Adjustment of the activity of α-amylase extracted from the style of the black mussel Choromytilus meridionalis (Krauss) in response to thermal acclimation

The mussel Choromytilus meridionalis (Krauss) is a common inhabitant of the intertidal zone on the west coast of the Cape Peninsula, South Africa, and experiences temperatures of between 8°C when immersed by the tide and at least 25°C on exposure to air. The activity of α-amylase extracted from the crystalline style of freshly-collected mussels has a low temperature coefficient of ≈ 1.12 over much of the temperature range experienced in the natural environment. Warm acclimation results in an increase in the α-amylase activity, despite the fact that individual rate: temperature curves for extracts from mussels acclimated to 8, 15 and 22°C have rather low temperature coefficients of 1.14–1.17 between 10 and 20°C. The increase of activity of the α-amylase following warm acclimation may form an integral part of the improved filtration, ingestion and assimilation which is necessary to offset increased metabolic losses during the warm conditions of the summer months.     

Prey selection and the impact of the starfish Marthasterias glacialis (L.) and other predators on the mussel Choromytilus Meridionalis (Krauss)

The diet of the starfish, Marthasterias glacialis (L.), consists of a variety of mollusc species, as well as ascidians and barnacles. Starfish densities are maximal where mussels, Choromytilus meridionalis (Krauss), are abundant and in such areas mussels form the bulk of the diet. Laboratory feeding experiments indicate that Marthasterias glacialis select mussels of particular sizes and that the length of prey taken is an increasing function of predator arm length. The time taken to consume each mussel is determined by the ratio of shell length to starfish size. The number of mussels consumed per day increases only slightly with starfish size, but because the prey taken increase in size, energy consumption is maintained at a relatively consistent 1% of predator body energy per day. Using prey selection and feeding rate data for different sized starfish, predictive three dimensional predation surfaces are developed for a natural starfish population feeding on either one or two cohort Choromytilus meridionalis populations. The models indicate that predatory effort should be concentrated on the smallest mussels when a single adult cohort is present, but on recruiting mussels just above the minimum prey size limit where two cohorts are present. Other major predators of mussels, the rock lobster, Jasus lalandii (Milne Edwards), and the whelk, Natica tecta Anton, appear to select similar size-ranges of prey to starfish, despite their differing body forms and feeding methods. Since the juveniles of all three predators can only take small mussels, predator recruitment may well depend upon the successful settlement of strong mussel cohorts. Evidence for such entrainment of predator cohorts to settlements of mussels is presented.     

Reproductive cycles in oregon populations of the echlnoid, Strongylocentrotvs purpuratus (Stimpson). I. Annual gonad growth and ovarian gametogenic cycles

Four annual reproductive cycles were followed in the echinoid, Strongylocentrotus purpuratus (Stimpson), at three places on the central Oregon coast near 44°45′N lat., where intermittent upwelling depresses coastal sea temperatures from June through September. Monthly measurements were made of the gonad index of samples of 30 urchins and the relative frequency of five stages in oogenesis were determined from sectioned ovaries from these samples.Individuals in these populations are synchronous in their annual cycle of gonad growth, oogenesis, and spawning, the latter taking place between late December and March. The population usually undergoes one major, complete spawning within a period of 30 days. When large reserves of stored nutrients are present, ova continue to mature over a longer period and may be present in quantity from December into April. Gonad weight does not change significantly from March through June. From July through November the gonad undergoes its annual growth at a mean instantaneous relative growth rate of ≈ 1 % per day. Gonad growth is not significantly correlated with sea temperature. Variable temperatures resulting from upwelling do not result in erratic fluctuations in the reproductive cycle, probably because of the annual change in feeding rate, the seasonal shift in energy utilization, and the constancy of the amount of food assimilated during gonad growth. Gonad size and annual growth rates may differ significantly between years and locations, indicating that both are influenced by local environmental factors, probably food availability and degree of wave action.The frequency of oogonial clusters is least in mid-winter, increases after spawning, reaches an annual maximum in June and declines in the fall. Primary oocyte growth is very slow until October, when it increases abruptly, and some oocytes become ova as early as late October. When stored nutrients are low, many oocytes do not complete growth by January, and are not spawned until May. Prolongation of the spawning period delays the increase in frequency of oogonial clusters in the following new cycle. The timing of the annual increase in oogonial cluster frequency and of the onset of rapid oocyte growth did not otherwise vary between places and years. In these populations, entrainment or synchronization of the reproductive cycle to seasonal environmental events probably occurs at the beginning of one or all of these critical annual events: oogonial proliferation, annual gonad growth and rapid oocyte growth.     

