''Brachycephalus pulex'', also known as the Brazilian flea toad and the Serra Bonita flea toad, is a species of small

frog A frog is any member of a diverse and largely Carnivore, carnivorous group of short-bodied, tailless amphibians composing the order (biology), order Anura (ανοὐρά, literally ''without tail'' in Ancient Greek). The oldest fossil "proto-f ...

s in the family

Brachycephalidae The Brachycephalidae () are a family of frogs confined to eastern and southern Brazil and northern Argentina. The family is composed of two externally quite different genera: the tiny, often (but not always) colourful and plump saddleback toads ( ...

. It is one of more than 35 named species within the genus '' Brachycephalus''. It has been suggested to represent the smallest known vertebrate, with an average

snout–vent length Snout–vent length (SVL) is a morphometric measurement taken in herpetology from the tip of the snout to the most posterior opening of the cloacal slit (vent)."direct line distance from tip of snout to posterior margin of vent" It is the most c ...

of in mature males.

Discovery

The first ''Brachycephalus pulex'' specimens were found between December 2009 and July 2010 in the Serra Bonita mountain range in the Camacan and

Pau Brasil ''Paubrasilia echinata'' is a species of flowering plant in the legume family, Fabaceae, that is endemic to the Atlantic Forest of Brazil. It is a Brazilian timber tree commonly known as Pernambuco wood or brazilwood ( pt, pau-de-pernambuco, ; ...

municipalities of

Bahia Bahia ( , , ; meaning "bay") is one of the 26 Federative units of Brazil, states of Brazil, located in the Northeast Region, Brazil, Northeast Region of the country. It is the fourth-largest Brazilian state by population (after São Paulo (sta ...

, Brazil. The

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...

specimen, MNRJ 69646, is an adult specimen. Many other specimens, including juveniles, sub-adults, and adults, were collected and assigned as paratopotypes ( paratype specimens found in the holotype locality). In January 2011, Marcelo Felgueiras Napoli,

Ulisses Caramaschi Ulisses Caramaschi is a Brazilian herpetologist specializing in neotropical frogs. He works at the National Museum of Brazil and is a professor at its Department of Vertebrates. Education Caramaschi possesses a bachelor's degree from the Botucat ...

Carlos Alberto Gonçalves da Cruz Carlos Alberto Gonçalves da Cruz (born 1944) is a Brazilian herpetologist. He works at the National Museum in Rio de Janeiro. Taxa named in Cruz's honor * '' Craugastor cruzi'' (McCranie, Savage & Wilson, 1989) * '' Hyla cruzi'' (Pombal & Bast ...

& Iuri Ribeiro Dias described ''Brachycephalus pulex'' as a new species of ''Brachycephalus'' based on these specimens.

Etymology

The

specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...

, "''pulex''", is also the generic name of the

flea Flea, the common name for the order Siphonaptera, includes 2,500 species of small flightless insects that live as external parasites of mammals and birds. Fleas live by ingesting the blood of their hosts. Adult fleas grow to about long, a ...

, ''

Pulex irritans The human flea (''Pulex irritans'') – once also called the house flea – is a cosmopolitan flea species that has, in spite of the common name, a wide host spectrum. It is one of six species in the genus ''Pulex''; the other five are all confin ...

''. This references the tiny size of the species and the comparable ability to jump well. It is also fitting since certain species of ''Brachycephalus'' are also known as "flea-toads". ''Brachycephalus pulex'' is also known by the common names "Brazilian flea toad" and "Serra Bonita flea toad".

Description

''Brachycephalus''—along with other related flea-toads—has a leptodactyliform body shape, with a slender pectoral girdle and body, well-developed hind limbs, and a long, narrow head and snout. This is in contrast to the bufoniform body plan of the

pumpkin toadlet The pumpkin toadlet (''Brachycephalus ephippium''), or Spix's saddleback toad, is a small and brightly coloured species of frog in the family Brachycephalidae. This diurnal species is endemic to southeastern Brazil where it is found among leaf ...

s within the genus ''Brachycephalus'', which have poorly-developed hind limbs and wider heads. Because of its developed hind limbs, ''Brachycephalus pulex'' was capable of long-distance jumping. Its describers noted this behavior when observing individuals ''

in natura ''In natura'' (Latin for "in Nature") is a phrase to describe conditions present in a non-laboratory environment, to differentiate it from ''in vivo'' (experiments on live organisms in a lab) and ''ex vivo'' (experiments on cultivated cells isolate ...

