The population metabolism and life history tactics of Neobisium muscorum (Leach) (Arachnida: Pseudoscorpiones)

Summary The population metabolism of N. muscorum at a beechwood site in southern England was determined for two separate year periods by two methods; a detailed computer analysis and a best estimate. These methods, which are based on data of biomass, population dynamics, field temperatures, and respiration rates of all life stages with temperature, are compared. The validity of extrapolating laboratory determined basal metabolic rates to field activity is discussed; and the population metabolism of N. muscorum is compared with that reported for other soil and litter invertebrate species, both predatory and non-predatory.The metabolic rates of the adults of a second species of pseudoscorpion found at the beechwood site (Chthonius orthodactylus (Leach)), were determined, and the life cycle and metabolism of this species is compared to N. muscorum. The influence of low environmental temperatures on poikilothermic predators, with reference to life cycle strategies, basal metabolism and geographic distribution, is discussed.     

Seasonal aspects of the life cycles of pseudoscorpions (Arachnida, Pseudoscorpiones)

Analysis of available information on the seasonal features of life cycles in pseudoscorpions (Arachnida, Pseudoscorpiones) shows that in the temperate climate of Europe with distinct seasonality, the development of these peculiar arachnids can be either eurychronous (= homodynamic), with a poorly pronounced seasonal arrangement, or stenochronous (= heterodynamic), with a distinct seasonal arrangement. This is similar to some other arachnids, particularly spiders and harvestmen. Eurychronous pseudoscorpions are characterized by the approximately year-round development (quite often with winter activity in the whole or part of the population), an overlapping of consecutive generations, the presence of alternative development with or without the dormant state (at all the postembryonic life cycle stages), lack of brood chamber production by females, and the start of free-living life at the protonymphal stage. Stenochronous pseudoscorpions, on the contrary, possess clearly arranged (usually univoltine) development with overwintering deutonymphs and tritonymphs (more rarely adults), a clear separation of adjacent generations, the production of brood chambers where the regressive protonymphs develop until their molt into deutonymphs, and the start of free-living life at the deutonymphal stage. These two types of life cycles are exemplified by two pseudoscorpions from South England, namely Neobisium muscorum with eurychronous development, and Chthonius orthodactylus with stenochronous, univoltine development (Goddard, 1976). There is no correlation between the taxonomic position and the seasonal characters of life cycles in representatives of Neobisiidae, Chthoniidae, and Chernetidae. There is, instead, a close connection between the eco-physiological state of these arachnids and the type of their gas exchange (continuous, diffusive and non-cyclic in the active state, as opposed to discontinuous, with cyclic emission of CO₂ and uptake of O₂ in the dormant state). The latter information may be useful for distinguishing different kinds of dormancy (diapause and quiescence) in these arachnids.     

Seasonal aspects of the life cycle of solifuges (Arachnida, Solifugae) as compared with pseudoscorpions (Arachnida, Pseudoscorpiones)

Solifuges (order Solifugae) and pseudoscorpions (order Pseudoscorpiones) united into the superorder Haplocnemata (Shultz, 2007) are nevertheless characterized by essential differences both in morphological and biological characters. Analysis of available information on the biology and life cycles of these arachnids revealed a clear difference between the daily rhythms of activity: their presence in solifuges and their absence in pseudoscorpions. However, this concerning the seasonal adaptations in the two orders is not simple since they demonstrate not only differences but also a lot of similarities. All the studied solifuges are characterized by the seasonally timed stenochronous (heterodynamic) type of development which is characteristic of species with uni-, bi-, and semi-voltine development (i.e., to life cycles completed within a year, half a year, and several years), as well as to species combining different forms of voltinism. This type of development is not only prevalent in solifuges (as in pseudoscorpions and other arachnids) but appears to be the only one, since no cases of eurychronous (homodynamic) development have been found in solifuges; whereas pseudoscorpions and other arachnids develop both steno- and eurychronously. The initial ontogenetic stages remain in underground shelters (brood burrows in solifuges and brood chambers in pseudoscorpions). The first nymphal stages (I instar nymphs in solifuges, protonymphs in pseudoscorpions) are embryonized; active life outside the brood burrows starts with II instar nymphs in solifuges and with deutonymphs in pseudoscorpions.     

