Population dynamics and phenology of two congeneric and sympatric lynx spiders Peucetia rubrolineata Keyserling, 1877 and Peucetia flava Keyserling, 1877 (Oxyopidae)

Numerous phenological studies on spiders belonging to the families Oxyopidae, Thomisidae, Lycosidae, Selenopidae (e.g. Selenops cocheleti) and Salticidae (e.g. Psecas chapoda and Psecas viridipurpureus) have been conducted in the neotropical region. However, studies that simultaneously compare population dynamics and age structure in populations of sympatric species are limited, especially in Oxyopidae. The population dynamics and phenology of two congeneric lynx spider (Peucetia rubrolineata and Peucetia flava) were examined in southeastern Brazil. Several characteristics of the age structure were compared between the two spider species. The variation in the total abundance of individuals and age structure and their relationship with climatic variables were similar between the two spiders. Adults of these spiders were present mainly in spring, indicating an annual reproductive cycle and a ‘stenochronous spring’ phenological pattern. The recruitment of spiders occurred in summer for P. rubrolineata and P. flava, followed by successive phenological peaks at all stages of development. Rainfall and temperature had a positive correlation to population flux in the two spider species studied. Despite the significant climatic effects observed in the Serra do Japi, the phenological pattern of the population in this study was not always repeated in other species of spiders (e.g. Selenops cocheleti).     

Colour change in Darwin's frogs (Rhinoderma darwinii,Duméril and Bibron, 1841) (Anura: Rhinodermatidae)

In the laboratory, wild-caught male Rhinoderma darwinii frogs, but not females, changed body colour from brown to green starting with the appearance of green dorsal spots or a greenish dorsal tone on a brown body colour. After a year in captivity, most males exhibited a greenish or complete green dorsal colour, probably induced by the terrarium's swamp (green) vegetation and season.     

Cercaria bucephalopsis haimeana (Lacaze-Duthiers, 1854) (Digenea: Bucephalidae) in the cockle,Cardium edule L. in South Wales

Summary

Some variations in the percentage infection of the cockle, Cardium edule L., on Llanrhidian sands, South Wales with Cercaria bucephalopsis haimeana (Lacaze-Duthiers, 1854) are described.

Vertical variations in percentage infection are related to the population density of the final hosts and the seasonal variation with the breeding cycle of the first intermediate host. Only spent adult cockles, over 18·0 mm long and one year old, are infected, the highest percentage infection occurring in three-year old cockles. A decline in the percentage infection in older cockles suggests an increase in the mortality of infected specimens together with an increase in resistance to infection with age. Medium-sized cockles have a higher percentage infection than smaller and larger cockles of the same age. The parasite causes a decrease in the host's shell growth rate but an improvement in the flesh yield.

The possible reasons for the variations in percentage infection and the effect of the parasite on the host are discussed.     

Nesting habits of the Japanese foliage spider,Cheiracanthium japonicum (Araneae: Miturgidae): host plant preference based on the physical traits of plant leaves

A Japanese foliage spider, Cheiracanthium japonicum, builds nests with plant leaves. The nests are classified into seven types in relation to the seasons and purposes of nesting. We investigated whether the spider selects a plant species according to the nest type and how the physical traits of leaves influence the spider's plant selection. The difference between the composition of the host plant species used for nesting and that of the seasonal vegetation cover was confirmed. This suggests that the spider chooses the host plant species regardless of its abundance in their habitat. Early juveniles use small living or large dead leaves of various plant species to build moulting nests. Females prefer long and large leaves found in Miscanthus sinensis and Phragmites japonica over other plant leaves to build breeding nests.     

Ultrastructural study of the proboscis of Malacobdella grossa (Nemertea: Hoplonemertea)

The proboscis of the symbiotic nemertean Malacobdella grossa was examined with transmission electron microscopy to reveal more features of bdellonemerteans for phylogenetic analysis. General morphology of the proboscis of Malacobdella corresponds to that of a typical hoplonemertean: the middle chamber is present; the nervous system of the proboscis is embedded in the connective tissue between the inner and outer longitudinal muscle layers; the radially arranged nerve trunks are clearly seen over a considerable portion of their extent. Unique features (i.e. autapomorphies) of Malacobdella’s proboscis include: interwoven longitudinal muscle fibres; nerve plexus in the anterior part of the proboscis; absence of mucus glands; presence of subepithelial glands; reduced musculature in the middle chamber; and absence of glandular epithelium in the posterior chamber.     