Endogenous tidal rhythmicity in the littoral pycnogonid Nymphon gracile (Leach)

The pycnogonid Nymphon gracile (Leach) has been shown to have an endogenous activity rhythm of tidal frequency, the peak of activity occurring at, or just after, expected high water. Animals collected littorally show some rhythmicity at all times of the year. The rhythm drifts in most individuals when recorded in the laboratory at 20°C, but some animals collected in winter and recorded at 9°C, did not show any drift.     

Temporal changes and sexual differences of impaling behavior in Southern Grey Shrike (Lanius meridionalis)

The Southern Grey Shrike (Lanius meridionalis) is a common resident along the rift valley. During 2007-2008 we studied the impaling behavior of Southern Grey Shrikes at the Shezaf nature reserve by food supplementation. Our findings indicate seasonal shifts in impaling behavior. During the winter, there was no difference between the sexes and shrikes impaled house mice (Mus musculus) close to their territorial boundaries with neighboring conspecifics. All impaled mice disappeared from the tree within a few hours of impalement. During the mating season, males impaled the whole prey and let females eat it, and prey was impaled by both sexes only in order to dismember and feed the nestlings. Shrikes impaled and cached meal worms only after they were satiated. The number of meal worms taken to be hoarded increased during the non-breeding season, but during the breeding season male shrikes preferred to feed the females. During the entire research period we did not find any specific cache sites or trees and no prey remained impaled for extended periods of time. In conclusion, impaling prey changed temporally and between sexes: from being a signal for conspecifics to pair bonding.     

Estimated, in situ, rates of egg production for the copepod centropages typicus (Krøyer) in the new york bight

Centropages typicus (Krøyer) and Pseudocalanus sp. are the two predominant copepods in the Continental Shelf waters immediately south of Long Island, New York. The estimated, in situ, rate of egg production for Centropages typicus ranged from 5 to 230 eggs female^?1 day^?1 during this study. Variability was partly attributed to seasonal variation in water temperature and partly to variations in the physiological condition of individual females. It could not be shown that the ability to produce eggs varied seasonally due to factors related to food. Egg production by Pseudocalamus sp. is probably from 1–10 eggs female^?1 day^?1. The two reproductive behaviours result in average abundances of adults that are approximately the same, although the peaks are at different times of the year, indicating that Centropages typicus has a higher mortality between the egg and adult stages than Pseudocalanus sp.     

Reproductive biology of Ranunculus weyleri (Ranunculaceae), a narrowly endemic plant from the Balearic Islands with disjunct populations

Ranunculus weyleri is a species endemic to Mallorca Island (western Mediterranean basin) that is currently threatened due to its reduced geographical distribution and disjunct, isolated populations. It is a small, perennial herb that inhabits rocky environments, together with other endemic plants with creeping life-forms. In the present study, for the first time the reproductive biology of the species was investigated in terms of its floral phenology (floral stages and times of formation), pollen/ovule (P/O) ratios, and fruit and seed setting under natural and pollen manipulation experiments, assessing the breeding system, pollination vectors and pollen limitations. Cross-pollinations among populations were performed to evaluate the levels of compatibility between populations. In addition, the floral displays and the reproductive outputs of four wild populations were determined. The observed high P/O ratios, results of the hand-pollination experiments, and flower traits indicate that this species is predominantly allogamous. Combinations of both insects (belonging to Coleoptera, Diptera, Lepidoptera and Hymenoptera) and wind (ambophily) constitute the main pollination vectors, and pollen limitation was observed. Interpopulation crossing was effective, and exogamic depression was not present, as evidenced by the fecundity levels. The predation of the floral stems by herbivores (mainly goats) severely limits the reproductive success of this endemic species in wild populations. Finally, several ways of action are proposed for R. weyleri conservation.     

