Correlation between increased postpubertal phallic growth and the initiation of cranial sexual dimorphisms in male Morelet's crocodile. Issue 10 (15th October 2019)

• Record Type: Journal Article
• Authors: Moore, Brandon C.; Holliday, Casey M.; McMurry, Scott T.; Platt, Steven G.; Rainwater, Thomas R.
• Is Part Of: Journal of experimental zoology. Volume 331:Issue 10(2019)
• Page Start: 562
• Page End: 570
• Publication Date: 2019-10-15
• Subjects: caniniform -- crocodile -- glans -- phallus -- puberty -- sexual dimorphism; Zoology -- Periodicals; Zoology; Animal Population Groups -- physiology; Zoology; Electronic journals; Periodical; Periodicals; 590
• DOI: 10.1002/jez.2325
• Languages: English
• ISSNs: 2471-5646

Abstract

Abstract: While puberty is an animal commonality, little is known of its timing or process in crocodylians. Males copulate with an intromittent phallus that has a distinct glans morphology which directly interacts with the female cloaca, putatively effecting effective semen transfer and ultimately increased fecundity. Here we present, during the Morelet's crocodile lifecycle, a well‐defined body length (65 cm snout‐vent length) inflection point that marks a subsequent increase of phallic glans growth rates. Putatively, this postpubescent growth produces a copulatory‐effective phallus. While not as robust of a trend as snout‐vent length, this growth inflection concomitantly begins with a body condition index (CI = BM/SVL 3 ) between 2.0 and 2.5 and is most distinct above a CI of 2.5. Also, in males, this 65 cm size threshold also aligns with the initiation of more robust growth in caniniform alveoli associated with prominent maxillary and mandibular teeth. This inflection was not observed in females, thus marking a sexual dimorphism that begins to present with the onset of puberty. This bodily manifestation of puberty other than those changes observed in the reproductive tracts is a novel observation for crocodylians and lays a foundation for further study among species of how changing endocrine signaling within sexually maturing males may also influence a broader range of secondary sex characteristics. Abstract : Male Morelet's crocodiles ( Crocodylus moreletii ) show a body size‐correlated maturation of the phallic glans morphology (a) and initiation of sexually dimorphic dentition (b, c). Research Highlight: Male Morelet's crocodile phalli increase growth rates of glans height and glans tip length after achieving 65 cm snout‐vent length. The glans size of increase corresponds with the initiation of sexually dimorphic maxilla and mandible features.