{{Short description|Species of fish}} {{Redirect|Malabar pufferfish|the dwarf Malabar pufferfish|Carinotetraodon imitator}} {{Redirect|Pygmy pufferfish|the pygmy pufferfish native to Central America|Sphoeroides trichocephalus}} {{Good article}} {{Use dmy dates|date=September 2020}} {{Speciesbox | image = アベニーパファー.jpg | image_alt = A side profile of an adult dwarf pufferfish against a white background, facing left and slightly upward. | status = VU | status_system = IUCN3.1 | status_ref = <ref name="iucn status 19 November 2021">{{cite iucn |author=Dahanukar, N. |date=2011 |title=''Carinotetraodon travancoricus'' |volume=2011 |article-number=e.T166591A174788004 |doi=10.2305/IUCN.UK.2011-1.RLTS.T166591A174788004.en |access-date=4 May 2022}}</ref> | taxon = Carinotetraodon travancoricus | authority = (Hora & K.K. Nair, 1941)<ref name="Hora 1941" /> | range_map = Carinotetraodon travancoricus Map.jpg | synonyms = * ''Tetraodon travancoricus''<br /><small>Hora & K.K. Nair, 1941</small> * ''Monotretus travancoricus''<br /><small>(Hora & K.K. Nair, 1941)</small> | synonyms_ref = <ref name="iucn status 19 November 2021" /><ref name="Hora 1941" /> }}

The '''dwarf pufferfish''' ('''''Carinotetraodon travancoricus'''''), also known as the '''Malabar pufferfish''', '''pygmy pufferfish''', or '''pea pufferfish''', is a small freshwater pufferfish endemic to Kerala and southern Karnataka in Southwest India. They are popular in aquaria for their bright colours and small size. At a maximum total length of 3.5&nbsp;cm, dwarf pufferfish are one of the smallest pufferfish in the world. They closely resemble the related ''Carinotetraodon imitator'', and the two can be difficult to distinguish. ''C. imitator'' was not recognised as a different species until 1999.

Dwarf pufferfish dwell at the bottom of heavily vegetated waterways, predating small animals. Unlike other species of pufferfish, they are found in large groups in the wild. They breed throughout most of the year, with spawning pairs producing 1–5 eggs in 1–4 day intervals. Habitat loss and overharvesting for the aquarium trade threaten wild populations of dwarf pufferfish.

==Taxonomy== The dwarf pufferfish was first described as ''Tetraodon (Monotretus) travancoricus'' in 1941 by S.L. Hora and K.K. Nair,<ref name="Devi 2000" /><ref name="Britz 1999" /> with the type locality given as "Pamba River, Central Travancore".<ref name="Hora 1941" /> The use of parentheses indicates ''Monotretus'' is the subgenus of ''Tetraodon''. ''Carinotetraodon'' was considered a synonym of ''Tetraodon'' until 1978, when J.C. Tyler treated it as a valid genus in a paper about ''Carinotetraodon lorteti'', which was an opinion followed by M. Kottelat ''et al.'' in 1993 and K.K.P. Lim and M. Kottelat in 1995.<ref name="Britz 1999" /> The first use of ''"Carinotetraodon travancoricus"'' was in 1999 by R. Britz and M. Kottelat when first describing ''Carinotetraodon imitator'', a superficially similar and closely related species previously mistaken for dwarf pufferfish.<ref name="Britz 1999" /> "''Carinotetraodon''" is derived from the Latin word "''carina''" (keel-shaped, shell) and Greek words "''tetra''" (four) and "''odous''" (teeth).<ref name=fishbase>{{FishBase |genus= Carinotetraodon |species= travancoricus |month=June |year=2023 }}</ref> The justification for moving to ''Carinotetraodon'' was based largely on osteological evidence and not on the presence of skin keels, which other members of the genus have, but which had not been confirmed in dwarf pufferfish until one year later in aquarium literature.<ref name="Britz 2012" /> Specifically, dwarf pufferfish possess vertebral modifications and a reduced number of total vertebrae similar to other members of ''Carinotetraodon'', in addition to a small size and the presence of sexual dimorphism, also found amongst other members of this genus.<ref name="Britz 1999">{{cite journal |last1=Britz |first1=R. |last2=Kottelat |first2=M. |title=''Carinotetraodon imitator'', a new freshwater pufferfish from India (Teleostei: Tetraodontiformes) |journal=Journal of South Asian Natural History |date=May 1999 |volume=4 |issue=1 |pages=39–47 |url=https://www.researchgate.net/publication/267843168 |access-date=19 May 2022 |publisher=Wildlife Heritage Trust of Sri Lanka |location=Sri Lanka |issn=1022-0828}}</ref>

