Detection of methanogens and methanotrophs in natural environments

The role of methane as a greenhouse gas and the contribution of bacteria to the production (methanogenesis) and destruction (methane oxidation) of methane is described. Using experimental approaches based on DNA sequences identifying either methanogen-specific or methanotroph-specific gene sequences methods were developed to broaden the detection and identification of methane metabolizing bacteria in natural environments. These methods were focused on blanket bog peat but are suitable for other environments. In addition to group specific 16S rRNA DNA sequences, specific functional gene probes based on methane coenzyme reductase sequences for methanogens and methane monooxygenase sequences for methanotrophs, were developed. These sequences were used in PCR-based protocols to detect and amplify specific gene sequences from the total DNA isolated from transverse sections of blanket bog peat. This permitted the analysis of the vertical distribution of methanogen and methanotroph populations, discrimination between different sub-sets of these populations, and the identification of novel organisms not previously detected by culture-based methods.     

Ultrasound production by genital stridulation in Syntonarcha iriastis (Lepidoptera: Pyralidae): long-distance signalling by male moths?

Males of the pyralid moth, Syntonarcha iriastis Meyrick, perch on vegetation at the tops of trees and bushes and produce ultrasound while their wings are spread and while sclerites at the end of the abdomen are spread to expose the genitalia. Exposing the genitalia appears to engage the sound-producing mechanism; the male genitalia and eighth abdominal sternite of this species are greatly modified and include a file and scraper and possible resonating areas. Sounds produced are consistent between individuals and comprise pulses which are narrow in frequency range, the first pulse being at about 42 kHz and two following pulses at about 57 kHz. The signal is detectable with an ultrasound 'bat' detector from 20 m. Two tettigoniid species (Orthoptera) at the same site produced ultrasonic calls of similar frequencies at the same times as the moth; differences in time-amplitude patterns could be used by orienting moths to recognize conspecifics. Signalling by male S. iriastis is compared with that of other pyralid species in which females are attracted to signalling males. The behaviour of S. iriastis males differs from that of other pyralids in that they do not signal in groups or from a resource attractive to females, and do not possess glands known to produce a 'calling' pheromone. It is suggested, because of these differences, that sound production in this species does not function at close range, as argued for the wax moth Achroia grisella (Fabricius), but instead as a long-distance calling signal.     

Brood division and transition to independence in Blackbirds Turdus merula

Blackbirds Turdus merula rearing young in the Botanic Garden, Oxford, were observed over three summers (1979–81). Between 0 and 10 days after fledging the young were divided between the parents so that each fed only certain fledglings and refused to feed others. This division was temporally stable. In broods where another nesting attempt followed, the male usually took responsibility for all the young, but in final broods they were divided fairly evenly. The probability of a fledgling surviving to independence declined as the number of young a parent fed increased; thus division should be favoured. However, if the female fed some young the inter-nest interval increased and the potential number of young that could be raised in that season was curtailed. This trade-off is examined by means of a model. After fledging the young improved in their ability to capture prey successfully and increased the size of the prey taken. At 15–24 days after fledging, self-feeding became more profitable than parental feeding and the young became fully independent. The timing of this transition is influenced by the parents, and it is suggested that by dividing the brood, parental feeding can be more carefully regulated so that finer control over the timing of independence is achieved.     

The herbaceous lycophyte Haskinsia Grierson and Banks from the Devonian of western Venezuela, with observations on leaf morphology and fertile specimens

The Devonian herbaceous lycophyte genus Haskinsia Grierson and Banks is characterized by narrow dichotomizing stems and helically arranged petiolate leaves with a broad, approximately deltoid, lamina. New specimens are reported from four horizons in the Lower Member of the Campo Chico Formation, Sierra de Perijá, western Venezuela. H. sagittaka Edwards and Benedetto has sagittate leaves, and fertile specimens are reported for the first time; the ellipsoidal/obovoid adaxially-flattened sporangium is attached to unmodified leaves towards the top of the petiole in the adaxial position. H. sp. has sagittate leaves which are larger than any yet attributed to the genus but is represented by only three specimens. H. hastata sp. nov. has hastate leaves; the sporangia are more globose but positioned similarly to those of H. sagittata. The occurrence of the sporangia on unmodified microphylls indicates that Haskinsia is a member of Protolepidodendrales. The status of Haskinsiaceae is discussed. The Venezuelan specimens are compared with other records of Haskimi and Haskinsia -like plants from North America, Kazakhstan, North China, North Africa and Antarctica.     