The occurrence of Podocotyle atomon (Rud., 1802)(Digenea), Bothriocephalus scorpii (Müller, 1776) (Cestoda), Contracaecum clavatum (Rud., 1809) (Nematoda) and Echinorhynchus gadi Zoega,in Müller, 1776 (Acanthocephala) in the five-bearded rockling,Onos mustelus (L.)

Summary

The variation in the incidence and intensity of infestation of the five-bearded rockling, Onos mustelus (L.) with Podocotyle atomon, Bothriocephalus scorpii, Contracaecum clavatum and Echinorhynchus gadi has been studied for a period of one year, on a shore at Mumbles Head, Swansea.

There is a general increase in the incidence and intensity of infestation by P. atomon and C. clavatum with increase in the length (age) of the host. With E. gadi and B. scorpii, however, infestation decreases in the larger fish.

The seasonal variations in the incidence and intensity of infestation with these parasites are influenced by tidal fluctuations, temperature and by the feeding habits and breeding cycle of the fish.

The frequency distribution of parasite specimens is also described and discussed.     

On the status of Arcitalitrus dorrieni (Crustacea: Amphipoda) on the island of Colonsay,Inner Hebrides

The presence of the landhopper Arcitalitrus dorrieni (Hunt) is reported on the island of Colonsay, Inner Hebrides. It is widely distributed there amongst deciduous leaf litter in forested areas but also occurs in bracken litter and scrub grassland. The species is an introduction from Australia, doubtless transported inadvertently among plants brought to the gardens at Colonsay House. It is, however, not restricted to the ornamental plantings but has colonized native woodland. Maximum population density recorded under leaf litter was 680 m². Amphipods avoid waterlogged or dry situations preferring to burrow in moist soil under litter from deciduous trees. Coniferous woodlands are more sparsely colonized. Rate of spread (minimum) from the original locus is calculated at c. 25 m/year. Arcitalitrus may prefer to eat sycamore leaves (cf. oak, beech). Ovigerous females are reported for May but no evidence exists for a release of young any earlier in the year. Immature amphipods seem to live more covert lives in the soil beneath the superficial litter layer. Eggs are relatively large and few in number. Amphipods may avoid ants but may have a mite living in phoretic or ectoparasitic association.     

Seasonal cycles of abundance of the flora and fauna associated with Cladophora albida (Huds.) Kütz in rockpools

Seasonal data for one year on the flora and fauna associated with Cladophora albida (Huds.) Kütz from four rockpools (3 high-shore, 1 mid-shore) on Great Cumbrae Island, Firth of Clyde, Scotland are presented. A total of 131 858 animals was censussed. The mid-shore pool had a significantly lower annual mean density than the high-shore pools. Only at the most exposed site was a distinct seasonal trend apparent (lowest faunal density in spring, highest in summer). Species number showed no marked seasonal fluctuations neither did equitability. The lowest diversity was found in the mid-shore pool. Epiphytic cyanobacteria were present throughout the year. Diatoms were absent in the summer; possibly because of intense grazing by meiofaunal herbivores. The reduction in overall faunal density in the mid-shore pool was caused by the absence of large numbers of nematodes at this site related to the reduced availability of detritus and sand grains, perhaps reflecting greater wave scouring at this level on the shore. Large meiofaunal populations overwinter successfully in Cladophora in these ice-free latitudes and sheltered waters. Nematodes and harpacticoid copepods dominate the fauna of Cladophora in these permanent pools. Even populations in high-shore situations are remarkably stable. The rhombognathid mites, the polychaetes Fabricia sabella and Janua pagenstecheri and the chironomid larvae all showed little or no seasonal fluctuations in numbers, though most harpacticoid copepods, ostracods, turbellarians and archiannelids had very definite population maxima. Cladophora also acts as a nursery ground for species whose adults live elsewhere on rocky shores.     

