Short Notes
The malereproductive cycleof thelizard Agama atra (Sauria: Agamidae) in centralSouth Africa
J.H. vanW yk,L. Ruddock
Department Zoology,University of Stellenbosch, Stellenbosch, 7600, South Africa e-mail: [email protected]
Thetiming of reproductive activity, including seasonal timing and synchronization be- tweensexes, is an important aspect of a species’reproductive strategy (Guillette and Méndez-de la Cruz, 1993) and could be an useful variable in understanding the life his- toryof aspecies,either relating to local ecological factors or thehistorical past. In most lizardspecies studied, males either exhibit a so-called“ prenuptial”pattern of spermatoge- nesiswith spermatogenic activity starting in autumnor spring,mostly well synchronized withthe ovarian cycle (Licht, 1984; Bradshaw, 1986; Guilette and Mé ndez-de la Cruz, 1993;van W ykand Mouton, 1998) or a“postnuptial”pattern of spermatogenesis,not well synchronizedwith the ovarian cycle, with peak spermatogenic activity following the pe- riodof mating,followed by testicularregression and sperm storage in the epididymis and vasdeferens for prolongedperiods (up to six months) after cessation of spermatogenesis (Lofts1977; van W yk,1995). Agamidreproductive cycles vary from fullycontinuous (Marshall and Hook, 1960) in theAfrican tropics to strictly seasonal in southernAfrica (vanW yk,1984a, b; Heideman, 1994,1998; Mouton and Herselman, 1994). The southern rock agama, Agama atra, is a widespreaddiurnal rupicolous lizard found throughout South Africa (Branch,1988). Mou- tonandHerselman (1994) recently reported vitellogenic and gravid females during autumn andwinter months in thewestern regions of SouthAfrica (Namaqualandregion) and con- cludedthat males from theNamaqualand region display a continuousspermatogenic cycle withonly a brieftesticular regression period in autumn. Males collected from thesouth-
© KoninklijkeBrill NV ,Leiden,2000 Amphibia-Reptilia22: 119-123 120 Short Notes westernCape, however, exhibit testicular regression in latesummer, followed by testicular recrudescencein autumnwith peak spermatogenic activity in spring and summer .Inthis studywe provideadditional information regarding the seasonaltesticular activity of A. atra malescollected in centralSouth Africa andcompare the data with the testicular cycles re- portedelsewhere in its distribution range. Weexaminedspecimens of A. atra inthe collection of the National Museum in Bloemfontein,South Africa. Thesespecimens were collectedin the Free Stateprovince ofSouth Africa during1972 and 1973 as part of an extensive survey of the reptiles in thisprovince (de W aal,1978). Lizards were xedin buffered formalin and preserved in70% ethanol (de W aal,1978). Data obtained from eachspecimen included snout- ventlength (mm, SVL) andlongest and shortest axes of testes(mm). Wethencalculated testicularvolume (TV), usingthe formula for thevolume of anellipsoid (V 4=3 ¼a2b, D where a 1=2shortestdiameter and b 1=2largestdiameter). The right testes were D D imbeddedin paraplast wax, sectioned at 7 ¹m,andstained with Harris’ hematoxylin and eosin.Spermatogenic activity was assessedqualitatively by using a stageclassi cation scheme(after vanW yk,1995, summarized in gure1). In addition, epithelial height and presenceof spermatozoain thelumen of theepididymis was notedto validate the staging oftesticularactivity. Testicularvolume (TV) datawere transformedusing normal logarithm (base e) and then subjectedto Kolmogorov-Smirnov’ s normalitytest and Bartlett’ s testfor homogeneity ofvariances respectively. The testicular volume data set failed the equal variance test (P > 0:05)and, therefore, we subjectedthe data to a Kruskal-WallisOne W ayanalysis ofVariationof Ranks(Kruskal-W allis-ANOVA)procedureto establishwhether signi cant seasonalvariation existed. Dunn’ s AllPairwise Multiple Comparison Procedure (Glantz, 1992)was usedto isolate groups (months) that differ signi cantly from others.In order to testif testicularvolumes were effectedby body size, we performeda linearregression analysison log-transformed variable (SVL, TV). Sincethis relationship did not prove tobe signi cant ( P > 0:05),we didnot ndit necessary to adjust testicular volumes. Allstatistical procedures were performedin concordance with Glantz (1992), using the SIGMASTAT(JandelScienti c) statisticalsoftware package. For characteristicclimatic conditions (temperature and rainfall) in the habitat of A. atra occurringin the Free State,meteorological data for thetownFauresmith, 29° 46 0S, 25°190E (see vanW yk,1989)were obtainedfrom theSouthAfrican W eatherBureau (WB40-report, 1980).Photoperiod regime for thissite was calculated,using the formula in vanLeeuwen (1981).The study area is characterized as a summerrainfall region (average monthly rainfallof 50-70 mm insummer and less than 20 mm duringthe winter months). Mean maximumambient temperature in summer months (Nov, Dec, Jan) are above 30 ±C, but close to 20 ±Cduringwinter months (Jun, Jul, Aug). Mean minimal ambient temperature rangesfrom 15 ±Cinsummer to lessthan 10 ±Cinwinter .Daylightlengths range from 14 hoursin summer to 10 hoursin winter .