The cephalopod macrosystem: A historical review, the present state of knowledge, and unsolved problems: 3. Classification of Bactritoidea and Ammonoidea

A new classification is proposed in which Bactritoidea and Ammonoidea are considered as subclasses. The subclass Bactritoidea includes a single order, Bactritida. The subclass Ammonoidea includes ten orders: Anarcestida (suborders Agoniatitina, Auguritina, Anarcestina, Gephurocerina, Timanocerina, and Prolecanitina), Tornocerida, Goniatitida (with suborders Goniatitina and Cyclolobina), Praeglyphiocerida, Clymeniida (with suborders Gonioclymeniina and Clymeniina), Medlicottiida, Ceratitida (with suborders Paraceltitina, Otocerina, Meekocerina, Sagecerina, Ptychitina, Ceratitina, Pinacocerina, Megaphyllitina, Arcestina, and Lobitina), Phyllocerida, Lytocerida (with suborders Lytocerina and Turrilitina), and Ammonitida (with suborders Psilocerina, Haplocerina, Stephanocerina, Cardiocerina, and Ancylocerina).     

幼虫密度对二点委夜蛾生长发育及繁殖的影响

【目的】在不同幼虫密度饲养条件下,研究二点委夜蛾Athetis lepigone生长发育及繁殖的情况,明确幼虫密度对该害虫的室内种群增长的影响。【方法】本实验设置5个幼虫饲养密度即1,5,10,20和30头/瓶(750 mL),分别观察5个饲养密度下该虫的各个龄期及整个幼虫发育历期及存活率、蛹重、蛹期以及成虫生殖情况。【结果】幼虫密度对该虫幼虫各龄期及整个幼虫发育历期及存活率、蛹重、蛹期以及成虫生殖情况均有显著性影响。整个幼虫发育历期随着密度的增加而缩短,10头/瓶达到最短(18.27 d),之后随着幼虫密度的增加而显著延长;幼虫至蛹的存活率随着密度增高而显著下降,30头/瓶最低(39.37%)。蛹期随着密度的增加而延长(10头/瓶除外)。蛹重和每雌产卵量均以1头/瓶最高,随着幼虫密度的增加而显著下降。雌雄蛾寿命均以10头/瓶最长,与1和5头/瓶没有显著性差异。生命表分析显示:二点委夜蛾的种群增长指数以5头/瓶最高,幼虫密度过低或者过高均不利于种群增长。【结论】幼虫密度是影响二点委夜蛾种群增长的重要因子之一。     

幼虫密度对草地螟生长发育及繁殖的影响

为了明确幼虫密度对草地螟Loxostege sticticalis种群增长的影响, 对室内条件下（温度22±1℃, RH 70%±5%, 光周期16L∶ 8D）不同幼虫密度[1, 10, 20, 30和40头/瓶（650 mL）］饲养的草地螟生长发育及繁殖进行了研究。结果表明: 幼虫密度对草地螟幼虫体色、 发育历期和存活率, 以及蛹重和成虫生殖等有显著影响。随着幼虫密度的增加, 幼虫体色黑化程度呈增强趋势, 幼虫密度大于10头/瓶时的体色黑化值均显著大于幼虫密度为1头/瓶时的体色黑化值（P<0.05）。20头/瓶的幼虫和蛹历期最短, 且随幼虫密度的增加而显著延长（P<0.05）。幼虫存活率以10头/瓶最高, 其他幼虫密度的幼虫存活率显著较低（P<0.05）。蛹重以1头/瓶的最重, 并随幼虫密度增加而显著下降（P<0.05）。成虫产卵量和交配率分别以1和20头/瓶的幼虫密度最高, 幼虫密度升高则产卵量、 交配率逐渐降低。成虫产卵历期随着幼虫密度的增加逐渐缩短。雌、 雄蛾寿命分别以10和20头/瓶幼虫密度时最长, 幼虫密度过高时雌雄蛾寿命又显著缩短（P<0.05）。生命表分析表明, 幼虫密度对草地螟种群增长指数有显著影响, 以10头/瓶幼虫密度的种群增长指数最高, 幼虫密度过高或过低时种群增长指数下降。据此认为, 幼虫密度是影响草地螟种群增长的重要因子之一。     

