Palynological evaluation of bee pollen load batches from the Venezuelan Andes of Misinta/Evaluacion palinologica de de lotes de carga de polen apicola de los Andes Venezolanos de Misinta/Avaliacao palinologica de partidas de cargas de polen apicola dos Andes Venezuelanos de Misinta.
Besides honey, bee pollen is the beehive product best known by the public for nutritional and medicinal purposes. Ten samples of fresh bee pollen loads were collected using pollen traps during ten months from December 2004 to October 2005 in the Paramo of Misinta, Merida, Venezuela. They were evaluated in the present study using two techniques, one considering single pollen loads, and the other a pool of two grams of mixed pollen loads. Pollen loads changed from light green and yellow to brownish and ochre; Rosaceae, Eucalyptus and Hyptis pollen load colors changed monthly. A unique pollen type was commonly predominant in each pollen load, therefore confirming the preference of the bees to collect pollen from one species until reaching the final weight to be carried in their corbicula. Pollen load color analysis showed four biftoral and six heterofloral batches. Pollen load pool analysis emphazised three monofloral batches of Brassica napus in March, April and September, and two bifloral pollen batches in June and November, beside the five heterofloral ones. This evaluation revealed better the potential of the regional pollen production.
KEYWORDS / Bee Pollen Loads / Floral Origin / Pollen Analysis / Pollen Evaluation /
Ademas de la miel, el polen apicola es el producto mejor conocido por los consulmidores en relacion a sus propiedades nutricionales y medicinales. Se recolectaron diez muestras de polen apicola fresco por medio de una trampa caza polen durante diez meses, de diciembre 2004 a octubre 2005, en el Paramo de Misinta, Merida, Venezuela. Las muestras fueron evaluadas en el presente trabajo utilizando dos' tecnicas, una considerando las' cargas" aisladas de polen y otra usando dos" gramos de cargas bien mezcladas ("pool") por lote. El color de las cargas de polen vario de verde claro y amarillo a marron y ocre; los" colores de las' cargas de polen de Rosaceae, Eucalyptus e Hyptis variaron mensualmente. En general, domino un tipo unico de polen en cada carga, confirmando de esta manera la preferencia de las abejas por la colecta de polen de una especie hasta llegar a el peso final que puede ser llevado en sus corbiculas. El analisis del color de las cargas de polen resulto en cuatro lotes biflorales y seis heteroflorales. El analisis de "pool" de cargas de polen resulto en tres lotes monoflorales de Brassica napus en marzo, abril y setiembre, y dos biflorales en junio y noviembre, ademas de cinco heteroflorales. Esta evaluacion del polen apicola revelo mejor el potencial regional para la produccion de polen.
Alem de mel, o polen apicola e o produto mais bem conhecido pelos consumidores em relacao a suas propriedades nutricionais e medicinais. Foram coletadas dez amostras de polen apicola fresco, por meio de um caca-polen, durante dez meses, de dezembro 2004 a outubro 2005, no Paramo de Misinta, Merida, Venezuela. As amostras foram avaliadas no presente trabalho usando duas tecnicas, uma considerando cargas isoladas de polen e a outra usando dois gramas de cargas bem misturadas ("pool") por partida. A cor das cargas de polen variou de verde claro e amarelo a marrom e ocre; as cores das cargas de polen de Rosaceae, Eucalyptus e Hyptis variaram mensalmente. Em geral dominava um unico tipo polinico em cada carga de polen, desta maneira confirmando a preferencia das abelhas pela coleta de polen de uma so especie ate chegar ao peso final que possa ser levado em suas corbiculas. A analise por cor das cargas de polen resultou em quatro partidas biflorais e seis heteroflorais. A analise do "pool" de cargas de polen resultou em tres partidas monoflorais de Brassica napus em marco, abril e setembro e duas biflorais' em junho e novembro, alem de cinco heteroflorais. Esta avaliacao do polen apicola revelou melhor o potencial regional para a producao de polen.
Besides honey, bee pollen is the beehive product best known by the public for nutritional and medicinal purposes. Its botanical origin, related to flower richness, local and regional vegetation, provides information about the capacity of the area where the apiaries are located, regarding qualitative and quantitative aspects of honey, bee pollen, royal jelly and bee wax production (Manrique, 1996; Rodriguez, 2006).
Identification of bee plants may be obtained using the pollen analysis technique, characterizing the local and regional vegetation and its potential for beekeeping (Barth, 2004). Few previous data about palynological bee pollen analysis in the Venezuelan Andes could be ob tained (Vit and Santiago, 2008). Results of bee pollen load sample analyses of neighboring countries of Venezuela have been published mainly in Brazil (Bastos et al., 2004; Luz et al., 2007; Barth et al., 2009), as well as in Surinam (Engel and Dingemans-Bakels, 1980) and Colombia (Sierra and Pardo, 2009).