The following cladogram is based on molecular evidence and demonstrates the polyphyletic nature of the genus ''Carinotetraodon''.<ref name="Sathyajith 2019">{{cite journal |last1=Sathyajith |first1=C. |last2=Yamanoue |first2=Y. |last3=Yokobori |first3=S. |last4=Thampy |first4=S. |last5=Vattiringal Jayadradhan |first5=R.K. |title=Mitogenome analysis of dwarf pufferfish (''Carinotetraodon travancoricus'') endemic to southwest India and its implications in the phylogeny of Tetraodontidae |journal=Journal of Genetics |date=December 2019 |volume=98 |issue=5 |pages=98–105 |doi=10.1007/s12041-019-1151-9|pmid=31819020 |s2cid=208020436 }}</ref><ref name="smallest" /> A polyphyletic genus is one in which members share common characteristics, but do not necessarily share an immediate common ancestor, and their placement is based on these shared traits rather than confirmed, empirical evidence. "''Carinotetraodon''" is represented in quotation marks to signify its polyphyletic status. Freshwater species are denoted with "FW".<ref name="Sathyajith 2019" /><ref name="smallest" /> The cladogram is incomplete due to the absence of species like ''C. imitator'', which have not undergone mitogenome analyses. thumb|The closely related ''Dichotomyctere nigroviridis''

{{clade |label1=Tetraodontidae |1={{clade |label1= |1={{clade |label1= |1={{clade |1=''Auriglobus modestus'' |label2= |2={{clade |1=''Leiodon cutcutia''<sup>FW</sup> |label2= |2={{clade |label1= |1={{clade |1=''"Carinotetraodon" salivator''<sup>FW</sup> |2={{clade |1=''"Carinotetraodon" lorteti''<sup>FW</sup> |2=''"Carinotetraodon" irrubesco''<sup>FW</sup> }} }} |label2= |2={{clade |1=''Pao palembangensis''<sup>FW</sup> |2=''Pao cochinchinensis''<sup>FW</sup> }} }} }} }} |label2= |2={{clade |label1= |1={{clade |label1= |1={{clade |1='''''"Carinotetraodon" travancoricus'''''<sup>FW</sup> }} |label2= |2={{clade |label1= |1={{clade |1=''Dichotomyctere nigroviridis'' |2=''Dichotomyctere ocellatus'' }} }} }} |label2= |2={{clade |label1= |1={{clade |1=''Pelagocephalus marki'' }} |label2= |2={{clade |label1= |1={{clade |1=''Canthigaster coronata'' |label2= |2={{clade |1=''Canthigaster rivulata'' |label2= |2={{clade |1=''Canthigaster jactator'' |2=''Canthigaster valentini'' }} }} }} }} }} }} |label3= |3={{clade |label1= |1={{clade |label1= |1={{clade |1=''Chelonodon pleurospilus'' }} |label2= |2={{clade |1=''Chelonodon patoca'' }} }} |label2= |2={{clade |label1= |1={{clade |1=''Tetraodon miurus''<sup>FW</sup> }} |label2= |2={{clade |1=''Tetraodon mbu''<sup>FW</sup> }} }} }} }} }} }}

