Melanophryniscus dorsalis (MERTENS, 1933)
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publication ID |
https://doi.org/10.5281/zenodo.15535980 |
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DOI |
https://doi.org/10.5281/zenodo.15535982 |
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persistent identifier |
https://treatment.plazi.org/id/03D087E5-FFB7-8459-FF65-FEB9FBD0913C |
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treatment provided by |
Juliana |
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scientific name |
Melanophryniscus dorsalis |
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In Melanophryniscus dorsalis View in CoL ,
A type calls had a variable duration of about 1-4 s, whereas B type calls were shorter on average lasting between 0.6 and 2.6 s ( Table 1 View Tab , Figs. 1A, B View Fig , 2A, B View Fig , 3A, B View Fig ). The dominant frequency range in both call types was between 2.3 and 3.2 kHz presenting weak harmonic frequency bands between 4.9 and 6.0 kHz and between 7.8 and 8.4 kHz. Type A consisted of 6-20 unpulsed notes, each lasting 20-65 ms with time intervals of 80-170 ms ( Figs. 2A, B View Fig ). Sometimes small groups of 5- 7 pulses were separated by 0.5-1 s lasting intervals ( Fig. 1A View Fig ). Type B consisted of 50- 180 pulses, each pulse with a duration of 7- 9.5 ms being separated by time intervals of 6.5-7.5 ms ( Figs. 3A, B View Fig ). The pulse rates were 4-7 pulses per s for type A and 60-80 pulses per s for type B (air temperature 20-21 °C). The call of M. montevidensis ( Table 1 View Tab , Figs. 1C, D View Fig , 2C View Fig , 3C View Fig ) differed in its higher pulse rates (type A with 8-10 pulses per s, type B with 85-95 pulses per s) and shorter pulse duration and pulse intervals. Parts of these differences may be explained by the higher air temperature (24 °C) in the recording of M. montevidensis but the call of this species presented also on average a lower dominant frequency (2.1-2.8 kHz versus 2.3-3.2 kHz in M. dorsalis ). In both species, certain specimens were able to change their calling frequency by up to 800 Hz within 100 ms. This considerable frequency modulation was observed especially in the B type call ( Fig. 1D View Fig ) and led to broadly overlapping spectral parameters between the species.
We recorded calling males of Melanophryniscus dorsalis and M. montevidensis in October and November. The habitats were similar in both species consisting of grassland or low dune vegetation on sandy soil in the coastal zones near the Atlantic Ocean. Males called from morning through afternoon and early night partially submerged in small temporary ponds. In a moist meadow in La Paloma, Uruguay, we observed many M. montevidensis being active in plain sunshine. In Torres, Brazil, we heard about 20 males of M. dorsalis calling in the afternoon and we observed an amplectant pair which attached a clutch with 20-30 eggs to an aquatic plant, about five centimeters below the water surface ( Fig. 4 View Fig ). In the laboratory, this pair spawned additional small clutches with a total amount of 105 black eggs, of 1.2- 1.4 mm in diameter, which did not develop into tadpoles.
Inter- and intraspecific morphological variation
Regarding the dorsal body pattern of Melanophryniscus dorsalis and M. montevidensis , we found considerable variation within both species. In a series of M. dorsalis from Torres (MCP 233-266), 28 out of 36 specimens exhibited a complete or partly interrupted red middorsal line, whereas the remaining specimens presented only a trace of this stripe between and behind the eyes, or above the anus ( Figs. 5 View Fig A-C). In a second series collected recently (MCP 6524-28), only one of the five specimens had a distinct middorsal line. The great variation in dorsal pattern is further expressed by several M. dorsalis in the MCN collection presenting yellow spots on their flanks (e. g., MCN 12588). Such lateral blotches are typical for M. montevidensis which, on the other hand, never show a red middorsal line ( Figs. 7 View Fig A-C). However, we also collected many M. montevidensis with no lateral blotches at all, although the uniformly black dorsal pattern is considered to be the main character for the identification of M. atroluteus ( Figs. 9A, C View Fig ; see also LANGONE 1994, 2002). Sixteen out of 25 individuals (64 %) of M. montevidensis collected in La Paloma, Uruguay (ZVCB 10625-10639, SMNS 11807-11816), were uniformely black on dorsum. This was also the case in 25 % of the specimens from Perla de Rocha, 50 km NE from La Paloma (ZVCB 10432- 10443), in 70 % of the specimens from Coronilla (ZVCB 11019-11035), and in 13 % of those from Cabo Polonio (ZVCB 10994- 11016).
In both M. dorsalis and M. montevidensis the ventral pattern varies considerably. Living specimens show a conspicuous pattern of symmetrically arranged red, orange-red or yellow blotches on black ground. In preservative, this colouration fades to a pale brown within some days. In living M. dorsalis all blotches are bright red, but never orange or yellow ( Figs. 6 View Fig A-C), whereas the ventral colouration of M. montevidensis varies from orange-red on the posterior half of belly and thighs, to orange or yellow on the anterior half of the belly and the throat ( Figs. 8 View Fig A-C). Due to this colouration, M. montevidensis is locally named “Sapito Bandera Española” (Spanish flag toadlet). There is also a considerable variation regarding size and shape of these blotches. In both species, most individuals are predominantly black on belly and throat, while in some specimens the red colouration predominates ( Fig. 6B View Fig ).
The ventral colouration of living M. atroluteus from the Brazilian type-locality in western Rio Grande do Sul and from Uruguay and Argentina is similar to that of M. montevidensis consisting of red, orange and yellow spots ( Fig. 9D View Fig ), but specimens from the Araucaria plateau of Rio Grande do Sul (São José dos Ausentes) are almost exclusively red with yellow colouration only on throat ( Fig. 9B View Fig ). Additionally, there are differences when comparing the snout-vent length of adult specimens from the Araucaria plateau (SVL in males about 25 mm, in females 28 mm; KWET & MIRANDA 2001) with that of individuals from western Rio Grande do Sul, Argentina and Uruguay (SVL in males between 19 and 21 mm, in females between 22 and 25 mm; LANGONE 1994). For M. dorsalis , our own measurements revealed a SVL of 20-25 mm in males and 24-27 mm in females, for M. montevidensis 20-23 mm in males and 22-27 mm in females, and for M. atroluteus 18-24 mm in males and 22-26 mm in females.
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