Rev. Brasil. Genet. 12,4, 747-759 (1989) (Brazil. J. Genetics) NOTES ON THE ECOLOGY AND KARYOTYPIC DESCRIPTION OF Strobilurus torquatus (SAURIA, IGUANIDAE) Miguel Trefaut Rodrigues! , Yatiyo Yonenaga-Yassuda? and Sanae Kasahara' ABSTRACT A relatively dense population of Strobilurus torquatus was found at Sao Jose, near Itabuna, State of Bahia, in the Atlantic forest of Brazil. This apparently rare lizard is a forest heliophile and ant specialist that forages at several levels on the trunks of large trees and occasionally on or near the ground. Sexual dimorphism is apparent in snout-to-vent and tibia length, males being larger and having a longer tibia than females. Pregnant females have a clutch of 2-3 eggs. Cytogenetic studies showed 2n =36 chromosomes characterized by 12 macrochro­ mosomes and 24 microchromosomes and an XX:XY type sex determination mechanism. C-banding patterns, localization of the nucleolus organizer regions (NORs), R-banding after in vivo treatment with 5-bromodeoxyuridine (5-BrdU) and meiotic data are also presented. INTRODUCTION The monotypic genus Strobilurus is a member of the tropidurine group of Iguanidae (Etheridge, 1964), has an enlarged occipital scale and is probably related to Plica, Uracentron, Uranoscodon, Tropidurus and Tapinurus (Etheridge, 1964; Rodri­ gues, 1986). Although the type species S. torquatus is well defined, the species remains very rare in collections. The reptile collection of the Museum of Zoology of the 1 Departamento de Zoologia, Instituto de Biociencias, Universidade de Sao Paulo, Caixa Postal 20520,01498 Sao Paulo, SP, Brasil. 2 Departamento de Biologia, Instituto de Biociencias, Universidade de Sao Paulo, Caixa Postal 11461, 05499'Sao Paulo, SP, Brasil. Send correspondence to Y.Y.-Y. 3 Departamento de Biologia, Instituto de Biociencias, Universidade Estadual "Julio de Mesquita Filho", Caixa Postal 178, 13500 Rio Claro, SP, Brasil. 748 Rodrigues etal. University' of Sao Paulo (MZUSP), undoubtably the largest in terms of South American lizards, includes only 15 specimens. At present, the species is distributed throughout the Atlantic forest of Brazil from the State of Pernambuco to the State of Espirito Santo, though ecological information about the species is virtualy non-existent. Vanzolini (1972) described S. torquatus as a forest form, but without detailed data, and patterns' of geographic differentiation ofS. torquatus were studied by Jackson (1978). We recently collected a relatively large series of the species ( 18 specimens) in the State of Bahia, near Itabuna, and in the present paper we report some data on the ecology ofS. torquatus. Wealso describe its karyotype as revealed by standard staining, C-banding, silver staining of the nucleolar organizer regions (NORs), R-banding after in vivo 5-BrdU incorporation, and meiotic analysis of some male specimens. MATERIAL AND METHODS lizards were collected by hand, noosed or shot with a 22 caliber pellet gun. Snout-to-vent length and body weight were measured for each animal, and pertinent information on structural habitat was recorded at the time and place where the lizards were sighted. live specimens were brought to the laboratory for cytogenetic analysis. A sample of five specimens (3 males and 2 females) was studied chromo­ somally. Animals were injected intraperitoneally with an aqueous solution of Fleischmann yeast plus dextrose (Cole and Leavens, 1971) 48 h before sacrifice, and with a solution of 5-bromodeoxyuridine and 5-fluordeoxyuridine (10 mg BrdU and 0,5 mg FudR in 2 m1 of 0.9% NaCI; about 0.1 mg/l0 g body weight) about 17 h before sacrifice (Schempp and Schmid, 1981). A 0.1% colchicine solution was then injected intraperitoneally (0.1 mg/109 of body weight) and the animal was killed about 2 h later. Mitotic chromosomes were obtained from bone marrow and meiotic prepara­ tions were also made from testes in males. C-banding patterns were obtained by the method of Sumner (1972) and NORs were Ag-stained by the method of Howell and Black (1980). R-banding patterns for the specimens injected with BrdU/FudR were obtained by the technique of Dutrillaux and Couturier (1981), with the chromosomes being differentially stained with 33258 Hoechst-Giemsa (FPG staining). All specimens were deposited in the Museu de Zoologia da Universidade de Sao Paulo (MZUSP) collection. RESULTS AND DISCUSSION Habitat and ecology lizards were observed in a disturbed region of the Atlantic forest at Sao Jose Ecology and Karyotype of Strobilurus 749 (Fazenda Unacau) near Itabuna, Bahia, Brazil (15 005' S, 39021' W). Fazenda Unacau is an experimental and extensive cocoa farm where the major forest habitats have been selectively cut