Variation in early developmental stages in two populations of an intertidal crab, Neohelice (Chasmagnathus) granulata

Duration of embryonic development, egg size, larval size at hatching, and starvation tolerance of the first zoeal stage were studied in an intertidal crab from the southwestern Atlantic, Neohelice (formerly Chasmagnathus) granulata. These reproductive traits were quantified comparing (a) two populations living in ecologically contrasting coastal habitats in Argentina, a brackish lagoon, Mar Chiquita, MC vs. an open marine habitat near San Antonio, Patagonia, SA, (b) beginning vs. end of the reproductive season, and (c) two temperatures during egg development (18 vs. 27°C). Eggs in an early stage of embryonic development were in both populations larger at the beginning than at the end of the season, and were consistently larger in the SA population. These size differences persisted through larval hatching, independent of the temperature during embryogenesis. At 18°C, eggs produced at the beginning of the season developed in both populations more rapidly than those from the end of the reproductive season, while the opposite trend was observed at 27°C. The stage duration of the zoea I was in both populations shorter at the beginning as compared to the end of the season. The nutritional flexibility of the zoea I stage was compared using as indices the point-of-reserve-saturation (PRS₅₀) and the point-of-no-return (PNR₅₀). The PRS₅₀ was consistently lower in larvae from SA than in those from MC. In the MC population, this index was lower at the beginning than at the end of the season, while no significant seasonal difference was observed in larvae from SA. The PNR₅₀ varied between temperatures of embryonic development and populations, showing also significant interactions between all three factors. The PRS₅₀ was on average lower, and the PNR₅₀ was higher, than values previously reported for N. granulata, suggesting a stronger nutritional flexibility in the larvae used in the present study. Our results indicate significant intraspecific variability among separate populations, seasonal variation, and carry-over effects of environmental conditions prevailing during the embryonic phase, all of which may affect the performance of the larval phase.     

Selection for an optimal monovoltine life cycle in an unpredictable environment. Studies on the beetleCatops nigricans Spence (Col., Catopidae)

Summary Catops nigricans reproduces in the autumn. Pre-imaginal development is temperature-dependent and takes place during the winter, followed by aestivation in the early adult stage. This summer diapause is obligatory and temperature independent. It synchronizes the monovoltine life cycle with the annual cycle. In three populations collected near Kiel (54°22′ N, 10°6′ E), K?ln (50°54′ N, 7°6′ E), and Paris (49°25′ N, 2°20′ E), pre-imaginal development slowed and the duration of summer diapause decreased with increasing latitude. Synchronization of the critical breeding interval with the appropriate environmental conditions was achieved through temperature- and photoperiod-dependent sensitivity of ovipositing adults, through different thermal thresholds in eggs, larvae, and pupae, and through sensitivity to photoperiod in third-instars larvae.C. nigricans copes with the unpredictability of climatic conditions in different ways. The local populations have evolved a mean diapause length which probably adjusts the life cycle in most years to the optimal date for reproduction. The mean diapause length was 77 days for Kiel, 98 days for K?ln and 138 days for Paris at 10°C, short-day (=SD).C. nigricans also spreads the risk by varying diapause length. Amongthe progeny of single females the range of diapause duration covered about 70% of the total range of the whole population. The oviposition rate of females confined to subterranean life was the same as females confined to subterranean life was the same as in those living under the influence of a varying photoperiod.C. nigricans should therefore be able to live both in the litter layer of forests and also in the nests and galleries of small mammals.     

Induction of ovarian maturation and development of eggs,Larvae and Juveniles of the Puffer,Takifugu exascurus,Reared in the Laboratory

