Gynaephora (rossii) lugens - a parthenogenetic species?

Vladimir V. Dubatolov

Siberian Zoological Museum, Institute of Animal Systematics and Ecology, Frunze street, 11, Novosibirsk 91, 630091, Russia.

Abstract: During field observations in a mountainous area of Eastern Yakutia and a tundra area of Western Chukotka in North Asia the author found that virgin females of Gynaephora (rossii) lugens can lay unfertilized eggs from which caterpillars appear. This observation is discussed.

Gynaephora lugens was described by I. Kozhantschikov (1950) as a bisexual Palaearctic species, a vicariant of the American Gynaephora rossii Curtis, 1835. Both range in Polar regions and high mountains of northern Asia and North America. In Asia G. lugens was recorded in the tundra zone from the North Ural Mountains and Yamal Peninsula in the west to the Chukotka Peninsula in the east. In the south it is distributed only in mountainous areas of Eastern and Southern Yakutia, northern regions of the Amur Province, the Magadan Province (the upper Kolyma River) and Kamchatka Peninsula. G. rossii was also recorded from Asia, namely from the East Sayan Mountains (G. rossii relicta O. Bang-Haas, 1927) and from the mountains of the Japanese island of Hokkaido (G. rossii daisetsuzana Matsumura, 1928).

The systematic position of G. lugens is still in question. By the wing pattern and genitalial morphology there are no significant differences between G. lugens and G. rossii, and they seem not to be bona fide species.

On an expedition to East Yakutia in June, 27, 1985 in a mountain area of the Suntar-Khayata Range, East Khandyga River headwaters, approximately 180 km ENE of Khandyga settlement, I found a cocoon of a Gynaephora species on a branch top of a Pinus pumila bush. This cocoon was placed in a glass vessel closed by gauze; a day later a female of G. lugens emerged from it. The specimen was left in this gauze-closed vessel for later collecting of males attracted by the female. Unexpectedly, a week later, on July, 5, I found that this virgin female had laid several tens of unfertilized eggs. Sixteen days later, on June 21, I found 43 young larvae hatched from almost all of these eggs. The larvae were fully viable and ate leaves of low shrub willows. After I left Yakutia, they were successfully fed in Novosibirsk on the leaves of Rosa, Rubus and Taraxacum; they ate the leaves of Spiraea less readily. Only 11.6% of them died during the summer season. The caterpillars underwent three moults: on July 31, August 11-14 and August 29-31. Unfortunately, due to poor overwintering conditions in a refrigerator they all died. This information was published in Russian only (Dubatolov and Vasilenko 1988).

The next year, 1986, on an expedition to West Chukotka, on July 25 I found a larva of G. lugens on a low shrub willow in the surroundings of Nature Station of the Institute of Biological Problems of the North (Magadan), that is located in North-Western Chukotka, near the delta of the Chaun River (100 km S of Pevek city). Then I left Chukotka to collect insects in Southern Primorye territory, 60 km SW from Vladivostok. The caterpillar was reared to a cocoon made in August 23. On September 9 a female of G. lugens appeared from this cocoon. The story above was repeated in detail. This unmated female laid eggs from which caterpillars appeared. They also ate leaves of willows. Unfortunately, again I failed to lead them through overwintering.

In spite of the failures to rear parthenogenetically produced larvae, the facts remain that in both cases virgin females laid eggs, in both cases caterpillars appeared from these unfertilized eggs, and in both cases caterpillars were fully viable during the whole summer period. From these observations I conclude that G. lugens is capable of multiplication by means of facultative parthenogenesis. It should be noted that males of this species are well known. I think that facultative parthenogenesis probably allows multiplication under conditions of prolonged bad weather frequent in the Extreme North and in highlands.

Mr. Dean Morewood (Canada), who has great experience in breeding G. rossii and G. groenlandica (Wocke, 1874), tells me (in litt.) that unfertilized females of these species are unable to lay viable eggs from which larvae could hatch.

My two females originated from very remote sites in the Palaearctic region, and the ability for facultative parthenogenesis therefore may be ascribed with a high degree of confidence to all Asian moths of the species. Perhaps this is the only species peculiarity of the Palaearctic G. lugens, if it is really a species distinct from G. rossii.

In Lepidoptera the female sex is heterogametic, allowing a judgement as to whether or not meiosis takes place during parthenogenesis. If it does not, all the progeny would be identical to the mother, i.e. females. If meiosis, followed by a mechanism supporting diploidy, does occur then it would result in equal numbers of ZZ and WW ovulae. One class would not be viable, the other would result in males only. So it would be extremely interesting to rear the progeny to the adult stage. A preliminary supposition can be put forward that meiosis does not occur, because the opposite case would result in half sterile eggs, while in our case all eggs seem to be fertile. On the other hand, lack of meiosis would probably be associated with an obligate rather than facultative parthenogenesis. The solution to this problem is a matter for further research.

Acknowledgements

I am very grateful to Mr. D. Morewood and Dr. O. Kosterin for useful discussion of the problem and to the latter for help in translating the paper.

References

Dubatolov, V. V. and Vasilenko, S. V. 1988. [Some new and little-known Lepidoptera (Macrolepidoptera) from Yakutia]. pp. 60-88 in Nasekomye lugovo-tayozhnykh biotsenozov Yakutii [Insects of a field-taiga biocenoses of Yakutia]. Yakutsk. (In Russian).

Kozhantschikov, I. V. 1950. Orgyidae - Lepidoptera. Fauna SSSR XII, No. 42. Moscow-Leningrad. 583 pp. (in Russian).