Lipid, fatty acid and protein utilization during lecithotrophic larval development of Lithodes santolla (Molina) and Paralomis granulosa (Jacquinot)

During the larval development of the subantarctic king crab, Lithodes santolla, and stone crab, Paralomis granulosa, we compared changes in the carbon, fatty acid and protein contents of larvae reared under constant conditions from hatching to metamorphosis, either in presence or absence of food (Artemia spp. nauplii). In both species the feeding condition had no influence on any of the chemical parameters studied, indicating a fully lecithotrophic (i.e. non-feeding) mode of development from hatching of the first zoea to metamorphosis of the late megalopa. Dry mass and carbon contents at hatching were similar in the larvae of both species, but L. santolla contained initially higher total amounts of fatty acids and protein than P. granulosa. Both species utilized considerable portions of their total fatty acid pool which decreased logarithmically throughout the time of development. At metamorphosis, it was almost exhausted in P. granulosa, while L. santolla had consumed only about 60%. Protein utilization, in contrast, was higher in L. santolla (40%) than in P. granulosa (20%). Triacylglycerol was the principal storage lipid in both species, accounting initially for about 75% of the lipid fraction; it was strongly utilized during larval development. Phospholipid constituted the second largest lipid class; it also decreased in P. granulosa, but to a lesser extent in L. santolla. The major fatty acids of both species were 18:1(n−9), 20:5(n−3) and 16:0 as well as, in lower proportions, 18:1(n−7), 22:6(n−3), 16:1(n−7) and 18:0. Monounsaturated fatty acids represented the dominant group in L. santolla, whereas P. granulosa contained similar amounts of mono- and polyunsaturated fatty acids. In L. santolla, monounsaturated fatty acids, especially 16:1(n−7), were preferentially utilized as compared to polyunsaturates. Due to a particularly strong lipid utilization in P. granulosa, all individual fatty acids were largely depleted at metamorphosis, showing similar extents of consumption. L. santolla had higher initial lipid and protein stores that seem to be used more economically as compared to P. granulosa.     

Field and laboratory observations on the foraging and feeding techniques of blue tits (Parus caeruleus) and coal tits (P. ater) in relation to their habitats

I have tried to show (a) that results in the literature suggest that blue tits and coal tits survive better in their usual habitats of broad-leaved and conifer woods respectively; (b) that the higher mortality in the ‘wrong’ habitat may be attributed at least in part to an inability to acquire an adequate supply of food; (c) from my own and other people's field observations, that wild coal tits and blue tits use different feeding techniques; (d) from my own laboratory experiments, that each species is ‘best’ at the feeding techniques which it in general uses in the wild, and also that each species prefers to use the feeding techniques at which it is ‘best’; (e) that the feeding techniques of coal tits may be adapted to exploit the type of food supply found in conifers, while those of blue tits may be adapted for feeding in broad-leaved trees.     

Structure of seasonal migrations of the littoral hermit crab Clibanarius vittatus (Bosc)

A seasonal migration in the hermit crab Clibanarius vittatus (Bosc) is described and its structure examined for size-related or sexual differences that might lead to differential mortalities. The largest crabs, which were nearly all males, began to leave the shore in early summer, but the smaller females stayed until late autumn. The smaller crabs also returned to the shore at least one month in advance of the large crabs in the spring. No size-related or sexual differences were found in the abilities of the crabs to regulate their volumes when moved from 34.5%. to 10.5%. salinity which is the observed salinity range in their usual habitat.     

