Adaptations of Crustaceans to Land: A Summary and Analysis of New Findings

Crustaceans have adapted to land through various morphological,physiological, biochemical, and behavioral modifications, ofwhich some are shared by all land-dwelling crustaceans and othersare unique to animals within a particular habitat. Among thethree groups of crustaceans having truly terrestrial members,the amphipods have achieved their success on land primarilyby behavioral means, while the isopods and the decapods havedeveloped many morphological, physiological, and biochemicaladaptations as well. In all three groups, behavioral modifications ensure that lossof water is minimal, that the animals are exposed to favorablerather than extreme environmental conditions, and that the fineline between evaporative cooling and excessive dehydration ismaintained. In most crustaceans the excretion of nitrogenous wastes requiresthat copious supplies of water be available for washing awaythe soluble end-products. Yet terrestrial isopods are able toexcrete ammonia as a gas, without being subject to toxic side-effects.In decapods, either ammonia or insoluble uric acid may be excreted,with ammonia the more likely product when water is available,uric acid when water is scarce. In adult land crabs water balance is maintained through theconcerted action of gills, pericardial sacs, and gut. Theseorgans may take up, store, and redistribute salts and waterin response to control exerted by the central nervous systemthrough its secretory products. In larvae of land crabs theseorgans are not known to function in this way. Rather, the larvaeare adapted to cope with osmotic problems of their planktonicexistence. Gaseous exchange in adult land crabs is carried on not onlyby the gills but also by the highly vascularized lining of thebranchial chambers, and the hemocyanin ot these crabs is adaptedto function in the environment peculiar to each species. Terrestrialcrabs seem unable to withstand low temperatures, but their highrate of cytochrome c oxidase activity may help them to survivewhen temperatures are high. Modifications in behavior must have occurred quite early inthe transition of crustaceans from sea to land. Then, as now,appropriate behavioral responses to light, temperatuie, humidity,tidal cycles, and so on. were crucial if a terrestrial animalwas to survive. Social interactions, both for courtship andfor aggression, required the sending and receiving of appropriatevisual and acoustic signals and were promoted by the ritualizationof potentially injurious patterns of behavior.     

Effect of water constraint on growth rate, activity and body temperature of yearling common lizard (Lacerta vivipara)

We investigated the effect of water constraints on yearling Lacerta vivipara, a widespread species of lizard inhabiting European peat bogs and heath land. We conducted a laboratory experiment to investigate plasticity of growth rate, activity level and preferred body temperature. We subjected individuals of two source habitats (dry vs humid) to two laboratory conditions of water supply resulting in different air relative humidity and water availability (high vs low). We observed that a low water supply induced a lower growth rate and lower activity level, suggesting that growth limitation is correlated with adaptive responses to avoid dehydration. However, individuals from the two habitats selected different body temperatures when restricted in water and showed different ratios between growth and activity. This suggests that there is population variability in phenotypic plasticity with respect to water availability in the habitat. Field observations conducted in six natural populations, classified into two groups (dry vs humid habitat) also suggest that growth rate in nature is constrained by water availability. Received: 8 June 1998 / Accepted: 16 November 1998     

Habitat use and behaviour of European hedgehogErinaceus europaeus in a Danish rural area

HedgehogsErinaceus europaeus Linnaeus, 1758 were radio-tagged and monitored during the summer of 2001 in a Danish rural area with the objective of quantifying home ranges, nightly distances travelled, habitat use, activity patterns, day-nesting habits, and body-weight changes of the five males and five females being recorded. Males had larger home-range sizes and travelled longer nightly distances than females. The two most common habitat types within the home ranges of the hedgehogs were deciduous forest and arable land, whereas the two most frequently used habitat types were deciduous forest and grassland. No differences between the sexes were found in the proportions of different habitat types within the home ranges or in habitat use. Non-random habitat use was found; forested areas and edge habitats seemed preferred to open areas. The most frequently used day-nesting habitat was deciduous forest. Foraging was by far the most time-consuming nightly activity for both sexes. Males lost weight during the study period (May–July), whereas females gained weight. A peak in the frequency of sexual behaviour was found from late-June to mid-July. The high level of male ranging activity and the weight loss of males are interpreted as a consequence of the promiscuous mating system of hedgehogs.     

