Experimental studies of ice nucleation in an Antarctic springtail (Collembola, Isotomidae)

Ice nucleation was studied in field-fresh and acclimated (4 degrees C without food for 11-20 days) samples of the springtail Cryptopygus antarcticus Willem (Collembola, Isotomidae) at Rothera Research Station, Adelaide Island on the Antarctic Peninsula. Ice nucleator activity (INA) was measured by a freezing droplet technique in addition to supercooling point (SCP) profiles and polyol, sugar, and water contents. Field and acclimated samples showed bimodal SCP distributions with a distinct high group (HG; mean SCP -8 to -10 degrees C) and low group (LG: mean SCP -23 to -25 degrees C), which were significantly different. Acclimation at 4 degrees C increased the proportion of individuals in the LG relative to that in the HG without significant effects on the mean SCP of both groups. INA of the HG was significantly greater than that of the LG, and acclimation further reduced the INA of the LG. The number of active ice nucleator agents (INAs) calculated for the HG of field samples increased by 23-100 times over the temperature range -5 to -8 degrees C compared to only 7 times for the LG over the same range. These differences were accentuated in the acclimation experiments. Glucose and galactose were the main carbohydrates in both field and acclimated springtails, with the latter compound occurring in almost twice the concentration in the LG compared with that in the HG. Acclimation reduced the concentration of both compounds (glucose by 77% and galactose by 54%), whereas water content increased significantly. Digestion of food may have continued during acclimation at 4 degrees C, which could reduce the LG INA. Lowering of temperature over time is more likely to elicit a cold hardening response than constant temperature acclimation. INA numbers calculated at the nucleation temperatures for C. antarcticus samples were higher in the LG than in the HG. However, inactivation of INAs may be a key mechanism underlying cold hardening in this species, either by sequestration within the cellular matrix or by being only seasonally active.     

Three species of Isotoma (Collembola, Isotomidae) based on morphology, isozymes and ecology

Morphological markers and isozymes were used for identifying three presumed species of the Isotoma genus. Morphological traits separated three taxa of the genus. 10 isozymes determined by at least 11 loci were analysed from each taxon, and 2 loci were taxon-specific, supporting the hypothesis that the three taxa represented three species. The genetic variation found within the taxa measured as fraction of polymorphic loci at the 99% level was 0.82, 0.55 and 0.55 with the corresponding observed heterozygosity 0.15, 0.09 and 0.12. Two populations of the same taxon from Denmark and Norway, respectively, were very closely related. Additional ecological criteria, obtained from a literature survey, also revealed pronounced differences between the three taxa. Due to these facts three distinct species are proposed, namely I. anglicana Lubbock 1862, I. riparia Nicolet 1841 and I. viridis Bourlet 1839.     

Phylogeographic structure suggests multiple glacial refugia in northern Victoria Land for the endemic Antarctic springtail Desoria klovstadi (Collembola, Isotomidae)

We carried out a phylogeographic study using mtDNA (COII) for the endemic springtail Desoria klovstadi (formerly Isotoma klovstadi ) from northern Victoria Land, Antarctica. Low levels of sequence divergence (≤ 1.6%) across 26 unique haplotypes (from 69 individuals) were distributed according to geographic location. Cape Hallett and Daniell Peninsula contained the highest nucleotide (both > 0.004) and haplotype (both > 0.9) diversity with 10 (of 16) and 8 (of 12) unique haplotypes, respectively. All other populations (Football Saddle, Crater Cirque, Cape Jones) had lower diversity with 2–4 unique haplotypes. Across the 69 individuals from five populations there was only a single haplotype shared between two populations (Daniell Peninsula and Football Saddle). Furthermore, nested clade analyses revealed that some of the Daniell Peninsula haplotypes were more closely related to Football Saddle haplotypes than to any other population. Such discrete haplotype groupings suggest historical (rare) dispersal across the Pleistocene (1.8 mya−11 kya) and Holocene (11 kya–present), coupled with repeated extinction, range contraction and expansion events, and/or incomplete sampling across the species range. The nested clade analyses reveal that a common pattern of climatic and geological history over long-term glacial habitat fragmentation has determined the geographic and haplotype distributions found for D. klovstadi .     

