Dynamics of locomotion in the seed harvesting ant Messor barbarus: effect of individual body mass and transported load mass

Ants are well-known for their amazing load carriage performances. Yet, the biomechanics of locomotion during load transport in these insects has so far been poorly investigated. Here, we present a study of the biomechanics of unloaded and loaded locomotion in the polymorphic seed-harvesting ant Messor barbarus (Linnaeus, 1767). This species is characterized by a strong intra-colonial size polymorphism with allometric relationships between the different body parts of the workers. In particular, big ants have much larger heads relative to their size than small ants. Their center of mass is thus shifted forward and even more so when they are carrying a load in their mandibles. We investigated the dynamics of the ant center of mass during unloaded and loaded locomotion. We found that during both unloaded and loaded locomotion, the kinetic energy and gravitational potential energy of the ant center of mass are in phase, which is in agreement with what has been described by other authors as a grounded-running gait. During unloaded locomotion, small and big ants do not display the same posture. However, they expend the same amount of mechanical energy to raise and accelerate their center of mass per unit of distance and per unit of body mass. While carrying a load, compared to the unloaded situation, ants seem to modify their locomotion gradually with increasing load mass. Therefore, loaded and unloaded locomotion do not involve discrete types of gait. Moreover, small ants carrying small loads expend less mechanical energy per unit of distance and per unit of body mass and their locomotion thus seem more mechanically efficient.

Flowering Dynamics in Alfalfa (Medicago sativa L.) Based on Heat Units

Objective: To describe the sequential pattern of reproductive development of Medicago sativa L. (flowering dynamic) using the relation between principal floral stem nodes and accumulated growing degree day (GDD) in different environmental conditions, and to determine the use of this relationship as a predictor of the seed harvesting date. Design/Methodology/Approach: It was carried out in random blocks and factorial arrangement of 2?5, with two repetitions. Each repetition was made up of 30 plants. Results: The flowering dynamic followed the same pattern between varieties, with a linear relation between GDD and number of floral nodes. The year A0 was different from the years A1 and A2. Therefore, A1 with cutting, and A2 with and without cutting presented less GDD during the flowering stage. In contrast, A0 showed more GDD during this period. In the different environmental conditions, the linear curves of flowering dynamic turned erratic after the tenth floral node (300 GDD) due to a low rate of plants with more than 10 floral nodes along the principal stem. Study Limitations/Implications: It is necessary to have a meteorological station near the alfalfa seed production site, in order to specify the GDD required for predicting the correct moment to harvest seeds. Findings/Conclusions: The reproductive development of M. sativa presents a linear relation between the number of floral nodes and GDD, which allows the prediction of the optimal seed harvesting date, in any environmental condition present.

Phenotypic variability of cowpea genotypes for immature seed harvesting

ABSTRACT Seed color, brightness and texture are important aspects for the consumption of immature beans. This study aimed to estimate the phenotypic variability among thirty cowpea genotypes for immature seed harvesting, in order to guide breeding programs. The experiment was carried out in a randomized blocks design, with three replications. The evaluated traits were immature seeds yield, pods and dry seeds production, number of immature pods, 100-immature seeds weight, immature pods length, number of seeds per immature pod, cooking time, harvesting period of immature pods, seed color, pod color, plant growth habit, opening of immature pods, seed threshing from immature pods, cultivation value and seed browning after threshing. Anova and three clustering methods were applied: UPGMA using the Jaccard coefficient of similarity; modified Tocher method based on the Gower algorithm; and k-means. All the analyses were performed based on the variable means of experiments evaluated in six environments. A statistically significant phenotypic variability was observed among all the quantitative traits. Discrepancies occurred in the accessions grouping and number of clusters. The accession BRS Acauã, in one group, and P508 and PCCR3F6L15, in other groups, showed a good quality for immature grain harvesting, were consistently grouped into different clusters and are recommended for use as parents in the development of new cultivars.

Temperature, potassium nitrate, substrate, and harvesting time on the germination of zoysia grass seeds

Zoysia japonica grass has commercial importance to Brazil due to its use in golf courses and football stadiums. The main concern about its commercial cultivation is the unevenness on seed germination as well as the ideal seed harvesting time. Therefore, the objective was to measure the effect of temperature and potassium nitrate on dormancy overcoming, and of substrate and harvesting time on germination of zoysia grass seeds (Zoysia japonica Steud). There were three experiments: 1) temperature and potassium nitrate treatments, with six temperature conditions (constants at 20 ˚C, 25 ˚C, 30 ˚C, and 35 ˚C, and alternating at 20-30 ˚C and 20-35 ˚C), under absence or presence of potassium nitrate; 2) temperature and substrate treatments, with two temperature conditions (alternating at 20-30 ˚C and 20-35 ˚C) and three types of substrates (on paper, between paper, and on sand); and 3) harvesting time treatments, which seeds were obtained by manual harvesting comprising 11 harvesting periods. Seeds germinated more rapidly on the sand and paper, at the alternating temperature of 20-35 °C. The best period for seed harvesting was from 18 to 19 days after ear emergence in the production field.