Mating frequency and interspecific matings in some freshwater cyclopoid copepods

Laboratory investigations with Cyclops vicinus and Metacyclops minutus documented that mating frequency decreased significantly after the initial mating, i.e. re-mating is relatively rare in cyclopoid copepods. Re-mating is unnecessary because females are able to fertilize multiple clutches of viable eggs from one insemination. Similar sized Cyclops vicinus and Cyclops furcifer interbreed frequently. Interbreeding does not occur when size differences and taxonomic differences are as great as between C. vicinus and M. leuckarti. In C. vicinus and M. leuckarti, the duration of the last mating phase (spermatophore transfer until release of the female) and consequently the duration of the entire mating process, is different. I conclude that the low re-mating frequency in cyclopoid copepods probably evolved to accelerate clutch production in unpredictable environments and to reduce predation risk. The occurrence of interspecific mating discourages the co-existence of similarly sized, related species. Mating behaviour may have a considerable influence on zooplankton community structure.     

The effect of temperature on the development times of eggs,naupliar and copepodite stages of five species of cyclopoid copepods

The duration times of eggs, combined naupliar instars and of the different copepodite stages of five species of cyclopoid copepods — Acanthocyclops robustus, Cyclops vicinus, Diacyclops bicuspidatus, Mesocyclops leuckarti, and Thermocyclops crassus — were investigated at five different temperatures. The five species can be divided in two groups: two species, C. vicinus and D. bicuspidatus, adapted to cold water conditions and three species, A. robustus, M. leuckarti and T. crassus adapted to warm water conditions. The cold water species showed a faster egg development than M. leuckarti and T. crassus at 5–15 °C. The eggs and instars of the warm water species M. leuckarti tend to develop faster than those of the former two species at higher temperatures. A. robustus showed the shortest egg and instar development at 10–25 °C. The warm water species T. crassus produced no eggs at 10 °C and temperatures below. At higher temperatures (20, 25 °C) the egg and instar duration times were similar or longer than those of the other species. When cultured in total darkness a great part of the C_IV respectively C_V copepodites of the summer forms entered arrest and the percentage of copepodites that showed an arrest of development was highest at lowest temperatures. The present results are compared with data from literature and differences are discussed.     

二化螟滞育幼虫与非滞育幼虫的抗药性比较研究

在室内测定了二化螟滞育幼虫与非滞育幼虫对杀虫单和三唑磷的抗药性。测试结果表明,二化螟滞育幼虫比非滞育幼虫具有更高的抗药性。杀虫单对二化螟滞育幼虫与非滞育幼虫的LD50分别为24．3452μg／头与10．4721μg／头;三唑磷的LD50分别为0．0685μg／头和0．0497μg/头.     

Trophic interactions involving mysid shrimps (Mysidacea) in the near-bottom habitat in the Baltic Sea

In a six month mesocosm tank experiment, hypotheses were tested concerning the role of benthopelagic mysid shrimps (Mysidacea) in the near-bottom food web of the Bothnian Sea, in the northern Baltic Sea. The first hypothesis tested was that the mysids interact, through predation, with benthic deposit-feeding Monoporeia affinis amphipods. A second hypothesis tested was that the sediment type is important for the overwintering success of the mysids. Changes in abundance and mass were recorded for M. affinis and mysids when separate and when coexisting, in two sediment types differing in organic content (food level); soft muddy clay (rich) and fine sand (poor). Despite the fact that newborn M. affinis offspring, a plausible target for predation by mysids, were present in substantial numbers in the tanks, no consistent evidence for any interaction between these taxa was found. The biomass of mysids was slightly higher in the muddy clay than in the sand tanks, and the mechanism behind this substrate effect is discussed. A third hypothesis, that the mysids interact with near-bottom zooplankton, was investigated. The tanks were continually supplied with in situ near-bottom sea-water containing a semi-natural assemblage of near-bottom plankton. As a result of mysid predation, tanks with mysids had lower abundance and biomass of cyclopoid copepods than tanks without mysids. Thus, the major interaction found was predation on near-bottom zooplankton by mysids and it is suggested that this interaction could potentially be an important food link, especially during periods with low food availability in the pelagic system.     

