The Australasian Beekeeper

Executive Summary

(Ed. Note: This is the Executive Summary from John Rhodes' HBRDC-funded research. The full Report (RIRDC Publication 08/130 is available from RIRDC, and is downloadable for free from www.rirdc.gov.au/reportsIn the interests of brevity, information of a technical nature has been omitted and only the Background, Objectives, Key Findings, Implications and Recommendations are included.)

Background

The importance of drone semen quality has its effect on the mating success of queen bees. Sufficient numbers of mature age drones, each producing a large volume of semen containing a high number of sperm are required to be present at commercial queen bee mating apiaries to result in queen bees with the maximum number of sperm present in their spermathecae after mating. Low numbers of sperm in the spermathecae of queen bees after mating contributes to early supersedure resulting in increased costs to the beekeeper from queen replacement and reduced colony production as colonies weaken in strength or become queenless during the period of queen replacement.

This project provides information to persons interested in bee breeding with particular reference to queen bee production by providing data relating to numbers of sperm produced by drones and highlighting the requirement of use of this data in the selection of queen bee drone mothers by including drone sperm production in the selection criteria and by identifying the most suitable method for collecting drone sperm data.

Objectives

The objective of this project was to examine the semen quality of drone honeybees at a range of drone ages over the seasons that queen bees are reared and mated from a number of commercial breeding lines in use in eastern Australia, and compare the obtained data with published data.

Key Findings

• 1) Drone ages, seasons and breeding lines were identified when drone semen was of a higher quality. No drone age, season or breeding line was found when drones were identified as not being suitable for mating with queen bees based on semen quality.
• 2) The significant differences identified for age, season and breeding line suggest the question of whether there is a time period for drones during one or more seasons each year when sperm quality is at its highest level, and if so, this would question the "mating quality" of queen bees mating with drones out of the peak sperm quality time period.
• 3) The average number of sperm produced per drone, in general, is low compared with published data from Australia, Europe and the USA, based on methodology used in this project.
• 4) The average volume of semen produced per drone was comparable with published data from Australia, Europe and the USA.
• 5) Of the four commercial breeding lines examined for semen volume produced per drone and number of sperm produced per drone, one line was constantly superior when compared with the other three lines suggesting that semen volume and sperm number per drone may be selectable traits. Results suggest that should volume of semen and number of sperm produced per drone be selectable traits then recessive genes may be involved.
• 6) The proportion of mature age drones which did not produce semen at the endophallus after manual eversion was high which suggested further investigation into the efficiency of manual eversion as a method for obtaining semen samples.
• 7) Drone survival rate was high for 14 and 21 day old drones with low numbers of drones surviving to 35 days of age.
• 8) Sperm viability percent and sperm motility rating were at the lower end but comparable with published data, with results suggesting that sperm viability percent and sperm motility rating may be improved through selection in a drone mother breeding program.
• 9) In a 2006 experiment, sperm was found present in the seminal vesicles of mature age drones which had not released semen after manual eversion.
• 10) A 2007 experiment based on semen release after manual eversion suggested that drone maturation occurs over a wide range of ages with drones 30 days old retaining sperm in the seminal vesicles after manual eversion.
• 11) In a 2007 experiment, low sperm viability and motility was not found to be a contributing factor for sperm remaining in the seminal vesicles of mature age drones after manual eversion.
• 12) Manual eversion was not found to be a suitable method for collecting semen samples required to provide accurate data on semen volume and number of sperm produced per drone.
• 13) Collecting semen/sperm samples from drone seminal vesicles was considered a more reliable method for providing accurate data on semen volume and sperm number per drone.
• 14) Amino and Fatty Acids. Eighteen free amino acids were identified in drone semen with high levels of arginine and proline and the remaining 16 amino acids present at levels less than 7% of the total amino acids in each sample. Thirty two fatty acids were identified with high levels of oleic acid and elaidic acid and levels of less than 7% for the remaining fatty acids present for the total percent in each sample.

