Description
Morerella cyanophthalma is a relatively small frog species that exhibits sexual size dimorphism, with females being significantly larger than males. Both sexes reach a maximum size of 35 mm and are slender. Females are slightly larger (27 - 37 mm) than males (23 - 34 mm), and individuals with a snout-urostyle length less than 21.5 mm are considered juveniles (17-21.5 mm) (Rödel et al. 2009, Soro et al. 2019). The relatively flat head has a width of about one third of the snout-urostyle length, the width behind the eyes ranges from 7.4 to 12.5 mm, the prominent and large eyes have a diameter of 2.5 - 4.6 mm. The pupil is horizontally oval. The snout is slightly pointed and the upper jaw has tiny teeth. The tongue is heart-shaped and to two thirds free. The eardrum is small (1.3 mm, reaches one third of eye diameter) but prominent. The nostrils are closer to the snout tip than to the eyes. Males have a large gular gland that varies in size but ranges from 12 - 51 mm² in surface area. The gular gland extends from the middle of the throat to the front of the chest and has no expandable skin under or around the gland. The females lack a gular gland (Rödel et al. 2009).

The dorsal skin surface is granular and has tiny spines, that become larger and denser towards the lower and outer part of the hind limbs. The fingers and toe tips end in enlarged round disks and there are only traces of webbing between the fingers. The third finger is the largest, followed by the fourth, the second, and finally the first. Fingers 1, 2 and 4 have one subarticular tubercle, finger 3 has two subarticular tubercles, and there is one small palmar tubercle. The length of femur (14.3 mm) and tibia (15.7 mm) reach about half of the body length. The foot, including the longest toe, reaches about two-thirds of body length (21.2 mm). The toes have the following relative formula for length: 1 < 2 < 3 = 5 > 4. The first toe has one subarticular tubercle; the second, third and fifth toes have two subarticular tubercles; and the fourth toe has three subarticular tubercles. Additionally, there is a small elongated inner metatarsal tubercle. The webbing between the toes has the following formula: 1 (1), 2 i/e (1 - 0.5), 3 i/e (1 - 0.5), 4 i/e (1), 5 (0.3). The ventral body parts are granular, and the underside of the feet is densely covered with flattened tubercles (Rödel et al. 2009).

The genus is comprised of only one species. As per Channing and Rödel (2019), the species exhibits a distinct appearance, particularly in female specimens possessing a bright orange dorsal coloration and large protruding blue eyes that are characteristic and distinguishable from any other species. Genetic analysis of mitochondrial DNA (16S, 12S, and Cytochrome b) indicates that M. cyanophthalma is a novel species (and the genus Morerella) possessing unique morphological, biological, and anatomical features within the range of inter-generic differentiation of the Hyperoliidae family. For example, the oval pupils in M. cyanophthalma set it apart from members of the genera Acanthixalus, Afrixalus, Arlequinus, Callixalus, Kassina, Kassinula, Opisthothylax, Paracassina, Phlyctimantis, Semnodactylus, and Tachycnemis. Another example is the distinct, but small tympanum in M. cyanophthalma distinguish it from members of the Acanthixalus, Afrixalus, Callixalus, Chrysobatrachus, Hyperolius, and Opisthothylax, which either lack tympani or have indistinct tympani. For more distinguishing characters please see Rödel et al. (2009)

The male holotype in preservation presents a dorsum of dark reddish brown color adorned with irregular black spots on the back, forearms, and lower legs. The dorsal side of the thighs is uniformly reddish brown, while the lower anterior half displays uniform pinkish brown color, and the posterior half is covered with numerous dark spots. The ventral portion of the lower leg appears uniformly pinkish. The canthal stripes encircling the eye are dark, and the lips and throat exhibit whitish color with brown spots. The gular gland appears in a yellow-beige hue. The flanks have a pale brown color on the dorsal side and gradually transition to a whitish color on the ventral side. The belly area is white, whereas the fingertips and toes are darker than the hands or feet. Furthermore, the feet's underside is grayish (Rödel et al. 2009).

Live individuals exhibit sexual dichromatic coloration. Females display uniform reddish-brown, red-beige, or orange coloration on their back, including their extremities, fingers, and toes. The belly is pale yellow to orange and the back legs are light yellow or orange. Female eyes are grayish to bright blue. Males have a dark brown to light beige color on their back and legs, sometimes with small dark or yellow spots. During the day, some males may change to an orange color similar to a female, but at night they turn yellow. The male iris can change color depending on the amount of sunlight. During bright sunlight, the iris can be porcelain white, while with less sunlight it can be grayish or yellow brown (Rödel et al. 2009; Konan et al. 2016).