Diapausing Colorado potato beetles are devoid of short neuropeptide F I and II

An extract of head ganglia and retrocerebral complexes of nondiapausing and diapausing Leptinotarsa decemlineata was prepared to characterize regulatory neuropeptides involved in adult diapause by using a differential peptidomics approach. To reduce sample complexity, both extracts were roughly separated by means of an identical chromatographic step. MALDI-TOF MS led to the identification of proctolin, an adipokinetic hormone, and short neuropeptide F I and II in the extract of nondiapausing beetles. In combination with nano-ESI-Q-TOF MS(2) evidence was found for the presence of three pyrokinins, the first to be identified in a coleopteran species. Pyrokinins, involved in the induction of embryonic diapause in Bombyx mori, were present in both physiological conditions suggesting that they are of minor importance in the regulation of adult diapause in the Colorado potato beetle. A striking difference, detected by the differential peptidomics approach, between both neuropeptide profiles was the absence of ions corresponding to the short neuropeptide F (sNPF) related peptides, also known as Led-NPF-I and -II, in the extract of diapausing animals. Therefore, we postulate that "short NPFs" are involved in the regulation of adult diapause, displayed by the Colorado potato beetle.     

Diapause in copepods (Crustacea) from ephemeral habitats with different hydroperiods in Everglades National Park (Florida,U.S.A.)

Water management practices in the Everglades have severely stressed the natural system, particularly by reducing the hydroperiods of much of the region. During the dry season of 1999, we investigated the influence of hydroperiod on the species composition and dormancy patterns of freshwater copepod communities in seasonal wetlands of Everglades National Park, Florida, U.S.A. The habitats were characterized by an annual dry season, from December through June. We sampled at two locations: the Long Pine Key area of the Rocky Glades region (short hydroperiod, ca. 4–5 months), and western Taylor Slough (intermediate hydroperiod, ca. 8–10 months). Both areas have experienced a reduction in natural hydroperiods and an increase in the frequency of dry-down. We collected weekly plankton samples from Rocky Glades solution holes to assess the potential species pool of copepods. To document the taxa capable of surviving dry-down by resting, we performed three immersion trials in which we rehydrated, in laboratory aquaria, sediment patches from solution holes and surface soils from all stations. Only a subset of the planktonic species collected emerged from the dried sediments. The cyclopoids Microcyclops rubellus and Paracyclops poppei were dominant. This is the first record of diapause for P. poppei. Species distributions from the different hydroperiod soil patches indicated that more diapausing species occurred at the sites that dried for shorter periods. Emerging individuals of M. rubellus and P. poppei were mainly ovigerous females, demonstrating a resting strategy seldom before recorded. The cyclopoid Diacyclops nearcticushad not been previously reported to diapause, but they emerged from the dried sediments in our trials. Our collections included six new records for Florida: Diacyclops nearcticus, Megacyclops latipes, Orthocyclops modestus, Elaphoidella marjoryae, Bryocamptus sp. and Bryocamptuscf. newyorkensis. Paracyclops poppei, Macrocyclops fuscus and Arctodiaptomus floridanus are new records for Everglades National Park. Clearly, diapause is an important strategy for the persistence of copepods in short-hydroperiod wetlands. The duration of the dry period appears to be inversely related to the number of species that emerge from diapause.     

Under-sized larvae from short-day adults of the blow fly, Calliphora vicina, side-step the diapause programme

Abstract. Larvae of Calliphora vicina R.-D. (Diptera: Calliphoridae) hatching from eggs laid by adult females exposed to short day length, and then raised in darkness at 11^oC, normally enter diapause rather than undergoing prompt pupariation. However, if the feeding stage is curtailed by premature extraction of larvae from their food, or if the larvae are subjected to severe overcrowding, smaller larvae side-step the diapause programme to become miniature puparia, whereas larger larvae proceed to diapause as fully-fed ones. In addition, smaller diapausing larvae show a shorter (or less intense) diapause than full-sized larvae. Apart from the smallest individuals, flies can emerge from these miniature puparia and in some cases are capable of laying eggs; this suggests that avoidance of diapause may allow undersized individuals an opportunity to reproduce before winter sets in. Fat determinations performed on larvae and pupae of various sizes, however, showed that short-day (diapause-destined) individuals lay down the same proportion of fat as long-day (non-diapause) individuals, and the same proportion of fat across all size classes. The possible functional significance of this phenomenon is discussed.     

