Fernand-Nestor Tchuenguem Fohouo

Foraging and pollination behaviour of Xylocopa calens Lepeletier (Hymenoptera: Apidae) on Phaseolus coccineus L. (Fabaceae) flowers at Yaounde (Cameroon)

To evaluate impact of carpenter bee, Xylocopa calens, on pod and seed set of Phaseolus coccineus, its foraging and pollinating activities were studied in Yaounde, for two seasons (May–July 2008 and April–June 2009). Observations were made on 40 inflorescences per treatment. The treatments included unlimited floral access by all visitors, bagged flowers to deny all visits, and limited visits by X. calens only. In addition, all flower visitors were recorded. The carpenter bees seasonal rhythm of activity, its foraging behavior on flowers, its pollination efficiency, the fructification rate and the number of seeds per pod were recorded. Individuals from 16 species of insects were recorded visiting flowers of P. coccineus in the 2 years. Xylocopa calens was the most frequent, followed by Chalicodoma cincta cincta and Apis mellifera. Apart from bees, wasps were also recorded as likely predators. Xylocopa calens mainly foraged for nectar resources. The mean foraging speed was 9.62 flowers/min. Flowers visited by X. calens had higher fruiting rate compared with others, while those bagged had the lowest. In addition, seed formation was higher in X. calens‐visited flowers compared with all others. The results show that this crop experiences pollination deficit even under normal circumstances, considering that flowers visited by X. calens had higher yields compared with those under unlimited access by all visitors. The fruiting rate, the number of seeds/pod and the percentage of normal seeds of unprotected inflorescences were significantly higher than those of inflorescences protected from insects. X. calens foraging resulted in a significant increment of the fruiting rate by 25.80%, as well as the number of seeds/pod by 14.97% and the percentage of normal seeds by 27.75% in 2008 and 18.39% in 2009. Conservation of X. calens nests close to P. coccineus fields could be recommended to improve pod and seed production in the region.

Exploitation of Dichrostachys cinerea, Vitellaria paradoxa, Persea americana and Securidaca longepedunculata flowers by Apis mellifera adansonii Latreille (Hymenoptera: Apidae) at Dang (Ngaoundéré, Cameroon)

In Cameroon, the demand for hive products is growing. Honey and pollen yields are low in the country, partly because of the poor knowledge of the apicultura! value of the flora. To determine the apicultural value of Dichrostachys cinerea (L.), Vitellaria paradoxa Gaertn. F., Persea americana Mill. and Securidaca longepedunculata Fres., Apis mellifera adansonii Latreille activity was observed on the flowers of these plants in Ngaoundéré, from December 2001 to May 2002 and from December 2002 to May 2003. The flowers of each plant species were prospected at least 4 days per month, between 0700 and 1800 h, for recording of the nectar and/or pollen foraging behaviour of A. m. adansonii workers. Results show that A. m. adansonii harvest nectar and pollen of V paradoxa, P. americana and S. longepedunculata. The flowers of D. cinerea were visited for pollen only. The greatest number of workers foraging simultaneously on a plant varied from 34 (D. cinerea) to 1640 (P. americana). A. m. adansonii workers that visited flowers of a given plant species once remained with this nectar source throughout the observation period. Thus V. paradoxa, P. americana and S. longepedunculata could be cultivated and protected to increase honey production, whereas D. cinerea could enable bee-keepers to increase their pollen production as a hive product. During foraging, A. m. adansonii workers increased pollination possibilities of each of the plant species.

Pollination efficiency of Apis mellifera adansonii (Hymenoptera: Apidae) on Callistemon rigidus (Myrtaceae) flowers at Dang (Ngaoundéré, Cameroon)

