HUNGER OVERCOMES FEAR IN NASSARIUS FESTIVUS, A SCAVENGING GASTROPOD ON HONG KONG SHORES

On protected intertidal sand flats, virtually worldwide, nassariidsnails scavenge carrion. Typically, they lie in repose beneaththe sand surface but emerge to feed when chemoreceptors detectcarrion. Distance from the potential food influences whetherthey move towards it and, if they do, whether they obtain ameal before it is consumed by others. This study shows that the rate at which Nassarius festivus movestoward food bait is similar for starved and well-fed individuals.That is, when individuals decide to feed, the rate at whichthey move toward food is always approximately the same. Thisstudy exposes another facet of nassariid nutrition related tothe degree of hunger. Recently fed individuals, i.e., thosewhich have fed for < 14 days, will cease feeding and departpalatable food if crushed conspecifics are added to it. Individualswhich have not fed for > 14 days tend to remain feeding,despite the addition of crushed conspecifics. Another studyhas shown that N. festivus consumes sufficient energy from afed-to-satiation meal to sustain it in repose for 20 days.These experiments clarify the observation. Between 14 to 20days since its last meal, N. festivus will feed when the possibilityarises, despite potentially adverse consequences. That is, hungerovercomes the fear of being consumed at a feeding assemblagebecause, without feeding, the alternative may be death by starvation.Thus, a nassariid makes decisions about whether or not to feed.The fear of predation causes N. festivus to abandon a meal ifthe previous one was obtained within a fortnight but, thereafter,it will risk predation to avoid starvation. (Received 14 March 1994; accepted 7 July 1994)     

Feeding behavior and differential absorption of biochemical components by the infaunal bivalve Mulinia edulis and the epibenthic Mytilus chilensis in response to changes in food regimes

We measured changes in the feeding rate and food absorption efficiency of two suspension feeding bivalves, cross-trasplanted between habitats with special emphasis on their capacity for differential absorption of biochemical components from their food supply. Mulinia edulis were moved from the intertidal zone to the subtidal zone, and Mytilus chilensis from the subtidal to the intertidal zone for a period of 7 days, and then compared with animal that had not been transplanted. Experimentally prepared diets similar to those available in the two different environments were offered to the bivalves, and their rates of feeding and differential uptake of biochemical components were determined and statistically compared. The two species did not achieve complete acclimation of their feeding behaviour during the transplant period since the highest ingestion rates for biochemical components occurred under dietary conditions that reflected their habitats of origin. Absorption efficiency showed greater acclimation than the other physiological parameters measured, indicating the capacity of these species to modulate their enzymatic-digestive activity depending on food composition. We conclude that both Mytilus and Mulinia have a certain degree of physiological plasticity in their feeding behaviour and assimilatory balance of biochemical components, being greater in Mytilus. When both species encounter ambient food conditions characteristic of their normal habitats, they show maximum values of food absorption, while under conditions where their typical diets are exchanged (Mytilus in intertidal and Mulinia in subtidal), the energy absorbed declines in each, but in ways very different between the two species. Thus, Mytilus exposed to high concentrations of low quality seston reduced the energy absorbed by 31.7% compared to its normal habitat, while Mulinia exposed to low concentrations of high-quality food reduced their energy absorption by 64%.     

Sand-dollar mellita quinquiesperforata (Leske) burrow trails: sites of harpacticoid disturbance and nematode attraction

The effect of sand-dollar Mellita quinquiesperforata (Leske) burrowing on a soft-bottom meiofauna community was examined at a subtidal site located off the northwest Florida coast. M. quinquiesperforata were common at the site with an average of 3 ind · 0.25 m ⁻² and their burrow trails were a distinctive feature of the sediment surface. At the site, sand dollars disrupted ≈ 14% of the sediment surface · h⁻¹. Sand-dollar burrowing did not decrease total meiofauna abundances significantly (P > 0.05); however, the abundances of one harpacticoid species, Halectinosoma sp., foraminifera and mites were significantly lower (P < 0.05) in samples collected from a burrow trail than in samples collected in front of the sand dollar. The lower abundances of Halectinosoma sp. and mites in the burrow trail were probably due to sediment disturbance. The lower abundances of foraminifera in the burrow trails were probably due to sand-dollar predation. In contrast to studies in intertidal areas, total nematode abundances were significantly higher (P < 0.05) in the samples collected behind a moving sand dollar than in samples collected in front of the sand dollar. Possible reasons for the enhanced abundances are: (1) increased food availability in the form of mucus and/or excreted cells that line the sand-dollar gut; and (2) increased pore space within the sediment.     

