Meiotic Karyotypes and Structure of Testes of Nineteen Species of Jumping-lice ( Hemiptera , Psylloidea ) from South Africa

The karyotypes of 19 species of Psylloidea from South Africa belonging to subfamilies Paurocephalinae, Euphyllurinae, Diaphorininae, Euphalerinae, Acizziinae, Ciriacreminae (Psyllidae), Calophyinae (Calophyidae) and Triozinae (Triozidae) were studied for the first time. In 16 species the modal diploid number of chromosomes was found to be 2n=24+X, while 3 species have other chromosome numbers. In Colophorina sp. the chromosomal set consists of 2n=22+X while in Peripsyllopsis speciosa 2n=8+X; the latter being one of the lowest numbers of chromosomes described in psyllids so far. On the other hand, Pauropsylla tricheata is the first species characterized by a chromosomal number higher than the modal one, 2n=26+X. The male gonads of 18 species were described. In 15 of these each testes consisted of two follicles and spermatocystes were arranged in one row. This structure is typical for the majority of psyllid species. Polymorphism in the number of testicular follicles in Calophya shini (2-3 follicles) was revealed. In two species, Trioza carvalhoi and T. thibae, each testis consists of a single follicle with spermatocystes arranged in two rows.

Jumping plant-lice (Psylloidea) currently include nearly 3000 described species (BURCK-HARDT & BASSET 2000) and are distributed in all parts of the world, although mainly in the Oriental region and in the tropics. However, their biogeographical diversity is unequal for all families. The systematics of Psylloidea is still a matter of discussion. The last 20 years have brought numerous papers on the classification of the superfamily based mainly on analyses of characters of larvae and adult insects, geographical distribution and their relationships with host plants (WHITE & HODKIN-SON 1985;HOLLIS 1987aHOLLIS , 1987BURCKHARDT 1987aBURCKHARDT , 1987bBURCKHARDT , 1988BURCKHARDT & LAUTERER 1987BURCKHARDT & MIFSUD 1998;HODKINSON & BIRD 2000;MIFSUD & BURCK-HARDT 2002). However, numerous taxonomic questions and phylogenetic relationships within Psylloidea remain unresolved. Studies of chromosome variation and differences in morphology of the internal male reproductive system are a source of new data which may be useful in clarifying some taxonomic and phylogenetic problems.
In psyllids, karyotypes of 153 species (i.e. approximately 5% of the world fauna of these insects) belonging to 52 genera are known (MARYAÑ- SKA-NADACHOWSKA 2002). Most of the karyological data concern representatives of Psyllidae and Triozidae, whereas Calophyidae, Homotomidae and Carsidaridae have been relatively poorly studied. Species belonging to Phacopteronidae have not been studied at all.
In this paper karyotypes of nineteen species and the testes structure of eighteen species belonging to three families of Psylloidea are described.

Material and Methods
Field collection of the material was carried out in South Africa by E. G£OWACKA. Species belonging to subfamilies Paurocephalinae, Euphyllurinae, Diaphorininae, Euphalerinae, Acizziinae, and Ciriacreminae (all belonging to Psyllidae), Calophyinae (Calophyidae) and Triozinae (Triozidae) were studied. For 19 species data on karyotypes, number of testicular follicles and spermatocyst arrangement inside follicles were obtained (Table 1).
Specimens for karyological and anatomical studies were fixed in an ethanol-glacial acetic acid solution (3:1). For karyological analysis male gonads were extracted from the abdomen, separated and squashed in a drop of 45% acetic acid. Afterwards, cover slips were removed by the dry ice technique (CONGER & FAIRECHILD 1953). Slides were air-dried and stained by a standard Feulgen-Giemsa procedure.
For anatomical studies, complete reproductive organs were dissected and histological slides were prepared according to the method elaborated by G£OWACKA (1975).