Gene-flow in the clouds: landscape genetics of a viviparous,montane grassland toad in the tropics

Anthropogenic habitat alteration often increases fragmentation and isolation, which decreases population sizes and increases extinction risk for species. Extrinsic threats may be buffered or enhanced by intrinsic factors. Within amphibians, the influence of different environmental and intrinsic factors on the population structure is not yet fully understood. Four factors were found to be important for population connectivity: life history traits, recent (anthropogenic) land use history, habitat, and topography, but the direction of their influence differed between studies. Here, we examine the genetic population structure and interpopulation connectivity within the complete distribution of Nimba toads (Nimbaphrynoides occidentalis), a toad from montane tropical West Africa. The Nimba toad is the only known viviparous, matrotrophic (foetuses are nourished during the gestation by their mothers) anuran on Earth. It occurs in three regions, the smallest is situated in disturbed, the largest population in partly disturbed habitat and the third was not yet impacted. We found small, but significant population differentiation, no indication of a recent bottleneck in the smallest population, but an indication of a reduction in population sizes in the more distant past in all three populations and no sex-biased dispersal. Correlations with landscape classifications indicate that high elevations, due to their high humidity levels, are the most important landscape characteristic facilitating dispersal. This underscores desiccation risk as an important landscape characteristic for amphibian population connectivity. We found indication that life-history traits (viviparity), land use history (mining-related activity) and topography (elevation) have an influence on Nimba toad population differentiation and gene-flow.     

Responses of nitrate assimilation and N translocation in tomato (Lycopersicon esculentum Mill) to reduced ambient air humidity

The impact of low humidity in ambient air on water relations,nitrate uptake, and translocation of recently absorbed nitrogen,was investigated in 5-week-old tomato (Lycopersicon esculentumMill cv. Ailsa Craig) plants grown hydroponically in a completenutrient solution. Plants were subjected to dry air (relativehumidity 2–4% for 6 h. The transpiration rate increasedseveral-fold and the shoot water content decreased by almost20%, whereas root water content was unaffected. No effect onin vitro nitrate reductase (NR) activity was detected when usingan EDTA-contraining assay buffer. Replacement of EDTA with Mg²⁺revealed a significant decline in shoot NR activity, which suggestsphosphorylation of the enzyme during the stress treatment. Plantswere grown in a split-root system, in which one root half wasfed ¹⁵N-nitrate during the treatment, in order to determinenitrate uptake and translocation of recently absorbed nitrogenin the plants. Uptake of nitrate was substantially inhibited,but the proportion of absorbed ¹⁵N that was translocated tothe shoots was only slightly affected. In untreated plants,71% of the ¹⁵N recovered in roots had been retranslocated fromthe shoots, whereas in plants subjected to stress the deliveryof ¹⁵N from shoots to roots appeared to be completely inhibited.The data show that lowered humidity in air has significant effectson both uptake of nitrate as well as translocation of nitrogenwithin the plants. Some of these effects appear to be commonwith those observed in plants subjected to reduced water potentialsin the root environment and point to the possibility of theshoot water relations being highly influential on nitrogen uptakeand translocation. Key words: Air humidity, nitrate assimilation, nitrate reductase activity, nitrogen translocation, tomato, water stress     

Photosynthesis and Transpiration in Rice as Influenced by Soil Moisture and Air Humidity

