Piabucus caudomaculatus

Piabucus caudomaculatus is a small freshwater fish inhabiting the rivers of South America. It was the first member of the family Iguanodectidae to be reported from Bolivia, and it remains endemic to the region, found solely in the Mamoré river basin. It displays a preference for slow-moving waterways and has a largely insectivorous diet.

Piabucus caudomaculatus
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Characiformes
Family: Iguanodectidae
Genus: Piabucus
Species:
P. caudomaculatus
Binomial name
Piabucus caudomaculatus
Vari, 1977

Description

Piabucus caudomaculatus reaches a maximum of 9.6 cm (3.8 in) standard length (SL).[2] This makes it the smallest member of the genus. The largest is Piabucus dentatus, at 12.9 cm (5.1 in) SL, and the second-largest is Piabucus melanostoma, at 11.5 cm (4.5 in) SL.[3] Members of Piabucus are characterized by a deep chest and long pectoral fins, which sets them apart from otherwise-similar members of sister genus Iguanodectes.[4]

Piabucus caudomaculatus lacks an adipose fin. There is a spot of dark pigmentation on the lower jaw, a feature it shares with Piabucus melanostoma.[5] There is another dark spot that extends from the caudal peduncle to the middle caudal-fin rays.[6]

Image description: Piabucus melanostoma, a rather slender fish with a body shape like a minnow's. It has a relatively deep chest and silver-yellow scales. Its fins are transparent, with the exception of a spot of color in the middle of its tail fin. There is a reflective yellow-green line running down its side. End image description.
Piabucus melanostoma, to which P. caudomaculatus bears a notable resemblance.

Visually, P. caudomaculatus bears similarities to congener P. melanostoma, but there are several differentiating characteristics in their respective morphometries. These include differences in lateral line scales (75-76 in caudomaculatus and 82-87 in melanostoma), dorsal-fin rays (8 or 9 vs. 11), and anal-fin rays (36-38 vs. 44-46).[7] As well as in appearance, the two species are similar in dentition, both bearing a single tooth row in the premaxilla.[8]

Sexual Dimorphism

Males from all three species of Piabucus develop lappets (fleshy extensions) and small hooks on the foremost few rays of the anal fin. Similar sexual dimorphism is seen in all members of family Iguanodectidae, and is somewhat more common in related genus Bryconops.[9]

Taxonomy

Piabucus caudomaculatus has retained its original name since discovery, given to it by Richard P. Vari in 1977.[10] It is the most recent addition to the genus.[11]

While the other two species of Piabucus demonstrate intraspecific genetic variation that suggests unnamed species of Piabucus, P. caudomaculatus is largely confirmed to be monophyletic.[12]

Etymology

"Caudo-" means "tail", and "-maculatus" means "spotted" (consider the word "immaculate", which means "without spots or blemishes"). The specific name for P. caudomaculatus originates in the dark spot of pigment across the caudal peduncle and the middle caudal-fin rays.[6] The generic name "Piabucus" is a Latinization of the Brazilian word "piabucu", which refers to various small fishes of similar shape.

Piabucus caudomaculatus lacks a widely-accepted common name, but hobbyists have reported a Piabucus species with strong resemblance to P. caudomaculatus being sold under the name "chin tetra".[13] In an evaluation of non-native species, the South African government referred to it as the "spot-tailed slender tetra".[14]

Distribution and habitat

Piabucus caudomaculatus is only known from Bolivia, in the Mamoré river basin. Its type locality is a small, muddy waterway known as the Rio Matucare (Matucare river).[4] The Mamoré river system generally has a high sediment load, and is considered a whitewater river, high in inorganic solids and particulates.[15][16] The Matucare specifically is a small river, sometimes referred to as an arroyo (which is usually a smaller creek or stream) in literature and cartography.[17][18]

Piabucus caudomaculatus demonstrates a general preference for slow-moving streams, including blackwater environments as well as its usual whitewater.[1]

Diet and ecology

Little is known of P. caudomaculatus in terms of diet or interactions with other fish species, but it is largely insectivorous.[1] The Mamoré river and its tributaries are dense in aquatic vegetation, which provides an adequate breeding habitat for the invertebrates and insects upon which P. caudomaculatus feeds.[19]

Presence and behavior in aquaria

It is unknown if P. caudomaculatus has an active presence in the aquarium industry, though fish bearing a strong resemblance to it are sometimes seen for sale.[13] These could either be specimens of P. caudomaculatus or one of its congeners, but specific identity is infrequently confirmed.

Conservation status

Piabucus caudomaculatus is considered a species of least concern by the IUCN.[1] Still, its habitat faces various anthropogenic hazards. While rivers in the Mamoré basin are unaffected by dams or levees, there is still notable degradation of natural resources, including pollution from gold mining and an increased risk of entanglement in fishing nets.[19] As it is a small species with a wide range, P. caudomaculatus is nonetheless unlikely to face increased survival pressures of particular remark.

