世居及移居高原青少年最大有氧能力的特征

本文报道海拔３４１７ｍ和４２８０ｍ地区世居藏族和移居汉族青少年运动状态下心肺功能的对比研究。结果显示：３４１７ｍ和４２８０ｍ世居藏族的最大氧耗量、无氧阈值及最大心输出量都明显大于汉族,血氧饱和度（Ｓａｏ２）随运动负荷的增加而降低。海拔３４１７ｍ藏、汉族的△Ｓａｏ２分别为７．４６％和１０．０３％,４２８０ｍ处为８．５７％和１３．７５％,最大心率随海拔升高而下降。研究提示,藏族青少年有较高的最大有氧能力,反映了他们对低氧环境的适应优势。     

The phylogeny of the ant tribe Formicini (Hymenoptera: Formicidae) with the description of a new genus

Abstract. The holarctic ant tribe Formicini is revised, the new genus Bajcaridris described, and possible phylogenetic relationships are discussed. The subgenus Iberoformica is synonymized with Formica. A synopsis, diagnosis and keys to the genera are provided.     

Reducing boll weevil populations by clipping terminal buds and removing abscised fruiting bodies

Cotton pests damaging fruiting bodies (squares and young bolls) are difficult to control and their damage results in direct yield loss. Small growers, with low technological inputs, represent a large portion of cotton growers worldwide comprising more than 76 countries; they rely mainly on cultural practices to counteract pest attack in their crops. Boll weevil, Anthonomus grandis Boheman (Coleoptera: Curculionidae), oviposition involves puncturing cotton squares and young bolls, causing abscission. We examined the impact on boll weevil population of collecting abscised cotton fruiting bodies and clipping plant terminals at 50% boll maturation in the field during two cotton‐growing seasons and under field cage conditions. Greatest numbers of damaged squares occurred ca. 117 days after planting and clipped plants resulted in reduction of abscised structures and adult boll weevils compared with non‐clipped plants, irrespective of cotton variety. Damaged young bolls were found ca. 128 days after planting in 2009 and 2011, but clipping had no effect. Numbers of boll weevils found in plants of the varieties BRS 201 and BRS Rubi (both in 2009) and BRS Rubi (in 2011) were, respectively, 13‐, 17‐, and 20‐fold greater when clipping plus collecting abscised fruiting bodies were not practiced. Furthermore, the average percentage of the boll weevil parasitoid Bracon vulgaris Ashmead (Hymenoptera: Braconidae) emerging from abscised and collected structures was similar between clipped and non‐clipped plant terminals in both seasons. Clipping plant terminals did not result in yield reduction and reduced adult boll weevil production. Collecting abscised reproductive structures, clipping plant terminals, and using both practices together reduced boll weevil populations by as much as 63, 57, and 79%, respectively, in cage trials. Thus, these practices cause significant impact on boll weevil populations and are feasible of adoption, especially for smallholder cotton growers.     

Role of oviposition preference in an invasive crambid impacting two graminaceous host crops

Oviposition preference studies of the Mexican rice borer, Eoreuma loftini (Dyar), on sugarcane, Saccharum spp., and rice, Oryza sativa L., showed that drought stressed sugarcane was 1.8-fold more attractive based on egg masses/plant than well watered sugarcane. The E. loftini susceptible sugarcane cultivar LCP 85-384 was 1.6-fold more attractive than HoCP 85-845 based on numbers of eggs per egg mass. Egg masses were 9.2-fold more abundant and 2.3-fold larger on sugarcane than on rice. Rice, however, was preferred to sugarcane on a plant biomass basis. Oviposition on sugarcane occurred exclusively on dry leaf material, which increased under drought stress. Egg masses per plant increased on drought stressed sugarcane and were correlated with several foliar free amino acids essential for insect growth and development. The more resistant (based on injury) but more attractive (based on oviposition) rice cultivar XL8 had higher levels of several free amino acids than the susceptible cultivar Cocodrie. The association of host plant characteristics to oviposition preference is discussed. Projected oviposition patterns relative to sugarcane and rice production areas were estimated for Texas and Louisiana based on the availability of each host in different regions of each state. These results suggest that, where sugarcane and rice co-occur, the majority of eggs would be found on sugarcane early in the season, because of this crop's substantially greater biomass compared with rice. Abundance later in the season would also favor sugarcane; however, the abundance on rice would be greater than expected solely based on host availability, largely because of the greater preference per gram of rice plant dry weight.     