中国伪蝎名录（蛛形纲：伪蝎目）

本文根据我国伪蝎目已有种类记述,归纳并列出10科34属73种（包括亚种）伪蝎的中文名、拉丁学名、引证及其地理分布,以供今后研究参考。     

Ecological and evolutionary pathways of social behavior in Pseudoscorpions (Arachnida: Pseudoscorpiones)

Despite the great biodiversity in the Arachnida, some taxa are still now poorly known, mainly in terms of biology, ecology, and behavior. Pseudoscorpions are small arachnids (2–8 mm) that live in cryptic environments, being in general solitary predators of other invertebrates. The most studied Pseudoscorpion species are those from temperate areas, which revealed that Pseudoscorpiones present some level of sociality based on maternal care. Most developed sociality is seen in tropical species. Here, we reviewed this issue, presented examples of social behavior, and suggested the steps involved in the evolution of permanent sociality in the Neotropical Atemnidae genus, Paratemnoides. We discussed that the extended parental care, division of labor, cooperative breeding and feeding, and the tolerance among members dividing the same share could be considered enough to characterize a true social life, same in invertebrates.     

The structure of encysted sperm of some British Pseudoscorpiones (Arachnida)

The sperm of pseudoscorpions consists of a coiled head (nuclear material), axial filament and an annular mitochondrion, all enclosed within a cyst.
Variations occur in the gross morphology of different pseudoscorpion sperm. These variations are discussed in terms of possible morphological relationships.     

Karyotype analysis and achiasmatic meiosis in pseudoscorpions of the family Chthoniidae (Arachnida: Pseudoscorpiones)

Karyotypes of pseudoscorpions (Arachnida, Pseudoscorpiones) are largely unknown. Here we describe for the first time karyotypes of the suborder Epiocheirata, represented by 9 European species of two genera of Chthoniidae, Chthonius and Mundochthonius. Diploid chromosome numbers of males range from 21 to 37. Karyotypes of both genera differ substantially. Acrocentric chromosomes predominate in karyotypes of the genus Chthonius, whereas M. styriacus exhibits a predominance of metacentric chromosomes. These differences suggest that the two genera belong probably to distant branches of the family Chthoniidae. It is proposed that karyotype evolution of the genus Chthonius was characterised by a reduction of chromosome numbers by tandem and centric fusions as well as gradual conversion of acrocentric chromosomes to biarmed ones, mostly by pericentric inversions. A tendency towards reduced chromosome numbers is evident in the subgenus Ephippiochthonius. All species display X0 sex chromosome system that is probably ancestral in pseudoscorpions. The X chromosome exhibits conservative morphology. It is metacentric in all species examined, and in the majority of them, a subterminal secondary constriction was found at one of its arms. In contrast to chthoniids, secondary constriction was not reported on sex chromosomes of other pseudoscorpions. Analysis of prophase I chromosomes in males revealed an achiasmatic mode of meiosis. Findings of the achiasmatic meiosis in both genera, Chthonius and Mundochthonius, indicate that this mode of meiosis might be characteristic of the family Chthoniidae. Amongst arachnids, achiasmatic meiosis has only been described in some scorpions, acariform mites, and spiders.     

Vicariance in a Cryptic Species Pair of European Pseudoscorpions (Arachnida, Pseudoscorpiones, Chthoniidae)

Following the first records of Chthonius (Ephippiochthonius) boldorii Beier, 1934 in central Europe, a species which was previously assumed to occur exclusively in Mediterranean caves, 116 series (595 specimens) of the cryptic taxa C. (E.) boldorii and C. (E.) fuscimanus Simon, 1900 (Syn. C. (E.) austriacus Beier, 1931) were re-examined. Although multivariate analyses suggest specific separation, there is only one unequivocal character for discrimination: the presence or absence of a single isolated tooth on the moveable finger of the chelicerae. The distributions were found to be largely allopatric, therefore it is concluded that the species rank of the two morphospecies is justified. North of the Alps, an almost vicariant pattern emerged: east of 14° E fuscimanus occurs, west of this line boldorii occurs. The results provide a basis for discussing the relevance of minute morphological differences in pseudoscorpion taxonomy.     

Mating Behavior and Spermatophore Morphology of the Cave Pseudoscorpion Maxchernes iporangae (Arachnida: Pseudoscorpiones: Chernetidae)

The mating behavior of the cave pseudoscorpion Maxchernes iporangae Mahnert & Andrade, 1998 (Chernetidae), was studied under laboratory conditions. A total of 24 pairings was observed. Mating was divided into three phases: predeposition (dance), spermatophore deposition and transfer, and posttransfer phase. The mean mating duration was 67.3 min based on 10 observations. Spermatophore morphology is described and consists of a stalk, a drop of fluid, and an -shaped sperm package. Males and females can mate several times in the same reproductive period. However, consecutive mating was not observed between a female and the same or another male.     