“秕谷草-伪褐飞虱-中华淡翅盲蝽”载体植物系统的可行性

为明确用于防治稻飞虱的“秕谷草-伪褐飞虱-中华淡翅盲蝽”载体植物系统的可行性,本文开展了靶标作物水稻、载体植物秕谷草和靶标害虫褐飞虱、替代猎物伪褐飞虱组合对中华淡翅盲蝽成虫形态、种群增长参数、产卵选择性和取食选择性的影响研究.结果表明: 中华淡翅盲蝽水稻种群(取食褐飞虱卵)的雌雄成虫个体均显著大于秕谷草种群(取食伪褐飞虱卵).取食褐飞虱卵的中华淡翅盲蝽种群增长参数单雌产卵量、净增长率、内禀增长率、周限增长率明显高于取食伪褐飞虱卵的种群,但取食伪褐飞虱卵也有较高的种群增长能力,足以扩繁种群.对于靶标作物水稻和载体植物秕谷草,无论是水稻种群还是秕谷草种群均偏好在水稻上产卵.同时,2个种群的雌虫、雄虫和若虫对褐飞虱卵和伪褐飞虱卵捕食量没有显著性差异.在上述研究基础上,讨论了在田间建立“秕谷草-伪褐飞虱-中华淡翅盲蝽”载体植物系统的可行性.     

Ultrastructural studies on experimental primary amoebic meningo-encephalitis (PAME) of mouse due to Naegler1a aerobia and Hartmannella culbertsoni

Primary amoebic meningo-encephalitis (PAME) in mouse can be easily produced by intranasal inoculation of Naegleria aerobia Singh & Das, 1970 and Hartmannella culbertsoni Singh & Das, 1970. The ultrastructural characteristics of N. aerobia and H. culbertsoni from infected mouse brain tissues showed many similar characteristics. The distinctive features between the two were the retention of phagocytic activity by N. aerobia as well as pinocytic activity in the ingestion of food as compared to H. culbertsoni where only pinocytic activity was observed. Staining characteristics of mitochondria suggested that N. aerobia was more active in the brain tissues than H. culbertsoni. Membrane-bound darkly stained bodies of unknown function were found in the brains infected with both N. aerobia and H. culbertsoni. They may have some bearing on the pathogenicity of these amoebae. Human cases of PAME so far reported are mostly due to N. aerobia and rarely with H. culbertsoni. This may be due to certain inherent characteristics present in N. aerobia which help them to survive on human brain tissue. On the other hand, the same may be lacking in H. culbertsoni. These ultrastructural differences in both N. aerobia and H. culbertsoni, as revealed by electron microscope studies of the infected brain tissues of mice, are presented in this paper.     

锁阳及其寄主白刺内生真菌的生态分布及遗传关系

首次研究了寄生植物锁阳及其寄主白刺内生真菌的分布特征及遗传关系.采用组织块法分离天然白刺、寄生体中锁阳和白刺的内生真菌,利用ITS-rDNA分子序列并结合形态学方法鉴定菌种,研究内生真菌的分离率、定殖率、分离频率、多样性指数、均匀度指数及相似性系数等的差异,以及寄生关系中内生真菌的多样性、遗传关系及分布特征等.结果表明: 本次获得的49株内生真菌隶属于18个分类单元,95.9%为子囊菌,4.1%为担子菌;内生真菌总分离率为15.3%,总定殖率为25.0%;天然白刺中内生真菌Shannon多样性指数最大,为2.13;锁阳花序与锁阳茎的内生真菌相似性系数最大,为0.50;镰孢菌属为白刺的优势菌属,青霉属为锁阳的优势菌属.锁阳与白刺寄生体中真菌类群的差异性分布表明寄生关系对内生真菌群落存在一定影响.     