Isotomiella (Isotomidae: Collembola) of China

Seven species of the genus Isotomiella Bagnall 1939 were collected in China, two of which from Hainan and Guangxi provinces (South China) are newly described and illustrated. Isotomiella longisensilla n. sp. has bidentate mucro and long sensilla on most tergites, a character never seen before in this genus. I. deharvengi n. sp. belongs to the minor group and is characterized by a pair of strongly curved sensilla on Abd. V.     

Experimental models for the study of chronoimmunomodulation (rhythms of the springtail Folsomia candida, Collembola: Isotomidae)

A third-generation cephalosporine, cefodizime, was tested in two experiments on the springtail, Folsomia candida, used as a model of infradian rhythmicity. Any effect on ecdysis (molt), oviposition and oviproduction was sought for 6, 20 or 60 ng of cefodizime administered with brewer's yeast every other day, as compared to controls given only the yeast. Results indicate that a 20-ng dose of cefodizime on alternate days may shorten an infradian period (of molt) in the springtail.     

Embryogenesis of a springtail,Tomocerus ishibashii (Collembola,tomoceridae): External morphology

The external features of the developing embryos of the springtail, Tomocerus ishibashii, are described. The clypeolabral anlage arises as a single, unpaired swelling. The entognathy is completed by the ventral growth of the tergal anlagen of mandibular, maxillary, and labial segments. These anlagen also form the posterior part of the cranium. The palpi of maxilla and labium are homologous with the telopodites, and proximal parts of these head appendages are homologous with the coxopodites. The sternal element of the labial segment does not participate in the postmentum formation. The anlagen of abdominal appendages appear in the first to the fourth abdominal segments. The first, third, and fourth appendage anlagen form the ventral tube, tenaculum, and furcula, respectively. The fused proximal parts of the first, third, and fourth appendage anlagen are homologous with the coxopodites, and the distal parts which do not fuse are homologous with the telopodites. The anlagen of the second abdominal appendages become flattened and spread over the ventral side of this segment. The ventral structures of the first four abdominal segments are appendicular in origin.     

New species of Desoria (Collembola: Isotomidae) from Korea

A new species, Desoria mulyeongariensis, shares some characters with D. choi (Lee), such as the number of setae on retinaculum and apical setae on manubrium. However, it could be easily distinguished from D. choi by the number of ommatidia. This species is also well characterized by having long and thickened smooth macrosetae on the body, and 6 basomedian setae on labium.     

Predation ofApochthonius minimus (Pseudoscorpionida: Chthoniidae) onFolsomia canadida (Collembola: Isotomidae)

Summary We investigated the functional response of the predaceous pseudoscorpion,Apochthonius minimus, to density of the springtail,Folsomia candida, as well as the effects of temperature and prey size on handling time and attack rate. Temperature slightly altered the overall rise in response. Both the rise and shape of the response differed for two prey sizes. The changes in number of prey eaten over a 48-hour period were also examined, and the attack and feeding behaviour ofA. minimus was described and discussed in relation to the predation experiments. The pseudoscorpion preferred young adultF. candida, 0.8–1.2 mm in length, when offered prey in the range, 0.2–1.5 mm.     