Dormant stages and their participation in adjustment and regulation of life cycles of harvestmen (Arachnida,Opiliones)

Information on seasonal adaptations in the life cycles of harvestmen (order Opiliones) summarized in this review reveals a great diversity of these arachnids with respect to duration, voltinism, and phenology of their life cycles, as well as to the number and ontogenetic position of the dormant stages required for survival during the winter season and also for synchronizing development with seasonal climate rhythms. Most harvestmen have stenochronous development with univoltine life cycles synchronized by arrest of development in hibernating eggs or (rarely) diapausing nymphs and adults. The number and arrangement of dormant stages represent stable species-specific traits, with some rare cases of interpopulation differences (e.g., in Phalangium opilio). Eurychronous harvestmen exhibit the year-round occurrence of main ontogenetic stages which show equal abilities for either active development or quiescence (depending upon the external factors). Two alternative types of development arrest are common in univoltine opilionids: (1) diapause induced at the early stage of embryogenesis and terminated during cooling (in Opilio parietinus and eleven other species) with transformation into postdiapause quiescence; (2) cold quiescence enforced by low temperatures at the last stage of egg development just before hatching (in Phalangium opilio and four other species). In conclusion, the systems of seasonal adaptations in Opiliones are compared with those in other arachnids, insects, and crustaceans. Some promising directions in the study of seasonal adaptations in opilionid life cycles are suggested.     

The genitalia and associated glands of five British species belonging to the family Chthoniidae (Pseudoscorpiones: Arachnida)

The male and female genitalia of five species representing the genus Chthonius are fundamentally similar in form. However minor differences do occur which are of possible taxonomic significance at both the sub-generic and specific levels. Thus, the two species C. kewi and C. tetrachelatus of the sub-genus Ephippiochthonius have a number of characters in common which differ from those of the remaining three species, C. ischnocheles, C. tenuis and C. orthodactylus of the subgenus Chthonius (s.st). Other genital characters can be used to separate the five species.
Such small differences in the genitalia suggests that spermatophore formation and deposition in the four species C. tenuis, C. tetrachelatus, C. kewi and C. orthodactylus is not different from that of C. ischnocheles (Legg, 1973). What differences that do occur, for example, the thickening of the roof of the medial diverticulcum, size of the males and the pheromone produced by the lateral glands, probably are aids to species isolation.     

Population dynamics, life stage and ecological modeling in Chrysomya albiceps (Wiedemann) (Diptera: Calliphoridae)

In this study we investigated the population dynamics of Chrysomya albiceps (Wiedemann) with laboratory experiments, employing survival analysis and stage structure mathematical models, emphasizing survival among life stages. The study also assessed the theoretical influence of density dependence and cannibalism during immature stages, on the population dynamics of the species. The survival curves were similar, indicating that populations of C. albiceps exhibit the same pattern of survival among life stages. A strong nonlinear trend was observed, suggesting density dependence, acting during the first life stages of C. albiceps. The time-series simulations produced chaotic oscillations for all life stages, and the cannibalism did not produce qualitative changes in the dynamic behavior. The bifurcation analysis shows that for low values for survival, the population reaches a stable equilibrium, but the cannibalism results in chaotic oscillations practically over all the parametric space. The implications of the patterns of dynamic behavior observed are discussed.     

Environment and life cycles influence distribution patterns of hydromedusae in austral South America

We analysed hydromedusa assemblages of South America (from 22°S to 56°S and from 040°W to 080°W), their association with water masses and the influence of the life cycle on medusa distributions. The geographic distribution of 130 species of hydromedusae was compiled from literature reports (62 publications between 1913 and 2012). Seven areas were defined: Atlantic Magellanic, Argentinean, Pacific intermediate zone, Pacific Magellanic, Peruvian–Chilean, South Brazilian and Oceanic. The variance of the species–environment relationship was explained by depth and temperature. Distribution patterns of Atlantic hydromedusae are associated with neritic water masses, supporting previously proposed biogeographical provinces. Assemblages on the Pacific side of South America are under the influence of the Humboldt Current system, with a break in species distribution around Chiloé Island. Only the oceanic assemblage contained the same species in both the Pacific and Atlantic zones. We found that meroplanktonic medusae contributed more to define the neritic assemblages, while the oceanic assemblage was better defined by holoplanktonic medusae. Therefore, our data suggest that meroplanktonic hydromedusae appeared to be more restricted in distribution than holoplanktonic ones.     