Arthropods associated with nests of Cacicus sp. and Psarocolius sp. (Passerida: Icteridae) in varzea forest near the meeting of the rivers Negro and Solimões (Central Amazonia,Brazil) at high water

We analysed the arthropod fauna from nine nests of Cacicus sp. and nine nests of Psarocolius sp. (Passerida: Icteridae), in the varzea forest of Central Amazonia, Brazil, during high water, establishing these nests as one of the probable refuges for several arthropods performing vertical migration during periods of flooding and high water, besides discussing the role of these arthropods in the nests. We also evaluate the effectiveness of the extraction of arthropods from nests using an apparatus based on the Berlese–Tullgren funnel. We obtained 15,128 arthropods from three subphyla, five classes and 16 orders. The nests were shown as complex ecosystems sheltering groups from different functional and trophic categories and revealed striking differences from those of terra firma, remarkably in Blattaria, Arachnida and Pseudoscorpiones. The increasing volume of the funnel and time of heat exposure was shown to be appropriate for extraction of the arthropods from the bulky nests of these birds.     

Temporal variation and structure of macro-epifauna associated with macrophytes in the Bizerte lagoon (Tunisia,SW Mediterranean Sea)

The temporal variation in composition and abundance of the macro-epifauna associated with seaweeds (Ulva lactuca, Cladophora sp., Gracilariopsis longissima and Gracilaria bursa-pastoris) and seagrass (Cymodocea nodosa) was investigated at Menzel Jemil station in the Bizerte lagoon. Twelve replicate samples (25 x 25 cm frame) were collected monthly from October 2009 to September 2010. Sampling data yielded 21,575 invertebrate specimens from floating seaweeds and the seagrass, belonging to 40 taxa, of which 18 species were arthropods, 13 molluscs, three echinoderms, three fishes, two polychaetes and one cnidarian. Crustaceans were the most dominant and the most species-rich group and Idotea balthica basteri the most abundant species, accounting for 28.94% of the total abundance. Minimum (9.25 ± 5.56 species) and maximum (19.75 ± 3.2 species) values of mean species richness were observed in December and June, respectively. Species richness and density of macro-epifauna showed similar trends to plant biomass and the highest values of both indices coincided with periods of maximal plant biomass. Mean values of Shannon’s index H′ and evenness J′ were low, ranging from 0.34 ± 0.02 bit to 1.08 ± 0.06 bit, and from 0.23 ± 0.03 to 0.52 ± 0.07, respectively. The high dominance of herbivores and detritivores highlighted the substantial role played by macrophytes as food source for associated macro-epifauna species. Multivariate analyses also indicated significant seasonal differences for the macro-epifauna assemblage and revealed significant relationships with environmental variables. According to the canonical correspondence analysis, concentrations of phosphates and nitrites, and temperature were the variables that explained the variation of the macro-epifauna abundance in the Bizerte lagoon.     

The identity of Orius tantillus (Motschulsky) and notes on other Oriental Anthocoridae (Hemiptera,Heteroptera)

Abstract

Studies on the biology of Toxoptera aurantii (Boy.) showed that populations of the aphid contain females only, and that reproduction is parthenogenetic and viviparous and occurs exclusively on the undersurface of flush leaves. The aphid is described and a key is drawn for the various instars. The development of the aphid is temperature-dependent but at the optimum temperature it takes 6 days to become adult. The incidence of alates in populations is influenced both by high aphid density and leaf age.     

Breeding biology and population structure of the intertidal crab Petrolisthes laevigatus (Anomura: Porcellanidae) in central-southern Chile

The present study describes the seasonal reproductive cycle and population structure of the porcellanid crab Petrolisthes laevigatus, a typical inhabitant of the rocky intertidal. A total of 960 individuals (including 372 females) was collected in monthly samples from October 1993 to December 1994 in central-southern Chile. Ovigerous females were present between August and December, and were absent between January and July. The breeding season started during late winter (August), and females with embryos close to hatching occurred between October and end of spring (December). Considering the gonadosomatic index and the duration of the incubation period, it is concluded that P. laevigatus has a markedly seasonal breeding period with probably two successive spawnings per female per season. Our results compared with previous studies in temperate intertidal porcellanids suggest a lower structural variability of the population during the sampling period, but a pronounced seasonal variation in both sex ratio and abundance. The influence of environmental habitat conditions (i.e. temperature) is suggested to be responsible for the lower variation in the crab population size structure in ovigerous females, and the almost constant size distribution observed in males.     