To evaluate the impact of the honeybee Apis mellifera adansonii Latreille on fruit and seed yields of Callistemon rigidus R. Br. 1819, its foraging and pollinating activities were studied in Ngaoundéré for two seasons (June–August 2009 and July–September 2010). Each year, observations were made on 120 inflorescences per treatment. The treatments included unlimited flower access by all visitors, bagged flowers to deny all visits and limited visits by A. m. adansonii only. In addition, all flower visitors were recorded. The worker bee’s seasonal rhythm of activity its foraging behaviour on flowers, its pollination efficiency, the fruiting rate, the number of seeds per fruit and the percentage of normal seeds were recorded. Individuals from five and ten insect species that visited C. rigidus flowers were recorded in 2009 and 2010, respectively. Apis mellifera adansonii was the most frequent, followed by Myrmicaria opaciventris Emery. Apis mellifera adansonii intensely and preferably foraged for nectar. The fruiting rate, the number of seeds per fruit and the percentage of normal seeds of unprotected inflorescences were significantly higher than those of inflorescences protected from insects. Apis mellifera adansonii foraging resulted in a significant increase in the fruiting rate by 92.04% in 2009 and 64% in 2010, as well as the number of seeds per fruit by 38.67% in 2009 and 59.16% in 2010, and the percentage of normal seeds by 84.67% in 2009 and 82.30% in 2010. Cultivation of C. rigidus plants could be recommended to increase seeds, fruits and honey production.

Foraging behaviour of Apis mellifera adansonii (Hymenoptera: Apidae) on Combretum nigricans, Erythrina sigmoidea, Lannea kerstingii and Vernonia amygdalina flowers at Dang (Ngaoundéré, Cameroon).

In Cameroon, the demand for hive products is growing. Honey and pollen yields are low in this country, partly because of the poor knowledge of the apicultural value of the flora. To determine the apicultural value of Combretum nigricans Lepr. ex Guill. & Perr., Erythrina sigmoidea Hua, Lannea kerstingii Engl. & K. Krause and Vernonia amygdalina Delile, Apis mellifera adansonii Latreille activity was observed on the flowers of these plants in Ngaoundéré from December 2001 to May 2002 and from December 2002 to May 2003. The flowers of each plant species were prospected for at least 4 days per month, between 07.00 and 18.00 h, for recording the nectar and/or pollen foraging behaviour of A. m. adansonii workers. Results show that A. m. adansonii harvested the nectar of each plant species. In addition, L. kerstingii and V. amygdalina were visited for pollen. The greatest number of workers foraging simultaneously on a plant varied from 26 (E. sigmoidea) to 4200 (V. amygdalina). Apis mellifera adansonii workers that visited flowers of a given plant species once generally remained with these nectar and/or pollen sources throughout the observation period. Thus C. nigricans, E. sigmoidea, L. kerstingii and V. amygdalina could be cultivated and protected to increase honey production; L. kerstingii and V. amygdalina could enable beekeepers to increase their pollen production as a hive product. During foraging, A. m. adansonii workers increased the pollination possibilities of each plant species.

Une abeille afrotropicale spécialisée dans la récolte du pollen de Graminées (Poaceae): Lipotriches notabilis (Schletterer 1891) (Hymenoptera Apoidea Halictidae)

Résumé Dans les zones de savanes de l’Afrique, un genre d’abeille, Lipotriches Gerstaecker 1858, s’est spécialisé dans la collecte du pollen de graminées. Un site de nidification et l’aire de butinage de Lipotriches notabilis ont été suivis pendant trois années dans la région de Ngaoundéré au Cameroun. Le régime alimentaire pollinique est composé presque exclusivement du pollen de graminées, notamment Brachiaria ruziziensis abondant dans cette région. Le maïs est aussi visité et l’abeille contribue indirectement à la pollinisation par la mise en suspension dans l’air du pollen. Comme les graminées n’offrent pas de ressource sucrée, les femelles comme les mâles de L. notabilis butinent de temps en temps les Asteraceae pour la collecte de nectar. La consommation du pollen de graminées par les femelles a été aussi observée. Lespèce niche en bourgades dont la taille varie d’une dizaine à une centaine de nids. Le nid creusé dans un sol horizontal est du type progressif. Il comprend un tumulus, une cheminée verticale, un conduit principal vertical pouvant atteindre 65 cm de profondeur et en moyenne 3 conduits latéraux obliques de 4 à 16 cm aboutissant dans une ou plusieurs cellules successives. Les cellules des conduits latéraux sont approvisionnées simultanément et fermées de manière régressive. On compte un maximum de 10 cellules par nid. Généralement un nid est habité par une seule femelle, mais certains nids sont habités par deux ou trois. Lactivité de butinage de cette espèce est limitée dans la matinée. Dès 7 heures, elle s’envole pour le site de butinage. Après 11 heures, il n’y a généralement plus de nids ouverts. Les mâles n’ont pas été aperçus au niveau du site de nidification et l’accouplement a lieu sur le site de butinage. La période d’activité commence avec la saison des pluies en avril et se termine au début de la saison sèche en décembre, avec la fanaison des graminées.

