A contribution to the taxonomy, cytogenetics and reproductive biology of the genus Aclerda Signoret (Homoptera, Coccinea, Aclerdidae)
Author
Gavrilov-Zimin, I. A.
text
Comparative Cytogenetics
2012
4
389
395
http://dx.doi.org/10.3897/compcytogen.v6i4.4320
journal article
http://dx.doi.org/10.3897/compcytogen.v6i4.4320
1993-078X-4-389
Aclerda pseudozoysiae
sp. n.
Fig. 1
Adult female.
Body elongate oval, up to 7 mm long, slightly curved. Antennae small, 1-segmented, with several setae. Eyes and legs absent. Spiracles in two pairs; each with large and nearly circular and heavy sclerotized peritrema, covered by numerous quinquelocular pores. Posterior end of body heavily sclerotized on both surfaces even in very young females, abruptly narrowed and acutely pointed, ridged. Anal cleft short, about the same length as anal plate. Form of anal plate shown on the enlargement of Fig. 1. In general, the structure of anal complex is poorly visible because of heavy sclerotization of anal region of body, but it looks like anal complex in other species of the genus. Tubular ducts of 3 sizes: large tubular ducts about 18
µm
long; medium
-
sized ducts about 10
µm
long; and microtubular ducts about 7-8
µm
long. All 3 types of ducts form ventral submarginal band as shown in Fig. 1. Microtubular ducts form also a group near labium. Quinquelocular pores form small groups near spiracles (with about 10-20 pores in each group). Dorsal invaginated setae (about 12-15
µm
long) arranged along submarginal area of abdomen.
Figure 1.
Aclerda pseudozoysiae
sp. n., holotype.
Taxonomic notes.
The large and widely distributed genus
Aclerda
was comprehensively revised by
McConnell (1953)
. After this review no new
Aclerda
species have been described from Australasian or Indomalasian regions and in view of this I consider the
McConnell'
s identification key as correct until now. Based on
McConnell'skey
, figures and descriptions,
Aclerda pseudozoysiae
sp. n. is similar to
Aclerda zoysiae
McConnell, 1953 which was described from the Philippine Islands, but differs in the presence of 3 types of tubular ducts which are all located on the ventrum only in contrast to
Aclerda zoysiae
having two types of ducts only (microtubular and macrotubular) distributed on both surfaces of the body.
Material.
Holotype: female, K 884, vicinity of Jayapura, under the leaf sheath of undetermined grass (
Poaceae
), 1.XI. 2011, specimen in a black circle. Paratypes: 1 female on the same slide; 3 females on other slides and series of unmounted females and larvae in acet-ethanol; all with the same collecting data as holotype.
Etymology.
The species name
"pseudozoysiae"
is composed of pseudo (false) and
"zoysiae"
, and is intended to show its similarity to the related species,
Aclerda zoysiae
.
Cytogenetics and reproductive biology
Both species are ovoviviparous; all stages of embryonic development occur inside the
mother's
body. In view of the absence of any notes on ovisacs in other species of
Aclerda
in the coccidological literature, I suppose that the genus as a whole is ovoviviparous.
Both species have a spermatheca, attached medially between two lateral oviducts (Fig. 2).
Figure 2. Schematic drawing of oviducts and spermatheca of studied
Aclerda
spp.
Unexpectedly, the mode of reproduction is found to be absolutely different in these two species.
Aclerda pseudozoysiae
has bisexual reproduction, with the presence of male stages of the life cycle in the analyzed population. The studied male ultimonymphs contained bundles of sperms in their testicles (Fig. 3). Specimens with meiotic divisions were not collected. Male larvae and nymphs, and about 50% of the embryos inside each of the four dissected adult females demonstrated a heterochromatinization of one haploid set of chromosomes (Fig. 4), that is common for the majority of cytogenetically studied groups of the superfamily
Coccoidea
(see, for example, the review of
Gavrilov 2007
). According to the special experimental studies, elaborated on different genera of
Coccoidea
(see
Brown and Nelson-Rees 1961
) the presence of heterochromatinized haploid set characterizes male developmental stages only and moreover, the heterochromatinized set is usually of the paternal origin. Based on this heterochromatinization,
Aclerda pseudozoysiae
is suggested to have either a Lecanoid or a Comstockioid genetic system,
these
systems being difficult to distinguish without special analysis of male meiosis (see, for example,
Nur 1980
). The diploid karyotype of
Aclerda pseudozoysiae
includes 16 chromosomes forming gradual size series (Fig. 5).
On the contrary, in the studied population of
Aclerda takahashii
, no male stages of the life cycle were found and adult females did not have sperms and their spermathecae and oviducts. So, the species demonstrates a parthenogenetic form of reproduction. The diploid chromosomal number of
Aclerda takahashii
was found to be 18 (Fig. 6, 7) with chromosomes forming more or less gradual size series. Some of the cells showed a nucleolus located at the end of one of the longer chromosomes (Fig. 7) (the localization of NORs in scale insects was discussed earlier by
Gavrilov and Trapeznikova 2007
). The heterochromatinization of one haploid set of chromosomes was not found in any of about 150 studied embryos from 4 females and, so, theoretically, all these embryos must be female embryos. However, only about 50 % of the embryos inside each studied female were diploid, and the others demonstrated haploid number (n=9) of chromosomes in each of the cells (Fig. 8). This sudden form of parthenogenesis seems to be unknown in scale insects. Usual haplo-diploidy is inherent in different species of
Iceryini
scale insects (superfamily
Orthezioidea
), but diploid progeny are characteristically produced by fertilized
Iceryini
females only (Hughes-Schrader 1948). In the superfamily
Coccoidea
, parthenogenesis with different ways of diploidy restoration is known in different families, but in all studied cases of deuterotoky and arrhenotoky, haploid embryos are not produced, diploidy is restored in all embryos and the heterochromatinization of one haploid set of chromosomes marks male embryos (
Nur 1971
,
1980
). Probably, in
Aclerda takahashii
the parthenogenetic diploidy re
storation
takes place in a part of embryos only. The question whether haploid embryos are able to produce viable males/ females can not be answered without additional observations in the field and laboratory experiments.
Figures 3-8. 3-5
Aclerda pseudozoysiae
sp. n.: 3 bundles of sperms, 4 heterochromatinization of one haploid set of chromosomes (black bodies inside the cells), 5 karyotype 6-8
Aclerda takahashii
: 6 diploid karyotype, 7 diploid karyotype with nucleolus (arrowed) 8 haploid karyotype. Bar = 10
µm
.