Further research is required on rearing and maintaining large numbers of drones with high sperm quality to a high age for commercial queen bee mating purposes.

Implications

• (i) Low numbers of sperm produced per drone. This characteristic has its principal economic effect at commercial queen mating apiaries when a large number of queen bees are on mating flights at the same time over a short period of time. Low numbers of sperm present in drones can be expected to result in low numbers of sperm present in the spermathecae of queen bees on completion of mating with the flow-on effects of poor performance and early supercedure of those queen bees.
• (ii) Selectable traits. Should semen volume per drone and sperm numbers per drone be selectable traits as data from this project suggests, then selection of queen bees as drone mothers whose drones produce large semen volume and high sperm numbers in breeding programmes would be of economic benefit to the commercial beekeeping industry. Such drones would provide queen bees with high sperm numbers in their spermathecae after mating, with those queen bees then expected to have an increased working life period in the hive before being superseded.
• (iii) Low longevity of drones. Data suggests that, in general, drones have a low longevity which is of economic importance in the context of reducing numbers of mature age drones available to mate with queen bees at commercial queen bee mating apiaries. Further research is required on rearing and maintaining large numbers of drones with high sperm quality to a high age for commercial queen bee mating purposes.
• (iv) Improvement of sperm viability and motility levels. Data suggest that sperm viability percent and sperm motility levels are able to be improved by selecting for these characteristics in drones from drone queen mothers in breeding programs. Economic benefits to commercial beekeeping from drones producing sperm with a high viability
• percent and high motility levels would result from increased egg fertilisation levels from the limited number of sperm each queen has stored in her spermatheca.
• (v) Drone manual eversion effectiveness. Because manual eversion does not result in all seminal fluid and sperm from the seminal vesicles being present in semen at the endophallus for all drones then it is not a suitable method for collecting semen samples where a high level of accuracy is required, e.g. for evaluating semen volume and number of sperm produced by an individual drone when evaluating these characteristics in drones from queen bees being selected as drone mother queens in breeding programs. Data suggests that dissection and counting of sperm numbers from the seminal vesicles provides a more reliable alternative than manual eversion for sperm sample collection.
• (vi) Fatty and amino acids. Amounts of fatty acids and amino acids in drone semen change with age and season with the implication of change in semen quality with semen from one age or season being of a higher quality than semen from drones of a different age or at a different season. As a minimum dietary requirement, results indicate that drone rearing colonies require access to the 18 amino acids and 32 fatty acids identified in this experiment with emphasis on the 2 amino acids and 2 fatty acids present at high levels.

Recommendations

• 1. Standard methods require development for obtaining a semen samples from a drone for examination, and for the determination of measurable data from each drone sampled for the volume of semen produced, the number of sperm produced, sperm viability percent and sperm motility rating.
• 2. Using standard methods drones from a range of commercial honeybee breeding lines in Australia to be surveyed for the four characteristics, volume of semen, number of sperm, sperm viability and sperm motility, to obtain a wider view of drone sperm quality within breeding stock available within the commercial beekeeping industry.
• 3. That the four drone characteristics, semen volume, sperm number, sperm viability and sperm motility be incorporated into standard selection criteria for drone mother queen bees in breeding programs.
• 4. Apiary management practices are required to be developed to promote the production and maintenance of large numbers of drones with high longevity and producing sperm of high quality to a high age, from drone mother hives at queen bee mating apiaries.
• 5. Fatty and Amino acids. Research is required into drone dietary requirements and to determine benefits from supplementary feeding with arginine and proline amino acids and oleic and elaidic fatty acids, in drone rearing colonies at queen bee mating apiaries.

The four drone characteristics, semen volume, sperm number, sperm viability and sperm motility (should) be incorporated into standard selection criteria for drone mother queen bees in breeding programs.

Apiary management practices are required to be developed to promote the production and maintenance of large numbers of drones with high longevity and producing sperm of high quality to a high age, from drone mother hives at queen bee mating apiaries.