Reproductive cycles in oregon populations of the echinoid, Strongylocentrotus purpvratus (Stimpson). II. Seasonal changes in oocyte growth and in abundance of gametogenic stages in the ovary

During the annual reproductive cycle in the echinoid, Strongylocentrotus purpuratus (Stimpson) two major seasonal events in oogenesis have been demonstrated by several different quantitative methods. Both seasonal changes in size and frequency distributions of stages of the oocytes indicate that in the intertidal populations studied, there is an abrupt increase in the growth rate of oocytes during October, accompanied by an increase in the rate at which oogonia become primary oocytes. Between March, just after spawning is completed, and October, oocytes increase in volume at a rate of ≈ 2 % per day. In October and November, the growth rate of oocytes approaches 6 % per day, and thereafter declines for oocytes reaching maturity in December.The absolute numbers of oocytes and oogonial clusters/mm² of ovary wall were estimated and adjusted for changes produced by volume changes in the gonad. The lowest numbers of oogonial clusters occur from December to March. Renewed proliferation begins soon after spawning. There is a significant increase in number of clusters in March, and the absolute cluster number increases to a maximum in June, reaching approximately four times the initial number. The proliferation rate during this period is ≈ 180 clusters/mm²/month; some proliferation continues into September. The number of small oocytes present remains the same from March to August, when it begins to increase. The total number of oocytes produced during the fall period is approximately three times the number initially present at the start of the annual cycle in March. Two populations studied differ in the absolute numbers of oogonial clusters and oocytes produced in the annual cycle; environmental factors must influence the processes involved. In S. purpuratus the large majority of oocytes differentiate from oogonia during the same reproductive cycle in which they reach maturity as ova.     

Movement of a non-flagellate spermatozoon: A study of the male gamete of Nematospiroides dubius (Nematoda)

The spermatozoa of Nematospiroides dubius were studied using the scanning electron microscope and time-lapse cinematography. Spermatozoa undergo a profound change in morphology after insemination: they change from an elongate structure, 16–18 μm long, to a more rounded form about 5–10 μm in diameter. Spermatozoa from female worms stuck to, and migrated across a glass surface by the production of pseudopodia, but they adhered more readily to a glass surface coated with egg albumin. The average speed of a sample of six differentiated spermatozoa was 7·3 μm/min. Their locomotion is not considered to be amoeboid but resembles the movement of monopodial neutrophils. A hypothesis for the mechanism of movement is presented, and other possible functions of the pseudopodial region are discussed.     

驯化温度与急性变温对南方鲇幼鱼皮肤呼吸代谢的影响

为了考查鱼类皮肤呼吸代谢的温度反应特征,在不同驯化温度(10、20、30℃)及双向急性变温(10→20℃、20→30℃、10→30℃;20→10 ℃、30→20℃、30→10℃)条件下采用自行设计的皮肤呼吸代谢装置测定麻醉后南方鲇(Silurus meridionalis)幼鱼的皮肤耗氧率(MO2skin)及鳃部耗氧率(MO2gill),并计算整体耗氧率(MO2total).研究显示:南方鲇幼鱼的MO2skin占MO2total 的16.4％-19.0％,随着驯化温度的升高,MO2skin上升的幅度显著低于MO2total(P＜0.05),MO2skin占MO2total的比例则呈下降趋势;急性升(降)温组的MO2skin与升(降)温前驯化温度组相比显著升高(降低)(P＜0.05),却与相应温度驯化组的MO2skin无显著性差异(P＞0.05);急性变温组MO2skin的Q10值与驯化温度组的差异不显著(P＞0.05),却显著低于MO2total的Q10值(P＜0.05).通过相关资料比较发现,南方鲇幼鱼MO2skin占MO2total的比例处于中上水平.研究表明,在驯化温度和急性变温条件下,实验鱼的MO2total分别存在代谢补偿反应和急性胁迫反应;MO2skin与MO2total的温度反应不同,它既不是一个完全的化学反应过程,也不是生物反应过程,而更倾向于是一个物理的扩散过程.     

