Engystomops petersi
| Engystomops petersi | |
|---|---|
| |
Scientific classification 
| |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Amphibia |
| Order: | Anura |
| Family: | Leptodactylidae |
| Genus: | Engystomops |
| Species: | E. petersi
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| Binomial name | |
| Engystomops petersi Jiménez de la Espada, 1872
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| Synonyms | |
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Physalaemus petersi (Jiménez de la Espada, 1872) | |
Engystomops petersi (common name: Peters' dwarf frog) is a species of frog in the family Leptodactylidae. It is found in Amazonian Colombia, Ecuador, and Peru. It is morphologically similar to its sibling species, Engystomops freibergi, and for a period the latter was considered to be a junior synonym of Engystomops petersi. Taxonomy and classification of this species is constantly evolving due to evolution of behavioral isolation and rapid speciation in the region. There are records from the Guianas that have not yet been allocated to either species.[2] Divergence of these two species seems to have been driven by behavioural isolation related to male call characteristics more than geographic isolation.[3]
Taxonomy and Description
The genus Engystomops is part of the family Leptodactylid. Previously, the genus Engystomops has been grouped in with other Amazonian genera like Eupemphix and Physalaemus.[4] These names are routinely exchanged making it hard to characterize differences among different species. Previously, Eupemphix paraensis, Eupemphix schereri, and Engystomops petersi were considered to be distinct species, however morphological analyses of these frogs revealed that they were conspecifics and synonymous species.[4]
Engystomops petersi are relatively small frogs. Males measure 21–31 mm (0.83–1.22 in) in snout–vent length and females 25–39 mm (0.98–1.54 in). Dorsal colouration is variable. Skin on dorsum is warty, bearing small tubercles with scattered larger tubercles.[5] This species lacks maxillary and premaxillary teeth.[4] E. petersi also has terminal phalanges that are T-shaped. E. petersi also has two salivary glands known as parotoid glands that are generally visible. The hands and feet of E. petersi are characterized by bulbous fingers in which the first finger is greater in length compared to the second finger.[4] The skin texture of E. petersi is said to be tuberculate. Their build varies from slender to stocky. They are also distinct from other similar frogs because of their concealed eardrum or tympanum in some females and prominent tympanum in males.[4]
Larval Morphology
The larval morphology of E. petersi has been thoroughly studied and compared to other members of the Engystomops genus. E. petersi is generally thought to have the largest size compared to other Engystomops larvae.[6] The larval structure is mainly composed of the body, snout, oral disc, vent tube, tail, dorsal fin, ventral fin, and other organs. The length of the larva usually is around 22.7 mm. Its body length comprises a little less than half of its total length.[6] It has a broad snout that is wide and round with nostrils that are slightly discolored on the outer rim. Its oral disc is filled with small papillae arranged rows with various tip lengths and shapes.[6] The jaw has a dark coloration and is marked by serrations that follow the arc-shaped pattern of the jaw. E. petersi tadpoles also have a vent tube that is attached to the ventral fin of the body.[6] E. petersi larvae have tails that are approximately 60% of their entire body length with a narrowly rounded tip. A distinguishing characteristic of E. petersi larvae compared to Engystomops species is the presence of prominent elliptical paravertebral glands.[6]
The coloration of E. petersi larva has only been studied after the sample has been preserved. In preservative, the coloration of the larva is mainly dark to light brown. One can also observe a spotty mesh pattern with speckles around certain regions of the body. The tail is also light brown with speckles all over.[6] Finally, the fins are translucent with threadlike markings.[6]
Habitat and Distribution
Engystomops petersi is a common species that inhabits primary and secondary forests and forest edges. They are terrestrial frogs often found in leaf-litter.[1] The genus Engystomops is a lineage of frogs located in the Andean foothills of Ecuador, Peru, Bolivia, to the Amazon basin in Brazil.[7] Speciation events of the genus are well studied and look towards mitochondrial DNA, mating calls, and cytogenetic variation among different frogs in the area. The Engystomops petersi makes up the northwestern clade of the genus Engystomops and has been found to be its own species located in northern Peru and Ecuador.[7] Puyo, Ecuador is a hub for Engystomops petersi frogs and has been used for comparative karyotypic analysis with other frog species in the area. Its karyotype is unique compared to other Engystomops species in the area and specifically diverges from the southwestern clade known as E. freibergi located in southern Peru and Brazil.[7]
Genetic Population Structure
Sexual selection has been thought to play a role in evolutionary speciation of Engystomops. Female E. petersi individuals discriminate against certain mating calls from foreign populations and will recognize calls from certain locations.[7] This has been thought to contribute to speciation of E. petersi due to behavioral isolation of the species. The genetic variation among different Engystomops species is also demonstrated by variations within karyotypes with different banding patterns and clade divergence.[7]
Feeding Behavior
E. petersi diet consists exclusively of termites.[8] This is in contrast to the Engystompos pustulosus which has a larger diet breadth compared to the specialized diet of the E. petersi.[8] E. petersi have been observed to feed in groups in some circumstances.[9] For instance, in a herpetological study in Bolivia, E. petersi have been observed feeding on termites in a semicircular formation.[9] This is one of the few examples of group feeding seen in herpetofauna in the region. They tend to feed on leaf litters on the rainforest floor.
