Contribución al conocimiento sobre la Taxonomía, distribución geográfica y ecología de la Tortuga "Bache" (Chelydra Serpentina Acutirostris)
1977; National University of Colombia; Volume: 12; Issue: 56 Linguagem: Inglês
ISSN
2357-3759
Autores Tópico(s)Wildlife-Road Interactions and Conservation
Resumo1. Studies on the external morphological characters of serpentina acutirostris are presented, the principal scope of which contributes to the knowledge about the taxonomic status of this form considered as valid subspecies. 2. These characteristics are compared with those of the other three subspecies, principally with serpentina rossignonii. 3. Based on 18 specimens of mainly from Colombia, and 16 of rossignonii, mainly from Honduras, certain characters are re-evaluated. 4. The type specimens of the four living representatives of the genus Chelydra, commonly known as Snapping Turtles, are as follows: a) serpentina serpentina (Linnaeus), 1758. Holotype: Originally deposited at the Museum Adolphi Friderici Regis (Museum Drottningholmense), according to the Prodromus Stockholm, 1764, tom. II, p. 16, but presently lost (fide Andersson, 1900, pp. 4, 23). b) serpentina acutirostris Peters, 1962. Holotype: ZBM 4500, hatchling, vicinity of Guayaquil, Ecuador, Carl Reiss. c) serpentina rossignonii (Bocourt), 1868. Syntypes: MNHNP 1501, 1501 A, hatchlings, swamp of Panzos, vicinity of Rio Polochic, Guatemala, and MNHNP 1230, hatchling, Mexico, without exact locality, datum and collectors. d) serpentina osceola Stejneger, 1918. Holotype: USNM 10369, Clearwater, Pinellas County, Florida, United States, September, 1879, S. T. Walker. 5. A redescription of the holotype of acutirostris is presented, and comparisons with the syntypes of rossignonii made. 6. Unfortunately, either the holotype or the syntypes all were described from hatchlings, many of the external morphological characters of which are markedly different from those of adults. 7. Certain external characters which are traditionally considered as constant in the keys of classification, although in reality they are not, but rather show considerable variation, therefore they are of no taxonomic value in relation to an exact subspecific classification. 8. It is proposed to change the text of the existing keys as follows: a) serpentina acutirostris. Length of anterior and lateral marginal shields equal to width in juveniles, markedly greater than width in subadults and adults; epidermal protuberances of nucal-cervical region few and short, rounded and blunt; sub-mandibular barbels from single to three pairs (2.6 barbels) ; gular shield divided; bridge covered by three infra-marginal shields in almost all specimens; snout narrow and pointed, extends markedly over the tip of mandible. b) serpentina rossignonii. Length of anterior and lateral marginal shields greater than width in adults and juveniles; epidermal protuberances of nucal-cervical region abundant and large, flat and pointed; sub-mandibular barbels in two pairs (4 barbels) in most specimens; gular shield divided; bridge covered by three infra-marginal shields in virtually all specimens; snout narrow and pointed, extends markedly over tip of mandible. 9. As shown, there is only one easily discernible external character for distinguishing acutirostris from rossignonii: The configuration of the epidermal nucal-cervical protuberances. The relation between the length and width of the marginals -not constant in but constant in rossignonii- may also serve to certain degree for distinction; however, they are easily discernible since the corresponding measurements of each shield have to be taken. 10. serpentina serpentina and serpentina osceola differ to certain extent from acutirostris and rossignonii by configuration of snout, length of bridge, number of infra-marginals, and the presence of an entire gular shield in most specimens. 11. The epidermal protuberances are short, rounded and blunt in serpentina, but large, flat and pointed in osceola (first mentioned by Richmond, 1958, p. 42). 12. The validity of the taxonomic status is discussed. Boulenger (1902) and Vaillant (1911) did accept acutirostris as valid subspecies because the name was not accompanied by an adequate description, and therefore used the name of rossignonii. The description given by Peters (op. cit., p. 627) is certainly adequate; possibly he considered acutirostris as mere variety since he wrote: Chelydra serpentina var. acutirostris, Carr (1952, p. 71) considered osceola as a weakly differenciated subspecies; in contrast, Richmond (op. cit., p. 43) even took it for valid species on the base of comparative anatomical studies. 13. We prefer to agree with Carr, and think that it would be more realistic to consider the four forms of the genus as local populations (demes) rather than as good subspecies, in accordance to our present and still scattered knowledge. 14. The following data on the ecology and geographical distribution are given: 15. The habitat of acutirostris consists of quiet waters, such as swamps, marshes, ponds and lagoons; it also lives in the headwaters of rivers and creeks either in the tropical rain forests or in the open valleys (which certainly were covered by abundant gallery forests in past times). 16. No sexual dimorphism exists, but the ♂♂ grow larger than the ♀♀. 17. From observations made of specimens kept in captivity, periods of sexual activity take place in June, July and November. 18. The egg-laying season takes place in February in the area of lower Rio Atrato (Choco); data from other regions are unknown. 19. About 27 - 30 either spherical or slightly ovoid hard-shelled eggs are laid in excavations made by the ♀ close to the waters. They measure between 3.5-3.3 and 3.9-3.2 centimeters; the weight was taken. 20. The geographical distribution of acutirostris ranges from Costa Rica, Panama and Colombia into north-western Ecuador; the approximate limit to the south comprises the Guayas River System. 21. The exact limits of distribution -if any- of either acutirostris or rossignonii in Central America are unknown; as is true for osceola and serpentina in northern Florida (Carr, op. cit.), an overlapping zone possibly exists somewhere in Nicaragua or Costa Rica. 22. In Colombia, acutirostris -locally known as la bache- is to be found within the following areas: a) Along the Pacific coast between Bahia de Solano (Choco] and Rio Mataje (Narino) which latter forms the border with Ecuador. b) In the Cauca Valley proper (Cauca and Valle). c) In the region of Armenia (Quindio) into which it evidently migrated from the Cauca Valley. Its migration into the Magdalena River System is blocked either by the Canon del Cauca, gorge situated between the Cordillera Occidental and Central, or by the western slopes of the Quindio Mountains which belong to the Cordillera Central. d) On the Atlantic sector of the Choco, between Cano Negro, Rio Tanela, lower Rio Atrato and its tributary, Rio Truando, as well as Rio Nercua, an affluent of the latter. Its presence on the middle and upper reaches of the Atrato is proved but can be suspected. e) On the upper Rio Sinu (Cordoba), between Cano Jui in the vicinity of the village Tierralta and Rio Manso, the uppermost tributary of the Sinu. 23. No studies exist about its presence between the eastern shore of the Gulf of Uraba or Darien and Rio Sinu, but certainly it once migrated from the Choco into the latter. 24. The center of evolution of the genus apparently was situated in the United States, from where the migration took place during the Terciary. Fossils are known from the Pleistocene of the United States (Carr, op. cit.), but no fossil material was described from Colombia until now. 25. Many more studies, carried out with large series of adults of both sexes, juveniles, and especially with living specimens, are badly needed in order to clarify the still remaining problems concerning the taxonomy, ecology and geographical distribution of acutirostris and rossignonii.
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