down. The remaining trees are large, 20-50 meters in height, frequently with large clumps of bromeliads attached, and spaced 10-40 meters to give sufficient shelter to the cocoa plants. There are only two strata in the vegetation: a taller one (20-50 meters) formed by the canopy of the large trees of the remaining primeral forest and a lower one, not exceeding 5 meters, formed by the cocoa plants. There is no underbrush, although leaf litter predominantly formed by cocoa leaves is abundant. At the periphery of the cocoa culture there are large patches of undisturbed forest in a mountainous area with sharp relief. However, despite intensive field work, we were unable to locate S. torquatus in the primary forest. In the modified forest, specimens were observed between 8:00 and 16:00 h at varying heights along the trunks oflarge trees or on the ground. Several specimens were observed on tree trunks, on small branches or on fallen trunks on the ground directly in the sun, suggesting that this lizard is a forest heliophile. Table I provides information on structural habitat and on the time of day when the lizards were first sighted. We never saw active lizards on cloudy or rainy days or during the first hours of the morning on sunny days. Two specimens were seen running upwards to more than 15 meters above ground level along tree trunks at the end of the day. Since the same specimens were observed on those trees during the early morning, they probably move into the canopy at night. Two other lizards were observed on the same tree, although at variable heights on consecutive days, suggesting that S. torquatus holds territories.· On two occasions, more than one specimen was seen on the same tree. On the first, there were four individuals: 2 adult females, 1 adult male and 1 juvenile; on the second, 2 adult males and a mature female. At this second site, the larger male (86 mm) was displaying to the smaller one (81 mm) by continuously .bobbing and rearing. No interaction was observed between females and juveniles. Although this species is poorly represented in collections, the 18 animals captured by us during 20 days of field work and the additional 12 observed show that this lizard may be reasonably abundant. Vanzolini (1972) reported on 8 specimens obtained by children at Agua Azul in Pernambuco, and suggested that the species is quite abundant when the appropriate habitat is available. It has been proposed that high densities of forest lizards are generally associated with habitat disturbances (Vanzolini and Reboucas-Spieker, 1969; Williams and Vanzolini, 1980). An intensive search for Strobilurus during a 20 day field trip near Porto Seguro, Bahia, in an undisturbed area of primary forest was unsuccessful, although one specimen collected there a few years ago unequivocally documents the presence of S. torquatus in that area. Therefore, a more appropriate hypothesis is that, at Sao Jose, S. torquatus is occupying a habitat very different from the original one. 750 Rodrigues et al. Table I- Structural habitat and time of day for the S. torquatus observations. Lizard observed Time of day General habitat* Trunk height (m) Trunk diameter (mm) 1 8:00 FL 0.5 40 2 8:00 T 7.0 70 3 8:00 T 0.5 30 4 8: 10 FL 0.5 40 5 8:15 FL 0.5 40 6 8: 16 T 1.0 70 7 8:20 FL 0.3 40 8 8:30 T 3.5 80 9 9:00 T 1.0 30 10 9:30 T 1.0 11 10:00 T 1.0 12 11:30 T 0.5 30 13 11:30 T 0.5 14 12:00 TW 3.0 15 12: 00 G 16 14:00 T 15.0 50 17 15:30 T 2.0 18 16:00 T 1.5 100 19 16:00 T 15.0 60 20 16:30 T 20.0 80 21 16:40 G • FL =fallen log; G =ground; T =tree trunk; TW =twig. Optimal sites for thermoregulation are not common on the lower portions of tree trunks in the primary forest, so that in undisturbed habitats, S. torquatus may be restricted to canopies of large trees for thermoregulatory requirements. However, after selective cutting of forest trees, the lizards may be found in the middle trunk niche or directly on the ground, a fact that makes the lizard more conspicuous to the observer and explains the apparent differential abundance between undisturbed vs. disturbed sites. Ecological information for the Amazonian genus Uracentron is scanty but the few data available indicate that these lizards are analogous to Strobilurus. Both are spiny-tailed arboreal iguanids of similar body size, and assumed to be closely related and relatively rare in primary undisturbed forests. Uracentron is though to be an inhabitant of the canopy. Dixon and Soini (1975) reported on a communal nest found Ecology and Karyotype of Strobilurus 751 in a tree where 17 specimens of U flaviceps were found. This leads us to think that the associations of more than one specimen per tree observed in S.