NUTRITION OF TRIDACHIA CRISPATA (MORCH) (SACOGLOSSA)

Autotrophic nutrition plays an important role in adult Tridachiacrispata in the western Atlantic Ocean and results from an endosymbioticassociation between the sacoglossan and the kleptoplastids ofChlorophyta. A series of living specimens 7-80 mm in length was studied inthe laboratory. After a body length of 10 mm has been attained,the parapodial lobes of the two sides meet and fuse. Microscopicexamination of faecal strings of specimens undergoing this transitionrevealed that algal remains were produced only by juvenilesless than 13 mm long. Larger specimens defaecated only rarelyand the diminutive faecal strings contained no recognizablealgal debris. This transition probably parallels the physiologicaltransition between juvenile heterotrophic nutrition and adultautotrophic nutrition. Microscopic examination of the radulae of transitional specimensshowed no diminution of the size, number or morphology of theteeth. This indicates that in an emergency heterotrophic nutritionmay be resumed. Growth rates of Tridachia were measured in the laboratory, withand without light and the provision of algal foods. Unfed animalslost weight rather rapidly in captivity, whereas those fed uponsuitable algae (Halimeda discoidea, Caulerpa verticillata, C.racemosa and Chaetomorpha sp) did not.Caulerpa sertularioideswas suitable for food for a limited time, but proved toxic afterabout a week. Of the other species tested, Caulerpa verticillatawas the least suitable, while Halimeda, Chaetomorpha and Caulerparacemosa were the best. Ironically, C. verticillata was theonly one of the algal species tested which is known to be takenin the natural diet in Floridean waters. These experiments confirmedthat heterotrophic feeding will be resumed in Tridachia if theculture-conditions do not favour autotrophic nutrition.     

Population structure and the impact of regional and local habitat isolation upon levels of genetic diversity of the endangered damselfly Coenagrion mercuriale (Odonata: Zygoptera)

1. Coenagrion mercuriale is one of Europe's most threatened damselflies. There is concern for the long‐term persistence of many of its U.K. colonies because adult lifetime movement is limited, making isolated populations susceptible to extinction. 2. Using 14 microsatellite loci we characterised levels of genetic diversity, evidence for a recent decline and the spatial genetic structure for C. mercuriale population in Wales, U.K. 3. Spatial isolation is not an absolute predictor of low genetic diversity at either local or regional scales. 4. One population inhabiting a remote, edge of range site is genetically impoverished with levels of variability (at microsatellite loci) among the lowest reported for any insect species. 5. Agricultural land and high ground are physical barriers to dispersal by adults. 6. Consistent with work from elsewhere, movement by mature C. mercuriale in Pembrokeshire is sufficient to prevent significant genetic differentiation throughout a habitat matrix of some 3–4 km if the suitable habitat sites are <2 km apart and lack barriers to movement. Even within a good habitat matrix, however, genetic isolation by distance develops within 10 km.     

Localized, Cold-Induced Inhibition of Translocation in Mycelia and Strands of Serpula lacrimans

Thompson, W., Brownlee, C, Jennings, D. H. and Mortimer, A.M. 1987. Localized, cold-induce inhibition of translocationin mycelia and strands of Serpula lacrimans. —J. exp.Bot. 38: 889–899 The effect has been investigated of localized low temperatureon translocation of ³²P across myceliui of Serpula lacrimansusing two gas-flow detectors capable of recording radioactivitycontinuously. When the temperature of a band of mycelium wasreduced to 0 ? C, radioactivity ceased to accumulai and in factdeclined under the detector (number 2) separated from the sourceof radioactivity by tr cold-treated mycelium. In the myceliumbeneath the other detector (number 1), closest to the sourceradioactivity, the rate of accumulation of radioactivity increased.When the temperature was raised t 20 ?C, radioactivity beganto accumulate in the mycelium under detector 2 and, apart froma sma fluctuation, continued to accumulate at a uniform rate.In the mycelium under detector 1, the accumulation of radioactivitystopped for a short time but then recommenced at a rate similarto thi found at 0 ?C. In other experiments the distributionof radioactivity (¹⁴C) throughout the myceliui was measuredat the end in homogenized samples. In these experiments a bandof mycelium we subjected to 0 ?C or to 20 ?C for the whole experimentalperiod, or only after the mycelium had bee translocating radioactivityalready for 16 h. These experiments showed that the changesin the rate of accumulation of ³²P in living mycelium underthe two gas flow detectors used for in situ measurements werenot due to a reversal of the flow of translocation. The resultsare consistent with an hypothesis that a turgor-driven massflow of solution is the mechanism for translocation in thisfungus and are considered in relation to the results of similarexperiments on phloem translocation in higher plants. Key words: Serpula lacrimans, mycelium, translocation, low-temperature, phloem transport     

EASTERN MEDITERRANEAN OPISTHOBRANCHIA: ELYSIIDAE (SACOGLOSSA = ASCOGLOSSA)