Ovarian maturation of the pufferTakifugu exascurus (Jordan et Snyder) was induced, and embryonic, larval and juvenile development was observed. The brood fish were collected in Tassha Bay, Sado Island (38°05′N, 138°15′E), during the spawning season in 1986 which seemed to extend from late June to mid-July. To each female 3 mg acetone-dried pituitary ofHypophthalmichthys molitrix was injected to induce ovarian maturation, which took place in about 77 hours at a water temperature of 19.5–21.0°C. The eggs obtained by hormone injection were artificially fertilized with the milt from a collected male. The hatched larvae were fed successively on rotifersBrachionus plicatilis, Artemia nauplii and minced fish meat, and reared for a period of about one year. The eggs were spherical, 1.24±0.04mm in diameter, demersal and adhesive. The egg-membrane Was transparent and yolk was orange in color, containing a cluster of small oil-globules. The incubation period was about 160 hours at a water temperature of 18.5–21.0°C. The newly-hatched larvae, measuring 2.9– 3.1 mm TL, had 8+15 = 23 myomeres. Absorption of the yolk was completed 3 days after hatching, by which time the larvae had attained 3.5–3.6 mm TL. Larval finfolds disappeared and rudimentary dorsal, anal and caudal fins formed at 4.1–4.4 mm TL, in 6 days after hatching. In 9-day old larva (5.4 mm TL), fin ray rudiments appeared on the dosai, anal and caudal fins and spine-like scale formed on the belly. In 16-day old specimens, 9.1–10.2 mm TL, the full complements of fin rays were completed on all the fins and the fish reached the juvenile stage. The growth of larvae and juveniles reared in 1986–1987 is expressed by the following equations, where y is total length (mm) and x is days after hatching. y₁ = 2.9420· 1.0639^x 0 ≦ x ≦ 19 (r = 0.998) y₂ = 4.0286· 1.0464^x 19≦ x ≦ 33 (r = 0.998) y₃ = 9.8854· 1.0180^x 33 ≦ x ≦ 72 (r = 0.996) y₄ = 20.1555· 1.0080^x 72 ≦ x ≦ 115 (r = 0.998) y₅ = 28.0610· 1.0049^x 115 ≦ x ≦ 202 (r = 0.995)     

Effects of extreme changes of sea water temperature and salinity on the development of the sand dollar <Emphasis Type="Italic">Scaphechinus mirabilis</Emphasis>

The combined effects of temperatures of 14, 17, 20, 22, and 25°C and salinities of 36–12‰ on embryos and larvae of the sand dollar Scaphechinus mirabilis was studied. Embryonic development is the most sensitive stage in the early ontogenesis of S. mirabilis. It is completed at a temperature of 14–20°C in a salinity range of 36–24‰ and at temperature of 22°C to 26‰. The fertilization proceeds in wider ranges of temperature and salinity. Among the swimming larvae, blastulae showed the greatest resistance to variations of these environmental factors. All the larvae survived at a temperature of 14–22°C and a salinity of 36–20‰, and more than 70% of them at 18‰. The pluteus I is the most vulnerable stage; probably this is related to the formation of the larval skeleton and transition to phytoplankton feeding. The survival of larvae at the age of 20 days was 100% at 14–22° C and a salinity of 36–24‰, most of them survived at 14–20°C and a salinity 18‰. The temperature 25 ° C is the most damaging for early development of S. mirabilis. The duration of development of that species lasts 28.5–29 days at 20°C and a salinity of 32.2–32.6‰. At 20 and 22°C, the larvae settled and completed metamorphosis more quickly if sand from the parental habitat was present. The larvae did not settle during the experiment (14 days) at 14 ° C and in the absence of sand.     

长江口水域夏季鱼卵和仔稚鱼年间变化

基于2005年、2008年、2009年和2011年8月(夏季)在长江口水域(30°30'—31°45'N,121°15'—123°10'E)4个航次的浮游生物拖网资料,分析了长江口水域鱼卵和仔稚鱼的种类组成、数量分布特征及其年间变化。结果表明:4个航次采集的鱼卵和仔稚鱼鉴定到种的种类有17种,隶属于8目13科,以鲈形目种类最多,11种,其次是鲱形目,5种,其他各目种类均小于5种;种类数存在明显年间差异,2005年种类数最多(鱼卵3种,仔稚鱼8种),其次是2009年和2011年,2008年种类数最少(鱼卵1种,仔稚鱼5种)。优势种年间更替明显,长蛇鲻(Saurida elongata)、虾虎鱼(Gobiidae spp.)和中华小公鱼(Stolephorus chinensis)在2005年是优势种,2008年优势种为鳀鱼(Engraulis japonicus),2009年优势种为鳀鱼、寡鳞飘鱼(Pseudolaubuca engraulis)、虾虎鱼等,2011年虾虎鱼和小公鱼(包括小公鱼属未定种Stolephorus spp.和中华小公鱼Stolephorus chinensis)成为优势种。2005年鱼卵和仔稚鱼数量分布的密集区在嵊泗列岛附近水域,2008年鱼卵和仔稚鱼出现较少,未出现明显的数量密集区;2009年鱼卵数量较少,仔稚鱼数量较多,密集区主要分布在在长江口以外123°E附近水域;2011年鱼卵主要分布在在长江北支口门外附近水域,仔稚鱼在调查区内分布相对均匀。     

