A novel exocrine structure of the bicellular unit type in the thorax of termites

Gonçalves, T. T., DeSouza, O. and Billen, J. 2010. A novel exocrine structure of the bicellular unit type in the thorax of termites — Acta Zoologica (Stockholm) 91 : 193–198 Studying the thorax of some Termitidae species, we found two pairs of hitherto unknown lateral glands in the mesothorax and metathorax of both workers and soldiers. The glands consist of distinct clusters of class 3 secretory cells accompanied by their duct cells, located in the upper lateral portion of the thoracic wall. Ultrastructural observations reveal numerous mitochondria, a well‐developed Golgi apparatus and vesicular smooth endoplasmic reticulum, indicating a cytoplasm with intensive metabolic activity. The gland is reported to occur in Microcerotermes strunckii, Cornitermes cumulans and Nasutitermes minor, three species comprising an interesting morpho‐behavioural gradient, respectively, from only mechanical, through mechanical–chemical, to only chemical defence systems. The extent of such a gradient allows speculations that this gland would be related to the general needs of termites, rather than to some specificities of a single group. We warn, however, that complementary studies are needed, before any conclusions can be drawn.     

象白蚁属一新种：等翅目：白蚁科,象白蚁亚科

本文记述我国浙江省龙王山自然保护区等翅目白蚁属一新种,安吉象白蚁Ｎａｓｕｔｉｔｅｒｍｅｓａｎｊｉｅｎｓｉｓｓｐ．ｎｏｖ．。     

Faunistique et répartition longitudinale des Trichoptères dans une rivière salmonicole de basse montagne,en Belgique

Trichoptera have been studied in the drainage basin of the Flavion, a small calcium-ion rich low altitude trout river in Belgium. During a one-year investigation, 45 species, which represent one fourth of the recorded Belgian Trichoptera, have been collected. As a whole, the caddis larvae show a rather weakly defined zonation. Longitudinal distribution of closely related species is discussed from the standpoint of interspecific competition.

     

Queen replacement in the termiteMicrocerotermes papuanus

In experimentally orphaned field nests ofMicrocerotermes papuanus Holmgren, 1911, large numbers of workers develop into replacement reproductives (ergatoids) in only one moult. The females become functional egg-layers after approximately two months. Nymphs normally reach the last instars in August–September; at that time, in the orphaned nests, some nymphs moult to nymphoid replacement reproductives. Over long time periods, these nymphoids completely replace the ergatoids and the females become physogastric. Although time-efficient, queen replacement seems energetically expensive for the society, suggesting that this process is under weak selective pressure inM. papuanus, compared with sympatric species such asNasutitermes princeps.

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Le remplacement de la reine chez le termiteMicrocerotermes papuanus

Résumé Dans les nids deM. papuanus rendus expérimentalement orphelins, un grand nombre d'ouvriers se transforment, en une seule mue, en sexués de remplacement ergatoïdes. Les femelles se mettent à pondre au bout d'environ deux mois. Les nymphes atteignent normalement leurs derniers stades en août-septembre. A ce moment, dans les nids orphelins, certaines d'entre elles se différencient en sexués nymphoïdes. Dans les expériences de longue durée, ces nymphoïdes remplacent complètement les ergatoïdes et les femelles deviennent physogastres. Bien que rapide, le remplacement de la reine paraît coûteux pour la société du fait du grand nombre d'individus, ouvriers et nymphes, impliqués. Ceci suggère que la pression de sélection sur ce phénomène est faible chezM. papuanus, par comparaison avec des espèces sympatriques telles queN. princeps.

     

长苞铁杉天然林群落种内及种间竞争关系研究

通过各种竞争指数的比较筛选,得到较能客观反映长苞铁杉种内、种间竞争关系的竞争指数,定量地分析了长苞铁杉种内和种间竞争强度。结果表明:长苞铁杉种内竞争随胸径的增大而逐渐减少;种间与种内竞争关系顺序为:长苞铁杉-长苞铁杉>猴头杜鹃-长苞铁杉>青冈栎-长苞铁杉>其它树种-长苞铁杉。竞争强度与对象木的胸高直径服从双曲线回归关系,利用模型预测了长苞铁杉种内、种间的竞争强度。     

Sensitivity analysis of Markov models for communities of competing sessile organisms

1. Communities of competing sessile organisms are often modelled using Markov chains. Sensitivity analysis of the stationary distribution of these models tells us how we expect the abundance of each organism to respond to changes in interactions between species. This is important for conservation and management. 2. Markov models for such communities have usually been formulated in discrete time. Each column of the discrete-time transition matrix must sum to 1 (column stochasticity). Sensitivity analysis therefore involves defining a pattern of compensation that maintains column stochasticity as a single transition probability changes. There is little biological theory about the appropriate compensation pattern, but the usual choices involve changing only the elements of a single column of the transition matrix. 3. I argue that if the underlying dynamics occur in continuous time, each transition probability is the net outcome of direct and many indirect interactions. 4. Determining the consequences of changing a single direct interaction will often be of interest. I show how this can be achieved using a continuous-time model. The resulting discrete-time compensation pattern is quite different from those that have been considered elsewhere, with changes occurring in many columns. 5. I also show how to determine which direct interactions are being changed under any discrete-time compensation pattern.     

