physiological responses to hypoxia were examined in three sympatric species of sharks: bonnethead shark Sphyrna tiburo, blacknose shark, Carcharhinus acronotus, and Florida smoothhound shark, Mustelus norrisi, using closed system respirometry. Sharks were exposed to normoxic and three levels of hypoxic conditions. Under normoxic conditions (5.5–6.4mg l^–1), shark routine swimming speed averaged 25.5 and 31.0cm s^–1 for obligate ram-ventilating S. tiburo and C. acronotus respectively, and 25.0cm s^–1 for buccal-ventilating M. norrisi. Routine oxygen consumption averaged about 234.6 mg O₂kg^–1h^–1 for S. tiburo, 437.2mg O₂kg^–1h^–1 for C. acronotus, and 161.4mg O₂ kg^–1 h^–1 for M. norrisi. For ram-ventilating sharks, mouth gape averaged 1.0cm whereas M. norrisi gillbeats averaged 56.0 beats min^–1. Swimming speeds, mouth gape, and oxygen consumption rate of S. tiburo and C. acronotus increased to a maximum of 37–39cm s^–1, 2.5–3.0cm and 496 and 599mg O₂ kg^–1 h^–1 under hypoxic conditions (2.5–3.4mg l^–1), respectively. M. norrisi decreased swimming speeds to 16cm s^–1 and oxygen consumption rate remained similar. Results support the hypothesis that obligate ram-ventilating sharks respond to hypoxia by increasing swimming speed and mouth gape while buccal-ventilating smoothhound sharks reduce activity.     

The temperature-dependent duration of development and parasitism of three cereal aphid parasitoids, Aphidius ervi, A. rhopalosiphi, and Praon volucre

Temperature dependencies were established for the egg-to-mummy and mummy-to-adult phases, for mummy mortality, and for parasitism of Aphidius ervi Haliday, Aphidius rhopalosiphi De Stefani-Perez, and Praon volucre (Haliday) (Hymenoptera, Aphidiidae), three parasitoids of Sitobion avenae (Fabricius) (Homoptera, Aphididae), at 8°C, 12°C, 16°C, 20°C, and 25°C on winter wheat (cv. Haven). A physiological model described temperature-dependent development over the full temperature range, whereas a linear model was fitted for data above 8°C and used to estimate the lower temperature thresholds and day-degrees (° D) required for development. The thresholds for A. ervi were 2.2°C for egg-mummy development and 6.6°C for mummy-adult development, those for A. rhopalosiphi were 4.5°C and 7.2°C, and those for P. volucre were 3.8°C and 5.5°C. The time to develop into mummies and adults differed significantly between the three species: A. ervi development into mummies required an average of 159 ° D, while development into adults took an average of 73 ° D. The corresponding average times required for A. rhopalosiphi and P. volucre to develop mummies were 124° D and 126° D, while their development into adults required an average of 70° D and 150° D, respectively. Mummy mortality was 25–35% at 8°C and less at the higher temperatures tested, but began to increase again at 25°C, showing a quadratic relationship between mortality and temperature. Parasitization was very low or, in the case of P. volucre, absent up to 12°C and thereafter increased with increasing temperature. The relationship between parasitization, recorded as percent aphids mummified, and temperature was linear at the temperatures tested and depended on species. A. ervisuperparasitized 11.1% aphids at 20°C and 16.6% aphids at 25°C, whereas superparasitism was low in A. rhopalosiphi and absent in P. volucre. From 16°C to 25°C the P. volucre sex ratio increased. For A. ervi and A. rhopalosiphi there was no trend with temperature, but at 20°C and 25°C it was close to even. Field data for 1996 and 1997 allowed for a comparison of actual and expected emergence of overwintering mummies. In both years, parasitoids were predicted to have emerged from overwintering mummies well in advance of the onset of aphid infestation, and more than a month earlier than the first parasitized aphids were found in winter wheat. Observations from trap plants in other crops supported the predictions of the models. Other factors that can affect biological control by cereal aphid parasitoids are discussed.     