The species is morphologically consistent, but there is evidence of color variation. Soro et al. (2019) report a deviation from the type localities in Banco National Park within the Tanoé-Ehy swamp forest, where some females display grey iris and males display blue iris. In addition, juveniles exhibit body coloration ranging from beige to orange, which is typically seen in adults. Male advertisement calls varied slightly in frequency (2.5- 2.67 kHz) and note repetitions (2 - 8 times), but the sample size was limited to one male. Kpan et al. (2014) reported that certain females from the same region exhibited a reddish-brown iris.

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Cote d'Ivoire

View distribution map in BerkeleyMapper.

Morerella cyanophthalma is an endemic species found in the coastal rainforests of Ivory Coast, West Africa. Currently, it has only been found in three forest locations. These locations include Banco National Park in Abidjan (Rödel et al. 2009), Azagny National Park in southern-central Ivory Coast (Konan et al. 2016), and the Tanoé-Ehy Swamp Forests in southeastern Ivory Coast, near the border of Ghana (Kpan et al. 2014). Morerella cyanophthalma inhabits elevations ranging from 0 - 300m, with mean annual temperatures of 26 - 27°C and mean annual precipitation of 1,600 - 2,500 mm (Rödel et al. 2009, Soro et al. 2019).

The species is found in wetlands, subtropical/tropical swamp forests, and evergreen forests. Assemian et al. (2015) observes that Morerella cyanophthalma serves as an indicator species for closed canopy forests and wet habitats in the Banco National Forest. In the Tanoé-Ehy swamp forest, the habitat includes Raphia palms, as observed in the Azagny National Park (Kpan et al. 2014). The type locality of this species is a water-filled ditch located at the forest edge between a clearing and a swampy forest (Rödel et al. 2009).

Life History, Abundance, Activity, and Special Behaviors
Morerella cyanophthalma is mostly active at night, beginning at dusk (6 - 7 pm) for adults. They perch at heights ranging from 39 to 175 cm, with adults perching higher (165 ± 4.5 cm) compared to juveniles (47.3 ± 4.6 cm) (Soro et al. 2019). Perching spots are typically found in areas with thick vegetation near stagnant or slow-moving bodies of water. The peak of calling activity happens at around 8 - 9 pm, and after 1 am, the calling can be heard infrequently. The male advertisement call is a tonal note that repeats 2 - 3 times. The calls are rather short, lasting from 76 to 90 milliseconds. Their dominant frequency falls into the 2.38 - 2.41 kHz range. These calls were detected and described from three male individuals (Rödel et al. 2009).

During the day, these animals prefer hiding among the leaves of shrubs and herbs, and they are rarely seen on the ground (occasionally, they hide in leaf litter).

The eggs are black and white and have a diameter of approximately 1.5 millimeters. These eggs are laid on leaves or overhanging vegetation that is above stagnant water, such as ditches or swamps. The eggs are laid on the top of leaves, 2 - 15cm above the water. The clutch ranges from 30 - 144 eggs. Egg laying occurs at night when they are most active (Rödel et al. 2009).

Adults have been found sitting near the eggs on plants. It is currently unclear if this behavior is related to parental care (Rödel et al. 2009).

Larva
Freshly hatched tadpoles have a body length of 2.3 mm, a total length of 5.6 mm, and have large yolk reserves. At Gosner stages 37 - 41, shortly before metamorphosis, the tadpoles reach a body length between 10.18 and 11.78 mm and a total length between 37.37 and 40.73 mm. Hatchling mouths are still closed, and they possess external gills. The free-swimming larvae (Gonser stages 25 - 28, (Gosner, 1960)) have an elongated, ellipsoidal body shape when viewed from the top and appear slightly compressed from the side. They have small eyes on the sides of their head, and their nostrils are large and located between their eyes and the end of their snout. The mouth is positioned in the anteroventral part of the head. The mouth opens one day after hatching, revealing narrow arches for the upper and lower jaws. The upper lip is wide and smooth, with a gap at the front that has marginal papillae. The bottom lip has large, double rows of marginal papillae. Most of the teeth on the lips are multidenticulate, only a few are unidenticulate and this is mostly on the upper lip. Their tail is more than twice as large as their body, with a height close to that of the dorsal fin's beginning at the junction of the tail and body. The dorsal fin's highest point sits just before the midpoint of the tail. The tail fin is nearly parallel to the tail axis, and the tail tip rounds out (Rödel et al. 2009).