The paper describes the effect of soil moisture content andair humidity on CO₂ exchange (P_N), CO₂ diffusion resistance(Cr) and transpiration (E) in four varieties of japonica rice(Oryza sativa L.). A decrease in soil moisture content reducedthe rate of photosynthesis to a varying degree in the varieties.Reduction in photosynthesis was attributed to increase in Cr.The effect of low soil moisture on photosynthesis and CO₂ diffusionwas further intensified by decrease in air humidity. By maintaininga high humidity in the air around the leaves however, the effectof soil moisture deficiency was reduced considerably, exceptin Rikuto Norin 21 which was very sensitive to soil-moisturedeficiency alone. Dryness of the air enhanced the transpirationrate, although the increase was relatively less in the plantsfacing a simultaneous water crisis at the root surface. In plantsgrowing under flooded conditions, a decrease in air humiditycaused a slight depression in P_N despite the simultaneous decreasein Cr. Oryza sativa L., rice, photosynthesis, transpiration, diffusion resistance, soil moisture, air humidity     

Effect of Evaporative Demand on Water Relations of Citrus limon

Conductance, transpirational flux and xylem pressure potentialwere measured in leaves of well-watered 5-year-old lemon trees(Citrus limon (L.) Burm. f.) subjected to different levels ofevaporative demand. Increased leaf-to-air absolute humiditydifference generally decreased stomatal conductance and increasedxylem pressure potential, with a good correlation between thelast two parameters; but this trend was reversed on days withvery high evaporative demand, when stomata opened in spite ofthe low humidity. Citrus limon (L.) Burm. f., lemon, water stress, stomatal conductance, leaf water potential, transpiration, air humidity     

Seasonal Shifts in Nocturnal Habitat Use by Coastal Bat Species

Sensitivity of bats to land use change depends on their foraging ecology, which varies among species based on ecomorphological traits. Additionally, because prey availability, vegetative clutter, and temperature change throughout the year, some species may display seasonal shifts in their nocturnal habitat use. In the Coastal Plain of South Carolina, USA, the northern long-eared bat (Myotis septentrionalis), southeastern myotis (Myotis austroriparius), tri-colored bat (Perimyotis subflavus), and northern yellow bat (Lasiurus intermedius) are species of conservation concern that are threatened by habitat loss. Our objective was to identify characteristics of habitat used by these species during their nightly active period and compare use between summer and winter. We conducted acoustic surveys at 125 sites during May–August and at 121 of the same 125 sites December–March 2018 and 2019 in upland forests, bottomland forests, fields, ponds, and salt marsh and used occupancy models to assess habitat use. The northern long-eared bat and southeastern myotis (i.e., myotis bats) used sites that were closer to hardwood stands, pine stands, and fresh water year-round. We did not identify any strong predictors of tri-colored bat habitat use in summer, but during winter they used bottomland forests, fields, and ponds more than salt marsh and upland forests. During summer and winter, northern yellow bats used sites close to fresh water and salt marsh. Additionally, during summer they used fields, ponds, and salt marsh more than upland and bottomland forests, but in winter they used bottomland forests, fields, and ponds more than upland forest and salt marsh. Our results highlight important land cover types for bats in this area (e.g., bottomland forests, ponds, and salt marsh), and that habitat use changes between seasons. Accounting for and understanding how habitat use changes throughout the year will inform managers about how critical habitat features may vary in their importance to bats throughout the year. © 2021 The Wildlife Society.     

Calorimetric Studies of Behavior, Metabolism and Energetics of Sessile Intertidal Animals