Effect of long-term cold storage on the fitness of pre-wintering <Emphasis Type="Italic">Harmonia axyridis</Emphasis> (Pallas)

The multicolored Asian ladybird beetle, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), is considered an important generalist predator that can be used as a biological control agent against Hemiptera Sternorrhyncha, Thysanoptera, and the eggs and larvae of Lepidoptera, Coleoptera and Diptera. There are currently abundant natural resources of overwintering H. axyridis in Asia and North America. Given its potential as a biological control agent, methods can be developed to increase its effectiveness for pest control. The availability of an adequate cold storage method would enable the use of field-collected pre-wintering ladybirds for pest suppression in the following season. We studied the effect of cold storage (30, 60, 90, 120 and 150 days stored at −3, 0, 3 and 6°C) on survival, fecundity and predation in field-collected populations. The survival of both female and male ladybirds decreased significantly as storage duration increased at −3°C and 0°C. The ladybirds showed more than 80% survival when they were stored for 150 days at 3°C and 6°C. Long-term cold storage had different effects on the fecundity of H. axyridis at different temperatures. Prolonged cold storage at both 3°C and 6°C shortened pre-oviposition duration and had no adverse effect on reproductive capacity as compared to that of unstored individuals. The adults that experienced 90-day storage at 0°C had the shortest pre-oviposition duration and the largest reproductive capacity. The individuals that were stored for 150 days at 3°C consumed significantly more aphids than the unstored ones. Generally, 3–6°C is a suitable temperature for cold storage of the ladybird without any reduction in fitness. This study will help the exploitation and application of pre-wintering H. axyridis for the biological control of insect pests.     

Larval fish distribution,growth and feeding in Patagonian fjords: potential effects of freshwater discharge

In fjord systems, freshwater inputs occur by ice melting and river discharge, affecting seawater salinity along fjord and adjacent waters, and potentially the ecology of early life stages of marine fish occurring in the area. During austral spring 2008, a bio-oceanographic cruise was carried out in southern Chile between 47°00′ and 50°09′S, an area influenced by Baker River discharge and ice melting of Northern and Southern Ice Fields, the largest glaciers from Patagonia. Surface salinity and temperature ranged from 1.22 to 32.80, and from 8.11 to 10.68°C, respectively. Larval lightfish Maurolicus parvipinnis (Sternoptychidae) and Falkland sprat Sprattus fuegensis (Clupeidae) were the dominant species, with abundances of 2.2–39.9 larvae 10 m⁻² and 3.4–77.1 larvae 10 m⁻², respectively. Postflexion stages of both species were collected mainly in surface density fronts. Otolith-based growth analyses estimated linear growth rates of 0.136 mm day⁻¹ for M. parvipinnis of 4.1–15.1 mm, and 0.448 mm day⁻¹ for S. fuegensis of 5.4–20.5 mm. Recent Otolith Growth Index (ROGI), based on the residual analysis of the relationship between increment width of outermost five microincrements and otolith radius, indicates that larval M. parvipinnis collected in low salinity waters showed a reduction of its recent growth rate compared those collected in saltier waters. Also, ROGI was positively correlated with salinity of the water column for larval M. parvipinnis. Gut content analysis showed that large larvae collected near sources of freshwater had lower number of prey in its guts and preyed on different items than fish larvae collected in saltier waters. Therefore, freshwater inputs from rivers and glaciers from Patagonia affected horizontal distribution, recent growth and feeding of larval fish in fjords and channels of southern Chile.     

Adaptation to reduced salinity in larvae of the mussel <Emphasis Type="Italic">Crenomytilus grayanus</Emphasis> from spring and summer spawnings

In this study, we investigated the capabilities for adaptation to reduced salinity in the larvae from spring and summer spawnings of the same population of the Pacific mussel Crenomytilus grayanus. Spring larvae normally develop and grow when salinity is reduced to 24‰. The lower salinity limit for summer larvae is 20‰. The differences in adaptive capabilities between the spring and summer larvae may be due to the different temperatures of spawning and cultivation of the larvae: 11 °C in the spring and 22 °C in the summer.     