An account is given of the elysiid sacoglossans collected ondiving expeditions to the eastern Mediterranean shores of Yugoslaviaand Greece during the period 1978–1986, supplemented bymaterial collected around Naples and some preserved specimensfrom other Mediterranean localities. In all, 6 species of Elysiaand 1 of Bosellia were investigated, including one new to science,E. gordanae from the Yugoslav Istrian Peninsula. The enigmaticElysia translucens Pruvot-Fol, 1957 was found in the easternbasin for the first time. The presence of the Bermudan, CanaryIslands and Jamaican E. flava Verrill, 1901 was confirmed inthe Greek Ionian and Aegean Seas, as well as in the Gulf ofCorinth. The geographical ranges of the other species were extendedby these collections from the eastern basin. The 7 elysiid specieswere illustrated from life and the radulae compared; great differencesin the size, shape and denticulation of the teeth of the differentspecies were evident (Received 8 May 1987;     

Internal Structure and Hydraulic Conductivity of Basidiomycete Translocating Organs

Eamus, D., Thompson, W., Cairney, J. W. G. and Jennings, D.H. 1985. Internal structure and hydraulic conductivity of basidiomycetetranslocating organs.–J. exp. Bot. 36: 1110–1116. The presence in rhizomorphs of Armillaria mellea and cords ofPhallus impudicus of wide diameter hyphae (5–20 {diaeresis}m),which run for considerable distances along these linear organs,has been demonstrated. The longitudinal hydraulic conductivityof these organs has been determined experimentally and similarvalues were obtained when the hydraulic conductivity was calculatedtheoretically on the basis that the vessel hyphae were the solechannel for water movement along these organs. The experimentaldata have been discussed in relation to other data for long-distancetranslocation in basidiomycete linear organs. It is concludedthat the vessel hyphae are the main channels for turgor-driventranslocation. Key words: -Basidiomycete fungi, translocation, hydraulic conductivity     

Translocation Profiles of [11C] and [13N]-Labelled Metabolites after Assimilation of 11CO2 and [13N]-Labelled Ammonia Gas by Leaves of Helianthus annuus L. and Lupinus albus L.

Tracer amounts of atmospheric [¹³N]-Iabelled ammonia gas, wereabsorbed by leaves of Lupinus albus and Helianthus annuus inboth the light and the dark. Exogenous [¹³N]-ammonia was onlyabsorbed in the dark when the feeding occurred shortly aftera period of illumination and the tissue was not depleted ofits carbohydrate reserves (e.g. starch). Incorporation of the[¹³N]-ammonia appeared to occur via the leaf glutamine synthetase/glutamatesynthase (GS/GOGAT) cycle since 2.0 mol m^–3 MSX, an inhibitorof the GS reduced uptake in both the light and dark. Photosyntheticincorporation of ¹¹CO₂ was not affected by this treatment Therate of movement of [¹³N]-assimilates in the petiole of attachedleaves of Helianthus and Lupinus was similar to that of the¹¹Cl-photo assimilates. Export of both [¹³N] and [¹¹C]-Iabelledassimilates from the leaf and movement in the petiole in boththe light and the dark was inhibited by source leaf anoxia (i.e.nitrogen gas). Translocation was re-established at the samerate when the feed leaf was exposed to gas containing more than2% O₂ which permitted dark respiration to proceed. After aninitial feeding of either ¹¹CO₂ or [¹³N]-ammonia at ambient(21%) O₂ exposure of the source leaf to 2% O2, or 50% O² didnot alter the rates of translocation, indicating that changesin photosynthetic activity in the source leaf due to photorespiratoryactivity need not markedly alter, at least during the shortperiod, the loading and translocation of either [¹¹C ] or [¹³N]-labelledleaf products. Key words: Translocation, CO₂, NH₃, Leaves, Helianthus annuus, Lupinus albus     

Germination of Species of Caryophyllaceae in Relation to their Geographical Distribution in Europe

Comparisons were made between the germination responses to temperatureof species of Caryophyllaceae collected in the wild from differentparts of Europe. Species occurring predominantly in the Mediterraneanzone were compared with those distributed in the deciduous woodlandzone of central and southern Europe; steppeland and grasslandareas of eastern Europe, and in the Taiga and Tundra of northernEurope. The geo-botanical distributions of different specieswere reflected in their germination responses. Species fromthe Mediterranean germinated over a range with a mean of 4.5to 24.2 °C; those from deciduous woodland over the range11.8 to 30.0 °C; those from steppelands over the range 6.0to 30.0 °C. There was little uniformity in the northernEuropean species. The significance of the results is discussedin relation to the distribution of different species, the variationwithin a species, and the climatic components of the variousgeo-botanical zones.     

Glauconema trihymene n. g., n. sp., a Hymenostome Ciliate from the Virginia Coast*

SYNOPSIS. Glauconema trihymene n. g., n. sp., a marine hymenostome ciliate, is described from the Virginia coast. Morphologic studies were made on specimens treated with the Chatton-Lwoff silver impregnation technic and on animals observed with the phase microscope. Particular attention is given to the buccal ciliature and its importance to generic assignment in the order Hymenostomatida.