Brachycephalus pitanga

Brachycephalus pitanga , el sapo calabaza rojo , es una especie de anuro pequeña y de colores brillantesde la familia Brachycephalidae . ^{[ 1 ] [ 2 ] [ 3 ]} Es endémico de las selvas atlánticas en el estado de São Paulo , en el sureste de Brasil, y solo se conoce en cuatro localidades a una altitud de 900–1140 m (2950–3740 pies) en Ubatuba (la localidad tipo ) y São Luiz do Paraitinga . ^{[ 4 ]} Puede ser muy común donde se encuentra, ^{[ 5 ]} y dos de las localidades conocidas están protegidas por el ^Parque Estatal Serra do Mar. ^{[ 4} ]A diferencia de muchos otros sapos calabaza (género Brachycephalus ), el sapo calabaza rojo no se considera amenazado . ^{[ 4 ]}  

Aunque muy pequeño, con una longitud desde el hocico hasta la cloaca de 10,8–12,1 mm (0,43–0,48 pulgadas) en los machos adultos y de 12,6–14 mm (0,50–0,55 pulgadas) en las hembras adultas, el sapo calabaza rojo es una especie de tamaño mediano de Brachycephalus . ^{[ 5 ]}    

Es predominantemente naranja, pero con marcas rojas irregulares en la parte superior. La extensión de estas marcas varía enormemente; desde individuos que casi no tienen ninguna (son casi completamente naranjas) hasta individuos cuyas partes superiores son casi completamente rojas. ^{[ 5 ]} Su nombre específico, pitanga, fue elegido porque significa "de color rojo" en las lenguas tupí-guaraní . ^{[ 6 ]} Los colores brillantes se consideran aposemáticos ; ^{[ 7 ]} aunque no se ha estudiado en el sapo calabaza rojo, los estrechamente relacionados y también de colores brillantes B. ephippium y B. pernix tienen tetrodotoxina y toxinas similares en su piel y órganos. ^{[ 8 ]}

The red pumpkin toadlet and its close relative B. ephippium have bones that are fluorescent, which is visible through their skin when exposed to UV light.^[7][9] It was initially speculated that the fluorescent colour also is aposematic or that it is related to mate choice (species recognition or determining fitness of a potential partner),^[9] but later studies indicate that the former explanation is unlikely, as predation attempts on the toadlets appear to be unaffected by the presence/absence of fluorescence.^[7]

The red pumpkin toadlet is diurnal and live in leaf litter on the rainforest floor. During dry weather they mostly remain hidden and there is little activity, but during the wet season and high humidity they can be seen walking on top of the leaf litter.^[5]

Calling by adults of both sexes and juveniles can be heard year-round, but follows the same wet/dry pattern as their general activity.^[5] Peculiarly, this species and its close relative B. ephippium are unable to hear the frequency of their own advertising calls, as their ears are underdeveloped. Instead their communication appears to rely on certain movements like the vocal sac that inflates when calling, mouth gaping and waving of their arms.^[10][11] It is speculated that their calling is a vestigiality from the ancestral form of the genus, whereas their reduced hearing ability (they do have some hearing ability in frequencies outside their call) is a novel change in these species. Sounds make them more vulnerable to predators, but there has likely been little direct evolutionary pressure to lose it because of their (confirmed in B. ephippium, presumed in B. pitanga) toxicity.^[10][11]

• Polka-dot tree frog (Hypsiboas punctatus) — the first frog discovered to be fluorescent, in 2017