Community regulation: the relative importance of recruitment and predation intensity of an intertidal community dominant in a seascape context

Predicting the strength and context-dependency of species interactions across multiple scales is a core area in ecology. This is especially challenging in the marine environment, where populations of most predators and prey are generally open, because of their pelagic larval phase, and recruitment of both is highly variable. In this study we use a comparative-experimental approach on small and large spatial scales to test the relationship between predation intensity and prey recruitment and their relative importance in shaping populations of a dominant rocky intertidal space occupier, mussels, in the context of seascape (availability of nearby subtidal reef habitat). Predation intensity on transplanted mussels was tested inside and outside cages and recruitment was measured with standard larval settlement collectors. We found that on intertidal rocky benches with contiguous subtidal reefs in New Zealand, mussel larval recruitment is usually low but predation on recruits by subtidal consumers (fish, crabs) is intense during high tide. On nearby intertidal rocky benches with adjacent sandy subtidal habitats, larval recruitment is usually greater but subtidal predators are typically rare and predation is weaker. Multiple regression analysis showed that predation intensity accounts for most of the variability in the abundance of adult mussels compared to recruitment. This seascape-dependent, predation-recruitment relationship could scale up to explain regional community variability. We argue that community ecology models should include seascape context-dependency and its effects on recruitment and species interactions for better predictions of coastal community dynamics and structure.     

Seroprevalence of Neospora caninum in dairy goats from Bahia, Brazil

Sera from 384 dairy goats in nine herds from Bahia State, Brazil, were assayed for Neospora caninum antibodies using an indirect immunofluorescent antibody test (IFAT). Animals were selected and divided in groups by age and breed. Antibodies against N. caninum were found in 15% (58/384) of goats. Serum titers ranged from 1:100 to 1:3200. There was no significant difference between the age groups. Seroprevalence was higher in Alpine breed (24%) than in Saanen (14%) and Nubian (3%) breeds. The 58 N. caninum-positive sera were also tested for Toxoplasma gondii and 71% of the samples reacted solely to N. caninum. These results indicate that N. caninum infection is common in goat herds in Bahia.     

夹竹桃灭钉螺效果初报

A laboratory experiment at 20±5℃ shows that the water extract of fresh Nerium indicum had an obvious effect on killing Oncomelania hupensis. Treated with 0.1% water extract for four days, the mortality of O. hupensis was up to 100%. The effect of different tissues of N. indicum on O. hupensis was in order of stem phloem>leaf>root phloem>flower. The effect of N. indicum on O. hupensis was about ten times higher than that of Pterocarya stenoptera and Rumex japonicus, and was equal to that of 1×10^-3mg·L^-1 niclosamidum.     

A comparative study of territoriality in intertidal and subtidal blennioids (Teleostei, Blennioidei)

This paper presents a comparative analysis of territoriality in three intertidal (Lipophrys pholis, Coryphoblennius galerita, Salaria pavo) and two subtidal (Tripterygion delaisi, Parablennius pilicornis) blennioid fishes. Focal-animal observations of males guarding eggs showed that: (i) intertidal species had smaller territories that were less frequently patrolled; (ii) in subtidal species feeding was limited to the territory, while in intertidal fishes a substantial proportion of the feeding acts occurred outside the defended area; (iii) intertidal species spent less time out of the nest and showed a lower level of locomotory activity; (iv) subtidal species were subjected to a higher number of territorial intrusions with more species intruding their territory, some of them potential egg predators; (v) subtidal species performed several water column displays that played a significant role in courtship, while in intertidal fishes these displays are almost absent. Signalling without the presence of a female was almost absent in intertidal species. It is argued that intertidal fishes minimize the time spent out of the nest and the loss of contact with the substrate, features that may be of high survival value in conditions of strong turbulence. Although intertidal species have a reduced time available for feeding, this may be compensated by lower levels of locomotory activity, territorial defense and risk of egg predation. This revised version was published online in August 2006 with corrections to the Cover Date.     

