Species Description: Glaw F, Hawlitschek O, Glaw K, Vences M. 2019. Integrative evidence confirms new endemic island frogs and transmarine dispersal of amphibians between Madagascar and Mayotte (Comoros archipelago). Sci Nat 106:19. https://doi.org/10.1007/s00114-019-1618-9
© 2019 Frank Glaw (1 of 2)
The arms are slender, and the subarticular tubercles are single. The fingers lack webbing, and the relative finger lengths are 1 < 2 < 4 < 3. The finger disks are distinctly enlarged. There are distinct nuptial pads on the first finger (Glaw et al. 2019).
The hind limbs are slender, and the tibiotarsal articulation reaches slightly beyond the snout tip when the hind limb is adpressed along the body. The lateral metatarsalia is separated, and the inner metatarsal tubercles are present, but the outer metatarsal tubercle is not recognizable. The webbing formula is 1(0), 2i(0.75), 2e(0), 3i(1), 3e(0), 4i(1), 4e(1), 5(0). The relative toe lengths are 1 < 2 < 3 < 5 < 4 (Glaw et al. 2019).
The skin on the dorsal surface of the head and body has numerous tubercles reaching anteriorly to the skin above the eyes. There are no distinctly enlarged tubercles in the cloacal region. The ventral skin is smooth on the throat, and slightly granular on the belly. There are no femoral glands (Glaw et al. 2019).
Boophis nauticus is assigned to the Sahona subgenus of the Boophis genus based on its typical treefrog morphology, absence of femoral glands, absence of webbing between fingers, and breeding in stagnant water. Boophis nauticus is only compared diagnostically to the other two species in the Sahona subgenus: B. tephraeomystax and B. doulioti. Boophis nauticus is most similar to these two species, but differs from these two species by its reddish iris coloration, genetic divergence, and different advertisement call. Calls of B. tephraeomystax usually consist of single yelping notes, while calls of B. nauticus are pulsed and numerous. Calls of B. doulioti have rapidly pulsed trill-notes, while calls of B. nauticus are not trilled. Males of B. nauticus are also slightly larger than those of B. tephraeomystax and B. doulioti, as the snout-vent length of B. nauticus ranges from 0.34 - 0.37 mm, while the snout-vent length of B. tephraeomystax and B. doulioti ranges from 0.32 - 0.35 mm. Since the differences in size between B. tephraeomystax and B. doulioti are insignificant, they were reported together in comparative studies (Glaw et al. 2019).
In preservative, the back and the upper surfaces of the legs and arms are almost uniformly gray-brown, and there are darker crossbones on the tibia. The flanks are yellowish-white with gray reticulations, especially in the inguinal region. There are whitish spots present on the lateral parts of the shank. The upper lip is whitish and marbled with brown. The tympanum is brown. The ventral surface is uniformly dirty cream-yellowish, with a more grayish area around the cloaca. Overall, color in life is very similar to preservative. The nuptial pads are yellow (Glaw et al. 2019).
There appears to be sexual dimorphism present in B. nauticus, as females of B. nauticus are larger than males, with an average snout-vent length of 57.1 mm compared to the average 42.5 mm snout-vent length of males. Females also have smooth dorsal skin, unlike males. There is little variation among individuals of the same sex in B. nauticus, although coloration may be slightly lighter or darker in general, and as individuals age. Also, most individuals have fewer whitish spots on the shanks than the holotype (Glaw et al. 2019).
Distribution and Habitat
Life History, Abundance, Activity, and Special Behaviors
Calls of two individuals were recorded at Lac Karehani in March of 2013, but many similar calling individuals were heard. Each call consisted of a series of 2 - 6 mostly pulsed notes, and the call duration ranged from 233 - 822 ms, averaging 530.1 ms. The starting notes of a call had a higher number of pulses, ranging from 17 - 37 pulses, and averaging 28.7 pulses. The starting notes also had a longer note duration, ranging from 59 - 89 ms, and averaging 80 ms. The pulse rate of the starting notes was high and quite regular, whereas the following notes had a lower and partly irregular pulse rate. They also often started with poorly recognizable and widely spaced pulses, and had an unpulsed end. The duration of the second notes was sometimes strongly shortened and unpulsed, ranging from 16 - 20 ms, and averaging 18.5 ms. The intensity of the notes decreased toward the end of a note series. The intervals between notes ranged from 47 - 124 ms, averaging 81.3 ms, and the interval between two calls of a male ranged from 5 - 23 s, averaging 15.3 s. Unlike many of its Madagascar congeners, B. nauticus does not trill notes often, nor does it perform single note calls (Glaw et al. 2019).
A pair, which was found in amplexus, was observed laying eggs in the plastic bag used for their transport. Tadpoles in approximately Gosner stage 28 were found in a muddy, stagnant, and sun-exposed pool. (Glaw et al. 2019).
Phylogenetic analysis was done on the mitochondrial 16S rRNA gene using Bayesian Posterior Probability. Specifically, the Jukes-Cantor model was used for Boophis cladogram alignment. From the analysis, B. nauticus was found to be sister to a clade consisting of B. tephraeomystax and B. dulioti. Together, these three species formed a clade sister to B. xerophilus. These four species form a clade that is sister to another clade formed by B. opisthodon, B. guibei, B. idae, and B. calcaratus. Finally, the clade formed of all the aforementioned species is sister to B. pauliani (Glaw et al. 2019).
The species epithet “nauticus” is an invariable Latin term, meaning “sailor” and refers to the successful overseas dispersal of the ancestor of this species in Madagascar (Glaw et al. 2019).
Boophis nauticus was initially assigned to B. tephraeomystax, due to the morphometric similarity between the actual B. tephraeomystax and B. nauticus. However, B. nauticus was then given its own species name, as B. tephraeomystax is restricted to Madagascar, while B. nauticus only inhabits Mayotte, an island near Madagascar (Glaw et al. 2006).
Boophis nauticus is one of only two species of the family Mantellidae, that are not endemic to Madagascar. The other species is a member of the Blommersia genus: B. transmarina. These two species occur synoptically in Mayotte, an island belonging to the Comoros archipelago near Madagascar. The geographic situation of this island lends credence to the hypothesis that their biota may have dispersed from Africa and Madagascar. However, the phylogenetic analysis and taxonomic distribution of B. transmarina and B. nauticus indicate that the most recent common exchange was with Madagascar rather than Africa (Glaw et al. 2019).
Glaw, F., Hawlitschek, O., Glaw, K., and Vences, M. (2019). ''Integrative evidence confirms new endemic island frogs and transmarine dispersal of amphibians between Madagascar and Mayotte (Comoros archipelago).'' The Science of Nature, 106(19), 1-14.
Glaw, F., Vences, M. (2006). ''Phylogeny and genus-level classification of mantellid frogs (Amphibia, Anura).'' Organisms Diversity & Evolution, 6(3), 236-253.
Originally submitted by: Alice Drozd (first posted 2020-11-20)
Edited by: Ann T. Chang (2020-11-20)
Species Account Citation: AmphibiaWeb 2020 Boophis nauticus <https://amphibiaweb.org/species/9000> University of California, Berkeley, CA, USA. Accessed May 16, 2021.
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Citation: AmphibiaWeb. 2021. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 16 May 2021.
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