SYNOPSIS: Behaviors to conserve water during intertidal exposureat the same time impair respiratory gas exchange, so that observedresponses to emersion may reflect compromises between theseincompatible needs. Behavioral isolation of the tissues fromair results in the complete or partial reliance on anoxic energymetabolism, which is most reliably measured directly as heatdissipation. Combined direct calorimetry and indirect calorimetry(respirometry) enable the partitioning of total metabolic heatdissipation into its aerobic and anoxic components, which mayvary according to physical and biological factors. The musselMytilus edulis is tolerant of anoxia and saves water and energyduring aerial exposure in its rocky intertidal habitat by closingits shell valves and becoming largely anoxic. Like most suspensionfeeders in this habitat, its compensation for reduced feedingtime involves energy conservation; there is little evidencefor energy supplementation such as increases in feeding rateor absorption efficiency. Ammonia production continues duringaerial exposure and is involved in acid-base balance in thehemolymph and mantle cavity fluid. Infaunal cockles (Cardiumedule) and mussels (Geukensia demissa) gape their shell valves,remain largely aerobic and have high rates of heat dissipationduring intertidal exposure, a response which appears relatedto the lower desiccation potential and exploitation of richertrophic resources in their soft-sediment habitats. The variableexpansion of the symbiotic sea anemone Anthopleura elegantissimareflects interaction among the responses to desiccation, irradianceand continued photosynthesis by its zooxanthellae during exposureto air.     

Take-off of Mould Spores in Relation to Wind Speed and Humidity

Using horizontal tube-cultures of various moulds belonging tothe genera Thamnidmmt, Phymatotrichum, Trichotheciwm, Ptptocephalis,Trichoderma, Mucor and Mycogone, the take-off of dispersal units(usually spores) under the influence of air currents of variousspeeds and of different humidities has been studied. It is foundthat in all the dry-spore forms the number of spores set freeincreases as the speed of the air stream rises. Further, atany given air-stream rate, the numbers of spores set free aregreatest in the first interval of time and rapidly fall offin subsequent intervals. In all species, spores are more readilyset free in air streams of relatively low as compared with thoseof relatively high humidity. Although Trichoderma viride hasbeen regarded as a slime-spore fungus, its conidia can readilybe blown from the conidiophores. No spores could be inducedto take off from Mucor ramarmianus even at the highest air speedsused.     

An empirical model of net photosynthesis for the desert plant Hammada scoparia (Pomel) Iljin

Summary An empirical model for describing daily courses of net photosynthesis in Hammada scoparia is being developed. The model is based on the functional relationships, by which various environmental factors affect the photosynthetic activity and which can be measured by experiment in the field. In a sequence of steady-states daily courses of net photosynthesis are predicted during a growing season considering the variability of the physiological states and the capacity for regulative adaptations. The rate of net photosynthesis at a certain date is calculated from the maximal rate of CO₂ uptake being expected at that season and from the effects of light, temperature, and air humidity which are scaled from 0 to 1. All factors are connected multiplicatively. The light function accounts for the seasonal changes in the light curve, the temperature function is based on the seasonal shift of the temperature optimum, and the humidity function considers the increasing sensitivity of the stomatal humidity response at increasing water stress. The model is built to be a submodel of a general ecosystem model, where various other submodels (i.e. water stress model, phenology model) are supplied. The present model is tested by predicting daily courses at extreme climatic conditions during the year and by comparing the predicted values of gas exchange with values being measured in an independent experimental procedure. The result shows that the model is able to simulate the natural behaviour of Hammada scoparia during the growing and dry season of a desert habitat. The problems of incorporating the influence of water stress, the interaction of the various factors, and the phenological aspect of the photosynthetic activity is being discussed.     

Effects of pasture and forest microclimatic conditions on the foraging activity of leaf-cutting ants

The fragmentation and transformation of land cover modify the microclimate of ecosystems. These changes have the potential to modify the foraging activity of animals, but few studies have examined this topic. In this study, we investigated whether and how the foraging activity of the leaf-cutter ant Atta cephalotes is modified by microclimatic variations due to land cover change from forest to pasture. We characterized the microclimate of each habitat and identified alterations in foraging behavior in response to relative humidity (RH), air temperature, and surface temperature along ant foraging trails by synchronously assessing foraging activity (number of ants per 5 min including incoming laden and unladen and outgoing ants) and microclimatic variables (air temperature, RH, and maximum and minimum surface temperature along the foraging trail). There were climatic differences between habitats during the day but not throughout the night, and A. cephalotes was found to have a high tolerance for foraging under severe microclimatic changes. This species can forage at surface temperatures between 17 and 45°C, air temperatures between 20 and 36°C, and an RH between 40% and 100%. We found a positive effect of temperature on the foraging activity of A. cephalotes in the pasture, where the species displayed thermophilic behavior and the ability to forage across a wide range of temperatures and RH. These results provide a mechanism to partially explain why A. cephalotes becomes highly prolific as anthropogenic disturbances increase and why it has turned into a key player of human-modified neotropical landscapes.     