Reproduction and Mating
The breeding period coincides with the rainy season.[1] The male call consists of a prefix and a "whine" component, and in some populations only, a third "squawk" component. Eggs are laid in foam nests.[5]
Mate choice and courtship
E. petersi females display preferential mate selection towards males with conspecific calls. The characteristic call of the E. petersi consists of two parts. The first part of the advertisement call is known as the prefix.[10] The prefix consists of one or two short bursts of sound at a frequency of about 20-70 ms. The second part of the advertisement call consists of the whine. The whine is the lower frequency sweeping call that occurs after the prefix. In certain areas E. petersi populations also add a suffix to the end of the of the whine that occurs at a higher frequency compared to the rest of the call.[10] Within E. petersi populations there has also been divergence in mating call patterns in geographically isolated regions.[10] In three geographically isolated regions in Ecuador, mating calls of E. petersi vary in frequency in different regions. This provides evidence of further speciation of E. petersi over time.
Female E. petersi tend to prefer local calls over male calls from E. petersi species from foreign regions.[10] They don’t tend to recognize different frequency calls and tend to prefer mating calls from local frogs. They also prefer the complex calls that include the suffix at the end compared to the more simple calls with the prefix and whine only.[10] The strong preference for local males shows patterns of behavioral isolation in this species. This is important for understanding genetic drift, sexual selection, and speciations in the Amazon where gene drift is so high. The rapid speciation of E. petersi makes it a good subject for analysis of evolutionary patterns in these environments.
Genetic Diversity
E. petersi are known to be in behavioral isolation. E. petersi females prefer conspecific chorus calls to calls from other species.[11] This is why the E. petersi frogs have evolved to be reproductively isolated. However, a few instances have been found involving reproduction between heterospecific species. This has led to hybrid specification with minimal phenotypic differences between frogs in close geographic proximity. However, E. petersi has general karyotype differences among different species making fertilization and development less likely to succeed.[11] Fertilization crosses with E. magnus and E. selva led to reduced fertilization rates and overall decrease in fertility.[11] This has been hypothesized to be because of high variation in chromosome structure, banding pattern, and length between the different species creating unstable karyotypes in future progeny.[11] Thus, it has been thought that sexual selection and mate choice has led to increased speciation among the E. petersi species.
Conservation and Threats
E. petersi have been used in conservation studies for the anuran population in the Andes.[12] E. petersi are potentially threatened by the invasive species of rainbow trout that has infested the water of the Ecuadorian Andes. Rainbow trout serves as a vector for pathological transmission of disease that affects tadpole survival rate of E. petersi. Studies have shown that rainbow trout can be a carrier of Saprolegnia diclina and can effectively transmit this disease to E. petersi tadpoles, decreasing mortality of the eggs and overall decreasing anuran populations in the area.[12] With the increases farms of rainbow trout in the area, this can be a potential threat to many anuran species in the area.
Habitat loss is also a major concern for E. petersi. The Ecuadorian forests have lost almost 60% of habitats due to deforestation.[13] There have also been many legal and illegal mining and logging activities that have also contributed to the habitat loss.[13] This is a threat not only to E. petersi but all other biodiversity in the region. Since E. petersi is localized to this small region this habitat loss could be especially devastating for this species.
References
- ^ a b c IUCN SSC Amphibian Specialist Group (2018). "Engystomops petersi". IUCN Red List of Threatened Species. 2018: e.T57270A85893490. doi:10.2305/IUCN.UK.2018-1.RLTS.T57270A85893490.en. Retrieved 17 November 2021.