Seasonal variations in biomass, abundance and composition of zooplankton in the subarctic waters north of Iceland

The seasonal variations in biomass, abundance and species composition of zooplankton in relation to hydrography and chlorophyll a were studied in the subarctic waters north of Iceland. The sampling was carried out at approximately monthly intervals from February 1993 to February 1994 at eight stations arranged along a transect extending from 66°16′N–18°50′W to 68°00′N–18°50′W. The mean temperature at 50 m depth showed a clear seasonal pattern, with lowest water temperatures in February (∼1.1°C) and the highest in July (∼5.4°C). The spring growth of the phytoplankton began in late March and culminated during mid-April (∼7.0 mg Chl a m⁻³). Both the biomass and the abundance of total zooplankton were low during the winter and peaked once during the summer in late May (∼4 g m⁻² and ∼38,000 individuals m⁻²). A total of 42 species and taxonomic groups were identified in the samples. Eight taxa contributed ∼90% of the total zooplankton number. Of these Calanus finmarchicus was by far the most abundant species (∼60% of the total zooplankton). Less important groups were ophiuroid larvae (∼9%), Pseudocalanus spp. (∼8%), Metridia longa (∼4%), C. hyperboreus (∼3%), Acartia longiremis (∼2%), chaetognaths (∼2%) and euphausiid larvae (∼2%). The dominant copepods showed two main patterns in seasonal abundance: C. finmarchicus, C. hyperboreus and C. glacialis had one annual peak in numbers in late May, while Pseudocalanus spp., M. longa and A. longiremis showed two maxima during the summer (July) and autumn (October/November). Ophiuroid larvae and chaetognaths (mainly Sagitta elegans) peaked during the middle of July, while the number of euphausiid eggs and larvae was greatest from May to July. The succession in population structure of C. finmarchicus indicated its main spawning to be in April and May, coincident with the phytoplankton spring bloom. A minor spawning was also observed sometime between August and October. However, the offspring from this second spawning contributed only insignificantly to the overwintering stock of C. finmarchicus. Received: 12 September 1997 / Accepted: 1 March 1998     

Niche separation between <Emphasis Type="Italic">Encarsia dispersa</Emphasis> and <Emphasis Type="Italic">Encarsia guadeloupae</Emphasis>, two biological control agents of the spiraling whitefly <Emphasis Type="Italic">Aleurodicus dispersus</Emphasis>, in Benin,West Africa

The spiraling whitefly Aleurodicus dispersus (Russell) is an insect pest that causes substantial damage to ornamental plants, shade trees and food crops. It was first observed in Benin in 1993. Two host specific parasitoids, Encarsia dispersa and E. guadeloupae, fortuitously introduced with its host, were recovered in the second half of 1993 in Southern Benin. Survey results from 1993 to 1995 (already published) showed the decline in the population of A. dispersus due to the parasitoids, and the spread from Cotonou (6°10′N) in a northern directions of both parasitoids and their host. Results from similar field surveys from 1996 to 2003 document that the spiraling whitefly and both its parasitoids spread to Natitingou (10°20′N, 540 km) in 1995 and Bembereke (10°14′N) in 1996, whereby E. dispersa arrived within less than a year of its host and quickly became dominant in the two localities on the northern front. In subsequent years, the parasitoids established their geographical niches, with E. dispersa being more abundant (up to 89%) in the coastal south bellow latitude 7°30′N and E. guadeloupae (up to 84%) in the north between latitudes 7°30′ and 10°30′N. We conclude that the gradual replacement observed over ten years and over 500 km has to do with longitudinal shifts in the length and severity of the dry season and the higher susceptibility to these conditions by E. dispersa.     

Methods of short-term storage of cultures of the blowfly <Emphasis Type="Italic">Calliphora Vicina</Emphasis> R.-D. (Diptera,Calliphoridae)

Three methods of short-term storage of the blowfly Calliphora vicina strains are considered based on the experimental study of 21 strains originating from different parts of the species range. The colony can be preserved as diapausing adults at 6° and darkness for 2–3 months or more, depending on the geographical origin of the population. During the first five days of adult life the flies should be kept at 12° and short day on a sugar diet, after which they should be transferred into a refrigerator. During artificial hibernation the flies also require periodic sugar feeding every 20 days (3–4 h at 20°C) to maintain their vital functions. The combination of temperatures of 20–23°C and a protein diet terminates reproductive diapause, and oviposition starts in 10–17 days. The fly strain may be preserved as reproductive females at 6°C and darkness with sugar feeding. Flies also require periodic sugar feeding at 20°C (3–4 hours). In this case the flies start laying eggs 2–3 days after being transferred to 20–23°C. The preservation of diapausing larvae is a more reliable method of prolonged strain storage. In this case the flies of maternal generation are maintained at 20–23°C on sugar and protein diet. The egg rafts laid during 5–6 hours are then transferred into 12°C and short day until hatchment. The hatched larvae should be immediately placed into a refrigerator (2–3 or 5–6°C), where they feed during 1–1.5 months and enter diapause. For strain restoration, the diapausing larvae should be transferred into 20–25°C, where they pupariate in 3–5 days and the flies emerge in nearly 10 days.     