Reproduction and larval development of two sympatric Pseudopolydora species (Annelida: Spionidae) in Japan

Pseudopolydora cf. kempi and Pseudopolydora cf. reticulata, which are morphologically similar, are sympatric in Gamo Lagoon, near Sendai on the Pacific eastern coast of Honshu, Japan. Reproduction, larval development, and larval morphology of these two species were compared. The larval developmental pattern of P. cf. kempi was determined to be short-term planktonic with lecithotrophy and adelphophagy, whereas that of P. cf. reticulata was long-term planktonic with planktotrophy. The number of embryos per capsule differed between the two species: 0–16 for P. cf. kempi and 62–405 for P. cf. reticulata. Nurse eggs were only found for P. cf. kempi. The results of this study suggest that some previous studies attributed to P. kempi may have been to P. cf. reticulata or to another species in this complex.     

Evolution of poecilogony from planktotrophy: cryptic speciation, phylogeography, and larval development in the gastropod genus Alderia

Poecilogony, a rare phenomenon in marine invertebrates, occurs when alternative larval morphs differing in dispersal potential or trophic mode are produced from a single genome. Because both poecilogony and cryptic species are prevalent among sea slugs in the suborder Sacoglossa (Gastropoda: Opisthobranchia), molecular data are needed to confirm cases of variable development and to place them in a phylogenetic context. The nominal species Alderia modesta produces long-lived, feeding larvae throughout the North Atlantic and Pacific, but in California can also produce short-lived larvae that metamorphose without feeding. We collected morphological, developmental, and molecular data for Alderia from 17 sites spanning the eastern and western Pacific and North Atlantic. Estuaries south of Bodega Harbor, California, contained a cryptic species (hereafter Alderia sp.) with variable development, sister to the strictly planktotrophic A. modesta. The smaller Alderia sp. seasonally toggled between planktotrophy and lecithotrophy, with some individuals differing in development but sharing mitochondrial DNA haplotypes. The sibling species overlapped in Tomales Bay, California, but showed no evidence of hybridization; laboratory mating trials suggest postzygotic isolation has arisen. Intra- and interspecific divergence times were estimated using a molecular clock calibrated with geminate sacoglossans. Speciation occurred about 4.1 million years ago during a major marine radiation in the eastern Pacific, when large inland embayments in California may have isolated ancestral populations. Atlantic and Pacific A. modesta diverged about 1.7 million years ago, suggesting trans-Arctic gene flow was interrupted by Pleistocene glaciation. Both Alderia species showed evidence of late Pleistocene population expansion, but the southern Alderia sp. likely experienced a more pronounced bottleneck. Reduced body size may have incurred selection against obligate planktotrophy in Alderia sp. by limiting fecundity in the face of high larval mortality rates in warm months. Alternatively, poecilogony may be an adaptive response to seasonal opening of estuaries, facilitating dispersal by long-lived larvae. An improved understanding of the forces controlling seasonal shifts in development in Alderia sp. may yield insight into the evolutionary forces promoting transitions to nonfeeding larvae.     

Erythritol ingestion impairs adult reproduction and causes larval mortality in Drosophila melanogaster fruit flies (Diptera: Drosophilidae)

Previous feeding studies showed the polyalcohol erythritol was toxic when ingested by adult laboratory fruit flies (Drosophila melanogaster). We asked whether erythritol could additionally affect fly population growth either through larval toxicity or through effects on adult reproduction. Females did not avoid laying on food substrates with 1M erythritol; laying rate on 1M erythritol food was similar to control food when females were given free‐choice access. Eggs laid or placed on 0.5 M to 2.5 M erythritol foods hatched at normal rates, suggesting erythritol was not toxic to eggs upon contact. Drosophila melanogaster larvae readily consumed food containing 1 M erythritol, but none of these larvae reached pupation. Longevity of larvae feeding on in 1 M erythritol food was significantly reduced relative to controls, and mean ± SE larval lifespan on erythritol was 1.54 ± 0.10 days (max. = 3 days). Exposing cohorts of second‐instar larvae to food with varying concentrations of erythritol showed the LD50 (at 24 hr) concentration was approximately 0.6 M. Taken together, these results suggest erythritol could be employed in effective larval‐sink baits. Adults flies fed with erythritol produced significantly fewer eggs on days when they fed on 1 M erythritol, and egg production was significantly reduced for one additional day after the adults were moved to control food. These findings suggest erythritol is rapid and effective at temporarily suppressing D. melanogaster reproduction, increasing its potential for use in effective insect population control.     

