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Cannabis and Bees

Contents

  1. Cannabis and Bees
    1. Introduction
    2. Bees
    3. Apis mellifera
    4. Cannabis sativa L.
    5. Cannabinoids
    6. Endocannabinoid system
    7. Bee nervous system
    8. Absence of the endocannabinoid system in bees
    9. Relationship between neonicotinoids, Apis mellifera and Cannabis sativa
    10. Conclusion
    11. Reference List
    12. Other Sources

Introduction

Bees are amongst the most important pollinators of various plant species, if not the most important one. They have formed a symbiotic relationship with flowering plants, whereby both organisms benefit from the relationship. In this case, the bees gather nectar and pollen from the flowering plants in order to feed their offspring and make honey. Conveniently, while doing so, they take part in spreading the pollen of one flowering plant to another, aiding in genetic variation of future flowering plants (Small & Antle, 2003). Many plants are fully dependent upon insect pollinators such as bees to be able to generate offspring as, without them, they would not thrive in their ecosystem. Other plant species are able to succeed without help from pollinating bees. The pollination process can also be carried out via self- pollination or wind pollination.

Cannabis plants, such as Cannabis sativa, contain cannabinoids which are compounds produced by the plant. Cannabinoids are similar to the endogenous molecules, endocannabinoids, produced in the body of animals.

As discussed later in this essay, the endocannabinoid system (ECS) is a complex cell signalling system that is involved with the regulation of lipid and glucose metabolism, as well as sleep, mood and memory in all vertebrates. The ECS comprises three main components; endocannabinoids: the two key ones being anandamide (AEA) and 2-arachidonoylglycerol (2-AG), enzymes, and receptors. Endocannabinoids can be compared to cannabinoids, which are compounds naturally found in Cannabis plants. It is important to note that with the absence of an ECS in insects, the cannabinoids produced by plants will not have an effect on bees as the specific receptor system is not present (McPartland et al., 2001).

Bees

Bees are the most important pollinators in an ecosystem since pollination is crucial in plant reproduction. Pollinators strongly influence relationships within an ecosystem, conservation, and genetic variation within plant communities. Pollination by bees works by the bees landing on flowers and getting the pollen from the stamen (male reproductive organ) stuck on the hairs of their body. Bees spend their lives collecting pollen and thus visit thousands of flowers in a day. When landing on the next flower, the pollen-covered hairs rub against stigma or pistol tip (female reproductive organs), thus making fertilization possible.

Bees rely on flowers as a food source, using either the nectar or pollen. Pollen is the main source of nutrients, particularly protein, for bees. Nectar is produced by plants in order to attract bees, so that pollination can occur. Honey bees use nectar to convert to honey, which is then the bee’s main source of carbohydrates, thus providing bees with energy for flying and colony maintenance.

Apis mellifera

The western honeybee (Apis mellifera) is the most common species of honeybee worldwide. The swarming of western honeybees typically occurs when nectar and pollen are plentiful, during spring and early summer. Bees use the nectar from flowering plants, however, cannabis plants are not known to produce nectar.

Hemp plants are typically wind-pollinated, however, produce a large amount of pollen that is attractive to honey bees. The flowering of hemp plants typically occurs during the darth period of other bee-pollinator-friendly plants, thus making hemp plants a crucial source of pollen for bees during this time, as this ensures a continuous supply of pollen. With hemp known to not produce nectar, it is the pollen-rich nature that makes hemp such an ecological important crop for honey bees (O'Brien & Arathi, 2019).

Cannabis sativa L.

Cannabis L. is a genus of the family Cannabaceae, and the species is called Cannabis sativa L. It has two subspecies: Cannabis sativa ssp. Indica L. and Cannabis sativa ssp. Sativa L.It is ranging naturally from India to Iran, but it is being cultivated all over the world because of its many different ways of being utilized (Pertwee 2014). The earliest evidence of humans domesticating the plant may date back as early as 10 000 BCE in Central Eurasia, and there is evidence of the plant being spread to Eastern Europe, the Middle East, and other parts of Asia around 2000 BCE (Schilling et al. 2020). It has a variety of reasons for being domesticated. The seeds are being used to derive hemp oil which is being used in a multitude of products ranging from paint, fuel, and plastic, to detergents and shampoo. The stems are being used in building materials, textiles, and rope amongst others. The most widely known use can be put on the account of the psychoactive properties in the flowers of the female plant.

Cannabinoids

The active compounds of Cannabis sativa are the cannabinoids. If we take the subspecies of Cannabis sativa ssp. Sativa L. there have been around 426 chemical compounds described in the plant, and more than 60 of these have been found to be cannabinoid compounds. Out of the over 60 compounds, we can distinguish these four which have been researched the most and are said to be of most importance: (Pamplona and Takahashi 2012)

These compounds do not exist in these forms in the plant, but rather in their cannabinoid acid form. Upon altering the product (storing, drying, and heating) the acids are decarboxylated to reach the desired form as mentioned in the list above (Atakan 2012). The main psychoactive component of Cannabis sativa L. can be put on the account of d-9-THC. The discovery of the different cannabinoids led to the discovery of the endocannabinoid system by Devane et al. (1992).