Evaporative water loss simulation improves models’ prediction of habitat suitability for a high-elevation forest skink

Accurate evaluation of habitat availability for wildlife is relevant for ecological applications. Researchers have frequently used models to simulate habitats thermally suitable for reptiles, but these results have limited application for species highly selective for habitat humidity. Here, we use the biophysical Niche Mapper™ model to investigate impacts of vegetation cover on the habitat quality of a high-elevation forest skink, Sphenomorphus taiwanensis, and to predict changes in habitat suitability in a future warmer climate (3 °C increase in air temperature). We assess habitat suitability with different densities of canopy cover in our study areas using two ecologically relevant estimates for lizards: maximum activity time and evaporative water loss (EWL) during the activity season. We measured preferred body temperature and EWL of this species for model parameterization, and behavioral response to EWL to supplement habitat quality assessment. The results indicated that this species is sensitive to EWL and reduces its activity when dehydrated. The model predicted that denser canopy levels increase microclimate cooling and humidity, and that most canopy levels are thermally suitable for this species, as the lizard can thermoregulate to manage adverse temperatures. Nevertheless, increasing canopy density could significantly decrease EWL during activity. In the warmer climate scenario, simulated maximum activity time and EWL changed little because of thermoregulation behavior. Our results suggest that habitat preference of this species is a consequence of water and energy requirements, and we note that combining EWL and maximum activity time data can enhance model accuracy of lizards’ habitat quality in a warmer climate.     

Responses to Saturation Deficit in a Stand of Groundnut (Arachis hypogaea L.) 1. Water Use

Stands of groundnut were grown in computer-controlled glasshouseson water stored in an undisturbed soil profile. The maximumsaturation vapour pressure deficit (D) of the air was either1.0, 2.0, 2.5, or 3.0 kPa, and the mean air temperature was27 °C. Transpiration (E), determined from the soil water balance, wasstrongly dependent on D, because D influenced both the fractionof incident solar radiation intercepted by foliage (f) and thetranspiration rate per unit f (E/f). When D exceeded 2 kPa,canopy expansion was restricted and f reduced during early growth,but differences in f diminished as the canopies closed. E/fincreased with D, implying that any restriction of transpirationthrough stomatal closure at large D was outweighted by a steeperhumidity gradient from leaf to air. In all treatments E/f decreased as the soil profile dried. Saturationdeficit per se had little influence on the proportional reductionin E/f with time, even though soil water deficit was considerablygreater at large D. This lack of response occurred because plantscompensated for the greater evaporative demand by extractinglarger amounts of water from deep in the profile. Groundnut, Arachis hypogaea L., humidity, rooting depth, transpiration     

