Evolution of the cloacal and genital musculature, and the genitalia morphology in liolemid lizards (Iguania: Liolaemidae) with remarks on their phylogenetic bearing

in Amphibia-Reptilia
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In this study, we describe the intra- and interspecific anatomical variations of cloacal and related muscles of male and female genitalia in species of five iguanian genera (three liolemid: Ctenoblepharys, Liolaemus, and Phymaturus plus Diplolaemus leopardinus and Tropidurus melanopleurus as outgroups). We found variations (seventeen characters) in topology, origin and insertion areas, tendon morphology and size of the musculature of this region. We also describe the variations of hemipeneal morphology, which is especially notable for the hemipenis of C. adspersa, D. leopardinus, and T. melanopleurus, as this is first time they are described in the literature. Among the most significant findings are the identification of three new muscles, two of them inserted on the roof of the cloacal chamber (anterior and posterior cloacal retractor) and the third inserted superficially in the floor of the cloaca, just before anterior to the precloacal glands row (superficialis cloacalis retractor). We report sexual dimorphism in seven muscle characters. Musculature related to hemiclitoris is reduced in proportion to its size in comparison to the degree of development of male genitalia and associated musculature. The evolution of characters was traced on the known phylogenetic hypotheses of relationships among families. Characters taken from the cloacal/genital myology bring similar support to the liolaemid tree even rooting the analysis using different outgroups. In addition, a phylogenetic study using only myological characters was performed. In this case, C. adspersa was found to be more related to Liolaemus species instead of being basal to Liolaemus plus Phymaturus.

Evolution of the cloacal and genital musculature, and the genitalia morphology in liolemid lizards (Iguania: Liolaemidae) with remarks on their phylogenetic bearing

in Amphibia-Reptilia



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    Ventral view of the cloacal region muscles in a male of Liolaemus irregularis (MCN 1885). The head of the specimen is located upwards, while the tail is located down. (A) General disposition of the superficial muscles. (B) Post cloacal superficial muscles. See the disposition of the posterior cloacal retractor, partially covering the transversus penis. (C) Pre-cloacal superficial muscles. (D) Anterior and posterior lateral retractor muscles. See the retractor lateral anterior division. (E) Compressor glandulae located dorsal to the transversus perinei (transversus perinei cut off from its position on the left side). (F) Disposition of the anterior cloacal retractor passing dorsal to the cloacal chamber and the origin of the ischiocaudalis tendon (superficial muscles dissected). Abbreviations as follows = H: hemipenis; Is: ischium; IC: ischiocaudalis; ILC: Iliocaudalis; PC: precloacal glands; PCR: posterior cloacal retractor; TP: transversus perinei; TPN: transversus penis; SCR: superficialis cloacal retractor; CG: compressor glandulae; ACR: anterior cloacal retractor; RLA: retractot lateral anterior; RLP: retractor lateral posterior; ICT: ischiocaudalis tendon. Scale = 0.5 mm.

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    The head of the specimen is located upwards, while the tail is located down. (A) Internal muscles in a male of Tropidurus melanopleurus (IBIGEO 5317). See the origin of the ischiocaudalis tendon in the lateral margin of the ischium, the common insertion of anterior and posterior cloacal retractors in a fascia dorsal to the cloacal chamber. (B) Internal muscles in the male of Phymaturus palluma (MCN 2894). See the dorsal insertion of the ischiocaudalis tendon in the ischial bone. (C) See how the posterior cloacal retractor partially covers the transversus penis. (D) Posterior cloacal retractor located medially to the ischiocaudalis, not in contact or covering the transversus penis. Abbreviations as follows = Is: ischium; H: hemipenis; IC: ischiocaudalis; PC: precloacal glands; PCR: posterior cloacal retractor; TPN: transversus penis; ACR: anterior cloacal retractor; ICT: ischiocaudalis tendon; CF: caudofemoralis. Scale = 0.5 mm.

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    (A) Hemipenis asulcate face of Liolaemus irregularis (MCN 1884). (B) Hemipenis sulcate face of L. irregularis. (C) Asulcate face of Liolaemus austromendocinus (MCN 3686). (D) Sulcate face of L. austromendocinus. (E) Asulcate view of hemipenis of P. patagonicus (MCN 3275). (F) Sulcate face of the hemipenis of P. patagonicus. See dark pigmentation of the sulcus spermaticus in this species. (G) Asulcate face of the hemipenis of P. palluma (MCN 2894). (H) Sulcate face of the hemipenis of P. palluma. The arrow indicates the extended ornamentation in P. patagonicus. Abbreviations = C: calices; P: plicae; SS: sulcus spermaticus; AL: apical lobes; RP: round prominence; SSP: sulcus spermaticus plicae. Scale = 0.5 mm.

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    (A) Asulcate view of hemipenis of Ctenoblepharys adspersa (MUSA 4613). (B) Sulcate face of the hemipenis of C. adspersa. (C) View asulcate face of hemipenis of Diplolaemus leopardinus (IBIGEO 5493). (D) View sulcate face the hemipenis of D. leopardinus. (E) View asulcate face of hemipenis of Tropidurus melanopleurus (IBIGEO 5317). (F) Sulcate face the hemipenis of Phymaturus T. melanopleurus. Scale = 0.5 mm.

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    Trees obtained from the data set of this work. (A) Consensus tree recovered performing an analysis of the present anatomical data with the Tropidurus melanopleurus as outgroup. (B) Consensus tree of the same analysis but rooting the tree with Diplolaemus leopardinus. (C) Rebuilt tree with Ctenoblepharys adspersa as the basal taxon in the Liolaemidae family following relationships recovered molecular and morphological in previous studies. Numbers on branches (apomorphies) correspond to characters described in the character list (see also table S1).

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