Simulated winter to summer transition in diapausing adults of the lady beetle (Hippodamia convergens): supercooling point is not indicative of cold-hardiness

ABSTRACT. Adults of Hippodamia convergens Guerin-Meneville (Coleoptera: Coccinellidae) form massive overwintering aggregations in the Sierra Nevada Mountains of California. These diapausing pre-reproductive adults may remain in the aggregations for up to 10 months. Beetles were collected from overwintering sites in Nevada County, California, and held at 4C for 6 weeks. In order to simulate the winter to summer transition, the beetles were transferred to 20C and 68% r.h. under a LD 12:12h cycle. Supercooling points increased slightly from - 16C on day 0 to - 12.9CC on day 21. In contrast, low temperature tolerance decreased markedly within 2 weeks. On day 0 nearly all beetles survive 2 h of exposure to - 5C, whereas only 50% survived this treatment on day 4. These data demonstrate the general lack of correlation between the supercooling point and the lower lethal temperature in warm-acclimated beetles. Within 1 day of transfer to 20C, oxygen consumption decreased by 26%. This decrease continued through day 14 when the rate of oxygen consumption had decreased to 40% of initial values. Beetles acclimated to 20C selected temperatures significantly higher than cold-acclimated beetles. The parametric shifts observed in this study are consistent with a physiological transition from cold-hardiness and energy conservation during winter to one of dispersal, feeding and reproduction in summer beetles.     

Biological activities of juvenile hormone III skipped bisepoxide in last instar nymphs and adults of a stink bug, Plautia stali

Juvenile hormone III skipped bisepoxide (JHSB₃), methyl (2R,3S,10R)-2,3;10,11-bisepoxyfarnesoate was recently determined as a novel juvenile hormone (JH) in a stink bug, Plautia stali. To further confirm the biological function of JHSB₃ in this insect, its juvenilizing, reproduction-stimulating and diapause-terminating activities and the presence in the hemolymph were examined. Topical application of JHSB₃ to last instar nymphs inhibited their metamorphosis in a dose-dependent fashion. In allatectomized and diapausing adults, JHSB₃ application exerted stimulatory effects on the development of ovaries and ectadenia in females and males, respectively. JHSB₃ was detected from the hemolymph of reproductively active females by gas chromatography-mass spectrometry analysis while its titer in the hemolymph collected from diapausing adults was too low to be detected. These results demonstrated that JHSB₃ has biological function as a JH in P. stali. Topical application of JHSB₃, its stereoisomers and 10R-JH III also indicated that compounds with the 2R,3S-configuration were more potent than those with the 2S,3R-configuration and 2,3-double bond.     

A new genus and species of cyclopoid (Crustacea,Copepoda, Cyclopinidae) from a coastal system in the Gulf of Mexico

A new, monotypic genus of the interstitial marine cyclopoid copepod family Cyclopinidae G.O. Sars, 1913 is described from male and female specimens collected at Laguna de Términos, a large coastal lagoon system in the southern Gulf of Mexico. Mexiclopina campechana gen. et sp. n. cannot be adequately placed in any extant genus within the family. It differs from other cyclopinid genera in having a unique combination of characters including: 1) absence of modified brush-like seta on the mandibular exopod; 2) maxillule exopod with stout setal elements and brush-like setae absent; 3) basis of mandible with one seta; 4) presence of a modified seta on endopod of fourth leg; 5) fifth leg exopod unsegmented, armed with three elements in the female and five in the male; 6) intercoxal sclerite of first swimming leg with two medial spiniform processes on distal margin. The new genus is monotypic and appears to be most closely related to Cyclopina Claus, 1863 and Heptnerina Ivanenko & Defaye, 2004; the new species was compared with species of Cyclopina and it resembles Cyclopina americana Herbst, 1982 and Cyclopina caissara Lotufo, 1994. This is the second record of a species of Cyclopinidae in Mexico and the first in the Gulf of Mexico; the number of cyclopinid species recorded from the Americas is now 13.     