Influence of age,nutritional status and season on the reproductive system in wild male mink (<Emphasis Type="Italic">Neovison vison</Emphasis>)

The objectives of this study on the reproductive system of wild male mink (Neovison vison) were to determine the influence of age, nutritional status and season on reproductive traits and to produce baseline data that may be used in environmental monitoring programmes. The 117 male mink included in the study were killed by hunters all over Sweden (from latitude 56° N to 67° N) during August to the end of April from 2005 to 2008. The weights of penis, testes, and epididymides were lower, the anogenital distance was shorter and the diameter of seminiferous tubules was less in juveniles compared with adult mink (p < 0.0001–p = 0.0024). There was a positive effect (p < 0.05) of nutritional status on the baculum length and on the anogenital distance, but not on any of the other reproductive traits. The season of sampling influenced the penis, testes and epididymes weights and the diameter of seminiferous tubules (p = 0.008–p < 0.0001). During spring, 86% of the mink had sperm in their epididymides, whereas the corresponding figure for autumn was 3%; in addition, when the average diameter of the tubules reached 138 μm, sperm were present in the epididymides. Sperm morphology was analysed in 29 of the mink, and the percentage of morphologically defect sperm were generally low. Taken together, this study suggests that when assessing male reproductive data in wild mink populations, season must be taken into account as well as whether the individuals are juvenile or adult. In contrast, the nutritional status seems not to be of any major significance.     

The limits of <Emphasis Type="Italic">Dreissena polymorpha</Emphasis> (Pallas) range in the Kama River basin

The distribution of Dreissena polymorpha in the northeastern part of the Kama River basin is limited to the area with the following geographic coordinates: 59°37′–54°00′ N and 57°10′–49°03′ E. The range of the zebra mussel is continuous along the Kama, Belaya, and Ufa rivers. Isolated populations of this mollusk exist in the Belaya and Vyatka river floodplains. The distribution of dreissena in the running waters of the Kama River basin is limited by the potamal conditions.     

Eggs and larvae of <Emphasis Type="Italic">Awaous melanocephalus</Emphasis> (Teleostei: Gobiidae)

The morphology of eggs and larvae of Awaous melanocephalus is described. The eggs measured 0.33–0.35 mm in long-axis diameter and 0.32–0.34 mm in short-axis diameter. Newly hatched larvae (0.90–0.99 mm in notochord length, NL; 0.93–1.04 mm in total length, TL) were poorly developed, lacking a mouth and having a large yolk sac and unpigmented eyes. The mouth opened and the eyes became fully pigmented 3 days after hatching (1.78–2.00 mm NL, 1.88–2.10 mm TL). The yolk sac was completely absorbed 5 days after hatching at a water temperature of 27°–28°C.     

Dynamics of chemical composition of the Black Sea gray mullet <Emphasis Type="Italic">Mugil cephalus</Emphasis> in the period of early ontogenesis and its dependence on temperature and salinity

Results of experiments on the study of the effect of temperature and salinity on dynamics of the chemical composition of gray mullet Mugil cephalus in the embryonic-larval period of development are presented. During the period of endogenous feeding (from the beginning of egg cleavage to transition of larvae to active feeding), lipids are spent with a greater rate than protein. After transition of larvae to exogenous feeding, an increase in the absolute concentration of proteins compared to lipids begins earlier and proceeds more intensively. The stage of irreversible starvation in larvae of gray mullet starts at a loss of 39–44% of protein and of the same amount of lipids of their initial content at the moment of hatching. Minimal protein losses over the period of embryonic development of gray mullet, as well as of protein and lipids towards the moment of termination of resorption of yolk sac, are observed in the range of temperatures of 21–25°C. Under conditions of low salinity (13–15‰) in the process of resorption of the yolk sac, lipids are spent more economically than at a higher salinity (17–19‰) at the expense of an increase in protein losses. Thus, a decrease in specific weight promoting the retention of buoyancy of larvae in water of low density is achieved.     

