Reproductive success of Varroa jacobsoni in brood of its original host, Apis cerana, in comparison to that of its new host, A. mellifera (Hymenoptera: Apidae)

Abstract

Reproduction of Varroa jacobsoni Oudemans has been extensively studied in colonies of the mite's recently acquired host, Apis mellifera Linnaeus. However, data on reproduction in colonies of its original host, A. cerana Fabricius, are still fragmentary. In order to compare reproductive success in naturally infested brood cells of A. cerana and A. mellifera, freshly capped worker and drone cells (0-5 h after capping) were marked and opened 9 days later. When one or more foundress Varroa mites were found, the number and stage of the offspring were recorded. In colonies of A. cerana, V. jacobsoni reproduced almost exclusively in drone cells. Surprisingly, however, these drone cells proved to be better suited for reproduction than drone (and worker) cells of A. mellifera. Firstly, in drone cells of A. cerana, 97-100% of the mites produced daughters and 98-99% of these mites also produced a son. In drone and worker cells of A. mellifera only 70-80% produced daughters and only 74-86% of these mites produced a son. Secondly, if a mite produced daughters, she produced more daughters in drone cells of A. cerana than in drone cells of A. mellifera: 4.5-4.6 vs 2.9-3.7 daughters per mite, respectively. Finally, infestation by two foundress females negatively affected reproduction per mite in drone cells of A. mellifera, but not in drone cells of A. cerana. Thus, V. jacobsoni seems to be better adapted to A. cerana than to A. mellifera, although population growth of mites in A. mellifera colonies is higher due to the exploitation of worker cells besides drone cells.

Number and position of wounds on honey bee (Apis mellifera) pupae infested with a single Varroa mite

“…If suffering from varroatosis, they are often co-infected with virus (Martin, 1998). In the original host, the Asian A. cerana, female Varroa mites invade worker brood but reproduce exclusively in drone brood (Koeniger et al, 1981;Tewarson et al, 1982;Boot et al, 1997). Why in A. mellifera colonies Varroa mites are also able to reproduce in worker brood is unknown (Garrido et al, 2001).…”

“…If the adult bee does not emerge from its cell, the mites are trapped in the sealed brood cell, as is observed in heavily infested drone brood of A. cerana (Boecking, 1999). Limited exploitation and minimum damage to the host will therefore increase the fitness of the Varroa female as it does not adversely affect the mite's reproductive potential (Boot et al, 1997). Such factors may have shaped the behaviour of this successful honey bee parasite.…”

Relating individual behaviour to population dynamics

“…However, the maximum populations in the simulation do fall short of the 800 mites seen in some real colonies and predicted by some other models of mite reproduction (Fries et al 1994;Martin 1997b). Such large populations of mites could be produced in our simulations if we increased b. example, b 4 has been observed as the successful reproduction rate of mites (Boot et al 1997). This estimate for b would give K 230:2 in a large colony and, after breeding, populations of over 1000.…”

Selecting honeybees for worker brood that reduces the reproduction of Varroa destructor

“…Patterns of reproduction of mites in brood of different species and types of honeybees suggest a genetic component in the host that could possibly be used in breeding. In their original host Apis cerana , two closely related mites, Varroa jacobsoni and V. destructor (Anderson and Trueman 2000), reproduce in drone brood but are largely infertile in worker brood (Koeniger et al 1981;De Jong 1988;Anderson 1994;Boot et al 1997). In contrast, V. jacobsoni did not reproduce in either worker or drone brood of A. mellifera (Anderson 1994), while V. destructor is generally highly reproductive in brood of both sexes in this new host.…”