New Carboniferous brachiopods from the eastern Great Basin, Nevada, USA: implications for loop ontogeny and evolution in Late Palaeozoic terebratuloids

Terebratuloid brachiopods from two localities in the eastern Great Basin, Nevada, USA, include the new taxa Cryptacanthia savagei sp. nov., Fletcherithyris infrequens sp. nov., Cryptonella simplex sp. nov., and Albelenina alvarezi gen. et sp. nov. The faunas are considered to be mid Desmoinesian (late Moscovian) in age. The brachiopods were found associated in clusters, and many of the specimens are well preserved. Records of Pennsylvanian terebratuloid brachiopods are uncommon, and these faunas have enabled an understanding of internal features previously unknown or poorly understood. Systematic analyses of the faunas have generated some new concepts on the ontogeny and evolution of the loop in Late Palaeozoic terebratuloids. From ontogenetic analyses, it is inferred that the stage of loop development may be the most important aspect in taxonomic classification. Analyses of loop evolution suggest the possibility of a transition from a teloform stage to long-flanged deltiform and deltiform stages. These transitions may be possible through reduction in length of the descending lamellae of the crura by resorption of calcium carbonate or posteroventral folding of flanges. Subsequently, these changes in loop morphology are retained by paedomorphosis within long-term evolutionary processes.     

Novel reproductive modes in freshwater clams: brooding and larval morphology in Southeast Asian taxa of Corbicula (Mollusca, Bivalvia, Corbiculidae)

While the majority of marine bivalves are oviparous, the two freshwater families among the order Veneroida, i.e. Corbiculidae and Sphaeriidae, comprise species with ovoviviparous and viviparous reproduction. Within the Corbiculidae, the genus Corbicula, which is well‐known for its invasive and, thus, ecologically important representatives, is characterized by (i) a wide range of limnic habitats, inhabiting both brackish water and freshwater environments, and (ii) contrasting modes of reproduction, including ‘planktonic’ development via a free‐swimming larva vs. intrabranchial incubation (brooding) of shelled juveniles. The present investigation of five species of Corbicula from the Indonesian islands Sumatra and Sulawesi, which were hitherto not studied anatomically, adds to the diversity in reproductive patterns in this genus. As a unique feature among Corbicula we here report on two newly observed modes of brooding in species endemic to Sulawesi, (i) tetragenous brooding (i.e. in both demibranchs) in Corbicula possoensis Sarasin & Sarasin, 1898 from Lake Poso, and (ii) prolonged incubation in the maternal gills, with juvenile shells reaching up to 1.3 mm in length and with a well‐developed hinge in C. linduensis Bollinger, 1914 from the Lindu River system. In contrast, a third method is seen in the following taxa that incubate their young in their inner demibranchs only until the stage of juveniles with straight‐hinged shells (D‐shaped): C. matannensis Sarasin & Sarasin, 1898 from Lake Matano and Lake Mahalona, C. loehensis Kruimel, 1913 from Lake Masapi (all on Sulawesi) and C. moltkiana Prime, 1878 from Lakes Maninjau and Singkarak (on Sumatra). Details of the anatomical and histological features of ctenidia are described for each type of brooding, and some trends in the evolution of reproductive strategies within the Corbiculidae are discussed, comparing them with those known from other limnic molluscs.     

Population structure is not a simple function of reproductive mode and larval type: insights from tropical corals

