Description
Cardioglossa congolia are plump bodied long-fingered frogs where males range in snout-vent length from 23.1 - 27.2 mm; no females have been described. The snout is triangular from a dorsal view and rounded from a lateral view. The canthus rostralis is rounded, the loreal region is flat. The external naris is close to the snout tip. The length from the eye to snout tip roughly equals the diameter of the eye. The prominent tympanum is large. The limbs are long and thin, and the thighs and calf are roughly equal in length while the foot slightly exceeds the calf in length. The toes and fingers are pointed instead of enlarging to disks. The toes and fingers are about the same width as the subarticular tubercles, which are rounded on the fingers and egg-shaped on the toes. Neither the feet nor the hands have webbing. The ventral hand surfaces have narrow ovoid palmar tubercles. The relative finger lengths are IV < I = II < III, and the third finger is 1.5 times the length of the second finger. The third finger also has 13 - 14 spines along the proximodistal axis of the medial surface, running from the metacarpal-phalangeal joint to close to the finger tips. Two or three smaller spines also decorate the bases of the second digits on their medial and lateral surfaces. The relative toe lengths are I < V < II < IV. The feet have an ovoid inner metatarsal tubercle that is close to half the length of the shortest toe. The skin of the snout, loreal region, and the majority of the dorsal and ventral surfaces is smooth, while the skin of the groin, dorsal thigh, and bottom of the dorsum have small white spines (Hirschfeld et al. 2015).

Like all other Cardioglossa species, Cardioglossa congolia has a slim body, elongated legs, a long third finger in males, and a recognizable color pattern. Analysis of the mitochondrial 16S rRNA gene indicates that Cardioglossa congolia is within the Cardioglossa genus and forms a subclade with Cardioglossa escalerae, Cardioglossa gratiosa, Cardioglossa nigromaculata, Cardioglossa trifasciata, and Cardioglossa annulata. Cardioglossa congolia is distinguishable from most other species in the genus by its markings, as it lacks the hourglass pattern or three large black spots that most others in the genus have on their dorsum. Other Cardioglossa that also lack these patterns are Cardioglossa oreas, Cardioglossa manengouba, Cardioglossa pulchra, and Cardioglossa venusta. Cardioglossa congolia is distinguished from these species by its infratympanal line. Morphologically, Cardioglossa congolia is most similar to Cardioglossa gratiosa and Congolia annulata, but is differentiated by its lack of dark cross bars on its limbs. Cardioglossa congolia also differs from Cardioglossa gratiosa through its less noticeable infratympanal line. Cardioglossa congolia further differs from Cardioglossa annulata by the black spots on its belly, while Cardioglossa annulata has meandering light and dark coloring (Hirschfeld et al. 2015).

In life, the dorsum is a greyish brown with irregular black spots that extend to the dorsal areas of the limbs. Black spots ringed by white lines occur on the anterior areas of the front and hind limbs and the posterior surfaces of the upper arms and thighs. The throat is dark grey and the head has a dark mask outlined by a thin white line. The mask covers the tympanum and wraps posteriorly behind the arm and along the flanks to about mid-body, where it breaks into irregular spots. The ventral edge of the mask has a thicker white line that ends just ventral to the eye. A large black inguinal spot spreads through most of the posterolateral surface of the dorsum. The ventral surface has crisscrossed light grey lines around irregular dark spots. In preservative, the color pattern fades over time (Hirschfeld et al. 2015).

Body size and number and extent of hand spines varies slightly in males, with one paratype entirely lacking spines on the medial surface of the third finger of left hand. The size and number of black spots on the lateral and dorsal surfaces and the pattern of grey lines on the venter also vary slightly. Some specimens have patterned throats. The overall coloration can be slightly lighter than the coloration of the holotype. No females have been collected, so any sexual dimorphism is unknown (Hirschfeld et al. 2015).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Congo, the Democratic Republic of the

View distribution map in BerkeleyMapper.

Cardioglossa congolia’s known range is close to the Congo River within the Democratic Republic of the Congo in the Bandundu and Orientale Provinces. The elevational range is 474 - 515 m. The habitat includes leaf litter in both primary and secondary rainforest. The range most likely expands further into the Congo Basin, especially to the south-east of the Congo and Ubangi Rivers. The distribution may be contained by the geographic barriers of the Congo and Ubangi Rivers (Hirschfeld et al. 2015).

Life History, Abundance, Activity, and Special Behaviors
The reproductive behavior, calls, and tadpole development of Cardioglossa congolia remain unknown, but they are expected to mate in small streams and have stream-adapted, elongated tadpoles (Hirschfeld et al. 2015).

Comments
The species authority is: Hirschfeld M, Blackburn DC, Burger M, Greenbaum E, Zassi-Boulou A-G, and Rödel M-O. 2015. Two new species of long-fingered frogs of the genus Cardioglossa (Anura: Arthroleptidae) from Central African rainforests. African Journal of Herpetology 64(2), 81-102.

Analysis of the mitochondrial 16S rRNA gene indicates that Cardioglossa congolia is within the Cardioglossa genus and forms a subclade with Cardioglossa escalerae, Cardioglossa gratiosa, Cardioglossa nigromaculata, Cardioglossa trifasciata, and Cardioglossa annulata. Analysis of the mitochondrial 16S gene showed low or moderate divergence in DNA sequences between Cardioglossa Congolia and other closely related Congolia species (Hirschfeld et al. 2015).

The species epithet, “Congolia”, comes from the name of a biological sub-center of the Guinea-Congolian rainforest region where Cardioglossa congolia is found (Hirschfeld et al. 2015).

One of the three specimens was previously categorized as Cardioglossa gratiosa (Hirschfeld et al. 2015).

References

Hirschfeld M, Blackburn DC, Burger M, Greenbaum E, Zassi-Boulou A-G, and Rödel M-O (2015). ''Two new species of long-fingered frogs of the genus Cardioglossa (Anura: Arthroleptidae) from Central African rainforests.'' African Journal of Herpetology, 64(2), 81-102.

Species Account Citation: AmphibiaWeb 2016 Cardioglossa congolia: Congolian Long-Fingered Frog <https://amphibiaweb.org/species/8379> University of California, Berkeley, CA, USA. Accessed Nov 21, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 21 Nov 2024.

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