Effect of aging on pheromone emission from a commercial beet armyworm (Lepidoptera: Noctuidae) lure and trap efficiency

The effect of aging on a commercial pheromone-based lure for attractiveness to male adult beet armyworms, Spodoptera exigua (Hübner), was assessed in terms of trapping efficiency and volatile emissions of two key components: (Z,E)-9,12-tetradecadienyl acetate and (Z)-9-tetradecen-1-ol. In field assays conducted in the Lower Rio Grande Valley, Texas, for 9 wk (June-August 2000) and for 8 wk (March-May) in Tamaulipas, Mexico, 0-1-wk-old lures collected greater than four-fold more male beet armyworm adults than lures that had been aged for 3-4 wk. Using solid phase microextraction and gas chromatographic analysis of the volatiles, mean (Z,E)-9,12-tetradecadienyl acetate emission declined by 32% after 5 wk of aging in a ventilated environmental chamber at 29.4 degrees C, 3.5% RH, to simulate subtropical summers. Mean (Z)-9-tetradecen-1-ol emission was reduced by 62% after 4 wk of aging. Under the tropical and subtropical conditions of this study, the capacity of the lure to attract moths into the trap declined after aging for 3 wk. The blend ratio (Z,E) -9,12-tetradecadienyl acetate: (Z)-9-tetradecen-1-ol declined 29% when the lure was aged for 5 wk. This study will assist in the development of a standard trapping system for assessing adult beet armyworm populations in the tropical and subtropical conditions to which the species is endemic.     

Relationships of different cotton square sizes to boll weevil (Coleoptera: Curculionidae) feeding and oviposition in field conditions

Feeding and oviposition preferences of the boll weevil, Anthonomus grandis grandis Boheman, for four different cotton square size classes in field conditions of the Lower Rio Grande Valley of Texas were studied during 2002 and 2003. Percentages of large (5.5-8-mm-diameter) squares used for oviposition and feeding were greater than pinhead or match-head squares. The preference for large squares as food and associated accelerated fecundity explain the substantial boll weevil population buildups that occur after large squares form. Medium-sized (3-5.5-mm-diameter) squares also were used but less than large squares. Feeding and oviposition on pinhead (1-2-mm-diameter) and match-head (2-3-mm-diameter) squares were negligible. Although planting date did not affect oviposition or feeding preferences for squares larger than pinhead and match-head sizes, the least amount of either damage to large squares was found in the earliest plantings during both years. This study indicates that pinhead and match-head squares, regardless of planting date, do not require pesticide applications to protect against boll weevil feeding and oviposition.     

Leptodictya tabida (Hemiptera: Tingidae): a potential threat to sugarcane production in Lower Rio Grande Valley of Texas

Areawide surveys and replicated cultivar trials were conducted in 2001 and 2002 in sugarcane (Saccharum spp.) fields in the Lower Rio Grande Valley of Texas to assess the distribution and incidence of the sugarcane tingid Leptodictya tabida (Herrich-Schaeffer). L. tabida was found in all fields surveyed during both years, infesting 60 and 68% of the plants, respectively. The average percentage of leaves infested was 11% in 2001 and 15% in 2002. In 2001, 'CP70-1133' was the most infested, 'CP72-1210' was the least infested, and intermediate infestation levels were evident in 'CP70-321' and 'TCP87-3388'. In 2002, however, TCP87-3388 and CP70-321 were more heavily infested, and CP71-1240 and CP71-1405 were the least infested. Mean densities of L. tabida recovered per plant varied between 1.2 bugs on CP72-1210 and 5.1 on CP70-1133 in 2001, and in 2002, from zero bugs on CP71-1240 and CP71-1405 to 5.3 on CP72-1210. In the cultivar trials, cultivar differences also were evident in both plant and leaf infestation levels, and the proportion of immatures to total L. tabida populations; 'HoCP91-555' had the lowest L. tabida infestations and 'NCo-310' had the greatest levels in both years. Although >5000 L. tabida from the field were collected and kept in the laboratory, no parasitoids were found. The distribution of the infestations during the surveys and in the field trial evaluations suggested that L. tabida populations have been spreading in sugarcane across the Lower Rio Grande Valley. Potential varietal resistance mechanisms are discussed.     

Sex differences in the rate of fatigue development and recovery

Background

Many musculoskeltal injuries in the workplace have been attributed to the repetitive loading of muscle and soft tissues. It is not disputed that muscular fatigue is a risk factor for musculoskeltal injury, however the disparity between gender with respect to muscular fatigability and rate of recovery is not well understood. Current health and safety guidelines do not account for sex differences in fatiguability and may be predisposing one gender to greater risk. The purpose of this study was to quantify the sex differences in fatigue development and recovery rate of lower and upper body musculature after repeated bouts of sustained isometric contractions.

Methods

Twenty-seven healthy males (n = 12) and females (n = 15) underwent bilateral localized fatigue of either the knee extensors (male: n = 8; female: n = 8), elbow flexors (male: n = 8; female: n = 10), or both muscle groups. The fatigue protocol consisted of ten 30-second sub-maximal isometric contractions. The changes in maximum voluntary contraction (MVC), electrically evoked twitches, and motor unit activation (MUA) were assessed along with the ability to control the sustained contractions (SLP) during the fatigue protocol using a mixed four-factor repeated measures ANOVA (gender × side × muscle × time) design with significance set at p < 0.05.

Results

There was a significant loss of MVC, MUA, and evoked twitch amplitude from pre- to post-fatigue in both the arms and legs. Males had greater relative loss of isometric force, a higher rate of fatigue development, and were less capable of maintaining the fatiguing contractions in the legs when compared to the females.

Conclusion

The nature of the induced fatigue was a combination of central and peripheral fatigue that did not fully recover over a 45-minute period. The results appear to reflect sex differences that are peripheral, and partially support the muscle mass hypothesis for explaining differences in muscular fatigue.