Foraging and pollination behaviour of Xylocopa olivacea (Hymenoptera: Apidae) on Phaseolus coccineus (Fabaceae) flowers at Ngaoundéré (Cameroon)

To evaluate the effect of the carpenter bee, Xylocopa olivacea Lepeletier 1841, on the pod and seed yields of Phaseolus coccineus L., in this study, its foraging and pollination activities were examined in Ngaoundéré during the June-July 2010 and July-August 2011 cropping seasons. Treatments included open floral access to all visitors, bagging of flowers to avoid all visits and floral access to limited visits of X. olivacea. Observations were made on 120 flowers per treatment. In addition, all flower visitors were recorded. The seasonal rhythm of the activity of the carpenter bee, its foraging behaviour on flowers and its pollination efficiency (fruiting rate, number of seeds/pod and percentage of normal or well-developed seeds) were recorded. Phaseolus coccineus flowers were visited by 13 insect species in 2010 and by 14 insect species in 2011. Xylocopa olivacea was the most frequent visitor and intensely and exclusively foraged the flowers for nectar. The mean foraging speed was 9.28 flowers/min. In 2010, the foraging activity of X. olivacea resulted in a significant increase in the fruiting rate (27.49%), number of seeds/pod (45.43%) and percentage of normal seeds (89.38%). In 2011, the corresponding values were 56.14% (fruiting rate), 74.44% (number of seeds/pod) and 66.44% (percentage of normal seeds). These results reveal that this crop experiences a pollination deficit, considering that flowers visited by X. olivacea had higher yields than those under unlimited access to all visitors. Hence, the conservation of X. olivacea nests close to P. coccineus crop fields is recommended for improving pod and seed production.

Nitric oxide-dependent vasodilation and Ca2+signalling induced by erythrodiol in rat aorta

Abstract Objective To evaluate the pharmacological property of erythrodiol, a natural triterpenoid contained in propolis, as vasodilatory agent, and to determine its mechanism of action. Methods Rats aortic rings were isolated and suspended in organ baths, and the effects of erythrodiol were studied by means of isometric tension recording experiments. Nitric oxide (NO) was detected by ozone-induced chemiluminescence. The technique used to evaluate changes in intracellular Ca 2+ concentration in intact endothelium was opened aortic ring and loaded with 16 μmol Fura-2/AM for 60 min at room temperature, washed and fixed by small pins with the luminal face up. In situ , ECs were visualized by an upright epifluorescence Axiolab microscope (Carl Zeiss, Oberkochen, Germany) equipped with a Zeiss×63 Achroplan objective (water immersion, 2.0 mm working distance, 0.9 numerical apertures). ECs were excited alternately at 340 and 380 nm, and the emitted light was detected at 510 nm. Results In aortic rings with intact endothelium pre-contracted with norepinephrine (10 −4 mol/L), the addition of erythrodiol (10 −8 −10 −4 mol/L) induced vasorelaxation in a concentration-dependent manner; in endothelium-denuded rings, the relaxant response induced by erythrodiol was almost completely abolished suggesting that vasorelaxation was endothelium-dependent. They had almost no relaxant effect on depolarised or endothelium-denuded aortic segments. The relaxation was significantly attenuated by pre-treatment with the NO synthase inhibitor Nv-nitro-L-arginine-methylester. Erythrodiol (10 −4 mol/L) was able to significantly increase NOx levels. This effect was completely abolished after removal of the vascular endothelium. Erythrodiol (100 μmol/L) caused a slow, long-lasting increase in intracellular Ca 2+ concentration. These results further supported the hypothesis that erythrodiol can induce activation of the NO/soluble guanylate cyclase/cyclic guanosine monophosphate pathway, as suggested by functional studies. Conclusions The present results suggest that the mechanism of relaxation seems to be mainly mediated by the endothelial production of NO. Such a vasorelaxation was an endothelium-dependent effect, via the NO/soluble guanylate cyclase/cyclic guanosine monophosphate pathway. This result also suggests that erythrodiol causes a slow influx of extracellular Ca 2+ release from the intracellular Ca 2+ stores and an inhibition of Ca 2+ extruding mechanism. It can be concluded that erythrodiol may have interesting therapeutic potential as a new vasodilator drug, for protecting the cardiovascular system.