Folsomia (Collembola: Isotomidae) of China. II. heterocellata group

An annotated list of species of the Folsomia heterocellata group recorded in China is given. Folsomia cephalota n. sp., F. dorsomediaseta n. sp., F. longiseta n. sp., F. manubriopilosa n. sp., F. longdeica n. sp., and F. plenosensilla n. sp. are characterized by having a simple maxillary palp, four prelabral setae and no eyes. They differentiate mainly by characteristics of the furca. We report other species of the group which are recorded for the first time in China: Folsomia tianshanica Martynova, 1969, F. pseudovtorovi Potapov & Gulgenova, 2013, and F. pseudodecemoculata Stebaeva, 1971. This excludes F. wanxianensis Ji, Ding & Chen, 2007, for which we provide morphological remarks based on the type material. The group is mainly distributed in the central part of China (Chongqing, Gansu, southern part of Inner Mongolia, Ningxia and Shaanxi provinces). A key to all blind species with a simple maxillary palp is given.     

上海地区(虫兆)两新种(弹尾目:等节(虫兆)科)

本文描述了等节科的两新种,中华尾四刺Tetracanthura sinensis sp.nov.和缺眼二刺Uzelia anommatos sp.nov..其中Tetracanthura Martynova 1971为中国新记录属.     

A morphometric analysis of mandibular teeth in Folsomia (Collembola: Isotomidae)

Morphological variation in the apical mandibular teeth of seven Folsomia species (F. bisetosa, F. brevicauda, F. Candida, F. fimentaria, F. inoculata, F. penicula , and F. quadrioculata) was examined by canonical variates analysis of a systematic 'truss' of measurements. Differences were found between all but two species (F. brevicauda and F. quadrioculata) showing that the morphology of 'biting-type' mouthparts can be used for species recognition. The results also show that the truss system of measurement is sensitive to small-scale differences in the mandible morphology of these insects. It is suggested that variation in mouthpart morphology, and in patterns of tooth wear, reflect differences in the feeding behaviour of Folsomia species.     

Formation of springtail (Collembola) communities during colonization of ant-hills

Formation of springtail assemblages in resettled nests of the ant Formica aquilonia was studied. The species composition and relative abundance of springtails was shown to depend on the age, hydrothermal regime, and condition of the ant nest. The abundance and species diversity of springtails increases during the initial period of the ant-hill growth. Old nests are characterized by the minimum species diversity, with one or two distinct dominants. High ecological plasticity, including resistance to high temperatures and low humidity, allows Lepidocyrtus violaceus to maintain its stable dominant position in the ant-hills. Species with relatively narrow hygro-and thermopreferenda quickly occupy temporal favorable niches, reach high abundance, and quickly disappear as the microclimatic conditions change.     

西沙群岛永兴岛类符属一新种(弹尾目:等节科)

类符(虫兆)属Folsomina是由Denis(1931)建立的,至今只报道过一种,Folsominaonychiurina Denis,1931,为世界广布种。类符(虫兆)属由于触角第Ⅳ节上特殊的感觉器,缺角后器和眼,腹部第Ⅳ—Ⅵ节愈合等特征,很容易与等节(虫兆)科的其他属相区别。Gisin(1960)和Christiansen ＆ Bellinger(1980)将其归入符(虫兆)属Folsomia,但绝大多     

The springtail (Hexapoda,Collembola) fauna of Wrangel Island

Analysis of the collembolan fauna of Wrangel Island based on published data and recent sampling was performed. The species richness of springtails on the island (89 species from 41 genera and 12 families) exceeds the levels characteristic of most other insular territories of the Arctic Ocean, except for Greenland and some small islands located within the southern tundra belt. The specificity of the species composition of the springtail fauna on the island depends on a high proportion of species with amphi-Pacific ranges, reflecting its formation within the Beringian Arctic sector. At the same time, the structure of the springtail fauna of the island is rather similar to those of the known tundra faunas of the Siberian sector, with no anomalies being detected.     