鼠类对栓皮栎和锥栗种子的贮藏:验证高单宁假说

种子中的单宁影响鼠类的取食和贮藏策略.高单宁假说认为鼠类倾向于优先贮藏单宁含量高的种子、取食单宁含量低的种子.同域分布的鼠类对种子的取食和贮藏选择是否符合高单宁假说的预测尚缺乏足够的实验证据.本研究通过围栏实验研究了四川都江堰地区亚热带常绿阔叶林中的小泡巨鼠(Leopoldamyys edwardsi)、针毛鼠(Niv...     

The decision to feed by a scavenger in relation to the risks of predation and starvation

Recent theoretical models have considered how nutritional status and predation risk affect the decision by an individual to forage. We consider the feeding behaviour of a scavenger under risk of predation. The intertidal gastropod Nassarius dorsatus Röding was used to test the following hypotheses: (1) a damaged conspecific should be a less preferred meal than a damaged predator or another species; (2) a scavenger should be able to discriminate between a damaged conspecific in the presence and one in the absence of its predator, preferring the latter; and (3) the decision by a scavenger to feed should reflect a trade-off between nutritional status and the above preferences. Results from the laboratory and field were consistent with predictions. Two hypotheses are suggested from the work: scavengers may generally be less willing to feed on carcases of conspecifics than on those of other species, and intertidal scavengers may commonly face a relative or absolute shortage of food.     

An ecological and economic review of meiofauna as food for fish*

After briefly reviewing the evidence that meiofauna are an integral part of the complex food web of invertebrate infaunal and epifaunal organisms, it is shown that, at least in intertidal and shallow subtidal habitats, meiofauna are an important food for the small (30–60 mm) juveniles of some commercially important fishes (flatfish and salmonids) or for fish which are themselves food for commercial species. The evidence that fish feed preferentially on a few species of harpacticoid copepod rather than on the numerically dominant meiofaunal taxa is presented and discussed. It is argued that, in addition to benthic copepods being energetically efficient as food for fishes, it is differences in the activity and availability between major taxa of meiofauna as they relate to the feeding strategies of the fish which go a long way to explaining this apparent general preference of fish for harpacticoid copepods rather than nematodes. From literature estimates of consumption rates, it is concluded that the supply of meiofaunal food to juvenile fish is unlikely to be limiting although this may not be the case in some shallow subtidal muddy sand habitats. Whilst it is recognized that fish predation may influence the magnitude of the seasonal peaks in numbers, predation is not the principal cause of seasonal fluctuations in harpacticoid copepod species abundances. The effects of predation on other aspects of community structure is unknown. Finally, the possible role of meiofauna in mariculture systems is briefly discussed.     

Population genetic structure among populations of three predaceous nabid species: Nabis alternatus Parshley, Nabis roseipennis Reuter and Nabis americoferous Carayon (Hemiptera: Nabidae)

An electrophoretic survey of 28 presumptive loci distributed among 15 enzyme systems was conducted to determine the genetic structure among local populations of three predaceous nabid species: Nabis alternatus, N. roseipennis and N.americoferous in human-disturbed habitat. For all three species, F_IS values indicated a deficiency of heterozygotes at most loci in most populations. The amount of genetic differentiation based on the standardized variance, F_ST when combined across all poulations was 0.100 for N. alternatus, 0.189 for N. roseipennis, and 0.335 for N. americoferous. When local populations were grouped according to a set of defined geographical limits, based on the naturally occurring spatial arrangement of the sampled localities, some unexpected patterns of genetic variation were revealed. The degree of genetic differentiation detected among local populations of nabids is discussed in light of the frequent disruptions and ecological changes in their ephemeral habitats.     