Colonisation of sub-Antarctic Marion Island by a non-indigenous aphid parasitoid <Emphasis Type="Italic">Aphidius matricariae</Emphasis> (Hymenoptera,Braconidae)

Over the past two decades seven non-indigenous vascular plant or arthropod species have established reproducing populations at sub-Antarctic Marion Island (46°54′S, 37°55′E). Here we record the eighth establishment, a braconid wasp Aphidius matricariae Haliday, which uses the aphid Rhopalosiphum padi (Linnaeus) as its only host on the island. Molecular markers (18S rDNA and mtCOI) support the conventional taxonomic identification and indicate that all individuals are characterized by a single haplotype. Surveys around the island show that adult abundance and the frequency of aphid parasitism are highest at Macaroni Bay on the east coast, and decline away from this region to low or zero values elsewhere on the coast. The South African research and supply vessel, the SA Agulhas, regularly anchors at Macaroni Bay, and Aphidius sp. have been collected from its galley hold. Current abundance structure, low haplotype diversity, and the operating procedures of the SA Agulhas all suggest that the parasitoid was introduced to the island by humans. Regular surveys indicate that this introduction took place between April 2001 and April 2003, the latter being the first month when this species was detected. The wasp’s establishment has significantly added to trophic complexity on the island. Low haplotype diversity suggests that propagule pressure is of little consequence for insect introductions. Rather, single or just a few individuals are probably sufficient for successful establishment.     

黄海中部近岸春夏季鱼卵、仔稚鱼群落结构特征

2013年4月下旬至7月上旬,采用浅水I型网垂直拖网的调查方式对黄海中部20m以浅海域(34°30'—35°30'N,119°20'—120°20'E)的鱼卵、仔稚鱼种类组成与数量分布进行了6个航次的综合调查。春夏季共采集鱼卵21种(未定种3种),共计2247粒,隶属于9科15属。仔稚鱼22种(未定种1种),共计286尾,隶属于13科17属。鱼卵优势种为日本鳀Engraulis japonicus、赤鼻棱鳀Thryssa kammalensis、江口小公鱼Stolephorus commersonnii、皮氏叫姑鱼Johnius belengerii和属Callionymus spp.。仔稚鱼优势种为大银鱼Protosalanx chinensis、白姑鱼Argyrosomus argentatus、日本鳀、赤鼻棱鳀和皮氏叫姑鱼。鱼卵丰度和分布与经度呈负相关、与SST呈正相关,但与其他环境因子如纬度、表层盐度(SSS)和水深等无显著相关性。仔稚鱼丰度和分布与上述环境因子均未表现出显著相关性。基于Bray-Curtis指数的聚类分析表明,鱼卵优势种包括集中分布于研究水域34°48'N以南海域(江口小公鱼、皮氏叫姑鱼和青鳞小沙丁Sardinella zunasi)、10m等深线以内(赤鼻棱鳀),以及北部水域(日本鳀和属)3种主要聚集类型;仔稚鱼优势种包括集中分布于34°48'N—35°12'N海域(赤鼻棱鳀和日本鳀)、连云港外海浅水区(白姑鱼、皮氏叫姑鱼和梭鱼Liza haematocheilus,以及南部水域(褐菖鲉Sebastiscus marmoratus和鲬Platycephalus indicus)3种主要聚集类型。研究结果揭示了黄海中部近岸海域鱼卵、仔稚鱼群落的时空分布格局动态,为科学认识环境变动下该海区渔业种群数量动态和资源变化提供了科学依据。     

Colony structure and reproductive sharing among queens in a tropical paper wasp, <Emphasis Type="Italic">Polistes olivaceus</Emphasis>