The tadpoles have a brownish dorsum and their sides and belly are almost clear. There is a brown band starting from the nostrils between the eyes, stretching towards the junction of the tail and body. A reddish-brown line outlines the band. Behind the eye, there are three silver spots that come together in the center of the body. The tail's musculature is cream white and has a skinny brown stripe on its back. The tail fins are clear (Rödel et al. 2009). It is unclear if this description is in life or preservative.

The tadpoles emerge 8 to 10 days after egg laying and drop into the water. They feed externally and grow in still water (Rödel et al. 2009).

Trends and Threats
The populations of Morerella cyanophthalma are believed to decrease, primarily due to ongoing factors that threaten its habitat. This includes an increase in logging and wood harvesting, along with the transition of forest swamps to rice paddy fields. Additionally, pollution from urban and sewage waste waters is a significant contributor to the population decline (Rödel et al. 2009, Kpan et al. 2014). The Tanoé-Ehy swamp forest faces a major threat from habitat degradation, making it imperative to implement an official protection status (Soro et al. 2019). The Forest Conservation Fund, in partnership with the Centre Suisse de Recherches Scientifiques en Côte d’Ivoire, provides support to the community comprising of 11 villages who serve as legal owners and stewards of the forest. In 2021, the Wildlife Division of the Ministry of Environment granted the community the right to manage the area as a community-managed reserve (Tanoe-Ehy Forest 2023).

Possible reasons for amphibian decline

General habitat alteration and loss
Habitat modification from deforestation, or logging related activities
Intensified agriculture or grazing
Urbanization
Local pesticides, fertilizers, and pollutants

Comments

Phylogeny:

References
Assemian, N. E., Kouamè, N. G., Tohé, B., & Gourène, G. (2015) Anuran communities as indicators of habitat types of a West African rainforest. International Journal of Multidisciplinary Academic research, 3(3), 28-38. [link]

Channing, A., and Rödel, M. O. (2019). Field guide to the frogs & other amphibians of Africa. Penguin Random House South Africa.

Gosner, K. L. (1960). A simplified table for staging anuran embryos and larvae with notes on identification. Herpetologica, 16(3), 183-190. [link]

Konan, J. C. B. Y. N., Kouamé, N. G., Kouamé, A. M., Adepo-Gourène, B., and Rödel, M. O. (2016). New data from Morerella cyanophthalma (Anura: Hyperoliidae) in Azagny National Park, southern-central Ivory Coast. Herpetology Notes, 9, 59-65. [link]

Kpan, T. F., Adeba, P. J., Kouamé, N. G., Koné, I., Kouassi, K. P., and Rödel, M. O. (2014). The anuran fauna of a volunteer nature reserve: the Tanoé-Ehy swamp forests, south-eastern Ivory Coast, West Africa. Zoosystematics and Evolution, 90(2), 261-270. [link]

Portik, D. M., and Blackburn, D. C. (2016). The evolution of reproductive diversity in Afrobatrachia: A phylogenetic comparative analysis of an extensive radiation of African frogs. Evolution, 70(9), 2017–2032. [link]

Rödel, M. O., Kosuch, J., Grafe, T. U., Boistel, R., Assemian, N. E., Kouamé, N. G., Tohé, B., Gourène, G., Perret, J.L., Henle, K., Tafforeau, P., Pollet, N., and Veith, M. (2009). A new tree-frog genus and species from Ivory Coast, West Africa (Amphibia: Anura: Hyperoliidae). Zootaxa, 2044(1), 23-45. [link]

Soro, N., Kouamé, A. K., Kouamé, N. G., Adepo-Gourène, B. A., and Rödel, M. O. (2019). Morerella cyanophthalma (Anura: Hyperoliidae) in south-eastern Ivory Coast: Additional data and implications for the species’ conservation. Herpetology Notes, 12, 1215-1223. [link]

Tanoe-Ehy Forest. Forest Conservation Fund. Retrieved 16 November 2023 from https://www.fundforests.org/tanoeehy-forest

Species Account Citation: AmphibiaWeb 2024 Morerella cyanophthalma: Morere´s Blue-eyed Frog <https://amphibiaweb.org/species/7278> University of California, Berkeley, CA, USA. Accessed Nov 26, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 26 Nov 2024.

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