Karyotypes of Some Members of the Grasshopper Families Lentulidae and Charilaidae

184 Karyotypes of Some Members of the Grasshopper Families Lentulidae and Charilaidae M. J. D. White Department of Genetics, University of Melbourne, Australia Received June 7, 1966 Introduction The Lentulidae are a family of peculiar wingless South and East African grasshoppers. Dirsh (1956) stated that "In the structure of the phallic complex, the Lentulidae have more chraracters in common with the Pyrgomorphidae than with any other Acridoid family". But "the external characters of these two families, however, are very different" and (Dirsh 1961) "it is not possible to relate this family (i .e. the Lentulidae) to any other known family". The Charilaidae is another small family of South African grasshoppers, including three genera. It has been supposed to be related to the Pamphagidae, but Dirsh (1961) notes some pronounced differences in the phallic complex. The Charilaidae have one external feature which is unique among grasshoppers, a double median pronotal carina. Because of uncertainties as to the relationships of these families, it seems desirable to place on record some observations on their chromosome cytology. Materials and methods The species studied, and the localities of collection, were as follows: Lentulidae Mecostibus cf. nyassae Uv. 1 mi. E of Tshipise, Northern Transvaal Shelfordites nanus Uv. 4mi. E of Windsorton Road, Cape Province; 22mi. N of Kimberley, Cape Province; 24mi. INTof De Aar, Cape Province; 17mi. SE of Hopetown, Cape Province; 12mi. N. of Aberdeen, Cape Province: Middelburg, Cape Province Syrgus sp. near rehni Dirsh The Downs, 16mi. W of Ofcalaco, Transvaal Paralentula? marcida Rehn 2mi. NE of Bandolierkop, Transvaal P. prasinata Rehn 30mi. E of Louis Trichardt, Transvaal Karruia paradoxa Rehn 18mi. NW of Aberdeen, Cape Province; 15 mi. S of Aberdeen, Cape Province Lentula callani Dirsh 24mi. SW of Middelburg, Cape Province Lentula n. sp. 5mi. NE of Haenertsburg, Transvaal Basutacris n. sp. cf. minuta 6mi. NE of Haenertsburg, Transvaal B. n. sp. 5mi. N E of Kaapsehoop, Transvaal Eremidium denticercus Dirsh 30mi. E of Louis Trichardt, Transvaal Karruacris browni Dirsh 5mi. SE of Hopetown, Cape Province, 16mi. SW of Murraysburg, Cape Province; 32mi. NW of Aberdeen, Cape Province; 15mi. S of Aberdeen, Cape Province; 4mi. N of Miller 1967 Karyotypes of Some Members of the Grasshopper 185 Station, Cape Province; 1mi. E of Miller Station, Cape Province; 9mi. E. of Miller Station, Cape Province; 9mi. W of Klipplaat, Cape Province; 6mi. E of Klipplaat, Cape Province; Middelburg, Cape Province Charilaidae Charilaus carinatus Stal 10 mi. NE of Nylstroom, Transvaal For most of these species aceto-orcein squashes of testis material were used, but for some testicular material was sectioned and stained with crystal violet. Karyotypes The basic karyotype in the Lentulidae seems to be 2n•‰=23 acrocentrics, as in the Acrididae. This is the situation in the species of Mecostibus, Paralentula, Karruia, Lentula, Basutacris and Eremidium which have been examined. Certain species such as Lentula callani (Fig. 1c) and Basutacris n. sp. cf. minuta have three of the autosomal elements very minute; but this disparity in size is less marked in the other species and Mecostibus sp. has no really small autosomes (Fig. Id). Fig. 1. Male first metaphases of various species of Lentulidae. a, Karruia paradoxa Rehn, b, Shelfordites nanus Uvarov. c, Lentula callani Dirsh. d, Mecostibus cf. nyassae Uvarov. Three species showed chromosome numbers which deviated from 2n•‰=23. Two individuals of Syrgus sp. near rehni apparently each possessed a small supernumerary chromosome in addition to the usual 23-chromosome karyotype; the 186 M. J. D. White Cytologia 32 interpretation is somewhat uncertain, however, since these were the only two individuals available for examination. No polymorphism for pericentric inversions was encountered in any of the Lentulidae examined. Shelfordites nanus has 2n•‰=21 acrocentrics instead of the usual 2n=23. Presumably one of the small chromosomal elements has been 'lost' by fusion. But there is no metacentric or J-shaped element, so that we cannot say for certain what has happened. Karruacris browni is an interesting species, which has two races, one with 2n•‰=20, the other with 2n•‰=19. Both races have one autosome J-shaped (no doubt as a result of a fusion for which the species is homozygous). The 'northern race', collected in the Karoo at localities near Hopetown, Middelburg, Murraysburg and Aberdeen, has an XY mechanism in the male (Fig. 2a), the original X having fused with an autosome of moderate length. The neo-X so formed, and the unfused autosome (=neo-Y) are invariably associated by a single terminalized chiasma at first metaphase. Fig. 2. Male first metaphases of Karruacris browni Dirsh . a, the XY race (15 miles S of Aberdeen). b, the X1X2Y race (4 miles N of Miller Station). m, the metacentric autosome . In the 'southern race' which was found at the following localities: 4 miles N of Miller Station, 1 mile E of Miller Station, 