REGENERATION FREQUENCES IN GECKOS OF TWO ECOLOGICAL TYPES (REPTILIA : GEKKONIDJE) Yehudah Werner To cite this version: Yehudah Werner. REGENERATION FREQUENCES IN GECKOS OF TWO ECOLOGICAL TYPES (REPTILIA : GEKKONIDJE). Vie et Milieu , Observatoire Océanologique - Laboratoire Arago, 1968, pp.199-222. hal-02952708 HAL Id: hal-02952708 https://hal.sorbonne-universite.fr/hal-02952708 Submitted on 29 Sep 2020 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. REGENERATION FREQUENCES IN GECKOS OF TWO ECOLOGICAL TYPES (REPTILIA : GEKKONIDJE) by Yehudah L. WERNER Department of Zoology, The Hebrew University of Jérusalem, Jérusalem, Israël CONTENTS ABSTKACT 200 INTRODUCTION 200 HISTORICAL 201 Frequency of regenerated tails in différent species 201 Sexual and ontogenetic différences 201 Anatomical basis of caudal autotomy and régénération .... 201 MATERIAL AND METHODS 202 FREQUENCY OF REGENERATED TAILS 203 Différences between species 203 Sexual and ontogenetic différences 204 AUTOTOMY 205 Hemidactylus turcicus 205 Stenodactylus sthenodactylus 206 Ceramodactylus doriae 207 DISCUSSION 209 Structure and function 209 Longevity and behaviour 210 Adaptation to environment 211 Convergence among geckos 215 SUMMARY 216 RÉSUMÉ 217 ZUSAMMENFASSUNG 218 ACKNOWLEDGEMENTS 218 REFERENCES 219 ABSTRACT Certain psammophile geckos differ from typical Gekkonidae in possessing a reduced autotomy System. Only 1-2 functional mid- vertebral autotomy splits occur at the base of the tail. Expérimental autotomy is difficult to induce, and natural régénération frequency is low. §|he tail may be of particular importance in the locomotion of thèse geckos. Cases of convergence in geckos of other ecological types are mentioned. INTRODUCTION The fréquent occurrence of regenerated tails in gekkonid lizards has been mentioned in many herpetological texts. Such regenerated tails resuit from the loss, usually through autotomy, of part of the original tail. Thus LOVERIDGE (1946) states that | in the matter of discarding tails, few lizards can compete with the geckos. Some species are so prodigal in this respect that it is diffi- cult to find one with original tail intact. Of the nearly 700 kinds of geckos, probably less than a dozen fail to make use of this défense ". The extent of this specialization may be seen from WAITE'S (1929) report of species which only occasionally include adults with complète tails, at least in muséum collections. In spite of this extensive emphasis, accurate reports on the frequency of regenerated tails are scarce. This paper describes différences in the frequency of regenerated tails between four species of geckos (Hemidactylus turcicus, Ptyodactylus hassel- quistii, Stenodactylus sthenodactylus and Ceramodactylus doriae), assignable to two ecological types. Thèse frequencies are correlated both to anatomical data and to experiments on autotomy. Some of the ecological and evolutionary implications are discussed. — 201 — HISTORICAL FREQUENCY OF REGENERATED TAILS IN DIFFÉRENT SPECIES The rare geckos of the genus Agamura apparently will not lose their tail, to judge from BLANFORD'S (1876) description of 13 spécimens ail with original tails. In other geckos the frequency of régénérâtes may vary considerably from species to species. Among the 200 Hemi- dactylus flaviviridis used in WOODLAND'S (1920) experiments, over 50 % bore regenerated tails. In Tarentola mauritanica, FURIERI (1956) found that 33 % had regenerated tails. BRAIN (1958) reports that 40 % or more of the spécimens of Hemidactylus mabouia and other nocturnal climbing geckos may have regenerated tails, while only 19 % (N = 82) of the ground dwelling Palmatogecko rangei had regenerated tails, ail of thèse having started at the base of the tail. A comparably low percentage of régénérâtes was found by BRAIN in two other ground dwelling species : Chondrodactylus angulifer and Ptenopus garrulus. Recently BUSTARD (1964) found only 9 % (N = 80) regenerated tails in the Australian Diplodactylus williamsi, which has a peculiarly specialized tail. BRAIN'S observations, supported by the earlier ones of BLANFORD, WOODLAND, and FURIERI, suggested a test whether the relation that ground dwelling désert geckos have fewer regenerated tails than climb- ing forms, held for Israeli species as well. SEXUAL AND ONTOGENETIC DIFFÉRENCES M. SMITH (1954) has reported that in British lizards regenerated tails are equally common in both sexes. In contrast, GAGLE (1946) found that among 126 Hemidactylus garnotii, 33 % of the maies and 29 % of the females (and 10 % of the juvéniles) had regenerated tails. A significant différence between sexes would suggest a structural différence, a beha- vioural différence perhaps influencing the exposure of the sexes to outside dangers, or intra-specific factors (like fighting between maies). A finding of equal proportions of régénérâtes in both sexes would not exclude intra-specific factors. ANATOMICAL RASIS OF CAUDAL AUTOTOMY AND REGENERATION The caudal vertebrae of the geckos used in this investigation have been described elsewhere (WERNER, 1965b). In Hemidactylus turcicus and Ptyodactylus hasselquistii the tail begins with 5 non-autotomous pygal vertebrae, behind which ail postpygals (excepting the 1-3 last — 202 — ones) are autotomous. Each autotomous vertebra is cleft in the mid- vertebral plane by a preformed ' autotomy split ', which divides the osseous tissue of the vertebra into anterior and posterior ' halves '. Information on the anatomy of nonskeletal caudal structures in Hemi- dactylus and similar geckos is also available (SCHMIDT, 1912; WOODLAND, 1920; other références in WERNER 1961, 1965b, 1967a). In essence, each autotomy plane manifests itself in ail caudal organs and tissues, ex- cepting perhaps the spinal cord. It is generally accepted that in the autotomy of such a tail fracture takes place at one of thèse predetermined intersegmental planes of weakness, rather than between vertebrae (BEL- LAIRS, 1957). Incidentally, it has recently been shown that the process of régénération is independent of thèse autotomy planes, and that normal régénération never starts from thèse planes (WERNER, 1967a). In Stenodactylus sthenodactylus and Ceramodactylus doriae there similarly are 4-5 and 6 pygal vertebrae respectively, but only the first, or first and second, post-pygals are autotomous — or rather semiauto- tomous, since the split fails to divide the apex of the neural arch. In thèse species the non-skeletal organs of the tail have apparently never been investigated. Furthermore, no information seems available con- cerning the relation of autotomy and régénération to the few (incom- plète) autotomy splits. MATERIAL AND METHODS The frequency of regenerated tails was determined from material in the collection of the Hebrew University of Jérusalem for 250 spéci- mens of Hemidactylus turcicus (Linnaeus, 1758); 218 spécimens of Ptyo- dactylus hasselquistii guttatus von Heyden, 1827; 61 spécimens of Steno- dactylus sthenodactylus (Lichtenstein, 1823); and 28 spécimens of Cera- modactylus doriae Blanford, 1874. AH spécimens were collected in Israël. The samples are random, since, as far as known, there had been no bias in selecting spécimens for préservation. The whole contents of each jar were used. Regenerated tails were externally distinguished from original ones by their différent scaltaion and coloration. Most spécimens with seem- ingly entire tails were radiographed. The regenerated part of a lizard's tail never contains vertebrae, but only an unsegmented cartilage tube. Thus radiography disclosed in a few spécimens of Hemidactylus externally undetectable regenerated tail tips; such spécimens were recorded as having regenerated tails. Spécimens of Hemidactylus were sexed by the présence ( $ 3 ) or absence ( 9 S ) of preanal pores. When spécimens with original tails were radiographed, sex was confirmed by the présence of postanal bones in S <?. In the absence of life history data, spécimens were arbitrarily designated as juvéniles when under 40 mm. (Adults of Hemidactylus reach snout-vent lengths of 52-56 mm in Israël). Ptyodactylus lacks — 203 — preanal or fémoral pores, and samples of the other species were too small to be split. The facility with which autotomy occurs was tested in spécimens of Hemidactylus, mostly collected in Jérusalem, at night, by hand, and kept a few days or weeks until used; and in Stenodactylus and Ceramo- dactylus collected in the Negev (Stenodactylus under stones, Ceramo- dactylus at night on the dunes) up to two years prior to expérimenta- tion. Ail autotomy experiments were made in the room housing the cages, at varying températures which had been kept constant for at least 30 minutes. The signiflcance of counts and results was tested by the X2 test for independent distribution, and checked for the signiflcance levels (a) 0.05 and 0.01 (ARKIN and COLTON, 1950). FREQUENCY OF REGENERATED TAILS DIFFÉRENCES BETWEEN SPECIES Figure 1 présents frequencies of original and regenerated tails for the species examined. Tail loss may occur after collection as the