Results and Discussion
The karyotypes of nineteen species are described for the first time (Table 1), and for 16 of these, the diploid number of chromosomes is 2n = 24+X. At meiotic first metaphases (MI) 12 autosomes and the X univalent are visible. Chromosomes of the set gradually decrease in size in every species ( Fig. 1b- (Fig. 1a), and in Peripsyllopsis speciosa (Diaphorininae), 2n=8+X ( Fig. 1g & h). In Pauropsylla tricheata (Triozinae) the chromosomal set is higher, 2n=26+X. In this species autosomes formed 13 bivalents and a small X univalent at MI (Fig. 1f). The chromosomal number 2n=24+X is the most common and described in the majority (95%) of 153 studied species. This is the modal and probably ancestral number for the whole superfamily Psylloidea. The occurrence of different chromosomal numbers at various taxonomic levels in psyllids is mainly the result of autosomal fusions, e.g. in species of the genera Psyllopsis, Baeopelma fo-ersteri, Craspedolepta bulgarica, Trioza remota, T. ilicina etc., or fusion of autosomes and sex chromosomes (for details see Table 1 in MARYAÑSKA-NADACHOWSKA 2002). Fusions of both types reduce the numbers of chromosomes in the karyotypes, but only the latter fusion leads to a change in the chromosomal type of sex determination XO to the neo-XY, e.g. in Cacopsylla mali and C. sorbi (GROZEVA& MARYAÑSKA-NADACHOWSKA1995).
A reduction of number of chromosomes is also observed in Colophorina sp. n. (2n=22+X) and Peripsyllopsis speciosa (2n=8+X). Especially interesting is Peripsyllopsis speciosa which shows one of the lowest chromosomal numbers described so far in psyllids. Karyotypes with a low number of Karyotypes  Pauropsylla tricheata (Triozinae) is the first species in Psylloidea that is characterized by a karyotype consisting of 13 pairs of autosomes creating a row gradually (not significantly) decreasing in size, and also the X univalent. The X chromosome is one of the smallest elements of the set (Fig. 1f). The chromosome number 2n=27 can be explained by the fission of one pair of autosomes in the modal karyotype (2n=25). More chromosomes than 2n=25 have been described only in two species, Pachypsylla celtidismamma and P. celtidisvisiculum (2n=26+X), by WALTON (1960). According to more recent studies both cases appear to be an example of karyotype polymorphism. For these two species RIEMAN (1966) and MARYAÑSKA-NADACHOWSKA and YANG (1997) described the basic karyotype 2n=24+X. In Psylloidea the presence of karyotypes with higher numbers of chromosomes than the modal are clearly rare. Mainly fusions play a role in chromosomal rearrangements and changes of karyotypes in psyllids.
The number of seminal follicles has been described for 176 psyllid species; the number in one A. MARYAÑSKA-NADACHOWSKA, E. G£OWACKA testis varies from one to five, up to eight in case of polymerization. In 141 of these, the arrangement of spermatocysts inside each follicle is known. Two follicles with one row of spermatocysts prevail in most species (G£OWACKA et al. 1995;G£OWACKA & MARYAÑSKA-NADACHOWSKA 1997;MARYAÑSKA-NADACHOWSKA & G£OWACKA 1998;MARYAÑSKA-NADACHOWSKA et al. 2001a, 2001bKUZNETSOVA et al. 1997). Table 1 presents new data on the structure of testes in males of 18 species of Psylloidea. In 15 species each testis consists of two follicles (Fig. 2) placed symmetrically on both sides of the abdomen. Spermatocysts inside testicular follicles are arranged in one row (Fig. 3). In Calophya schini polymorphism in number of follicles was found (2 and 3 follicles). In Trioza carvalhoi and Trioza thibae each testis consists of a single follicle (Fig. 4). Such oligomerization in representatives of Triozidae is described for the first time. Spermatocysts inside follicles are arranged in two rows (Fig. 5), which has been found only in one species of Trioza sp. from Cuba, however its testes consist of two follicles (G£OWACKA et al. 1995). One follicle in one testis was described in species belonging to subfamilies Rhinocolinae, Spondyliaspidinae and Carsidarinae and is typical for these taxa. On the other hand the arrangement of spermatocysts inside follicles is different and specific for each mentioned subfamily (G£OWACKA et al. 1995;MARYAÑSKA-NADA-CHOWSKA et al. 2001a). The sufamilies Rhinocolinae and Spondyliaspidinae, beside oligomerization of testicular follicles, are characterized by karyotypes with low numbers of chromosomes 2n=11,13 and 2n=7, 9, 13 (one species 2n=20), respectively.