Developmental morphology of the cyprinid fish Horadandia atukorali

Embryonic, larval, and juvenile development of a small Indian cyprinid, Horadandia atukorali, is described from laboratory-reared specimens. The eggs, measuring 0.7–0.8mm in diameter, were demersal, almost spherical in shape, transparent and unpigmented, with a pale yellow yolk without oil globules. Hatching occurred 47–54h after fertilization at 26.3–27.5°C. The newly hatched larvae, measuring 2.3–2.6mm in body length (BL) with 16+13=29 myomeres, had no melanophores, except on the eye, a single melanophore occurring on the lower margin, and xanthophores surrounding the pupil. The yolk was completely absorbed at 3.0mm BL. Notochord flexion was initiated at 4.0mm BL and finished at 4.4mm BL. Aggregate numbers of all fin rays were completed at 8.0mm BL. Squamation was initiated at 6.4mm BL and completed at 9.5mm BL. Although the eggs of Horadandia atukorali resembled those of other small danionin species, including Aphyocypris chinensis, Chela dadiburjori, Danio rerio, Devario malabaricus, and Hemigrammocypris rasborella, they differed from those of Danio rerio and Devario malabaricus in having a narrower perivitelline space. The larvae and juveniles of Horadandia atukorali were also similar to those of the latter five species in general morphology, especially in the presence of a melanophore on the lower margin of the eye at hatching, as in C. dadiburjori. However, the early life stage morphology of Horadandia atukorali differed from the other danionin species in having a conical yolk sac at hatching, no cement organ on the forehead in the yolk-sac larval stage, a divided gas bladder in the flexion larval stage, two dark lateral streaks on the head and chevron-like melanophores on the ventral body surface from the preflexion to postflexion larval stages, and xanthophores on the eyes at hatching.     

Recombinant Components of the EcoRII Restriction–Modification System: Restriction Endonuclease Can Interact with DNA · RNA Duplexes

To obtain recombinant restriction endonuclease (R) and methylase (M) of the EcoRII restriction–modification system, bacterial strains overproducing their functional hexahistidine derivatives were constructed. Active full-length R·EcoRII was produced only in cells that also expressed M·EcoRII from a multicopy plasmid. Recombinant R·EcoRII bound with hybrid DNA·RNA duplexes.     

Competition between <Emphasis Type="Italic">Eucalyptus victrix</Emphasis> seedlings and grass species

Competition in a natural system may be interspecific or intraspecific. In semiarid ecosystems, competition for resources between established neighboring grass species and newly recruited seedlings is very high. To examine the effects of grass species density, growing space and time of establishment on Eucalyptus victrix seedlings (interspecific competition), and the effect of density and growing space within E.victrix (intraspecific competition) we conducted an experiment under controlled conditions. We tested four hypotheses (i) E.victrix seedling growth is not affected by grass density; (ii) there is no difference in E.victrix survival and growth between early and later grass establishment; (iii) interspecific competition is not more intense than intraspecific competition in E.victrix; and (iv) growth of E.victrix seedlings is not dependent on available growing space. In a monoculture of E.victrix, seedling mortality was higher (10%) in large pots. In mixed culture pots, where E.victrix seedlings and grass seedlings were planted on the same day, E.victrix seedlings survived for up to 4weeks, but started to die after week five in the smallest pots. However, mortalities occurred in pots of all sizes when grass was established before E.victrix seedlings. Results also indicated that the resources necessary for the growth of individual E.victrix seedlings were more limiting under conditions of increased density of neighboring grass species rather than intraspecific competition. In particular, photosynthetic area of E.victrix seedlings was drastically reduced in mixed cultures. Although density, pot size and time of planting had impacts on E.victrix seedlings, the patterns of these impacts were variable.