Endocannabinoid system

Endocannabinoids are responsible for the regulation of the endocannabinoid system (abbreviated ECS). The ECS is a physiological signalling system taking part in the regulation of lipid and glucose metabolism in all vertebrates. An increased fat storage and imbalance of the metabolism may be consequences of overactivation of the EC system (McPartland et al. 2001). Endocannabinoids are endogenous molecules that bind to a group of G-protein-coupled receptors within which we can find the CB1 and CB2 cannabinoid receptors. The two main endocannabinoids are anandamide, abbreviated AEA, and 2-arachidonoylglycerol, abbreviated 2-AG. They are both derived from arachidonic acid, and they resemble other lipid molecules such as prostaglandins and leukotrienes (de Fonseca et al. 2005).

The CB1 and CB2 receptors that the endocannabinoids react on can be found in different concentrations in different parts of the body. CB1 receptors are predominantly found in distinct parts of the brain like the limbic system, basal ganglia, hippocampus, substantia nigra, and cerebellum. It is not only present in the brain. It is also being found in the peripheral nervous system, bones, uterus, testicular tissue, thyroid, and liver (Atakan 2012). While you may find CB2 receptors in the brain, their main area of prevalence is the immune cells, the gastrointestinal system, and spleen (Pertwee 2006). Upon the activation and release of various neurotransmitters, namely -gamma-aminobutyric acid (GABA), dopamine, serotonin, noradrenaline, acetylcholine, and glutamate, the activation of the CB1 receptors mediates the inhibitory action of the above-mentioned neurotransmitters. Due to this, the endocannabinoids have an effect on various functions ranging from cognition to pain receptors.

In normal conditions, AEA and 2-AG are released from postsynaptic sites to the synaptic clefts as a reaction to elevated intracellular calcium to prevent uncontrolled neural activity. They do this by acting as retrograde neurotransmitters on the CB1 receptors, before being removed from the synaptic cleft by the anandamide membrane transporters and subsequently broken down (Terry et al. 2009). When d-9-THC is involved, it binds to the CB1 receptors as a partial agonist and thereby inhibits the release of neurotransmitters that usually are being modulated by the endocannabinoids. The above explained mechanism can be visualised in Figure 1 below. At the same time, it is said to increase the release of glutamate, acetylcholine, and dopamine in some regions of the brain. The method that is being hypothesized is the inhibition of a molecule, GABA, that usually inhibits the neurons releasing the aforementioned neurotransmitters (Bhattacharyya et al 2009).

Figure shows the EC synaptic transmission. The endocannabinoids: 2-AG and anandamide (AEA) are produced in the post synaptic terminals after neuronal activation. Being lipids, they easily travel across cell membranes to activate the CB1R in the presyanptic terminal. CB1R activation inhibits neurotransmitter realease due to calcium influx suspension. Activation of CB1R in the astorcytes produce glutamate. Left over 2-AG in the synaptic cleft is taken up by the presynaptic terminal to be degraded into arachidonic acid and glycerol. AEA also activates presynaptic CB1Rs. ||Figure 1 Figure shows the EC synaptic transmission. The endocannabinoids: 2-AG and anandamide (AEA) are produced in the post synaptic terminals after neuronal activation. Being lipids, they easily travel across cell membranes to activate the CB1R in the presyanptic terminal. CB1R activation inhibits neurotransmitter realease due to calcium influx suspension. Activation of CB1R in the astorcytes produce glutamate. Left over 2-AG in the synaptic cleft is taken up by the presynaptic terminal to be degraded into arachidonic acid and glycerol. AEA also activates presynaptic CB1Rs. ||

Bee nervous system

A bees nervous system consists of approximately one million neurons and it is presumed that bees are not hardwired. Bees, like all other insects, have a brain, along with a series of neuron ganglia that are present in the chest and abdomen. There are two areas where a sensory nerve synapses with a ganglia, followed by a neuron to the brain. Insects also possess two different types of neurons that are involved in movement, motor neurons and descending pre-motor neurons. Within the brain, there are also multiple interneurons. Compared to other insects, bees have a larger brain, mushroom bodies, which are involved in the integration of many senses, as well as more complex visual systems.