The spider assemblage (Arachnida,Aranei) in agroecosystems of the Kuban Plain: Species composition,spatial distribution,and seasonal dynamics

During two years of observations of winter wheat fields, their margins and areas adjacent to forest shelterbelts, 139 species of spiders from 18 families and 92 genera were found using net-sweeping and pitfall trapping. In the fields proper, 87 species were recorded. The species number and species diversity decreased towards the central areas of the fields. High species diversity was recorded in the field edges but not in their central parts. Spiders of the families Philodromidae, Thomisidae, and Araneidae predominated in the herb-layer; the fractions of these families were greater in the fields than in their margins. Species of the family Salticidae were more numerous in the field edges and margins. Representatives of Lycosidae were the most common among epigeic spiders, their fraction reaching 90% in the field center. The dominant forms comprised 10% of the species and 80% of the number of individuals. Agrobionts common to the temperate zone of Europe predominated in the central part of the fields. They colonized the fields rapidly and distributed uniformly over the territory in spring, and then redistributed as the crops grew. The species for which the ecological conditions of the fields were favorable colonized the fields regardless of their size; other species were restricted to the field periphery.     

Population structure and inbreeding in a rare and declining bumblebee, Bombus muscorum (Hymenoptera: Apidae)

Owing to habitat loss populations of many organisms have declined and become fragmented. Vertebrate conservation strategies routinely consider genetic factors, but their importance in invertebrate populations is poorly understood. Bumblebees are important pollinators, and many species have undergone dramatic declines. As monoandrous social hymenopterans they may be particularly susceptible to inbreeding due to low effective population sizes. We study fragmented populations of a bumblebee species, on a model island system, and on mainland Great Britain where it is rare and declining. We use microsatellites to study: population genetic structuring and gene flow; the relationships between genetic diversity, population size and isolation; and frequencies of (sterile) diploid males - an indicator of inbreeding. We find significant genetic structuring (theta = 0.12) and isolation by distance. Populations > 10 km apart are all significantly differentiated, both on oceanic islands and on the mainland. Genetic diversity is reduced relative to closely related common species, and isolated populations exhibit further reductions. Of 16 populations, 10 show recent bottlenecking, and 3 show diploid male production. These results suggest that surviving populations of this rare insect suffer from inbreeding as a result of geographical isolation. Implications for the conservation of social hymenopterans are discussed.     

Population dynamics and vertical distribution of Scaptocoris carvalhoi Becker (Hemiptera: Cydnidae) in pastures

Studies on population dynamics and vertical distribution in the soil of Scaptocoris carvalhoi Becker were carried out in a pasture area in Paraúna, State of Goias, Brazil, from November 2004 to October 2005. One meter-deep holes were excavated in the soil, except on the season of lower precipitation, when 2-meter holes were excavated (June, August and September 2005). On each evaluation, the specimens were collected and grouped according to the depth they were found in the soil profile (0-20, 21-40, 41-60, 61-80 and 81-100 cm). Nymphs occurred during the entire length of the study and were more abundant than adults. Adult population augmented with the increase of rainfall. Nymphs and adults were located in the top layer of the soil during the rainy season and were found deeper in the soil during droughts. However, adults were less tolerant to hydric stress and burrowed deeper into the soil at the beginning of the dry season, while nymphs burrowed deeper only at the end of the season. Results of this study are in accordance to other studies on various species of Scaptocoris, in other regions of Brazil.     

Population ecology ofGoniosoma spelaeum, a cavernicolous harvestman from south-eastern Brazil (Arachnida: Opiliones: Gonyleptidae)

Goniosoma spelaeum (Mello-Leitão) is a widespread trogloxene harvestman in caves of the Ribeira Valley in São Paulo State. It inhabits walls and ceilings near cave entrances. Populations inhabiting six selected caves of the region were analysed during this study. Mark-recapture techniques were used to estimate population sizes. Populations vary from tens to hundreds of individuals in each cave, and vary throughout the year. Barra Bonita cave had the largest population and was used to identify other ecological features of the species. These harvestmen show a high degree of philopartry, and recapture rate was high. They remain motionless inside the caves during the day, leaving them after dark to forage, and return just after dawn. They always feed outside the caves and do not carry food into the caves. Soft-bodied insects were the main food observed in the field. In the laboratory, they accepted plant and animal items and industrial foods. Their main predators are the spider Ctenus fasciatus , the heteropteran Zelurus travassosi , and the marsupial Philander opossum , and their main parasites are dipteran larvae (probably Phoridae).     