Development of the plerocercoid I of Ophiotaenia europaea in reptiles

The existence of a two-host life-cycle in ophiotaeniid proteocephalideans was tested experimentally using Ophiotaenia europaea as a model. Three species of reptiles, Natrix natrix, Natrix tessellata and Lacerta viridis, were fed with experimentally infected copepods containing a large number of infective plerocercoids I. A few plerocercoids, most of which were dead, corresponding morphologically to the plerocercoid II developmental stage of O. europaea, were found encysted in the intestinal wall of N. natrix (8 days p.i.), N. tessellata (5 and 150 days p.i.) and L. viridis (40 days p.i.), while no plerocercoids or adult worms were recovered from their intestines. The results indicate that the infective plerocercoid I of O. europaea cannot undergo further development when ingested directly by the final host (a reptile), and that environmental temperature stimuli cannot initiate a reverse plerocercoid migration to the gut followed by strobilization.     

Metabolism of CO2 by leaves of different photosynthetic types of Neurachne species

Following a series of continuous exposures to ¹⁴CO₂ for different lengths of time, leaves from Neurachne munroi (C₄), N. minor (C₃-C₄) and N. tenuifolia (C₃| were estimated to assimilate 100%, 9% and 2–4%, respectively, of atmospheric CO₂ by the C₄ pathway. The percentage of ¹⁴C-label appearing in malate and aspartate in leaves of N. minor progressively increased with longer exposure times indicating that a significant proportion of its C₄ acids are formed as secondary products. In ¹⁴CO₂/¹²CO₂ pulse/chase experiments, the ¹⁴C-label in leaves of N. munroi was rapidly transferred from C₄ acids to sugar monophosphates plus sugar diphosphates, and finally to sucrose. In leaves of N. minor, the ¹⁴C-label was slowly metabolized from the C-4 carboxyl of malate and asparate (apparent half-time = 250 s), and the formation of C₄ acids as secondary products was again evident. ¹⁴C-label in serine/glycine accumulated to comparable magnitudes in both N. minor and in N. tenuifolia, but there was an initial lag phase in the accumulation of label in N. minor. C₄ photosynthesis is apparently of minimal importance in reducing photorespiration in N. minor, but leaf anatomical specializations and a possible compartmentation of photorespiratory metabolism may be of considerable importance.     

Behavioral ecology of Strongylocentrotus droebachiensis (Muller) (Echinodermata: Echinoidea)

Summary Field observation indicated that extensive aggregation behavior occurs in Strongylocentrotus droebachiensis, an important echinoid herbivore in rocky subtidal zones of northern New England. The relationship of this behavior to the behavioral ecology of this species was investigated. Laboratory studies indicated that urchins are chemically sensitive to the stimuli of food and other urchins. Quantitative field experiments with tagged animals and transects showed the existence of two types of aggregations: feeding and nonfeeding, which appear to be pervasive phenomena in the biology of S. droebachiensis.It is concluded that, depending upon their hunger state, urchins shuttle between feeding aggregations in exposed locations and non-feeding aggregations located in relatively sheltered areas (where they spend most of their time). Individuals of S. droebachiensis aggregate actively through response to other urchins in the form of chemotaxis. The aggregative behavior may be maintained for its selective value in terms of defense from predation and, to lesser extents, facilitation of feeding and breeding.     

Revision of the genus Noculacia Mayer, 1903 (Crustacea: Amphipoda: Caprellidea) with the description of two new species

The genus Noculacia Mayer, 1903 is reviewed. Two new species, N. africana n. sp. and N. australiensis n. sp., are described based on material collected from southeast Africa and western-southern Australia, respectively. Noculacia bullata Mayer, 1903, the type species of the genus, is redescribed. Noculacia bogisa Mayer, 1903 is transferred to the genus Pseudoprotella Mayer, 1890 mainly on the basis of the presence of a well developed molar, the structure of pereopods 3 and 4, and the setal formula of the mandibular palp being 2-x-1. The genus Noculacia is presently composed of three species: N. africana n. sp., N. australiensis n. sp, and N. bullata Mayer, 1903. The genus Pseudoprotella is composed of P. bogisa (Mayer, 1903), P. inermis Chevreux, 1927, and P. phasma (Montagu, 1804).     