9 miles E of Miller Station and 9 miles W of Klipplaat, a further fusion, but in this case a Y-autosome one, has occurred. This has converted the XY mechanism of the northern race into an X1X2Y one (Fig. 2b). The autosome which underwent fusion to the Y was one of the smaller ones. The X1X2Ytrivalent which is found at first metaphase in the male resembles those seen in the North American grasshoppers Paratylotropidia brunneri and P. morsei (King and Beams 1938, White 1953) and the South American species Scotussa daguerrei, Eurotettix lilloanus, and Dichroplus dubius (Mesa 1962, 1963, Mesa and Mesa 1967). The distribution of the two races in the southern Karoo, is shown in Figure 3. The species is associated with spiny Lycium bushes and other Karroo shrubs (Rhigozium obovatum, Penzia incana, Erioeephalus spinescens etc.). Presumably there exists a zone of overlap between the two races some 1967 Karyotypes of Some Members of the Grasshopper 187 where to the north of Miller Station and Klipplaat, in which two kinds of males coexist. The females in such populations would, of course, be all of one type. Charilaus carinatus has 2n•‰=23 acrocentrics, the X-chromo some being one of the middle sized chromo Fig. 3. Map of a portion of the Karroo region, South Africa, showing the location of some XY and X1X2Y colonies of Karruacris somes. The browni. The range of the XY race extends far to the north of the smaller biva map, to the vicinity of Middelburg and Hopetown. Records of the lents show a XY race indicated by black dots, records of the X1X2Y race shown by hollow circles. single chiasma, the larger ones one or two. The karyotype thus does not diverge in any way from the typical one found in the Acrididae. In particular, there is no resemblance to the karyotype found in the Pamphagidae where all the genera that have been investigated (including the South African genera Lamarckiana, Hoplolopha, Batrachotettix, Transvaaliana and Thrincotropis) have 2n•‰=19 acrocentrics. Discussion It is now clear that the families Acrididae, Lentulidae, Pauliniidae, Charilaidae, Trigonopterygidae, Xyronotidae and Pneumoridae share a 'typical' karyotype of 2n•‰=23 acrocentrics. In all the larger families some species show lower chromosome numbers, as a result of centric fusions that have established themselves in phylogeny. Less frequently we do find species in which one or more chromoso mes have become metacentric as a result of pericentric inversions. The South American Ommexechidae seem, in general, to have 2n•‰=23, with one chromosome J-shaped (Mesa 1963b); but even here some genera have all the chromosomes acrocentric (Mesa 1964). In the case of the Trigonopterygidae, Xyron otidae and Pneumoridae, all we know of the karyotypes is a bare mention of the 188 M. J. D. White Cytologia 32 chromosome numbers of single species by Helwig (1958). The uniformity of the karyotypes within this complex of families is an extreme example of cytotaxonomic conservatism in view of the great diversity in gross morphology. Contrasting sharply with the above families of grasshoppers we have the Pyrgomorphidae and Pamphagidae, with a typical number of 2n_??_=19 acrocen trics. It seems probable that these families were derived from the 23-chromosome stock by 'loss' of two chromosome pairs. Such loss probably occurred by two fus ions, followed by pericentric inversions which re-converted J-shaped chromosomes to acrocentrics once more. Morphologically aberrant Pyrgomorphidae (e. g. the Australian Psednura and Pyopsednura and the West African Chapmanacris) have the typical 2n= _??_19, but a number of South African species in the genus Pyrgomorpha or closely related to it have lower chromosome numbers, as a result of fusions. The diversity of karyotypes is much greater in the Eumastacidae than in the families previously mentioned (Helwig in Rehn 1948, White 1956, 1965, 1966, White and Cheney 1966, White, Blackith, Blackith and Cheney 1966). In part this may reflect the rather heterogeneous nature of the 'subfamilies' of Eumastacidae, some of which may be regarded as families in the future. But considerable karyotype diversity is also found within the single subfamily Morabinae, where the chromo some numbers (2n •‰) range from 21 down to 13, as a result of fusions, and where numerous XY and X1X2Y species occur. Biologically, the South African Len tulidae resemble the Australian Morabinae in being entirely wingless and in their population structure (small local colonies, due no doubt to specialized feeding habits). Many species of Morabinae are polymorphic for pericentric inversions and still more have karyotypes which prove that pericentric inversions have reached fi xation in their past history. Thus, by comparison with the Morabinae, the Lentulidae seem karyotypically conservative and rather uniform, although Karruacris browni is certainly exceptional. Acknowledgements The South African species dealt with in this paper were collected in 1963 when the author was working temporarily in the Zoology Department of Witwatersrand University.

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