白符(虫兆)胚胎发育的形态观察(弹尾纲:等节(虫兆)科)

对白符(Folsomiacandida)胚胎发育全过程进行显微观察,记述了白符从卵裂、囊胚期、原肠期、组织分化期、孵化前期等不同发育阶段的形态变化和发育过程。其结果表明,白符卵为聚产,形成大小不等的卵块,卵初产时为乳白色,卵壳表面覆盖有细密的颗粒状突起,直径为110—126μm。随着白符发育的进行,胚膜直径增大到180—185μm,其卵裂方式为完全均等卵裂,整个胚胎发育历期7—10d。     

Blastodermic cuticles of a springtail,Tomocerus ishibashii Yosii (Collembola : Tomoceridae)

The formation and structure of the blastodermic cuticles of a springtail, Tomocerus ishibashii Yosii (Collembola : Tomoceridae) are described together with the change of egg membrane. The blastodermic cuticles of the Collembola are 2-layered, and formed in the early stages of the embryonic development, preceding the differentiation of germ band. The first blastodermic cuticle is thicker (about 0.8-1.5 μm in thickness) and its surface is provided with complex structures, whereas the second one is thinner (about 0.2-0.4 μm in thickness) and smooth. About 3 days after oviposition, the chorion (about 2 μm in thickness) splits into 2 and the first blastodermic cuticle, provided with many projections and 4 large spines appear on the surface of the egg. Three types of projections are distinguished: button-, cone- and seta-like structures. The halves of the ruptured chorion are attached to the first blastodermic cuticle on both sides below the spines, and no projections are found in the regions concealed by the ruptured chorion. The projections of the first blastodermic cuticle are formed by cellular protrusions of the blastoderm. The conspicuous large spines on the first blastodermic cuticle are formed by the evaginations of the blastoderm. Tendrils of the primary dorsal organ run between the first and second blastodermic cuticles.     

A novel method of self-righting in the springtail Sminthurus viridis (Insecta: Collembola)

Photographic evidence shows that the ventral tube can be used as a tentacle-like mechanical aid for self-righting from an inverted position. It is proposed that the extraordinary length of the vesicles of the ventral tube in globular springtails has been evolved in order to combat postural instabilities resulting from spherical symmetry of body form.     

Mesoderm formation in a springtail,Tomocerus ishibashii Yosii (Collembola : Tomoceridae)

The mesoderm formation of Tomocerus ishibashii (Collembola : Tomoceridae) is described. Mesodermal cells are formed after the beginning of the formation of the primary dorsal organ, and originate from the entire region of the embryonic area. After completion of the blastodermic cuticles, cells of mesoderm and ectoderm concentrate towards a ventral midline and form a well-defined 2-layered germ band. The manner of mesoderm formation in the Collembola is similar to that in Diplura and Myriapods, except for the Chilopoda; the mesoderm of the Thysanura s. lat. and Pterygota originates from a localized zone of the embryo. Within the Hexapoda, mesoderm formation is categorized into 2 types: Type 1—unlocalized origin, in the Collembola and Diplura, and Type 2—localized origin, in the Thysanura s. lat. and Pterygota. Types 1 and 2 are thought to be plesiomorphic and apomorphic, respectively.     

Morphological variation in British Folsomia quadrioculata Tullberg (Collembola: Isotomidae): a multivariate study

Abstract. Morphological variation among freshly caught specimens resembling Folsomia quadrioculata Tullberg was examined using principal components analysis and canonical variates analysis. Two distinct groups were identified corresponding with F. quadrioculata and F.manolachei Bagnall. Previous workers have questioned the specific status of F.manolachei and regarded these two species as inseparable using morphometric characters. A study of specimens previously identified as F. quadrioculata suggested that many were mis-identified and that F.manolachei is more abundant in the British Isles than is usually thought. Variation in some characters traditionally used to identify Folsomia species was examined and a method for distinguishing adult and juvenile F.quadrioculata from F.manolachei is provided. The synonomy of F.nana Gisin with F.manolachei is supported. The separation of F.diplothalma Axelson from F. quadrioculata is discussed, concluding that no characters are known which can reliably separate British specimens of these species.