Development of neuropeptide analogs capable of traversing the integument: A case study using diapause hormone analogs in Helicoverpa zea

Diapause hormone and its analogs terminate pupal diapause in Helicoverpa zea when injected, but if such agents are to be used as effective diapause disruptors it will be essential to develop simple techniques for administering active compounds that can exert their effect by penetrating the insect epidermis. In the current study, we used two molecules previously shown to have high diapause-terminating activity as lead molecules to rationally design and synthesize new amphiphilic compounds with modified hydrophobic components. An assay for diapause termination identified 13 active compounds with EC₅₀'s ranging from 0.9 to 46.0 pmol per pupa. Three compounds, Decyl-1963, Dodecyl-1967, and Heptyl-1965, selected from the 13 compounds most active in breaking diapause following injection, also successfully prevented newly-formed pupae from entering diapause when applied topically. These compounds feature straight-chain, aliphatic hydrocarbons from 7 to 12 carbons in length; DH analogs with either a short-chain length of 4 or an aromatic phenethyl group failed to act topically. Compared to a high diapause incidence of 80–90% in controls, diapause incidence in pupae receiving a 10 nmole topical application of Decyl-1963, Dodecyl-1967, or Heptyl-1965 dropped to 30–45%. Decyl-1963 and Dodecyl-1967 also remained effective when topically applied at the 1 nmole level. These results suggest the feasibility of developing DH agonists that can be applied topically and suggest the identity of new lead molecules for development of additional topically-active DH analogs. The ability to penetrate the insect epidermis and/or midgut lining is critical if such agents are to be considered for future use as pest management tools.     

Prey features affecting ingestion rates by Acanthocyclops robustus (Copepoda: Cyclopoida) on zooplankton

Summary (1) Ingestion rates by adult female and juvenile Acanthocyclops robustus on a number of prey types were measured at a prey concentration of 100/l in experimental volumes of 300–400 ml. (2) For the adult predator, Synchaeta pectinata was most vulnerable (22.3, standard error 1.4, prey ingested per predator per day) as compared to Brachiomus calyciflorus, Brachionus diversicornis, Keratella cochlearis (two morphs), Asplanchna priodonta, Polyarthra major, Synchaeta kitina, Pompholyx sulcata, Daphnia spec., and Bosmina longirostris. For these latter prey, the lowest ingestion rate was on one morph of K. cochlearis and the highest on A. priodonta, being, respectively, 1.0, SE 0.5, and 11.3, SE 1.0, prey per predator per day. (3) With regard to the juvenile predator (mostly copepodite stages I, II and III), ingestion rates on K. cochlearis and P. sulcata were low (respectively 1.2, SE 0.7, and 0.3, SE 0.1, prey per predator per day) but quite high on S. kitina (5.7, SE 0.6). (4) In addition, the effect of increasing prey concentration on the ingestion rate (functional response) by the adult female predator was examined for B. calyciflorus, K. cochlearis, S. pectinata, S. kitina and Daphnia spec.. Increases in ingestion rate with prey density were minimal for B. calyciflorus and K. cochlearis, greater for Daphnia spec., still greater for S. pectinata and of greatest magnitude for S. kitina. (5) The reasons for these results are discussed with particular reference to prey features.     

家蚕滞育的分子机理2.蛹期滞育激素基因的表达与滞育决定

滞育激素是由食道下神经节分泌的重要昆虫神经肽,诱导昆虫的滞育。选择具有ＲＮＡ聚合酶能够识别的启动子的质粒载体,将滞育激素ｃＤＮＡ克隆进去,在体外大量合成单一的滞育激素ｃＲＮＡ为参照,测定食道下神经节分泌滞育激素ｍＲＮＡ量来确定滞育激素的分泌量。结果证明食道下神经节分泌的滞育激素的数量决定昆虫的滞育。     

