Odorrana graminea

Odorrana graminea have a dorsoventrally compressed body with large eyes. Dorsum is green with smooth skin; flanks are brown with yellow marbling and with slight granulations. They are relatively large frogs, particularly the females: females grow to a snout–vent length of 78–100 mm (3.1–3.9 in), whereas males attain a more modest length of 42–53 mm (1.7–2.1 in). Apart from size, males differ from females by their smaller digital disks, stronger forearms, larger tympanum, velvety nuptial pads on thumb, and paired gular pouches below jaw articulations.[6]

Odorrana graminea can produce ultrasonic calls. This is very rare among non-mammalian vertebrates, but has been shown for the related concave-eared torrent frog Odorrana tormota. However, O. graminea does not have recessed ears, a feature believed to be important for ultrasonic hearing in O. tormota. Exactly how O. graminea detects ultrasound remains yet to be determined.[4]

Odorrana graminea is found in southern China (from southern Anhui and northern Zhejiang west to extreme southern Gansu, southeastern Sichuan, and southern Yunnan to the border of Vietnam, Laos and Myanmar, although it has not yet been recorded in the latter two countries. Its type locality is the Wuzhi Mountain in Hainan.[7] Until the revision of "Rana livida" in 2003,[6] this frog was considered a synonym of Odorrana livida.[7] The species occurs near fast-flowing rivers and streams in montane (sub-)tropical forests.[1]

Odorrana graminea is one of 56 species in the genus Odorrana.  All Odorrana frogs live in tropical and subtropical mountainous regions in East and South Asia. The genus is rapidly growing, with over twenty new species documented since 2005.[8]

The conservation status of Odorrana graminea is Least concern according to the International Union for Conservation of Nature.[1] Species in genus Odorrana ranges from “Least Concern” (e.g., Odorrana schmackeri) to “Endangered” (e.g., Odorrana splendida) - with many other species also documenting data deficiency.[1]

Information on the O. graminea diet is lacking. However, studies of the related Odorraa morafkai in Southern Vietnam suggest a diverse diet of both aquatic and terrestrial prey. 90% of O. morafkai prey consists of insects, especially beetles. Distribution of prey type varied with season, likely due to increased range of access during the rainy versus dry season.[10]

Odorrana graminea has a large repertoire of calls. They are highly variable both between and within individuals. Odorrana graminea has six basic types of calls with variation within each category: a. short tonal call (dominant type), b. long tonal call, c. multi-note calls, d. tonal calls with shallow or no frequency modulation, e. narrow-band call, and f. staccato call. All except for narrow-band and staccato contain ultrasonic frequencies (20 kHz or higher). Narrow-band and staccato calls are specifically used for short-range communication.[5]

Genus Odorrana exhibits notably abundant levels of anti-microbial peptides (AMPs) compared to other amphibians. Antimicrobial defense is considered a necessary tool to enable general amphibian colonization of damp or aquatic habitats, which tend to be pathogen-rich.[16] AMPs function as a crucial innate immunity defense against pathogenic microbes.[17] They are generally 10-50 residues long and vary in both sequence and structure for species across genus Odorrana. AMPs function by damaging the membranes of target organisms such as bacteria, fungi, parasites, and viruses. Different AMPs target unique ranges of microbes. Growing concern regarding increased antibiotic resistance has prompted further interest into the use of AMPs in medicinal applications.[18]

Research conducted on 22 AMPs derived from relative Odorrana tiannanensis demonstrated low potency against bacteria that are relevant to human health. Researchers hypothesize that either 1) these bacteria are not harmful to the frog, and friendly colonization helps to defend the frog against harmful environmental pathogens, or 2) these bacteria are eliminated by an immune system other than AMP.[18]

Four Odorrana tiannanensis AMPs were tested for antioxidant properties against free radicals, which can arise due to factors such as oxidative stress of UV exposure. Three of the four exhibited significant radical scavenging activity. Level of radical scavenging activity was correlated with the number of cysteine residues and disulfide bridges present in the AMP.[18]

Unlike certain other amphibians, the Odorrana tiannanensis AMPs under study did not demonstrate any cytotoxic or tumor cell anti-proliferative properties.[18]

Gut microbiota is affected by a large set of factors such as diet, habitat, health, and age. Temperature has been observed to induce direct changes in microbiome diversity and composition in terrestrial amphibians.[19] Habitat proximity agriculture is known to impact expression levels of bacterial genes associated with pesticide degradation. In this way, the microbiome was observed to adapt in a way that increased frog health and survival.[20]

A 2022 study investigating gut microbiome determinants compared the compositions of O. graminea and closely related Odorrana tormota and Amolops wuyiensi .[21] All three species are sympatric in Eastern China and tend to exist on rocks nearby running water. Researchers found significantly differing microbiota in all three species in terms of relative abundance of gut microbiota and predicted gene function. In all three species of this study, the present phyla include (in decreasing abundance): Proteobacteria, Bacteroidetes, Verrucomicrobia, and Firmicute. Proteobacteria is hypothesized to facilitate stress tolerance to cold streams.[21] Relative abundance of various microbiota depends on habitat - but does not severely impact core microbiome functionality.[20]