Steatococcus samaraius Morrison, 1927

Gavrilov-Zimin, Ilya A., 2020, Chromosomal and reproductive features of some Oriental and Australasian scale insects (Homoptera, Coccinea), Comparative Cytogenetics 14 (3), pp. 339-352 : 339

Steatococcus samaraius Morrison, 1927 Figs 1a , 2

Material.

K 922, Indonesia, Sulawesi, vicinity of Kendari, on twigs of undetermined bush, 10.XI.2011, I.A. Gavrilov-Zimin. K 1071, Malaysia, Borneo, Damai Peninsula, on inflorescences of palm tree (probably Areca catechu Linnaeus, 1753), 14.I.2013, I.A. Gavrilov-Zimin.

New data.

2n = 4; hermaphroditism: the studied female-like ultimolarvae contain sperm bundles in the ovo-testicles. Early stages of embryogenesis (before anatrepsis) occur inside of ovary; then the eggs are laid in the marsupium, where the embryogenesis ends. Hermaphroditic reproductive system is generally similar to the usual female system in bisexual species of scale insects, but contains testicular parts, located between numerous ovarioles (Fig. 2 ).

Comments.

Hermaphroditism is an exceptionally rare phenomenon in Insecta (see, for example, Royer 1975). Up to now hermaphroditic species are known for sure only in the scale insect tribe Iceryini ( Margarodidae : Monophlebinae ) ( Hughes-Schrader 1948, Gavrilov 2007, Gavrilov-Zimin 2018a). Previously, the presence of ovo-testicles in female-like diploid insects has been shown for Icerya bimaculata De Lotto, 1959 (Hughes-Shrader 1963), I. multicicatrices (Kondo & Unruh, 2009) ( Gavrilov-Zimin 2018a: 27, 190) and I. purchasi Maskell, 1879 (Schrader and Hughes-Schrader 1926, Royer 1975). Closely related genus Steatococcus Ferris, 1921 (18 species), which differs from Icerya Signoret, 1876 (45 species) by the presence of peculiar marsupium, was previously almost unstudied in respect of cytogenetics and reproductive biology, excluding the only American species, S. tuberculatus Morrison, 1941. This species was investigated by Hughes-Schrader and Ris (1941) who found that it had 2n = 4 and reproduced bisexually with the appearance of haploid males via facultative parthenogenesis. Here, another species of the genus, S. samaraius , a widely distributed Oriental and Australasian pest, was studied and the same chromosome number, 2n = 4, was discovered. However, males were totally absent in any populations of S. samaraius , inspected by me in the different countries of the Oriental region and seem to have never been reported in the literature. The preparation of the mature females and larvae expectedly revealed a hermaphroditic condition of the reproductive system of S. samaraius . Such a combination of hermaphroditism and haplo-diploidy in closely related species of one genus and even in different populations of the species (as is the case of Icerya purchasi ; Schrader & Hughes-Schrader 1926) is a peculiar feature of the tribe Iceryini (Hughes-Shrader, 1963, Gavrilov-Zimin 2018a). Some authors ( Unruh and Gullan 2007) do not consider Steatococcus as a separate genus and place its species either in the genus Icerya or in another related genus Crypticerya Cockerell, 1895. However, such approach leads to the total overlapping of the generic diagnostic characters and to the practical impossibility of assigning newly described species to a certain genus (see Gavrilov-Zimin 2018a: 174, 184, Gavrilov-Zimin and Stekolshikov 2018).

Figures

Figure 1. Embryonic cells and chromosomes of the studied species (Margarodidae, Pseudococcidae, Eriococcidae). a Steatococcus samaraius (2 n = 4) b Antonina parazonata (2 n = 30) c A. vietnamensis (2 n = 20) d Mollicoccus guadalcanalanus (2 n = 10) e Acanthococcus prope onukii (2 n = 16) f, g Gossypariella siamensis (2 n = 16). g Shows interphase cells of male embryos with a Lecanoid heterochromatinization of the paternal set of chromosomes (arrowed in each cell). Scale bars: 10 µm.

Figure 2. General anatomy of the female (or female-like hermaphrodite in Steatococcus samaraius) reproductive system in the studied species (Margarodidae, Pseudococcidae, Eriococcidae).