1. For a wide range of organisms, heritable variation in life-history characteristics has been shown to be strongly subject to selection, reflecting the impact that variation in characters such as genotypic diversity, duration of larval development and adaptations for dispersal can have on the fitness of offspring and the make-up of populations. Indeed, variation in life-history characteristics, especially reproduction and larval type, have often been used to predict patterns of dispersal and resultant population structures in marine invertebrates. 2. Scleractinian corals are excellent models with which to test this relationship, as they exhibit almost every possible combination of reproductive mode and larval type. Some general patterns are emerging but, contrary to expectations, genetic data suggest that while populations of broadcast spawning species may be genotypically diverse they may be heavily reliant on localized recruitment rather than widespread dispersal of larvae. 3. Here we use microsatellites to test the importance of localized recruitment by comparing the genetic structure of populations of two broadcast spawning corals with contrasting modes of reproduction and larval development; Goniastrea favulus is self-compatible, has sticky, negatively buoyant eggs and larvae and is expected to have restricted dispersal of gametes and larvae. In contrast, Platygyra daedalea is self-incompatibile, spawns positively buoyant egg-sperm bundles and has planktonic development. 4. Surprisingly, spatial-autocorrelation revealed no fine-scale clustering of similar genotypes within sites for G. favulus, but showed a non-random distribution of genotypes in P. daedalea. Both species showed similar levels of genetic subdivision among sites separated by 50-100 m (F(ST) = 0.03), suggesting that larval dispersal may be equivalent in both species. 5. Interestingly, as fragmentation has been considered rare in massive corals, our sample of 284 P. daedalea colonies included 28 replicated genotypes that were each unlikely (P < 0.05) to have been derived independently from sexual reproduction. 6. We conclude that the extreme life history of G. favulus does not produce unusually fine-scale genetic structure and subsequently, that reproductive mode and larval type may not be not good predictors of population structure or dispersal ability.     

Presence of larval and adult diapauses in a subtropical scarab beetle: graded thermal response for synchronized sexual maturation and reproduction

Abstract The white grub Dasylepida ishigakiensis has a 2‐year life cycle and spends approximately 9 months as a nonfeeding larva, pupa and adult on a subtropical island. Evidence is presented indicating that this beetle has two diapauses that appear to synchronize this long life cycle with the seasons. Larvae exposed to 20, 22.5, 25 and 27.5 °C late in the third (last) stadium pupate rapidly except for some individuals kept at the highest temperature. The latter pupate upon transfer to 22.5 °C, indicating that larval diapause is maintained at high temperature but terminates upon transfer to a lower temperature. Pupal development is directly temperature‐dependent in the range 20–30 °C. Adults develop reproductive organs (i.e. the ovary in females and the seminal vesicles and accessory glands in males) rapidly at 15 and 20 °C, whereas those kept at 25 °C take a long time to do so. Ovarian development is completely suppressed at 30 °C but initiated upon transfer to 20 °C. In the laboratory, males with well‐developed reproductive organs mate even with sexually immature females , whereas females with undeveloped ovaries show no sexual behaviour. Although the two diapauses of this species are thermally regulated (i.e. a characteristic commonly expressed by insects in summer diapause), adults of this beetle emerge from pupae late in the autumn and remain in the soil for 2 months. Adult diapause effectively serves to synchronize the time of sexual maturation with the coldest month of the year.     

When similar beginnings lead to different ends: Constraints and diversity in cirripede larval development

Summary

Cirripedes are fascinating models for studying both functional constraints and diversity in larval development. Adult cirripedes display an amazing variation in morphology from sessile suspension feeders that still retain many crustacean characters to parasites that have lost virtually all arthropod traits. In contrast, cirripede larval development follows a common scheme with pelagic larvae comprising a series of nauplii followed by a cyprid. Variations are mostly concerned with whether or not the nauplii are feeding and the degree of abbreviation of development, culminating in species where the larvae hatch as cyprids. The cypris larvae are very similar among the ingroups of the Cirripedia, but interesting variations occur in structures used for substrate location and attachment. The cyprid is specialized to both swim through the water and actively explore the substratum by walking on the antennules and using an array of sensory organs in search for a suitable site to attach. This unique morphology and behavior of the cyprid have enabled the Cirripedia to colonize widely different habitats ranging from hard rock to soft animal tissue. Yet, the cyprid can metamorphose into juveniles as different as a setose feeding barnacle and the vermiform stages of the parasitic forms. This emphasizes the importance of the cyprid as one of the key features for the evolutionary success of the Cirripedia.     

