Integrative taxonomy reveals a new but common Neotropical treefrog, hidden under the name Boana xerophylla

Boana xerophylla is a common treefrog widely distributed in northern Brazil, Colombia, French Guiana, Guyana, Panama, Suriname, Trinidad and Tobago, and Venezuela. A recent study found molecular, acoustic, and morphometric differences between the populations located on opposite sides of the Orinoco River. Here, we carry out an updated molecular phylogenetic analysis, including new samples from all the countries along the distribution area, and analyzed additional call recordings from Brazil, Colombia, French Guiana, Panama, Trinidad and Tobago, and Venezuela. Our phylogenetic inference reveals three geographically restricted lineages: one in the eastern Guiana Shield (corresponding to B. xerophylla sensu stricto), another in the western Guiana Shield, and a third one north of the Orinoco River. Morphological and acoustic data agree with the differentiation between the populations north of the Orinoco River and the eastern Guiana Shield despite the low genetic p-distances observed (16S rRNA: 0.7–2.2 %). We argue that the populations north of the Orinoco River correspond to a new species, sister of B. xerophylla. We name and describe Boana platanera sp. nov. from the southern versant of the Cordillera de Mérida (08º48’26’’ N, 70º30’46’’ W, WGS 84; 947 m asl), Venezuela, and refer all the populations north of the Orinoco River currently identified as B. xerophylla to this species. The new species can be readily diagnosed from B. xerophylla (characters of the latter in parentheses) by a pale orange-yellow or light brown dorsal coloration (dark brown to green), palpebral membrane with dark pigments (pigments absent); pericloacal region dark brown (cream), advertisement call with shorter first note length than B. xerophylla. This study represents an empirical example regarding false negatives behind genetic thresholds for species discovery, appraising the use of integrative taxonomic approaches.

A new species of driftwood catfish Centromochlus Kner, 1858 (Siluriformes, Auchenipteridae, Centromochlinae) from Tocantins-Araguaia River drainage

The genus Centromochlus includes eight catfish species in the Amazon and Orinoco river systems: C. schultzi from Xingu and Tocantins-Araguaia rivers; C. melanoleucus from Tapajós and Teles Pires rivers; C. macracanthus from Negro River; C. orca from Nhamundá River; C. heckelii and C. existimatus from Amazon and additionally at the Essequibo rivers; C. carolae and C. musaica from Orinoco River system. Recent field expeditions and collection examination revealed an undescribed species of Centromochlinae that has compatible features with Centromochlus. We herein describe a new species of Centromochlus from the Tocantins-Araguaia River drainage, diagnosed among most Centromochlinae by having a vermiculated color pattern on the dorsum and included in Centromochlus by sharing the derived features: ventrolateral position of eye socket; sphenotic notched for the exit of infraorbital canal; and posterior serrations along pectoral-fin spine numerous. The new species is diagnosed from congeners by having the pectoral-fin spine with dark bars, alternating with light bars (vs. pectoral-fin spine with light and uniform color in all Centromochlus); and it is further distinguished from its congeners (except C. carolae) by the ventral surface of head moderate to largely pigmented (vs. ventral surface of head unpigmented in C. heckelii, C. existimatus, C. orca, C. musaicus, C. schultzi, with few scattered dark chromatophores in C. macracanthus and C. melanoleucus; see diagnosis). A discussion about the systematics of the genus, plus the conservation status of the new species, and an identification key to species of Centromochlus, are also provided.

The Negative Impact of Biomass Burning and the Orinoco Low-Level Jet on the Air Quality of the Orinoco River Basin

Biomass burning (BB) is a common activity in developing countries and has been identified as a serious air pollution threat. The present work evaluates the air quality of the largest town in the extensive Colombian savannas (250,000 km2) for the first time, from measurements over three consecutive years (2017-2020). Although the air quality in Villavicencio is good in terms of PM10 and O3 for most of the year, the pollution levels for both pollutants exceed the World Health Organization recommended limits during the dry season (February to April). The combination of the Orinoco low-level jet (OLLJ) with the BB emissions from the Venezuelan and the Colombian savannas was identified as the main cause of the poor air quality episodes during the dry season in this city. Organic carbon derived from reanalysis was identified as the main component of the high PM10 concentrations during the dry season. However, mineral dust and sea salt particles were also found to play an important role in the poor air quality observed in Villavicencio and likely along the Orinoco river basin region. Finally, between November and March, the OLLJ was found to be an efficient mechanism for the transport of air pollutants from the Atlantic Ocean and the savannas regions in the Orinoco River Basin in Venezuela and Colombia towards southern regions of Colombia, and in some cases, Ecuador.

The Anaconda Challenge

This chapter focuses on the llanos, Venezuela’s natural floodplain, where the author decided to start his study of anacondas. The llanos is a flatland that comprises about a third of both Venezuela and Colombia. It is composed of an extensive system of natural, seasonally flooded grasslands. The llanos is located to the north and west of the Orinoco River and sits on the northern borders of the Amazon basin. Because of this, most of the wildlife of the Amazon can be found in the llanos, where it is easier to observe animals in the open vegetation of the savanna. The extreme seasonality of the llanos made all the difference in the success of the author’s anaconda research. Anacondas, being aquatic, concentrate in the few water bodies that hold water during the dry season. During this time, the chance of finding anacondas was much higher. The chapter then explores the physical build of snakes. Most snakes have adaptations of the skull and jaws involving mobile hinges, and a whole arrangement of joints and muscles evolved for swallowing large prey. The extra mobility of the snake’s jaws is obtained by giving up solid skull sutures that the ancestral lizards had, rendering the snake’s head more vulnerable to damage.

First confirmed record of the Guianan White-eared Opossum, Didelphis imperfecta Mondolfi & Pérez-Hernández, 1984 (Didelphimorphia, Didelphidae), from Colombia

We report the first confirmed occurrence of the Guianan White-eared Opposum Didelphis imperfecta Mondolfi & Pérez-Hernéndez, 1984 (Didelphimorphia: Didelphidae) from Colombia. The individual was captured in a tropical lowland rain forest in the easternmost portion of the Colombian Orinoco Llanos region. The species is endemic of the Guiana Shield and has the smallest distribution area among the species of the genus. Our record shows that the Orinoco river does not constitute a biogeographical barrier for the species. To date, only two species of the genus Didelphis Linnaeus, 1758 have been recorded in Colombia, our results increase the reported number of records for this genus.

A new species of Pimelodella Eigenmann & Eigenmann, 1888 (Siluriformes: Heptapteridae) from the Orinoco River basin

A new species of Pimelodella is described from western Andean tributaries of the Orinoco River basin. The new species differs from all congeners by a unique set of characters that includes long maxillary barbel, surpassing the dorsal lobe of the caudal fin; relatively short adipose fin (32.8–36.4 of SL); 40–42 total vertebrae; posterior margin of pectoral-fin spine with 12–18 retrorse dentations along basal two thirds; laterosensory canal foramina of dentary and preopercle large and externally conspicuous; a brown faint and narrow midlateral stripe extending from the pseudotympanum, fading posteriorly along the caudal peduncle, and ending as a spot at the caudal-fin base; and dorsal-fin base darkly pigmented, from spinelet to posteriormost interradial membrane. Taxonomic status of P. pallida and presence of P. cruxenti in Colombia are also discussed.