影响武夷山景区松墨天牛种群动态变化的因素分析

为了监测武夷山景区松墨天牛Monochamus alternatus Hope的发生,防范松材松材线虫Bursaphelonchus xylophilus病的入侵,于2005-2007年每年4-9月,在武夷山景区10个地点进行了调查,研究了气象因素和环境因素对松墨天牛数量变化的综合影响规律及其程度,对调查结果进行了矢量递进因子分析。结果表明：环境因子和气象因子是松墨天牛羽化孔数和诱集成虫数变化的主要因素,影响松墨天牛成虫诱集数的环境因子按重要性排列依次为：郁闭度、地被物覆盖率、海拔、林龄、坡位、坡向和树高;影响羽化孔数的环境因子按重要性排列依次为：郁闭度、地被物覆盖率、树高、林龄、海拔、坡位和坡向。影响松墨天牛诱集成虫数和羽化孔数的气象因子按重要性排列依次为：月平均温度、最高与最低温差、总降雨量（mm）、气压（hpa）和平均湿度（%）。单从环境因子和气象因子的统计数据分析,环境因子的重要性次序是：坡位、郁闭度、地被物覆盖率、海拔（m）、 林龄（a）、树高（m）、坡向;气象因子的重要性次序是：气压（hpa）、 平均温度 （℃）、最高与最低温差（℃）、 总降雨量（mm）、平均湿度（%）。按月分析和按年度分析时其相对重要性基本上是一致的。结论认为,环境因子和气象因子对松墨天牛的数量变化有重要影响。     

热带雨林林内小生境对木奶果和染木种子萌发与幼苗存活的影响

森林生态系统中小生境的差异可能影响种子萌发与幼苗的建立,并形成物种不同的分布格局。为探讨生境异质性对植物分布的影响,该研究在西双版纳热带季节性雨林中选取5个具有不同海拔和地形的小生境,人工散布木奶果与染木种子,定期监测种子萌发与幼苗存活,同步记录小生境的近地面（距地面3 cm）温度、近地面(3 cm)空气湿度和表层土壤(5 cm)含水量变化,并在实验室开展种子脱水和不同水势条件下的种子萌发实验。结果表明：（1）实验所选的5个小生境中,沟底地带的土壤水分含量在一年中始终都高于其他小生境;5个小生境的空气相对湿度在雨季与雾凉季都接近饱和,只有在干热季出现明显的差别,即随海拔的升高,空气湿度下降。同时,在旱季,近地面温度随海拔的升高而升高, 出现1~2个月的山地逆温现象。（2）木奶果与染木具有不同的种子传播与萌发规律,而且染木种子在不同生境下,其种子萌发率和幼苗存活率有显著的差异。其中：木奶果种子在雨季成熟散布并快速萌发,以幼苗的形式度过干热季,其种子可以在相对较低的水势下萌发;染木种子在雨季末期成熟并进入休眠期,以种子的形式度过干热季,其种子相对较抗脱水。研究认为,地形是决定西双版纳热带季节性雨林生境异质性的重要因子,小生境在温度和水分方面的差异在干热季时尤为明显,并对木奶果和染木种子的萌发或幼苗存活产生了重要影响, 而木奶果与染木种子自身的特性使其对于西双版纳季节性的干旱具有不同的适应对策。     

不同海拔高度高寒草甸光能利用效率的遥感模拟

利用植被光合模型模拟了藏北高原3个海拔高度(4300,4500 m和4700 m)的高寒草甸生态系统的光能利用效率.海拔4500 m的光能利用效率均值(0.47 g C/MJ)显著高于海拔4300 m(0.38 g C/MJ)和4700 m(0.35 g C/MJ),而海拔4300 m和4700 m两者间差异不显著.相关分析和多重逐步回归分析表明,影响每个海拔光能利用效率季节变化的主要因子为空气温度,相对湿度以及地表水分指数,这3个因子共同解释了99％以上的光能利用效率的季节变化,其中空气温度的贡献最大,相对湿度的贡献次之,地表水分指数的贡献最小,这说明在3个海拔的任何一个海拔高度,温度对光能利用效率季节变化的胁迫作用大于水分对光能利用效率季节变化的胁迫作用.多重逐步线性回归分析表明,生长季节均土壤含水量是决定生长季节均光能利用效率沿海拔高度分布的主导因子.单因子线性回归分析表明,地表水分指数可以定量化高寒嵩草草甸生态系统水分状况,它同时可以反应土壤水分、近地表空气湿度以及生态系统植被含水量状态.因此,在高寒嵩草草甸生态系统,用地表水分指数反应生态系统尺度水分对光能利用效率的胁迫作用是可行的.     