Life cycle and population structure of the terrestrial isopod Hemilepistus klugii (Brandt, 1833) (Isopoda: Oniscidea) in Iran

The life cycle and population structure of Hemilepistus klugii were studied in a population in Varamin, Iran. The population was sampled monthly (or fortnightly during the breeding season) from February 2008 to June 2009 and a total of 7015 individuals, comprising 1069 males, 1079 females and 4867 juveniles, were collected. As in other Hemilepistus species, five distinct phenophases, namely pair formation, gestation, hatching, growth and stationary, were recorded during the life cycle of H. klugii. The overall sex ratio was 1 : 1 but varied over time. Ovigerous females were observed only in April, indicating a seasonal and very short breeding period. With a short lifespan after breeding, females demonstrated true semelparity. The mean cephalothorax width for ovigerous/post-ovigerous females was higher in 2008 than in 2009. These females attained the largest size in the population throughout the year. The number of eggs per female ranged from 28 to 147 (mean ± SE, 78 ± 1.8). There was a positive correlation between female size and fecundity. Recruitment occurred in late April and resulted in the highest population density in this month, whereas the lowest densities were observed during November to January. Despite a high percentage of ovigerous females carrying undeveloped eggs (72.3%), intramarsupial mortality was low (3.5%).     

Seasonal reproduction in deep-sea Crustacea (Isopoda: Asellota)

A collection of Crustacea Isopoda (suborder Asellota) from a 10-year sampling programme in the Rockall Trough, NE Atlantic (54°40′N, 12°15′W) was analysed for evidence of breeding seasonality. No evidence of seasonal activity was found — adults and newly released juveniles were present throughout the year — but there was a strong seasonal pattern for breeding intensity. A significantly higher proportion of females was brooding during the winter months (25%) compared to the summer (5%), and the percentage of females brooding varied significantly with depth. The breeding pattern was synchronized to the seasonal deposition of organic detritus known to occur during the summer in the NE Atlantic. There were more newly released juveniles in samples during the summer than during the winter, with most females appearing to release their young at the time the deposition began. This deposition appears to be a major seasonal factor dominating the life-cycles of most benthic species in the Rockall Trough. Juvenile settlement for a range of taxa (echinoderms, molluscs and crustaceans) occurs while the detritus is present and most species maximize vitellogenesis at this time.     

Ecological aspects of the pumpkin toadlet,Brachycephalus garbeanus Miranda-Ribeiro, 1920 (Anura: Neobatrachia: Brachycephalidae), in a highland forest of southeastern Brazil

Brachycephalus garbeanus is an aposematic toadlet, endemic to the Atlantic Forest in the mountains of the state of Rio de Janeiro, southeastern Brazil. Information regarding the ecology of species in this genus is scarce, with no information on most species, including B. garbeanus. We provide ecological information about B. garbeanus, in particular regarding microhabitat use, sexual dimorphism in body size, and feeding habits. Our study was conducted in a montane area of the Parque Estadual dos Três Picos, the largest State park in Rio de Janeiro. Most of the B. garbeanus in the study area were found on the forest floor leaf litter. Females were larger on average than males. Brachycephalus garbeanus consumed a wide array of prey, comprising exclusively invertebrates and predominantly arthropods. There were seasonal differences in the diet composition, but mites and ants were important in both wet and dry seasons.     

The association of Amphisbaena alba (Reptilia: Amphisbaenia) with the leaf-cutting ant Atta cephalotes in Trinidad

Evidence suggests that Amphisbaena alba is a facultative inquiline of nests of the leaf-cutting ant Atta cephalotes in Trinidad. The evidence is culled from three main sources: (i) direct excavation of Atta nests; (ii) the ability of A. alba to follow Atta trail pheromones; (iii) the analysis of A. alba intestinal or faecal contents. When inside ant nests, A. alba may feed primarily on arthropods, notably beetles, which are themselves inquilines in ant nests. Studies on the life-cycle of a pentastomid parasite of A. alba, which depends for transmission on ant and beetle inquilines, also indicates that A. alba and Atta are intimately associated. The literature suggesting a regular association between ants (and termites) and amphisbaenians in general is reviewed.     