Predation by Callinectes sapidus (Rathbun) within Spartina alterniflora (Loisel) marshes

This study examined predation by the blue crab, Callinectes sapidus Rathbun, within intertidal Spartina alterniflora (Loisel) marshes of Dauphin Island, Alabama. Species and size preferences displayed by the predator when foraging within the marsh were investigated using nektonic, epifaunal, and infaunal prey populations including Fundulus similis Baird and Girard, Littorina irrorata Say, and Geukensia demissa Dillwyn.

Short-term field experiments involving the use of predator inclusion cages, in which the relative abundances of all prey species and the density of macrophyte vegetation were manipulated, indicated that mean mortality differed significantly among species. Blue crabs exhibited a distinct species preference for Littorina, and to a lesser extent, for Fundulus. However, the predator rarely choses infaunal individuals. Within predator inclusion cages, size selection by the crabs among three size classes of each prey was evident for Littorina and Fundulus but not for Geukensia. Blue crabs tended to select intermediate-sized snails and large fish while not exhibiting a size preference for infaunal bivalves.

In the marsh, mean percentage of the Littorina population within the 14–18 mm size class exhibited an increased mortality as compared to two other size classes, which was negatively correlated with increasing tidal height. Such a relationship may have been due to a decreasing gradient of crab predation associated with increasing tidal height. Geukensia size class distributions showed little evidence of differences along the tidal height gradient. No data are available for Fundulus, a mobile species which would not experience such differential predation along a marsh gradient.

In comparing crab predation patterns among prey species, it is apparent that Callinectes utilizes prey species differentially. Such differential utilization may be based on optimization of energy yield and minimization of energy expenditure. Thus, the preference of blue crabs for nektonic and epifaunal prey is hypothesized to be the result of a smaller energy expediture as a result of the crab's visual evaluation of these prey. Infaunal prey species (e.g., Geukensia) require a greater energy investment because of the necessity of excavating the prey item. Such prey also allow little selection by size because of being cryptic.     

Predation by gulls on crabs in rocky intertidal and shallow subtidal zones of the Gulf of Maine

Most organisms in intertidal areas are marine in origin; many have distributions that extend into the subtidal zone. Terrestrial predators such as mammals and birds may exploit these animals during low tide and can have considerable effects on intertidal food webs. Several studies have shown that avian predators are capable of reducing densities of sessile and slow-moving intertidal invertebrates but very few studies have considered avian predation on mobile invertebrate predators such as crabs. In this study, we investigated predation by Great Black-backed Gulls (Larus marinus Linnaeus) on three species of crabs (Cancer borealis Stimpson, Cancer irroratus Say, and Carcinus maenas Linnaeus). The study was at Appledore Island, ME (a gull breeding island) and 8 other sites throughout the Gulf of Maine, including breeding islands and mainland sites. On Appledore Island, intertidal and subtidal zones provided over one-third of prey remains found at gull nests, and crabs were a substantial proportion (∼ 30% to 40%) of the total remains. Similarly, collections of prey remains from intertidal areas indicated that crabs were by far the most common marine prey. C. borealis was eaten far more often and C. irroratus and C. maenas less often than expected at each site. Comparing numbers of carapaces to densities of crabs in low intertidal and shallow subtidal zones at each site, we estimated that gulls remove between 15% and 64% of C. borealis during diurnal low tides. The proportion of C. borealis eaten by gulls was independent of proximity to a gull colony. Approximately 97% of the outer coast of Maine is within 20 km of a breeding island. Thus, a lot of gull predation on crabs may occur throughout the Gulf of Maine during summer months. Crabs are important predators of other invertebrates; if predation by gulls reduces the number of crabs in intertidal and shallow subtidal areas, gulls may have important indirect effects on intertidal food webs.