Exceptional preservation in Lower Devonian coalified fossils from the Welsh Borderland: a new genus based on reniform sporangia lacking thickened borders

Reniform sporangia, comprising two equal valves and containing retusoid spores, recovered from Lower Old Red Sandstone strata of Devonian age (micrornatus-newportensis Spore Biozone: lower Gedinnian lower Lochkovian) on North Brown Clee Hill in the Welsh Borderland are placed in Resilitheca salopensis gen. et sp. nov. Conventional compression fossils from Targrove, Ludlow of fertile axes showing isotomous branching with limited overtopping are considered conspecific because the terminal reniform sporangia contain the same spores. Spore ultrastructure is described using scanning and transmission electron microscopy. Sections show faint traces of lamellae. Particles associated with spores and sporangium wall are compared with the globules of pteridophytes and Ubisch bodies of angiosperms, and related to the development of the sporangium. The new plants are compared with Cooksonia caledonica Edwards known only from impressions, and with Renalia Gensel showing far more pronounced pseudomonopodial branching.     

Exceptional preservation in Lower Devonian coalified fossils from the Welsh Borderland: a new genus based on reniform sporangia lacking thickened borders

Reniform sporangia, comprising two equal valves and containing retusoid spores, recovered from Lower Old Red Sandstone strata of Devonian age ( micrornatus-newportensis Spore Biozone: lower Gedinnian lower Lochkovian) on North Brown Clee Hill in the Welsh Borderland are placed in Resilitheca salopensis gen. et sp. nov. Conventional compression fossils from Targrove, Ludlow of fertile axes showing isotomous branching with limited overtopping are considered conspecific because the terminal reniform sporangia contain the same spores. Spore ultrastructure is described using scanning and transmission electron microscopy. Sections show faint traces of lamellae. Particles associated with spores and sporangium wall are compared with the globules of pteridophytes and Ubisch bodies of angiosperms, and related to the development of the sporangium. The new plants are compared with Cooksonia caledonica Edwards known only from impressions, and with Renalia Gensel showing far more pronounced pseudomonopodial branching.     

The size,distribution and germination requirements of the soil-stored seed-bank of Grevillea barklyana (Proteaceae)

Abstract Fire-triggered release from seed dormancy is a characteristic of many Australian plant species. We investigated aspects of the seed-bank dynamics and dormancy characteristics in seeds of Grevillea barklyana, an understorey shrub of coastal sclerophyll vegetation in the Jervis Bay Region on the south coast of New South Wales. We used two soil core sizes to compare the number and distribution of stored seeds in soil cores taken from underneath and outside the limits of plant canopies at three study sites. Core size did not affect the estimate of seed density. No seeds were found outside the existing canopies. Even in under-canopy samples, seed numbers were small. Mean seed densities were estimated as 10. 9, 14. 1 and 4. 3 seeds per for the three sites. A hierarchical series of laboratory experiments was used to test the germination response of both fresh and soil-stored seeds. Likewise, we attempted to simulate ‘natural’ disturbance conditions in a glasshouse experiment. Both laboratory and glasshouse experiments indicated polymorphism in germination behaviour. A constant proportion of seeds exhibited enforced dormancy, when moist at room temperature, while a smaller number of seeds showed either an induced dormancy or a non-seed-coat linked innate dormancy. The majority (75%) of seeds were innately dormant due to a hard seed-coat. This dormancy was broken when the seed-coat was damaged, for instance, by heat. The level of polymorphic germination behaviour will be dependent on the length of the inter-fire periods. We conclude that the expression of polymorphism within and between species across a range of environments and fire regimes is an important consideration for any further study attempting to assess the role of the seed-bank.