The Paramo of Misinta, Municipality of Rangel, state of Merida, in the Venezuelan Andes, comprises altitudes around 3300-3400masl. Beekeeping activities in this region are limited. In the last 20 years, honeybees shifted their foraging habits to collection of more pollen than nectar (Juan C. Schwartzenberg, personal communication). Consequently in the apiaries, honey crops dropped while harvests of bee pollen increased.
Using two palynological techniques, the present paper intends to investigate the validity of bee preferences when collecting pollen grains from plants in the Misinta region of the Venezuelan Andes. The chemical composition (moisture, ash, fat, pH, proteins) of the same pollen samples from this region has been published elsewhere (Vit and Santiago, 2008).
Material and Methods
The apiary is located (Figure 1) in the Paramo of Misinta, Merida state, Venezuela. Samples of fresh bee pollen loads were collected during three days in ten hives during ten months, from December 2004 to October 2005, using pollen traps. The samples were kept frozen until botanical analysis was carried out applying two different techniques.
For the first procedure, that of pollen load batch botanical origin evaluation (Barth et al., 2009), pollen loads of two gratos of each sample were distributed, according to color, in batches or sub-samples. A unique load of each colored batch was used for pollen grain identification. Pollen grains were macerated with the aid of one drop of 70% ethanol directly on a microscope slide.
For the second technique, pollen loads of two grams of each sample were homogenized in 70% ethanol using ultrasound. After a second wash in ethanol and ultrasonic treatment, the sediment obtained was left for a half hour in a solution of distilled water/glycerin 1:1. One drop of the well mixed pollen grain suspension was placed on a microscope slide, covered with a 22x22mm cover slide, and sealed with enamel. The slide must be maintained in a horizontal position. Pollen has to be examined within one month or less, when drying starts and the pollen grains are selectively pressed against the air bubbles.
[FIGURE 1 OMITTED]
The evaluation of single pollen loads does not require counting. More than 500 pollen grains of each sample were counted (pollen sum) for pool evaluation. For identification of the botanical taxa the plant species list of Vareschi (1970) and pollen descriptions and illustrations in Vit (2005) were used.
Results and Discussion
The color of pollen loads changed during the ten months of this study from yellow and ochre, light gray and greenish gray, to orange and brown. The data obtained are presented in Table I, considering the pollen types representing [greater than or equal to] 3% of the pollen sum. Twelve pollen types were detected by single pollen load analysis and eight pollen types (one was not identified) by pollen load pool analysis. A total of fourteen pollen types were detected using both techniques. This aspect illustrates a very low richness of bee plant species in the studied region when compared with data of areas covered with tropical vegetation, where 37 plant species were related by Engel and Dingemans-Bakels (1980).
Pollen types could be identified at the level of family, genus or species of plants occurring in the vegetation of Misinta (Vareschi, 1970; Vit et al., 2008). Nearly all single pollen loads analyzed were composed of a unique plant speeies pollen (Table I, columns 2 and 3). Only in September bees have mixed pollen grains of several plant taxa in a single ochre colored pollen load.
Brassicaceae pollen grains were the most frequent all over the year. The species Brassica napus is abundant in the studied region. It blooms in yellow and gives to the mountains a characteristic pattern. The pollen load pool analysis detected this species mainly in the months from November until May (Table I, column 4), and in lower concentration from June to October. Analyzing the pollen loads according to its color, this period was shortened from December to May, and no pollen grains of this species were detected in June, October and November. Sensorial parameters of B. napus pollen loads in comparison with those of Rosaceae (Fraxinus americana), Zea mays and Datura arborea, obtained at Merida state, showed significant differences (Vit et al., 2008).
The second most frequent pollen type was from Rosaceae, comprising at least three pollen types. This taxon was found during the pool analysis as dominant in June and October and in lower concentration during all months, except May. Using color analysis (Table I, column 3) it was only observed in some months.
The third important taxon of pollen contribution was Eucalyptus (Barth and Barbosa, 1972; Barth, 1989), which is an introduced plant species. The pool analysis did not detect these pollen grains in June and November, and by the color analysis only in the months of March and April. Therefore, Eucalyptus trees may be of lower value for pollen production in the Misinta region.
Considering the pool analysis, the remaining four pollen types with >3% frequency (Carica papaya, Medicago denticulatea, Myrcia acuminata and Rumex acetosella), never reached a significant representation. B. napus was the dominant plant species in three of the ten batches analyzed, and were the only monofloral ones, occurring in the months of March, April and September. Bifloral pollen loads of B. napus and Rosaceae were found in June and November, and heterofloral samples in December, January, February, May and October.
Color analysis of pollen loads showed no monofloral batches. The use of weight of different colored pollen batches may be helpful, as it was exemplified by Barth et al. (2009). The error in this analysis consists in the presentation of different colors by pollen grains of a given species. In the present study this observation can be exemplified (Table I, columns 2 and 3) with yellow, ochre and light brown colored pollen loads of B. napus, dark brown and greenish gray pollen loads of Eucalyptus, greenish gray and brown ones of Fragaria vesca, and ochre and orange of Hyptis. The identification of pollen grains of different colored pollen loads results in a larger number of pollen types.