- ^ Frost, Darrel R. (2014). "Engystomops petersi Jiménez de la Espada, 1872". Amphibian Species of the World: an Online Reference. Version 6.0. American Museum of Natural History. Retrieved 1 March 2014.
- ^ Funk, W. C.; Cannatella, D. C.; Ryan, M. J. (2009). "Genetic divergence is more tightly related to call variation than landscape features in the Amazonian frogs Physalaemus petersi and P. freibergi". Journal of Evolutionary Biology. 22 (9): 1839–1853. doi:10.1111/j.1420-9101.2009.01795.x. PMID 19583696.
- ^ a b c d e Lynch, John D. (1970). "Systematic Status of the American Leptodactylid Frog Genera Engystomops, Eupemphix, and Physalaemus". Copeia. 1970 (3): 488–496. doi:10.2307/1442276. ISSN 0045-8511.
- ^ a b Funk, W. C.; Angulo, A.; Caldwell, J. P.; Ryan, M. J.; Cannatella, D. C. (2008). "Comparison of morphology and calls of two cryptic species of Physalaemus (Anura: Leiuperidae)". Herpetologica. 64 (3): 290–304. doi:10.1655/08-019.1.
- ^ a b c d e f g do Nascimento, Filipe A. C.; de Sá, Rafael O.; Garcia, Paulo C. de A. (October 2022). "Larval morphology of Amazonia foam‐nesting frogs of the genus Engystomops (Anura: Leptodactylidae: Leiuperinae)". Journal of Morphology. 283 (10): 1299–1317. doi:10.1002/jmor.21503. ISSN 0362-2525.
- ^ a b c d e Targueta, C. P.; Rivera, M.; Souza, M. B.; Recco-Pimentel, S. M.; Lourenço, L. B. (2010-03-01). "Cytogenetic contributions for the study of the Amazonian Engystomops (Anura; Leiuperidae) assessed in the light of phylogenetic relationships". Molecular Phylogenetics and Evolution. 54 (3): 709–725. doi:10.1016/j.ympev.2009.10.018. ISSN 1055-7903.
- ^ a b Narváez, Andrea E.; Ron, Santiago R. (December 2013). "Feeding Habits of Engystomops pustulatus (Anura: Leptodactylidae) in Western Ecuador". South American Journal of Herpetology. 8 (3): 161–167. doi:10.2994/SAJH-D-13-00012.1. ISSN 1808-9798.
- ^ a b Powell, Randy L.; Eversole, Cord B.; Lizarro, Dennis; Crocker, Ashton V.; Calderón Vaca, Gonzalo; Surovic, Elizabeth A. (2020-09-11). "Bothrops taeniatus Wagler, 1824 (Serpentes, Viperidae): additional country record and list of voucher specimens for Bolivia". Check List. 16 (5): 1143–1147. doi:10.15560/16.5.1143. ISSN 1809-127X.
{{cite journal}}: CS1 maint: unflagged free DOI (link) - ^ a b c d e Guerra, Mónica A.; Ron, Santiago R. (2008). "Mate choice and courtship signal differentiation promotes speciation in an Amazonian frog". Behavioral Ecology. 19 (6): 1128–1135. doi:10.1093/beheco/arn098. ISSN 1465-7279.
- ^ a b c d Trillo, Paula A.; Narvaez, Andrea E.; Ron, Santiago R.; Hoke, Kim L. (2017-04-07). "Mating patterns and post-mating isolation in three cryptic species of the Engystomops petersi species complex". PLOS ONE. 12 (4): e0174743. doi:10.1371/journal.pone.0174743. ISSN 1932-6203. PMC 5384746. PMID 28388628.
{{cite journal}}: CS1 maint: unflagged free DOI (link) - ^ a b Martín-Torrijos, Laura; Sandoval-Sierra, Jose Vladimir; Muñoz, Jesús; Diéguez-Uribeondo, Javier; Bosch, Jaime; Guayasamin, Juan M. (2016-01-01). "Rainbow trout (Oncorhynchus mykiss) threaten Andean amphibians". Neotropical Biodiversity. 2 (1): 26–36. doi:10.1080/23766808.2016.1151133.
- ^ a b "New report reveals northern Ecuadorian region has lost 61 percent of forests". Mongabay Environmental News. 2019-09-04. Retrieved 2022-11-09.