The occurrence of Parvatrema homoeotecnum James, 1964 (Trematoda: Gymnophallidae) in a population of Littorina saxatilis tenebrosa (Mont.)

Summary

Marking experiments, seasonal variations in the population density and observations on the breeding cycle indicated that healthy adult Littorina saxatilis tenebrosa (Mont.) migrate down to the lower supralittoral fringe in order to give birth to the young in July–August and in January–February. The young and adults then migrate up towards the upper supralittoral fringe. Specimens infected with Parvatrema homoeotecnum, unlike those infected with two other digenean species investigated, migrate in the same way as healthy specimens. This ensures that although initial infestation takes place in the lower supralittoral fringe, parasitized specimens occur throughout the supralittoral fringe. Only juvenile hosts, below 7·0 mm long and usually below 5·0 mm long are infected, highest percentages occurring in specimens measuring 1·1–2·0 mm long. The seasonal variations in percentage infection are corellated with the breeding cycle, growth, mortality and migration of the host.     

Habitat use and diet of the endemic lizard Ameivula nigrigula (Squamata: Teiidae) in Caatinga domain,Northeastern Brazil

ABSTRACT

The lizard Ameivula nigrigula is endemic to Caatinga vegetation and the transition zone between the Caatinga and Cerrado domains in Brazil. It was recently described, but little is known about its biology. We analysed microhabitat use and the diet of this species in Caatinga vegetation in Santo Inácio, Bahia State. Its diet consisted mainly of arthropods and plant material, and in particular aggregate (e.g. termites) and large preys (e.g. Coleoptera, insect larvae and spiders), reflecting their nutritional and energy values and high water contents. With regard to habitat use, we found A. nigrigula using microhabitats with tall vegetation over accumulated leaf litter, which could potentially contribute to temperature regulation. Together, those characteristics contribute to the survival of lizards in environments with low water availability and high temperatures, such as the Caatinga domain.     

Population dynamics of the gall inducer Eriogallococcus isaias (Hemiptera: Coccoidea: Eriococcidae) on Pseudobombax grandiflorum (Malvaceae)

Eriogallococcus isaias Hodgson and Magalhães is a Neotropical species of gall-inducing scale insect (Coccoidea: Eriococcidae), whose phenological synchrony with its host plant, Pseudobombax grandiflorum, is fundamental to the maintenance of its population. Furthermore, E. isaias is unusual among gall-inducing Eriococcidae because its galls are not sexually dimorphic and are induced by the second-instar nymphs. We studied the life cycles of the host plant and the galling insect, and followed the development of the insects and the structure of the gall. The results showed that gall induction is synchronous with leaf flushing, and that the galls and leaves mature concomitantly. Males have a 36–48-day life cycle within the gall, whereas females have a 75–100-day life cycle.     

Potential host range of myrmecophilous Arhopala butterflies (Lepidoptera: Lycaenidae) feeding on Macaranga myrmecophytes

“Plant-ants”, i.e. those symbiotic with myrmecophyte plants, defend their hosts against herbivores. Plant-ants are expected to affect the host-plant ranges of herbivores that feed on myrmecophytes. This study aimed to experimentally determine whether anti-herbivore defences by plant-ants restrict the larval host-plant ranges of four Arhopala (Lycaenidae) butterflies that feed on Macaranga (Euphorbiaceae) trees, some of which are myrmecophytes. We fed Arhopala larvae with the leaves of five Macaranga species under ant-excluded conditions to examine their potential host-plant ranges. Under ant-excluded conditions, three Arhopala species survived to the pupal stage when fed species not used in the field as well as their normal host species. Our data suggested that the aggressive behaviours of plant-ants towards leaf-feeding insects restrict the potential host-plant ranges of some Macaranga-feeding Arhopala butterflies.