Absence of the endocannabinoid system in bees

The endocannabinoid system (ECS) can be traced back to ancient times, and in mammals exerts a notable neuromodulatory role. To identify whether or not honey bees have an endocannabinoid system the activity of cannabinoid (CB) receptors were investigated by testing the ability or inability of tetrahydrocannabinol (THC) and HU-210, the latter being a synthetic cannabinoid and commonly found in cannabis, to stimulate the activity of the G- proteins in the tissues of the insect with the use of guanosine-5’thio-triphosphate. Although the ECS can be found in most animals, including some invertebrates, research shows a lack of CB receptors in Apis mellifera, thus absence of the endocannabinoid system. This was confirmed by McPartland et al. (2001) as in their study, honey bees, Apis mellifera, did not show proof of any active CB1 or CB2 receptors as they could not detect any anandamide compounds in the honey bees. To further investigate this result, they also put to use genome searches with no success in finding the above functioning receptors in honey bees. A. mellifera were initially used to explore the presence of the endocannabinoid system due to the abundance of neuromodulators and neurotransmitters which, consequently, make them ideal organisms for neurobiological studies. Some neurotransmitters and neuromodulators found in copious amount in honey bees include acetylcholine (Ach), dopamine, bombesin, U0001d6fe-aminobutyric acid (GABA) and noradrenaline, to name a few. Furthermore, due to the plethora of the above mentioned neurotransmitters, one must look into their respective receptor systems which perhaps compromise for the absence of the endocannabinoid system.

Relationship between neonicotinoids, Apis mellifera and Cannabis sativa

Within the central nervous system of insects, including in honeybees, acetylcholine (Ach) is known as the major excitatory neurotransmitter. Honey bees express both neuronal and non- neuronal acetylcholine receptors (AchR). As this neurotransmitter is so abundant in insects, including bees and crop pests alike, many insecticides contain neonicotinoids, synthetically derived from nicotine. Since the cholinergic system of insects differs from that of mammals, who will eat the crops that have been treated with the insecticide, neonicotinoids do not affect vertebrates the way they do insects. While it has great success in the removal of pests from damaging crops, it also negatively affects beneficial pollinators such as the honey bee (Grunewald and Seifert 2019).

With honey bees expressing great amounts of neurotransmitters and neuromodulators studies on the effect of neonicotinoids have been carried out on them. One such study includes that of Grunewald and Siefert (2019). They found that some of the effects of neonicotinoids affect many developmental processes including those independent of neuronal acetylcholine receptors such as gland dysfunction and neuronally causing memory and learning impairments. The effect of neonicotinoids on AChRs in honeybees can be seen in Figure 2. Consequently, this will cause a decrease in honey bee colonies.

The figure shows the functions of acetylecholine on the endocrine system, metabolism and developement duration of honeybees and the effect of neonicotinoids on the whole cycle. Neonicotinoids will alter the gene expression with an increase of juvenile hormone (JH) and because of this will alter the amount of proteins metabolised. This elongates the duration of honey bee development, thus, reducing hypopharyngeal gland (HG) activity and consequently ACh production. Reduced ACh production will affect the endocrine system and the cycle repeats. ||Figure 2 The figure shows the functions of acetylecholine on the endocrine system, metabolism and developement duration of honeybees and the effect of neonicotinoids on the whole cycle. Neonicotinoids will alter the gene expression with an increase of juvenile hormone (JH) and because of this will alter the amount of proteins metabolised. This elongates the duration of honey bee development, thus, reducing hypopharyngeal gland (HG) activity and consequently ACh production. Reduced ACh production will affect the endocrine system and the cycle repeats ||

In a study carried out by John M McPartland and Zahra Sheikh (2018) they investigated the use of Cannabis sativa based pesticide by using the plant as a companion plant. By being a companion plant, it is planted alongside crops that are in need of protection from pests. The cannabis plant contains multiple compounds that exhibit insect repellent behaviour as they have “touch- sensitive” gland heads that release phytocannabinoids and terpenoids that act as physical disenablers of the pests. For this reason, apart from being a good substitute for a pollen source for the honey bees, they are also mostly safe from neonicotinoids as they are already naturally insect repellents.

Conclusion

Honey bees are important pollinators of flowering plants, and although cannabis plants are mostly wind pollinated, honey bees are known to be attracted to the sweet pollen produced by these plants. With pollen being such an important source of nutrients for bees, it is beneficial that cannabis plants flower during the dearth periods of other flowering plants. Cannabis plants produce cannabinoids, which in mammals can be detected by the endocannabinoid system. With bees lacking any form of cannabinoid receptor systems such as the endocannabinoid system, it can be said that the cannabinoids produced by cannabis plants have no effect on bees whatsoever. Additionally, it can be concluded that honey bees benefit off of the Cannabis sativa plant for both nutrition and protection. The honey bee is able to gather pollen for nutrition from the cannabis plant when flowering plants are scarce. In terms of protection the honey bee is safe from neonicotinoids found in insecticides, which are detrimental to their health, commonly added to crops to deter pests.

Reference List

Other Sources

cannabis_bees (last edited 2021-05-08 17:31:18 by 4473E)