Pollination efficiency of Xylocopa olivacea (Hymenoptera: Apidae) on Cajanus cajan (Fabaceae) flowers at Yaoundé, Cameroon

To assess the impact of the carpenter bee, Xylocopa olivacea Fabricius 1787, on the pod and seed yields of Cajanus cajan (L.) Millsp. 1900, in this study, its foraging and pollinating activities were examined in Nkolbisson during two seasons (July 2008-January 2009 and June-December 2009). Observations were made on 180 inflorescences per treatment. The treatments included unlimited floral access to all visitors, bagging of flowers to prevent access to all visitors, and floral access to limited visits by X. olivacea only, fn addition, information on all floral visitors was recorded. The carpenter bee’s seasonal rhythm of activity, its foraging behaviour on flowers, its pollination efficiency, the fruiting rate (Fr) and the number of seeds per pod were recorded. Nineteen species of insects were recorded visiting the flowers of C. cajan. Chalicodoma cincta cincta was the most prominent one, followed by X. olivacea, Apis mellifera adansonii, Megachile bituberculata and Xylocopa albiceps, and the bees were the most frequent floral visitors. Xylocopa olivacea mainly foraged for nectar and pollen and its foraging speed was 11.75 flowers/min. The Fr, the number of seeds/pod and the percentage of normal seeds of unprotected inflorescences were significantly higher than those of inflorescences protected from insects. The foraging activity of X. olivacea resulted in a significant increase in the Fr by 22.26%, as well as the number of seeds/pod by 34.98% and the percentage of normal seeds by 12.09% in the two study years. Placing X. olivacea nests close to C. cajan fields is recommended to increase pod and seed production in Cameroon.

Diversité des insectes floricoles et son impact sur les rendements fruitiers et grainiers de Glycine max (Fabaceae) à Yassa (Douala, Cameroun)

Afin d’evaluer l’impact des insectes anthophiles sur les rendements de Glycine max (Fabaceae), des observations ont ete faites sur les fleurs de cette Fabaceae de juin a juillet 2013 puis de mai a juin 2014 a Yassa. Deux traitements ont ete determines a partir du marquage de six parcelles differenciees par la presence ou l’absence de protection des plantes vis-a-vis des insectes. L’activite de butinage et de pollinisation des insectes a ete etudiee. Le taux de fructification, le pourcentage de graines normales et le nombre moyen de graines par gousse ont ete evalues. Les resultats montrent que 13 et 14 especes d’insectes ont visite les fleurs du soja respectivement en 2013 et 2014. Sur les fleurs de G. max , les insectes recoltaient intensement et regulierement le pollen et le nectar. Lasioglossum sp . et Leuconomia granulata sont respectivement les especes les plus frequemment observees en 2013 et 2014. Par le biais de leur activite pollinisatrice, les insectes anthophiles ont augmente le taux de fructification de 37,92% et 41,91%, le pourcentage de graines normales de 20,86% et 40,57%, le nombre moyen de graines par gousse de 12,76% et 12,60% respectivement en 2013 et 2014. La protection des nids des Halactides dans les plantations de G. max est recommandee pour accroitre la production des gousses et des graines. Mots cles: Insectes anthophiles, Glycine max , butinage, pollen, nectar, rendements.

A New Centre of Applied Apidology in Cameroon

In 2014 a new Centre of Applied Apidology will open its doors in Cameroon and will offer bee biology and beekeeping classes to biology students, beekeepers and interested members of the public.