Ph.D. in Biology, Murylev A. V.

Perm State Humanitarian Pedagogical University, Russia

SUPERCOOLING POINTS OF APIS MELLIFERA MELLIFERA AND APIS MELLIFERA CARPATHICA

INTRODUCTION

Perm krai marks the northern limit of the natural distribution range of honeybees. Honeybees of the Apis mellifera mellifera L. successfully overwinter in this area and display high degrees of productivity. In the Perm krai Region, the Kama Region population of A. m. mellifera has been recognized [7], distinguished by morphological and ecophysiological characters from other A. m. mellifera populations of Russia. Honeybees of this population have a genetically secured complex of adaptations to northern environmental conditions. In addition to the Perm krai Region population of A. m. mellifera, some beekeepers have started breeding at their apiaries the more peaceful Apis mellifera carpathica. The A. m. carpathica have been brought to the Perm krai Region for this experiment from the Mukachevo Purebreed Bee Nursery, Ukraine. It is known that not all organisms are able to successfully adapt to new ecological and geographical conditions, however, some positive qualities encourage beekeepers to acclimatize separate races of bees outside the borders of their natural habitats. The adaptations of these bees evolved under the conditions of their southern range and are distinguished by some peculiar features. They have a body size smaller than that of the A. m. mellifera, but their proboscis length is slightly longer, allowing them to use a wider range of meliferous plants [2]. Ecological and biological characteristics of bees Carpathian race for them in unusual climatic conditions remain poorly studied.

The cold-hardiness of insects is usually estimated by the supercooling point (SCP), a parameter of proposed by Bakhmet'ev [1]. Crystallization is usually lethal to the insect, because it damages the tissues of its body. In the light of new technical abilities and the emergence of new technologies, the study of the SCP parameter continues also at the current stage of scientific development [4; 5]. It is especially important for characterizing different honeybee subspecies [6].

The purposes of this study were to analyze the resistance to low temperatures in honeybees of the Kama Region population of the A. m. mellifera and those of the A. m. carpathica on individuals of the spring, summer, and autumn generations and the total percentage of water in the body of honeybees during different periods of bee family development.

MATERIALS AND METHODS

The experiments were performed monthly from 2010 to 2013. The materials included bees of the Kama Region population of the A. m. mellifera from the Nizhnesypovskoe Bee Breeding Farm (Uinskoe district, Perm krai) and bees of the A. m. carpathica brought to Perm krai from the Mukachevo Purebreed Bee Nursery, Ukraine.

Instruments and testing methods for the testing of SCP

SCP was measured according to the method proposed by Es'kov [3], in each of the three tagmata (head, thorax, and abdomen). A total of 20 bees of the studied races were used every month. The measurements were taken using a chrome/copel thermocouple fixed on a wooden base. The thermocouple was attached to one of the body parts of bees vaseline, and then placed in the freezer compartment of the refrigerator. The temperature values of SCP were recorded with a Termodat-38M2 device. SCP is determined by measuring the heat released in the course of crystallization, when matter transforms from the liquid to the solid state (fig. 1). Simultaneously, SCP was compared to the total water content in the body of honeybees of different generations.

Testing of water content

The total amount of water in the body was determined as the difference between two results of weighing the bee's body: wet weight and constant weight after drying the specimen at 102°C for 48 hours.

Fig. 1. Supercooling point of insects

RESULTS

Research results showed that the total water content in the body of honeybees changes over the year. With the cessation of flying activity in September or October and gradual advent of the cold period, the water content in the body of bees of the autumn generation decreases by 8 %, leading to a slowdown of metabolic processes. Bee families enter a period of physiological dormancy of development and reproduction. During this period, a decrease in the supercooling point has been recorded (table).

In February, bees display the lowest water content in the body; by this time, the supercooling point also reaches its lowest subzero values. Significant differences in these parameters have been found between the studied races in bees of the autumn generation (t = 4.08, p<0.01). In April, overwintered bees are replaced by young bees of the spring generation.