白血病抑制因子mRNA的表达受雌激素的调控

运用RT-PCR方法检测了体外培养的大鼠成骨样细胞Ros 17/2.8在17β雌二醇(E2)刺激前后细胞中一些细胞因子的mRNA水平。发现在E2刺激后,细胞中白血病抑制因子(LIF)的mRNA水平明显上升,且呈现E2浓度依赖的特点。该结果提示,LIF可能参与替代性治疗过程中雌二醇对于骨质硫松症的缓解作用。这为进一步研究细胞因子与骨质疏松症的相关性,阐明细胞因子在骨代谢中的作用打下了基础,并将有利于发展治疗骨代谢疾病的药物。 Abstract　With RT-PCR techniques,we examined the expression pattern of some cytokines in rat osteoblast-like cell line ROS 17/2.8, which was stimulated with 17 β-estradiol. After treatment, the obvious increase of LIF(Leukaemia Inhibitory Factor)mRNA level in the cell was observed. It indicates that LIF may involve in the estrogen replacement treatment of osteoporosis. This work will found the base for clarifying the relationship between expression of cytokines and bone remoldeling, and may even facilitate the developement of drug for bone metabolism abnormality.     

Reduction of respiration rates by forming aggregations in diapausing adults of the shield bug, Parastrachia japonensis

Parastrachia japonensis adults in diapause live mostly in aggregated conditions and can survive more than 1 year on only water. In this study, we demonstrated that diapausing adults had a high tendency to form clusters with no sexual bias. When 3-40 insects were enclosed in chambers of equal volume used to measure respiration, oxygen consumption was reduced to nearly half that when a single individual was enclosed. However, this reduction in metabolic rate was lost when the bugs were prevented from having physical contact with other individuals, partly lost by being enclosed with dead individuals, totally lost with the ones being washed with dietylether, and not influenced by humidity. No such effect of aggregation on respiration was found in adults in the reproductive stage, nor in two other diapausing bugs, Erthesina fullo and Plautia crossata, which hibernate in groups. From these results, we concluded that the reduction in oxygen consumption in P. japonensis was due mostly to physical contact with other individuals and partly to chemical cue that functioned to settle them down and resulted in a greatly reduced respiration rate. This trait is an effective strategy that allows diapausing adults to conserve energy and prolong survival.     

Adjustments of the enzymatic complement for polyol biosynthesis and accumulation in diapausing cold-acclimated adults of Pyrrhocoris apterus

The capacity to accumulate winter polyols (mainly ribitol and sorbitol) during cold-acclimation in Pyrrhocoris apterus is restricted only to the adults that have previously entered diapause. The enzymatic complement involved in polyol biosynthesis was found to differ in a complex manner between diapause and non-diapause adults. Nearly 100% of glycogen phosphorylase (GPase) was present in its active form in non-diapause adults irrespective of their acclimation status. In contrast, less than 40% of GPase was present in its active form in diapause adults prior to cold-acclimation and the inactive form was rapidly activated upon transition from 5 to 0 degrees C, concomitantly with the start of rapid polyol accumulation. The flow of carbon released by activation of glycogen degradation might be routed to the pentose cycle because the activity of glucose-6-P dehydrogenase (G(6)P-DH) was significantly higher and it increased with cold-acclimation in diapause adults while it was relatively low and it decreased with cold-acclimation in non-diapause adults. Reducing equivalents in the form of NADPH, which were generated in the pentose cycle, might require re-oxidation. Such re-oxidation might be achieved during reduction of sugars to polyols. The activity of NADP(H)-dependent aldose reductase (AR) was about 20-fold higher in diapause than in non-diapause adults. Similarly, the activity of NAD(H)-dependent polyol dehydrogenase (PDH) was higher in diapause adults. In addition, we found a very high activity of an unusual enzyme, NADP(H)-dependent ketose reductase (KR), exclusively in diapause adults. KR might be involved in reduction of fructose to sorbitol. Although its affinity for fructose as a substrate was low (K(M)=0.64M), its activity was about 10-fold higher than that of PDH with fructose. Moreover, the activity of KR significantly increased with cold-acclimation while that of PDH remained unchanged. Different electrophoretic mobilities in PAGE gel suggested that KR and PDH are two different enzymes with specific requirement for NADP(H) or NAD(H), respectively, as co-factors.