BIOLOGY AND POPULATION DYNAMICS OF A CREVICE-DWELLING LANDSNAIL, CRISTATARIA GENEZARETHANA (CLAUSILIIDAE)

Crevice-dwelling land snails emerge only infrequently to theexposed surface, and very little is known about their naturalhistory. Here we report on the biology, life cycle, populationdynamics and longevity of one such species, Cristataria genezarethana,which we studied over a period of three years. C. genezarethana spends 95–98% of its lifetime withinrock crevices. In winter the crevice serves as an egg layingsite, and as a retreat during periods of inactivity. Throughoutsummer it serves for aestivation adults aestivate near CTeviceopenings, young apparently deeper inside. The surface of the rock serves mainly as a lichen-feeding andcopulating site, to which the snails emerge during brief periodsof activity. Both for the onset and for the continuation ofits activity season, C. genezarethana is absolutely dependentupon rain. However, activity ends before the end of the rainyseason, suggesting that aestivation is not merely a direct responseto dry climate. Though the population as a whole was active on each rainy day,no more than 15%–20% of the population were active simultaneously.An individual snail was active, on average, for only 6–12days per year. Population size of the study-rock reached 2000–2900individuals, and mean density was 150–200 snails m². Thissnail carrying capacity of the rock is broadly similar to thatof densely populated bushy habitats (when snail weight is considered).In these dense populations, low mating frequencies and growthinhibition may regulate population size. In all three seasons, the population consisted of two main large,well defined age groups: adults and young. As compared to theadults, the young were active on different parts of the rockand at different times. Although a third, intermediate groupof sub adults was found, it was always very small. A fourthgroup, of juveniles, appeared during winter; later, most ofthem disappeared. We did not observe any shift from the young to the adult sizegroup. This suggests a broadly stable population, with virtuallyno recruitment, in which final growth to adulthood is inhibitedby the adults. Growth was very slow, suggesting that maturityin nature is reached in about 11 years, and that individualslive sixteen years at least. Mortality occurred in all age groups,and about 5% of the population died each year. There was noevidence for heavy predation. Crevices might be a suitable habitat for land snails in whichthe hatching period, and period of juvenile growth, are verylong. (Received 1 February 1993; accepted 27 March 1993)     

Morphological and Physiological differences between Epilithic and Epiphytic populations of the Lichen Parmelia pastillifera

CO₂ exchanges, morphology and chlorophyll content of epiphyticand epilithic populations of Parmelia pastillifera growing inthe same locality (Bristol, UK) were investigated. Epilithicsamples had reduced net photosynthetic rates and a lower chlorophyllcontent, apparently caused by the high levels of irradianceof the exposed habitat, not completely buffered by the increasedthickness of the upper cortex. These samples also had much moredeveloped rhizinae; this modification is interpreted as a mechanismto increase the water storage capacity of the thallus. Physiologicaldifferences between the two populations seem to be due to themore extreme environmental conditions of the epilithic population.Copyright1995, 1999 Academic Press Chlorophyll content, CO₂-exchange rates, habitat, lichen, morphology, Parmelia pastillifera     

MORPHOLOGICAL VARIATION IN THE PAINTED TOPSHELL, CALL1OSTOMA ZIZYPHINUM (L.) (PROSOBRANCHIA: TROCHIDAE), FROM INTER-TIDAL RAPIDS ON THE IRISH COAST

Shell shape variation in Calliostoma zizyphinum (L.) is examinedwith different techniques of analysis (profile, discriminant,canonical variate and ratio analysis). Shells are collectedfrom five tidal rapids systems, all in very sheltered inlets,where C. zizyphinum is to be found at shore levels higher thanthe normal shore distribution of LWNT to the sublittoral. Shellmorphology varies consistently with the local habitat conditions,such as water flow rate, relative exposure and shore level.populations can be distinguished using various shell parametersand shell profiles. Shells from two different levels in thesame rapids show the effects of their subtly different habitats. (Received 5 February 1987;