The young bees display a higher water content in the body and an increase of SCP in the tagmata. During the period of intense growth and accumulation of inactive bees, which start working during the period of principal honey flow, the supercooling point in the tagmata continues growing. Bees of the summer generation emerge, which display the highest water content in the body and the highest values of SCP. These parameters remain high until October, and then decrease again. In bees of the summer generation, differences between the subspecies proved insignificant (t = 2.48, p>0.05). Positive correlation has been observed between the values of SCP and the total water content in the body: the correlation coefficient is 0.84 in the Kama Region bees of the A. m. mellifera and 0.92 in those of the A. m. carpathica.

Dynamics of SCP and water content in the body of bees

of the Apis m. mellifera and Apis m. carpathica

Generation of bees	Apis m. mellifera				Apis m. carpathica
	Water content, %, n = 180	SCP, (Т±m), °С, n = 180			Water content, %	SCP, (Т±m), °С, n = 180
		head	thorax	abdomen		head	thorax	abdomen
Spring	65.67	–7.45± 0.08	–5.67± 0.10	–4.93± 0.02	71.29	–7.01± 0.12	–5.56± 0.12	–5.01± 0.04
Summer	72.42	–4.45± 0.02	–4.56± 0.07	–3.98± 0.08	74.19	–4.42± 0.04	–4.50± 0.01	–4.02± 0.04
Autumn (October-December)	64.31	–7.83± 0.12	–6.68± 0.09	–5.81± 0.09	69.25	–7.12± 0.13	–5.81± 0.08	–5.54± 0.11
Autumn (January-March)	63.22	–10.61± 0.06	–8.25± 0.05	–8.04± 0.07	67.34	–9.74± 0.09	–7.12± 0.12	–7.24± 0.10

Analysis of SCP values recorded in different tagmata of honeybeesshows that in the Kama Region population of the A. m. mellifera the lowest values of SCP in the head were observed in February, reaching -10.61 ± 0.06°C (n = 180), while in the A. m. carpathica the lowest values were observed in March, reaching -9.74 ± 0.09°C (n = 180) (table). The values of SCP in the thorax were higher: in bees of the Kama Region population of the A. m. mellifera they reached ‑8.25 ± 0.05°C (n = 180) in February, and in those of the A. m. carpathica they reached -7.12 ± 0.12°C (n = 180) in March. In the abdomen, the lowest values of SCP in the Kama Region population of the A. m. mellifera were observed in March, reaching -8.04 ± 0.07°C (n = 180); in bees of the A. m. carpathica they were also observed in March, reaching -7.24 ± 0.10°C (n = 180). In addition, it has been noted that at the end of overwintering A. m. carpathica switch to the active state 15 to 20 days earlier than A. m. mellifera ones. Bees of the former race start nurturing their brood already in March, according to their genetic program, although the flying period starts only some 20 days later. A. m. mellifera start nurturing their brood only after the start of their flight. In March they continue to build a winter club.

CONCLUSIONS

The lowest supercooling point values have been recorded in bees with the lowest water content in the body. The water content in the body of bees from the Kama Region population of the A. m. mellifera is lower during the entire annual cycle than in those of the A. m. carpathica. Summer bees had the highest SCP temperature and high water content. It has been shown that A. m. carpathica are less physiologically adapted to long overwintering under low temperatures. In combination with other factors (such as diseases or the duration of the flightless period), these parameters can have an adverse effect on the overwintering of A. m. carpathica in Perm krai.

REFERENCES

1. Bakhmetyev P. (1898) – The temperature of insects. Scientific Review., 5: 1602–1611.

2. Bodnarchuk L. I., Gaidar V. A., Pilipenko V. P. (2008) – Carpathian bee, what are they? Bee J., 2: 1–2.

3. Eskov E. K. (1991) – Methods and techniques of experimental zoology. Ryazan. ped. Inst. Press, Ryazan.

4. Eskov E. K. (2007) – The temperature of maximum supercooling and the state of the fat body of bees. J. Beekeeping., 6: 22–23.

5. Heinrich B. (1993) – The Hot-blooded Insects, Strategies and Mechanisms of Thermoregulation, Springer Press, Heidelberg, Berlin.

6. Murylev A. V., Petukhov A. V. (2011) – The point of crystallization of different parts of the body bee populations Kama. J. Beekeeping, 1: 18–19.

7. Shurakov A. I., Petukhov A. V., Eskov E. K. (1999) – Saving the gene pool of the Central Russian bees, and basic directions of development of beekeeping in the Perm region. Perm. State. ped. University Press, Perm.