Correlated responses to selection for faster development and early reproduction in Drosophila: the evolution of larval traits

Studies on selection for faster development in Drosophila have typically focused on the trade-offs among development time, adult weight, and adult life span. Relatively less attention has been paid to the evolution of preadult life stages and behaviors in response to such selection. We have earlier reported that four laboratory populations of D. melanogaster selected for faster development and early reproduction, relative to control populations, showed considerably reduced preadult development time and survivorship, dry weight at eclosion, and larval growth rates. Here we study the larval phase of these populations in greater detail. We show here that the reduction in development time after about 50 generations of selection is due to reduced duration of the first and third larval instars and the pupal stage, whereas the duration of the second larval instar has not changed. About 90% of the preadult mortality in the selected populations is due to larval mortality. The third instar larvae, pupae, and freshly eclosed adults of the selected populations weigh significantly less than controls, and this difference appears during the third larval instar. Thereafter, percentage weight loss during the pupal stage does not differ between selected and control populations. The minimum amount of time a larva must feed to subsequently complete development is lower in the selected populations, which also exhibit a syndrome of reduced energy expenditure through reduction in larval feeding rate, larval digging and foraging activity, and pupation height. Comparison of these results with those observed earlier in populations selected for adaptation to larval crowding and faster development under a different protocol from ours reveal differences in the evolved traits that suggest that the responses to selection for faster development are greatly affected by the larval density at which selection acts and on details of the selection pressures acting on the timing of reproduction.     

水稻条纹花叶病毒对介体电光叶蝉生长繁殖及取食行为的影响

【目的】由电光叶蝉Recilia dorsalis传播的水稻条纹花叶病毒(rice stripe mosaic virus, RSMV)目前在我国华南稻区大面积发生并对水稻生产造成严重危害。本研究旨在明确RSMV对介体电光叶蝉生长繁殖及取食行为的影响。【方法】通过生物学实验测定RSMV侵染后电光叶蝉的生长和生命表参数;利用刺吸电位(electrical penetration graph, EPG)技术比较携带和未携带RSMV的电光叶蝉成虫在健康水稻上的取食行为差异;采用Y型嗅觉仪测定电光叶蝉成虫对感染和未感染RSMV水稻的寄主选择倾向性。【结果】与无毒电光叶蝉相比,携带RSMV的电光叶蝉若虫发育历期延长,而若虫存活率、成虫羽化率、雌虫繁殖力和卵孵化率下降。无毒电光叶蝉成虫倾向于选择取食RSMV侵染的水稻,而带毒电光叶蝉成虫倾向于选择取食健康水稻。与无毒电光叶蝉相比,带毒电光叶蝉成虫取食健康水稻所产生的刺探波、障碍波和唾液分泌波次数和持续时间均显著增加,被动取食波和休息波次数减少但时间均延长。【结论】与无毒电光叶蝉相比,感染RSMV使带毒电光叶蝉若虫发育历期延长且不利于其种群的繁殖。R...     

短时高温对烟蚜生长发育、繁殖和取食行为的影响

【目的】烟蚜Myzus persicae是一种世界性的重要农业害虫,本研究测定了短时高温对烟蚜生长发育、繁殖和取食行为的影响。【方法】测定初产若蚜每天在30, 35和40℃下处理1, 2和4 h的发育历期及成蚜在相同处理下的繁殖力,应用刺吸电位技术（electronic penetration graph, EPG）测定成蚜在30和35℃下处理1和2 h后以及在25, 28, 30和35℃恒温下的取食行为。【结果】短时高温（30~35℃）对各龄若蚜发育历期影响较小,但40℃下处理2 h后其发育历期显著增加（P<0.05）;若蚜存活率、成蚜寿命及其繁殖历期随温度和处理时间的增加而降低;在25~35℃下,随温度和处理时间的增加,成蚜繁殖率变化较小,但40℃下处理2和4 h后,其繁殖率显著降低（P< 0.01）;短时高温对烟蚜的取食行为影响显著,随温度和处理时间的增加,非刺探波np数量（P<0.05）及其持续时间（P<0.01）显著减少,而韧皮部刺吸波E持续时间显著增加（P<0.05）;但持续高温下,随温度升高,np波数量及其持续时间先减少后增加,而E波则相反。【结论】短时高温对烟蚜若蚜发育速率影响较小,但使若蚜存活率、成蚜寿命及其繁殖历期显著降低,且对成蚜繁殖有一定的抑制作用,而对成蚜的取食有一定的促进作用。研究结果有助于了解烟蚜不同年份间夏季种群数量的变化机制。