Table 1.—Variation in Certain Characters in the Species of Ptychohyla. (Means Are in Parentheses Below the Ranges.)
|
Hand.—The species in the Ptychohyla euthysanota group have a vestige of web between the first and second fingers; the other fingers are about one-third webbed. Breeding males have a cluster of horny nuptial spines on the thumb. The spines are largest in P. spinipollex ([Fig. 1]) and vary in number from 35 to 66 (average 47.4) on each thumb. In the other species of the Ptychohyla euthysanota group the spines are smaller and usually more numerous; the numbers of spines on each thumb (means in parentheses) in members of this group are: P. euthysanota euthysanota, 44-143 (83.8); P. euthysanota macrotympanum, 40-110 (63.0); P. leonhardschultzei, 24-80 (54.7). The species in the Ptychohyla schmidtorum group have no web between the first and second fingers and only a vestige of web between the other fingers. Furthermore, these species lack nuptial spines in breeding males. Like the usual horny [excrescences] on the thumbs of many species of frogs, the horny spines on the thumbs of members of the Ptychohyla euthysanota group are seasonal in development.
Fig. 1. Palmar views of right hands of (A) Ptychohyla spinipollex (KU 58054) and (B) Ptychohyla schmidtorum schmidtorum (KU 58043). × 4.
Many workers have used the presence of a bifid subarticular tubercle beneath the fourth finger as a diagnostic character of certain species of hylids. Examination of the subarticular tubercles in Ptychohyla reveals considerable intraspecific variation. Bifid tubercles beneath the fourth finger are found in all species except P. ignicolor, which is known from only two specimens. In P. euthysanota euthysanota nearly 60 per cent and in P. schmidtorum schmidtorum about 90 per cent of the specimens have a bifid tubercle beneath the fourth finger on one or both hands. All specimens of P. leonhardschultzei have either a bifid or double tubercle beneath the fourth finger, and some have a bifid distal tubercle beneath the third finger.
Feet.—Members of the Ptychohyla euthysanota group have a weak tarsal fold, whereas in the species comprising the Ptychohyla schmidtorum group the tarsal fold is absent. Webbing on the foot extends to the discs of the third and fifth toes and to the base of the penultimate phalanx of the fourth toe, except in P. ignicolor, which has less webbing.
Ventrolateral Glands.—Breeding males develop thickened, pigmented glandular areas on the sides of the body. In living specimens of P. schmidtorum and P. ignicolor the glands are not readily visible, but in preservative they show as distinctive orange-colored areas. These glands are most distinct in P. euthysanota; in many specimens of this species the glands are elevated above the surrounding skin. The extent of the glands is variable ([Fig. 2]); probably this variability is due to different degrees of development in individual frogs rather than to interspecific differences. All Ptychohyla ignicolor and some P. schmidtorum chamulae have a small, round glandular area on the chin; to my knowledge this does not occur in the other species. Superficial examination of microscopic preparations of the glands reveals no histological differences between species. The glands occupy most of the thickened area and have narrow ducts leading to the exterior. Detailed studies of the histology will be reported elsewhere. Since the glands are developed only in breeding males, it is surmised that the glands are associated with some phase of the breeding activity.