Therefore, the pollen load pool analysis is much more accurate quantitatively for commercial interest than the color analysis. On the other hand, the identification of pollen grains of different colored pollen loads provides a larger number of pollen types, showing a better resolution of the bee floral composition.
[FIGURE 2 OMITTED]
In summary, the analysis of different colored pollen loads provides better information about the regional vegetation, while the analysis of a pollen load pool reveals the regional potential for pollen production. The practical result for beekeepers is, first, to know through pool analysis which plant species really are the best for obtaining pollen, and second, to find out, using pollen load color analysis, which plant species were visited by the bees. However, some plant species may be of less value in a study area, and of higher importance in another region.
The authors acknowledge Juan Carmona, Universidad de Los Andes, for his advice on the botanical sources from Misinta, Venezuela, and the financial support of Conselho Nacional de Desenvolvimento Cientifico e Tecnologico/CNPQ, Brazil (Fellowship 301525/2009-9 to the first author) and Consejo de Desarollo Cientifico, Humanistico y Tecnologico, Universidad de los Andes, Venezuela (Project CDCHTULA/FA-337-04-01-B of the last author).
Received: 01/20/2010. Modified: 03/09/2011. Accepted: 03/10/2011.
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Ortrud M. Barth. Ph.D. Researcher, Instituto Oswaldo Cruz (Fiocruz), Brazil. Address: Laboratorio de Morfologia e Morfogenese Viral, Pavilhao Helio e Peggy Pereira, Fiocruz. Avenida Brasil 4365. 21040-900 Rio de Janeiro, R J, Brazil. e-mail: firstname.lastname@example.org
Alex da Silva de Freitas. Biologist. Collaborator, Instituto de Biologia, Universidade Federal do Rio de Janeiro (UFRJ), Brazil.
Erika de Oliveira Sales. Biologist. Collaborator, Instituto de Biologia, Universidade Federal do Rio de Janeiro (UFRJ), Brazil.
Patricia Vit. Ph.D., Professor, ULA, Venezuela.
TABLE I COMPARISON OF TEN SAMPLES OF POLLEN LOADS (2g OF EACH BATCH) FROM Apis mellifera EVALUATED BY ITS COLOR AND BY A POOL OF 2g OF EACH BATCH * Single pollen load analysis according to color Samples Sub-samples Pollen types (++++) December 2004 yellow Brassica napus ochre Hyptis light gray Rosaceae brown Myrcia acuminata and yeast January 2005 yellow B. napus greenish gray Rosaceae February 2005 yellow B. napus greenish gray Fragaria vesca orange aff. Guazuma ulmifolia March 2005 ochre/yellow B. napus light brown B. napus dark brown Eucalyptus April 2005 yellow B. napus greenish gray Eucalyptus May 2005 ochre B. napus brown Medicago denticulata June 2005 brown R vesca dark brown Parkinsonia aculeata September 2005 yellow B. napus ochre several pollen types greenish gray Rosaceae orange Hyptis October 2005 ochre Cercidium praecox greenish gray Rosaceae brown Coriandrum sativum November 2005 ochre C. praecox light brown Rumex acetosella dark brown unknown Analysis of pollen load pools Samples Pollen types identified Evaluation of the sample December 2004 Brassica napus (++) Heterofloral Eucalyptus (++) Myrcia acuminata (++) Rosaceae (++) January 2005 B. napus (+++) Heterofloral Eucalyptus (++) with dominance Rosaceae (++) of Brassica napus February 2005 B. napus (+++) Heterofloral of Eucalyptus (++) B. napus, Rosaceae (++) Eucalyptus and Rosaceae March 2005 B. napus (++++) Monofloral of Carica papaya (+) B. napus Eucalyptus (+) Rosaceae (+) April 2005 B. napus (++++) Monofloral Eucalyptus (+) of B. napus Rosaceae (+) May 2005 B. napus (+++) Heterofloral Carica papaya (+) with dominance Eucalyptus (+) of B. napus Medicago denticulate (+) Rumex acetosella (+) June 2005 Rosaceae (+++) Bifloral of B. napus (++) Rosaceae and Myrcia acuminata (+) B. napus R. acetosella (+) September 2005 B. napus (++++) Monofloral of Eucalyptus (+) B. napus Rosaceae (+) M. acuminata (+) October 2005 Rosaceae (++) Heterofloral B. napus (+) Eucalyptus (+) M. denticulata (+) November 2005 B. napus (+++) Bifloral of B. Rosaceae (++) Napus and R. acetosella (+) Rosaceae unknown (+) Only the pollen types with frequency >3% were considered, as very frequent (++++, >85%), frequent (+++, 45-85%), less frequent (++, 15-45%), rare (+, 3-15%).