Observations on the distribution patterns,behaviour, diets and reproductive cycles of sand-dwelling clinids (Perciformes: Clinidae) from South Africa

Synopsis Twenty-two samples of sand-dwelling fishes were collected from sublittoral sandy substrata off the Cape Peninsula, South Africa using a novel quantitative technique in which the ichthyocide, rotenone, was introduced beneath 6.25 m² plastic sheets weighted around the perimeter with chain. A total of 94 fish of eight species and four families were recorded. Of these, four species of the family Clinidae made up 92% of the material. Fish densities varied from 0.10–2.96 fish m^–2 (0.17–1.14 g m^–2). Distribution patterns amongst the Clinidae were explained by sediment particle size, with all of the newly discovered species, Cancelloxus longior, inhabiting fine sand (median grain size 0.25–0.50 mm), and all Xenopoclinus leprosus, C. elongatus and Pavoclinus smalei occurring in gravel (> 1 mm). Xenopoclinus kochi was found in all sediment types, but was most abundant in coarse substrata. Diets of all four species were similar, consisting chiefly of amphipods and isopods. However, small differences in prey preference were evident. All four species reached sexual maturity at 25–30 mm standard length, were viviparous, exhibited superembryonation and gave birth to live young of approximately 14 mm. Breeding seasonality occurred in all species except P. smalei.     

Population structure and distribution patterns of the rare and endangered Ardisia violacea (Myrsinaceae)

Ardisia violacea (Myrsinaceae), one of China’s rare and endangered species, occurs only in Zhejiang and Taiwan provinces. We examined the population dynamics of this species to reveal details related to the development of populations. Assembling intensity indices were used, such as V/m, K, m^*, PAI, CA and I. Age class structure and the time-specific life tables were analyzed by the contiguous grid quadrate method. The population structures and distribution patterns of A. violacea in different habitats, age classes and quadrat scales are discussed and the life parameters such as the survival curve, mortality curve and life expectancy were estimated. The results show the age class distribution of the entire population generally fits a reverse “J” type curve, suggesting a growing population. The population spatial distribution pattern was clumped in all three habitats, especially in the age classes I–III, and had a uniform distribution in the age classes VII and IX. The plants mainly occurred at microsites with generally adequate light, water, nutrients and air. Micro-environmental factors and human factors can also have a great impact. In the age class structure pattern, the individual percentage of the first three age classes accounted for 71.19% in H1 (habitat 1), 68.18% in H2 (habitat 2) and 88.24% in H3 (habitat 3), which indicated the number of individuals in the first three age classes were larger than any other age classes. The population size peaked in the age classes III and X and only 13.1% individuals survive age class III to enter class IV. As a result, fewer middle and advanced aged individuals were found. Age class IV had the highest life expectancy for A. violacea. The survival curve approached to Deevy-II. The spatial distribution pattern of A. violacea populations was decided mainly by the interaction of biological and ecological characteristics of its environment, habitat heterogeneities, microenvironments and human disturbance.     

Population dynamics of two Scottish Ultramafic (serpentine) rarities with contrasting life histories

Summary

The paper reports demographic studies of the endemic Cerastium nigrescens and the very rare Arenaria norvegica ssp. norvegica on the Keen of Hamar ultramafic outcrop on Unst, Shetland from June 1994 to November 1996. Plants of Cerastium nigrescens showed a Deevey type II curve and mature plants had a half-life of 3.8 years. Plants of Arenaria norvegica ssp. norvegica showed a Deevey type I curve with high mortality after flowering in the second year. There was some evidence of increased mortality during droughts but this had little impact on the total population. Seed production and seedling recruitment for both species was good throughout the study period. Seed bank measurements ranged from 12–13 m² for Cerastium nigrescens and 24–43 m^-2 for Arenaria norvegica ssp. norvegica. The study showed that there was no immediate threat to the populations of the two species but because of their isolated occurrence they are susceptible to extinction and should be carefully monitored.