Reproductive partitioning among group members is a key feature in social Hymenoptera. We investigated the genetic colony structure of a tropical paper wasp Polistes olivaceus, with an emphasis on variation in the number of queens and reproductive sharing among queens. Among 22 P. olivaceus colonies, 6 were monogynous, 9 polygynous, and 7 were queenless. Adults and brood (eggs and larvae) were genotyped based on six polymorphic microsatellite loci. In each of the polygynous colonies, progenies were assigned to their mothers using maximum-likelihood methods. Nestmate queens were full sisters. The vast majority of reproduction appeared to be monopolized by the dominant queen (α), and the overall reproductive skews were 0.63 ± 0.04 (B index) and 0.97 ± 0.02 (S _c index). Although all nestmate queens had equal reproductive potential, the high magnitude of reproductive skew was enigmatic in this species. Although 9.55 ± 2.07 workers contained developed ovaries in 11 of 15 queen-right colonies, they were unrelated to the nestmate queens but related to each other as full sisters, suggesting that they were the remaining offspring of superseded queens. In 2 of the 11 colonies, we detected male eggs produced by reproductive workers. On average, 7.27 % of the total genotyped male eggs were derived from reproductive workers among the colonies. These results suggest three possibilities regarding the presence of reproductive workers in the P. olivaceus colonies: drifting between colonies, putative remaining offspring from superseded queens, and the offspring of unrelated females who joined the colonies and reproduced there. We found no worker-derived larvae or adult males, suggesting that male eggs were removed by nestmates at some point between oviposition and hatching.     

Adaptive latitudinal variation of the duration and thermal requirements for development in the ground beetle Amara communis (Panz.) (Coleoptera, Carabidae)

The data are obtained on development time at six constant temperatures (12, 14, 16, 18, 20, 22°C) and thermal requirements for preimaginal development in a ground beetle Amara communis from Arkhangelsk (64°34′N) and St. Petersburg (59°53′N). The larval and pupal development times were found to be significantly shorter in the Arkhangelsk than in the St. Petersburg population under all temperatures. As a result, total preimaginal development appeared to be shorter by 6.2–6.6% in the Arkhangelsk population. The regression lines of the larval, pupal and total (egg-to-adult) development rate on temperature for the Arkhangelsk population run above and steeper than the respective lines for the St. Petersburg population. Both populations share the similar values of the thermal thresholds (7.2–8.2°C). This explains faster preimaginal development in the northern population under all temperatures above the threshold. Thus, the slope of the regression lines increases, i.e., the sum of degree-days decreases, whereas the thermal threshold for development exhibited no distinctive changes from south to north in this species. Adults from Arkhangelsk reared in the experiments appeared heavier on the average in comparison with those from St. Petersburg, especially at 18–22°C. Temperature did not significantly affect adult weight, except the fact that the beetles were slightly heavier at 20 and 22°C. Consequently, the well-known “temperature-size rule” is violated in this species. Relative growth rate in larvae of A. communis increased considerably with temperature rise from 14 to 22°C. It was significantly higher in the beetles from Arkhangelsk at 18–22°C. There were no differences in larval growth rate between the two populations at 14 and 16°C.     

Predation on eggs by conspecific males in two Japanese damselfishes,Pomacentrus nagasakiensis andChromis notatus notatus,after removal of egg-guarding males

Egg predation by conspecific males of damselfishes,Pomacentrus nagasakiensis andChromis notatus notatus, was studied at Bohnotsu (31°15′ N, 131°15′ E) and Tsuyazaki (33°47′ N, 130°29′ E), respectively. InP. nagasakiensis, 7 egg-guarding males were removed from nests, and intrusion and egg predation by conspecific males took place in all of the nests within an average time of 12.2 min. Frequency of attacks on eggs by other reef fishes during the period between the removal of egg-guarding males and intrusion of conspecific males was lower than expected, considering the frequency of aggressive displays of the egg-guarding males. The results of male removal experiments forChromis notatus notatus were almost the same, with intrusion and egg predation by conspecific males occurring in all 12 of the nests from which egg-guarding males had been removed. SixP. nagasakiensis and 15C. notatus notatus which intruded into the nests and preyed on eggs were collected. All were males except for 1C. notatus notatus female. Results suggest that these males which intruded into vacant nests to eat eggs did not have clutches of their own during the spawning bouts when the experiments were done. Results also showed that the intruding males were not inferior to egg-guarding males in standard length, gonadosomatic index, and condition factor. It is clear that males which do not have their own clutches during at least 1 spawning bout and prey on others' eggs when egg-guarding males disappear are common in these 2 gregariously nesting damselfishes. It is discussed that conspecific eggs are potentially a good food source not only for other species of reef fishes but also for conspecific males which do not have their own eggs during the spawning bouts. The origin of males wich prey on eggs of other conspecifics is also considered. Some aspects of egg-guarding and aggressive behavior of males in damselfishes are discussed.