'', when one specimen feigned death after jumping several times and landing on a leaf. Buniform pumpkin toadlets, however, have very poor jumping ability. The skeletal structure of ''Brachycephalus pulex'' is nonhyperossified, meaning that the skull bones and spinal processes of the

sacral Sacral may refer to: *Sacred, associated with divinity and considered worthy of spiritual respect or devotion *Of the sacrum The sacrum (plural: ''sacra'' or ''sacrums''), in human anatomy, is a large, triangular bone at the base of the spi ...

and presacral vertebral lack sculpturing.

Distribution and conservation

''Brachycephalus pulex'' has only been found in the type locality. It lives in mountainous evergreen

subtropical The subtropical zones or subtropics are geographical zone, geographical and Köppen climate classification, climate zones to the Northern Hemisphere, north and Southern Hemisphere, south of the tropics. Geographically part of the Geographical z ...

to tropical moist montane forests in the

Atlantic Forest The Atlantic Forest ( pt, Mata Atlântica) is a South American forest that extends along the Atlantic coast of Brazil from Rio Grande do Norte state in the northeast to Rio Grande do Sul state in the south and inland as far as Paraguay and th ...

biome, ranging from an elevation of

above sea level Height above mean sea level is a measure of the vertical distance (height, elevation or altitude) of a location in reference to a historic mean sea level taken as a vertical datum. In geodesy, it is formalized as ''orthometric heights''. The comb ...

. In can most easily be found inhabiting dense leaf litter in areas with

epiphytic An epiphyte is an organism that grows on the surface of a plant and derives its moisture and nutrients from the air, rain, water (in marine environments) or from debris accumulating around it. The plants on which epiphytes grow are called phoroph ...

bromeliads. There is a low abundance of this species, and populations are decreasing in numbers due to

habitat loss Habitat destruction (also termed habitat loss and habitat reduction) is the process by which a natural habitat becomes incapable of supporting its native species. The organisms that previously inhabited the site are displaced or dead, thereby ...

. The

IUCN The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...

listed

urban expansion Urban sprawl (also known as suburban sprawl or urban encroachment) is defined as "the spreading of urban developments (such as houses and shopping centers) on undeveloped land near a city." Urban sprawl has been described as the unrestricted growt ...

agriculture Agriculture or farming is the practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that enabled people to ...

, and livestock grazing as the leading causes for habitat loss—and thus declining populations—in this species.

Classification

''Brachycephalus pulex'' is considered to be a "flea-toad", one of the two major subcategories of frogs within the genus ''Brachycephalus'' (the other being pumpkin toadlets). Pumpkin toadlets are the more speciose of the two groups, with only four named flea-toad species, which form a

paraphyletic group In taxonomy, a group is paraphyletic if it consists of the group's last common ancestor and most of its descendants, excluding a few monophyletic subgroups. The group is said to be paraphyletic ''with respect to'' the excluded subgroups. In co ...

. ''Brachycephalus'', along with ''

Ischnocnema ''Ischnocnema'' is a genus of frogs from eastern Brazil and north-eastern Argentina. They comprise the former ''Eleutherodactylus'' from this region, but they are closer to '' Brachycephalus'' than the "true" ''Eleutherodactylus''. Consequently, ...

'', are the two genera comprise the family

. The relationships of this clade in relation to other frog families are shown in the cladogram below: In 2020, Condez, Haddad & Zamudio tested the

phylogenetic In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...

relationships of ''Brachycephalus'' species. In their first analysis, fellow flea-toad '' Brachycephalus hermogenesi'' was recovered as the

basalmost In phylogenetics, basal is the direction of the ''base'' (or root) of a rooted phylogenetic tree or cladogram. The term may be more strictly applied only to nodes adjacent to the root, or more loosely applied to nodes regarded as being close to th ...

member of the genus, followed by ''B. pulex'', which was the

sister taxon In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and t ...

to all other species in the genus. Their second analysis placed ''B. hermogenesi'' as the sister taxon to ''B. pulex'', with this clade within one of two major ''Brachycephalus'' clades. Their results from this analysis are displayed in the cladogram below, including new, unnamed species. Flea-toads are noted in orange. In contrast, dos Reis ''et al''. (2020) also analyzed the phylogenetic relationships of ''Brachycephalus'' species, in the context of skull morphology and skeletal ossification. They recovered ''Brachycephalus pulex'' as the basalmost member of the genus, as the sister taxon to all other species.

References

{{Taxonbar, from=Q2923287

pulex ''Pulex'' is a genus of fleas. It comprises seven species. One is the human flea (''P. irritans''), and five of the others are confined to the Nearctic and Neotropical realms. Species ''Encyclopedia of Life'' lists seven species: *''Pulex alvare ...