Analysis of the insect community in a stored-maize facility

Maize samples were obtained at two depths [0–30cm (top sample) and 30–60cm (bottom sample) from the maize surface] at 19–28 locations from a naturally infested maize storage facility in Wisconsin, USA. Based on identification of insects in stored-maize samples from 13 weekly sampling events, four topics were addressed: (i) the seasonal fluctuation in the insect community; (ii) ordination analysis was conducted to examine the association among insect taxa and to determine their distribution along abiotic and geographic gradients; (iii) the demographic characteristics of insect communities in maize samples with high abundance of either Plodia interpunctella (Plodia samples) or Sitophilus zeamais (Sitophilus samples); and (iv) to what extent natural enemies were spatially associated with their prey species. We identified a total of 18 different taxa, composed of adults and larvae of 14 determined species, and others identified to genus, family or order. Insect density was significantly higher in top samples compared to bottom samples, and the insect taxa occurred more frequently in top samples compared to bottom samples. In the ordination analysis, the three explanatory variables accounting for eastern, northern and vertical position of maize samples explained the largest part of the total variance. There was a gradual time trend with some of the insect species mainly occurring early or late in the monitoring period. Moisture content of the maize was the weakest of the significant explanatory variables, while temperature in the grain mass did not explain a significant part of the total variance. Plodia samples and Sitophilus samples had significantly different spatial distribution patterns and had markedly different insect species composition. Plodia samples were characterized by low abundance of all granivores and fungivores, except P.interpunctella. Conversely, Sitophilus samples had high abundance of T.castaneum, A.advena, and C.ferrugineus. Consequently, Sitophilus samples seemed to comprise more diverse insect communities than Plodia samples. Natural enemies were not significantly associated with their most common hosts. In a highly homogeneous habitat (stored maize), we demonstrated that stored-product insect species had significantly different distribution patterns mainly along geographic gradients. Stochasticity of the initial infestation process or interspecific competition are two of the possible explanations for the spatial segregation of stored-product insects, and the spatial segregation of insects on the same trophic level may have profound implications for the understanding of how these ecosystems develop over time and thereby how integrated pest management strategies are implemented to control insect pest populations.     

Interspecific variation in the defence secretions of Nasutitermes soldiers

Termite soldiers of the genus Nasutitermes (Isoptera, Termitidae, Nasutitermitinae) eject a viscous, sticky defense secretion composed of non-polar monoterpene hydrocarbons and polyoxygenated diterpenes from the frontal gland. Chemical compositions are described in detail for the East African species, N. kempae and N. infuscatus, and for the Neotropical species N. ephratae. Additional comparisons with the new world species N. costalis, N. rippertii and N. octopilis are presented. The structure of a new monohydroxykempene from N. ephratae is described, and a physicochemical model for the stickiness of the glue is presented. Although the structures of the individual secretion components vary within the genus, the glue-like nature of the secretion remains essentially unchanged. Chemical analysis of soldier defense secretions may be useful in studying the systematic biology of termites.     

Caste developmental potentialities in the termite Nasutitermes novarumhebridarum

The normal development pathway and caste system of Nasutitermes novarumhebridarum (N. & K. Holmgren) (Isoptera; Termitidae) conform to the general Nasutitermes pattern. Queen-removal experiments in N. novarumhebridarum resulted in the production of replacement reproductives derived from workers (ergatoids), but never from the sexual brood (nymphs and alates). Three moults are necessary to complete the tranformation from the worker to the ergatoid. This pathway is longer than those previously konwn in other termites, in which two moults are sufficient. In a colony with functional ergatoids, some nymphs gave rise to worker-like individuals. The caste potentialities of N. novarumhebridarum differ from those of the sympatric species, N. princeps and N. polygynus, in which imaginal replacement reproductives are easily obtained. Colony reproduction in N. novarumhebridarum seems to be accomplished exclusively by independent alate founders, which colinize massive, but finite and widely spaced resoures such as dead or damaged tree trunks. N. princeps and N. polygynus societies abundantly use colony budding to expand their territory, and exploit various sources of dead wood scattered over their foraging range. We suggest that N. novarumhebridarum caste potentialities are adapted to channelling a maximum of resources into the production of dispersing alates that can colonize new nest sites.