References
  1. Sarmiento, J. & Carvajal, F. 2016. Piabucus caudomaculatus. The IUCN Red List of Threatened Species 2016: e.T49829582A53817168. https://dx.doi.org/10.2305/IUCN.UK.2016-1.RLTS.T49829582A53817168.en. Accessed on 04 January 2023.
  2. Froese, Rainer; Pauly, Daniel (eds.) (2023). "Piabucus caudomaculatus" in FishBase. January 2023 version.
  3. Froese, Rainer and Pauly, Daniel, eds. (2023). Species of Piabucus in FishBase. January 2023 version.
  4. Check list of the freshwater fishes of South and Central America. Roberto E. Reis, Sven O. Kullander, Carl J. Ferraris, Pontifícia Universidade Católica do Rio Grande do Sul. Museu de Ciências e Tecnologia. Porto Alegre, Brasil: EDIPUCRS. 2003. pp. 172–173. ISBN 85-7430-361-5. OCLC 54496178.{{cite book}}: CS1 maint: others (link)
  5. Guimarães, Erick Cristofore; Ottoni, Felipe Polivanov; Katz, Axel M. (January 2017). "Range extension of Piabucus dentatus (Koelreuter, 1763) for the Pindaré River drainage, Mearim River basin, Brazil (Characiformes: Iguanodectinae)". International Journal of Ichthyology. 41 (3): 287–289. Retrieved 12 January 2023.
  6. Scharpf, Christopher; Lazara, Kenneth J. (15 September 2020). "Order CHARACIFORMES: Families IGUANODECTIDAE, TRIPORTHEIDAE, BRYCONIDAE, CHALCEIDAE and GASTEROPELECIDAE". The ETYFish Project. Retrieved 12 January 2023.
  7. Vari, Richard P. (26 January 1977). "Notes on the characoid subfamily Iguanodectinae, with a description of a new species". American Museum Novitates (2612). hdl:2246/2012 – via AMNH Digital Repository.
  8. Zanata, Angela M.; Akama, Alberto (June 2004). "Myxiops aphos, new characid genus and species (Characiformes: Characidae) from the rio Lençóis, Bahia, Brazil". Neotropical Ichthyology. 2 (2): 45–54. doi:10.1590/S1679-62252004000200001. Retrieved 12 January 2023.
  9. "THE FISH FAMILIES". Field Guide to the Fishes of the Amazon, Orinoco, and Guianas, edited by Peter van der Sleen and James S. Albert, Princeton: Princeton University Press, 2017, pp. 95-96. https://doi.org/10.1515/9781400888801-009
  10. "Piabucus caudomaculatus (Vari, 1977)". Global Biodiversity Information Facility. Retrieved 12 January 2023.
  11. Nicolas, Bailly (21 November 2014). "WoRMS - World Register of Marine Species - Piabucus Oken, 1817". www.marinespecies.org. World Register of Marine Species. Retrieved 12 January 2023.
  12. Ribeiro-Silva, L.R.; Melo, B.F.; Foresti, F.; Oliveira, C. (19 June 2021). "Molecular identification of Neotropical fish species of the Video only genus Piabucus Oken 1817 (Characiformes, Iguanodectidae)" (YouTube Video). www.youtube.com. Systematics, Biogeography, and Evolution Meeting Organization. doi:10.5281/zenodo.4904236. Retrieved 12 January 2023.
  13. Clarke, Matt (June 2007). "Chin tetra, Piabucus sp.". www.practicalfishkeeping.co.uk. Practical Fishkeeping Magazine. Retrieved 12 January 2023.
  14. van Schalkwyk, Marthinus (February 2006). "Notice Under Chapter 5 of the National Environmental Management: Biodiversity Act" (Government Notice). Department of Environmental Affairs and Tourism. p. 32. Retrieved 12 January 2023.
  15. "Mamoré River, Bolivia". eros.usgs.gov. USGS. Retrieved 12 January 2023.
  16. Guizada, Luis; Aliaga-Rossel, Enzo (1 September 2016). "Abundance of the Bolivian River Dolphin (Inia boliviensis) in Mamore River, Upper Madeira Basin" (PDF). Aquatic Mammals. 42 (3): 330–338. doi:10.1578/AM.42.3.2016.330. Retrieved 12 January 2023.
  17. Tyuleneva, Vera (January 2010). "Reseña del libro: La Reduccion Imposible de Diego Villar, Lorena Córdoba e Isabelle Combès". Revista Andina. 50: 288–291. Retrieved 12 January 2023.
  18. Author unknown. San Joaquin (Map). 1:100,000. Series H632, sheet 3944. Washington, D.C.: U.S. Defense Mapping Agency, 1988.
  19. Karuga, James (25 April 2017). "The Mamore River". www.worldatlas.com. WorldAtlas. Retrieved 12 January 2023.
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