Potential predation pressure of littoral mysids on herring (Clupea harengus membras L.) eggs and yolk-sac larvae

The predation potential of littoral mysid shrimps (Mysidacea) on Baltic herring (Clupea harengus membras L.) eggs and yolk-sac larvae was studied experimentally. The results showed that littoral mysids feed actively on both eggs and yolk-sac larvae. It was shown that Neomysis integer preys on eggs, which are not attached to the substrate. Alternative food (yolk-sac larvae or zooplankton) did not decrease feeding rate on eggs. Only gravel as a bottom material lowered the ingestion rate to nearly zero. The largest of the mysid species Praunus flexuosus ate yolk-sac larvae more than other mysids and most efficiently. Mysids switched to feed on eggs when larvae and eggs were offered simultaneously, thus predation focused on eggs. It is possible that hydrodynamic signals of moving larvae induced mysids to prey and eggs were easier prey to catch as well as more numerous. In addition egg size is optimal and the nutritive value (measured as C:N ratio) is better compared with larvae. The results indicate that mysids may have local effects on populations of Baltic herring by eating the early life stages, mostly eggs. Especially when large swarms of N. integer shoal in the spawning areas. However, the effect on recruitment of herring is still hard to evaluate.     

Reproductive biology and pollination of southeastern Brazilian Stanhopea Frost ex Hook. (Orchidaceae)

Reproductive biology and pollination of Stanhopea lietzei and Stanhopea insignis were studied in a semi-deciduous mesophytic forest in the Serra do Japi (SJ), and in the coastal plain of Picinguaba, both in the State of São Paulo, Brazil. Floral morphology, pollination, breeding system and fruit set of both species were investigated. S. lietzei and S. insignis are pollinator-specific, being pollinated by male bees of Eufriesea (Apidae, Euglossini), which collect the fragrance produced by pluricellular osmophores at the base of the saccate hypochile. S. lietzei and S. insignis were pollinated by Eufriesea pulchra and Eufriesea purpurata, respectively. Observations using substances present in the floral fragrance of both studied species as chemical baits were also performed. E. purpurata was attracted by benzyl alcohol, the major compound of the perfume of S. insignis, while E. pulchra was attracted by none of the compounds used. Both studied Stanhopea are self-compatible but pollinator dependent. Self-pollination, however, tends to be avoided by floral mechanisms. In experimental self- and cross-pollinations the proportion of fruit abortion was high and related to resource limitation. The reproductive success of S. lietzei and S. insignis was low as a consequence of deficient pollen transference while pollinator scarcity was the main factor.     

Phelipanche ramosa (L.) Pomel populations differ in life-history and infection response to hosts

Phelipanche ramosa (broomrape) is a root-holoparasitic angiosperm that attacks a wide number of annual crops. According to the host, the duration of its life cycle can range from 14 weeks (on tomato/tobacco) to 40 weeks (on oilseed rape). We conducted a cross-infection experiment to evaluate the intensity and kinetics of infection of broomrape populations. Two parasitic populations, P-long collected on oilseed rape and P-short collected on tobacco, were cultivated on two crops (their natural and outsider hosts). After, 4, 8, 12 and 16 weeks, the intensity of infection and the distribution of developmental stages (fixation to fructification) of broomrape were determined. The two broomrape populations showed distinct patterns of intensity and kinetics of infectivity. P-long showed a higher infection success in the early stages than P-short. Both parasitic populations showed a higher aggressiveness on their natural hosts than on outsider hosts. Only the P-short population completed its life cycle on the two hosts, and with similar development rates on both hosts, while the P-long population was unable to complete its life-cycle during the 16 weeks of the experiment. It is suggested that the shift in host specificity that allowed P. ramosa to infect oilseed rape in recent times has led to a divergence of pathovars having different life-cycle durations.     

A quantitative description of the behaviour of wild juvenile plaice (Pleuronectes platessa L.)

The behaviour of young plaice (Pleuronectes platessa L.) as they migrate up and down sandy beaches with the tide is described. Their behaviour during this migration consists mainly of swimming and feeding interspersed with rarer behavioural acts. Over short periods swimming behaviour can be described by a random model in which the probability of a swim occurring remains constant. This probability varies markedly, however, from hour to hour. Two types of swimming movement are recognized: one of very short duration represents searching for food and the other, longer, category serves to transport the fish up and down the shore. Variations in the feeding rate and in the frequency, duration, and direction of swimming movements over the tidal cycle are described and related to the changing physical and biological conditions that the fish experience during their intertidal movements.