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Résumé Les voies de développement et le système de castes chez Nasutitermes novarumhebridarum sont conformes au schéma général du genre Nasutitermes. L'enlèvement expérimental de la reine chez N. novarumhebridarum entraîne le développement de sexués de remplacement à partir d'ouvriers (ergatoïdes), mais jamais à partir de la lignée sexuée (nymphes et ailés). La transformation de l'ouvrier en ergatoîde fonctionnel nécessite trois mues. Ce développement est plus long que ceux décrits précédemment chez d'autres termites, où deux mues sont suffisantes. Dans une société où se sont développés des ergatoïdes fonctionnels, quelques nymphes se sont transformées en individus rappelant les ouvriers. Les potentialités des castes de N. novarumhebridarum diffèrent de celles des espèces sympatriques N. princeps et N. polygynus, chez lesquelles des sexués de remplacement imaginaux pauvent être obtenus aisément. La reproduction des sociétés de N. novarumhebridarum semble s'effectuer uniquement par des ailés essaimants, qui colonisent des sources de nourriture massives, mais limitées et largement espacées, tels les troncs d'arbres morts ou endomagés. N. princeps et N. polygynus étendent fréquemment leurs territoires par le bourgeonnement de nouvelles sociétés, et exploitent des sources de bois mort variées, dispersées dans leur champ d'exploitation. Nous suggérons que les potentialités des castes chez novarumhebridarum sont adaptées pour diriger un maximum de ressources vers la production d'ailés qui se dispersent et peuvent ainsi coloniser de nouveaux sites favorables.

     

山西稀有濒危植物脱皮榆种内和种间竞争

通过对山西太岳山一块100 m×100 m样地中128株脱皮榆对象木及1093株竞争木的调查,运用Hegyi的单木竞争指数计算分析了脱皮榆的种内和种间竞争强度。结果表明:(1)脱皮榆种群所受到的竞争强度随着对象木胸径的增大而逐渐减小;(2)调查样地内尽管其他物种种类较多,但数量较少,与脱皮榆种间竞争相对较弱,脱皮榆种内与种间竞争关系的顺序为:脱皮榆-脱皮榆>千金榆-脱皮榆>五角枫-脱皮榆>茶条槭-脱皮榆>其他树种-脱皮榆;(3)竞争强度和对象木胸径的关系服从幂函数关系,当脱皮榆胸径在25 cm以上时,竞争强度变化不大,所得的预测模型能很好地预测脱皮榆种内种间竞争强度。     

天柱山黄山松种内与种间竞争的研究

采用改进的竞争指数模型研究安徽天柱山黄山松的种内和种间竞争强度。结果发现:(1)随对象木胸径的增大,黄山松种群因自然稀疏过程中密度调节作用,植株距离增加,种内竞争强度降低;(2)黄山松群落内其它物种虽然较多,但个体普遍较小,结果种间竞争相对较弱,种内与种间竞争关系顺序为:黄山松—黄山松>杉木—黄山松>枹栎—黄山松>其它树种—黄山松;(3)竞争强度和对象木胸径的关系服从幂函数关系(CI=AD-B),当黄山松胸径达到20cm以上时,竞争强度变化不大,所得的预测模型能很好地预测黄山松种内和种间的竞争强度;(4)改进的竞争指数模型能很好地度量黄山松的种内和种间竞争强度,改进的确定邻体范围的方法能有效地确定黄山松的竞争范围。     

天然东北红豆杉(Taxus cuspidata)种内和种间竞争

竞争是植物种内和种间关系的主要形式之一。通过对黑龙江穆棱东北红豆杉自然保护区的95株东北红豆杉对象木及980株竞争木的调查,运用Hegyi的单木竞争指数计算分析了东北红豆杉的种内和种间竞争强度。东北红豆杉的种内竞争强度不大,占总竞争的4%。竞争压力更多的来自于种间竞争,占总竞争的96%。与东北红豆杉竞争激烈的树种主要是冷杉、紫椴、色木槭和红松等地带性植被的优势种。随着东北红豆杉胸径的增大,所受到的竞争压力逐渐减小,胸径在20cm以前所受到的竞争压力最大,竞争强度与对象木胸径符合幂函数（CI=AD^-B）关系。     

濒危植物宝华玉兰种内与种间竞争

利用Hegyi单木竞争指数模型对江苏镇江宝华山国家森林公园特有濒危植物宝华玉兰种内、种间竞争强度进行定量分析。结果表明:宝华玉兰竞争压力主要来自种间,占总竞争的90.7%。宝华玉兰种内竞争、种间竞争强度大小顺序为:紫楠>野核桃>建始槭>宝华玉兰种内>毛竹>化香>枫香>皂荚>朴树。整个林分竞争木对对象木的竞争强度与对象木的胸径大小近似服从幂函数关系,而伴生树种竞争木对对象木的竞争强度与对象木的胸径大小近似服从对数函数关系。种间竞争强度和对象木的胸径大小呈显著负相关。利用模型预测,当宝华玉兰的胸径达到30cm后,竞争强度几乎没有变化。研究认为,将无性系分株换算为一株与其胸高断面积之和相等的个体更为合理。