Tetranychus

André, H. M. & Van Impe, G., 2012, The Missing Stase In Spider Mites (Acari: Tetranychidae): When The Adult Is Not The Imago, Acarologia 52 (1), pp. 3-16 : 12

Paedogenesis in Tetranychus and actinotrichid mites

Identifying the last stase in Tetranychus as a tritonymph implies that it is paedogenetic. Is this acceptable? Paedogenesis in actinotrichid mites has been reported in various groups, in Podapolipidae by Volkonsky (1940), Pyemotidae by Rack (1972), Tenuipalpidae by Baker (1979) and Cheyletidae by Atyeo et al. (1984). The penultimate case is of special interest as Tenuipalpidae are part of Tetranychoidea. The missing link is however provided by Ochoa (1989) who reported paedogenetic tritonymphs coexisting with imaginal females in Tuckerella knorri . This particular ontogeny is summarized in Fig. 1G and links ontogenies A (usually observed in Tuckerellidae, Beard and Walter, 2005 ) and H (that of T. urticae ). A second intermediate case is provided by Tuckerella saetula and T. cf. pavoniformis in which the male directly emerges from the deutonymph (Beard and Ochoa, 2010).

In the context of the stase theory, Hammen (1975) called alassostasy the variations in the number of stases and the process of loosing a stase during the ontogeny was named meristasy by AndrØ (1988). The ontogeny in Tetranychidae is thus characterized by the meristasy of the imaginal stase.

Figures

FIGURE 1: Ontogeny in Tetranychoidea (A – H) and other mites (I – J). A – Plesiomorphic ontogeny observed in Tuckerellidae; B – Tetranychidae (traditional interpretation – hypothesis Ho); C – multiple protelattosis in Tetranychidae (hypothesis Hm); D-E-F – metelattosis in Tetranychidae (intervening calyptostasis, hypothesis Hi); G – Tuckerellidae with a paedomorphic tritonymph; H – progenesis in Tetranychidae (hypothesis Hp); I – three calyptostasic nymphs in Ereynetidae (Speleognathinae); J – only four active stases in Astigmata (Psoroptidae). Im: imago; TN: tritonymph; DN: deutonymph; PN: protonymph; Lv: larva; PL: prelarva. Close square: active homostase; Open circle: calyptostase; P: paedomorphic tritonymph; *: reproductive system.