==Description== thumb|left|Dwarf pufferfish have dark, iridescent patches on their flanks and dorsal surfaces|alt=A dwarf pufferfish in an aquarium, displaying its iridescent patches. The maximum documented size is {{convert|3.5|cm|in|abbr=on}} total length (TL),<ref name="Jhingran 1991" /> with individuals typically reaching less than {{convert|2.5|cm|in|abbr=on}} TL,<ref name=fishbase/> making dwarf pufferfish one of the smallest pufferfish in the world.<ref name="smallest">{{cite journal |last1=Santini |first1=F. |last2=Nguyen |first2=M. T. T. |last3=Sorenson |first3=L. |last4=Waltzek |first4=T. B. |last5=Lynch Alfaro |first5=J. W. |last6=Eastman |first6=J. M. |last7=Alfaro |first7=M. E. |title=Do habitat shifts drive diversification in teleost fishes? An example from the pufferfishes (Tetraodontidae) |journal=Journal of Evolutionary Biology |date=May 2013 |volume=26 |issue=5 |pages=1003–1018 |doi=10.1111/jeb.12112 |pmid=23496826 |s2cid=25969423 |url=https://onlinelibrary.wiley.com/doi/full/10.1111/jeb.12112 |access-date=24 October 2023|url-access=subscription }}</ref><ref name="Ebert">{{cite book|last=Klaus |first=Ebert |year=2001 |title=The Puffers of Fresh and Brackish Water |publisher=Aqualog |isbn=3-931702-60-X |pages=19, 46–49}}</ref> Both sexes are primarily greenish-yellow, with dark green to brown-black iridescent patches on the flanks and dorsal surface. Patterns and colouration vary considerably between individuals. Their pectoral fins are short, fan-shaped, and described as "slightly emarginate", that is to say, slightly indented at the tip. The dorsal and anal fins are situated opposite each other toward the posterior of the fish, both short and round, while the caudal fin is larger than the other fins and truncate, in that it terminates in a more-or-less vertical edge. Their bodies are round and oblong.<ref name="Hora 1941">{{cite journal |last1=Hora |first1=S.L. |last2=Nair |first2=K.K. |title=Notes on Fishes in the Indian Museum: XLI. New Records of Freshwater Fish from Travancore. |journal=Records of the Indian Museum |date=1941 |volume=43 |pages=387–393 |url=https://archive.org/details/records-indian-museum-43-387-393/page/n4/mode/1up |access-date=4 May 2022}}</ref><ref name="Anna Mercy 1999" /> As with other members of the genus, sexual dimorphism is apparent in mature fish, with males being more brightly coloured than females<ref name="Ebert"/> and having a yellow ventral surface.<ref name="Hellweg 2007">{{cite magazine |last1=Hellweg |first1=Mike |date=March 2007 |title=The Dwarf Puffer: A Pleasant Little Surprise |url=https://www.tfhmagazine.com/articles/freshwater/the-dwarf-puffer-a-pleasant-little-surprise |access-date=5 May 2022 |website=www.tfhmagazine.com |publisher=TFH Magazine |language=en}}</ref> Males can also have a dark stripe down the centre of their pale belly and iridescent, blue "eye wrinkle" patterns that females do not have. Females are more rounded, tend to be larger than males, and may have more small spots between their larger dark markings. Their abdomens are white, and they may have a yellow patch on their throat.<ref name="Hellweg 2007" /> {{clear}}

===Natural defenses=== All pufferfish can inflate, or "puff up", their bodies by quickly ingesting large amounts of water (or air when necessary) into their highly elastic stomachs.<ref name="Nat Geo Pufferfish" /><ref name="Live Science">{{cite web |last1=Geggel |first1=Laura Geggel |title=Puffed-Up Blowfish Aren't Holding Their Breath |url=https://www.livescience.com/49010-pufferfish-breathe-during-inflation.html |website=livescience.com |publisher=Live Science |access-date=18 October 2023 |language=en |date=4 December 2014}}</ref> Inflating tires pufferfish and can put them at greater risk of predation.<ref name="Live Science" /> Like many other pufferfish, in the absence of scales, dwarf pufferfish have skin spines on most of their body.<ref name="Britz 1999" /><ref name="Britz 2012">{{cite journal |last1=Britz |first1=R. |last2=Ali |first2=A. |last3=Philip |first3=S. |last4=Kumar |first4=K. |last5=Raghavan |first5=R. |title=First record from the wild of ''Carinotetraodon imitator'' in Peninsular India (Teleostei: Tetraodontiformes: Tetraodontidae) |journal=Ichthyological Exploration of Freshwaters|date=October 2012 |volume=23 |issue=2 |pages=105–109 |url=https://www.researchgate.net/publication/256202390 |access-date=1 May 2022 |issn=0936-9902}}</ref><ref name="Shono, et al. (2019)">{{cite journal |last1=Shono |first1=T. |last2=Thiery |first2=A.P. |last3=Cooper |first3=R. L. |last4=Kurokawa |first4=D. |last5=Britz |first5=R. |last6=Okabe |first6=M. |last7=Fraser |first7=G.J. |title=Evolution and Developmental Diversity of Skin Spines in Pufferfishes |journal=iScience |date=September 2019 |volume=19 |pages=1248–1259 |doi=10.1016/j.isci.2019.06.003 |pmid=31353167 |pmc=6831732 |bibcode=2019iSci...19.1248S }}</ref> These spines become erect when the fish is inflated.<ref name="Shono, et al. (2019)" /> Dwarf pufferfish, like many other Tetraodontiformes, produce tetrodotoxin, a highly lethal neurotoxin for which there is no antidote.<ref name="lin, et al. (2012)" /><ref>{{cite web |title=Tetrodotoxin: Biotoxin {{!}} NIOSH {{!}} CDC |url=https://www.cdc.gov/niosh/ershdb/emergencyresponsecard_29750019.html#:~:text=Initial%20treatment%20is%20primarily%20supportive.&text=There%20is%20no%20antidote%20for%20tetrodotoxin%20toxicity.&text=Remove%20the%20patient%2Fvictim%20from,order%20to%20avoid%20more%20casualties. |website=www.cdc.gov |access-date=12 May 2024 |language=en-us |date=25 May 2023}}</ref> The neurotoxin accumulates in the glands of the epidermis (surface layer of skin), ovaries, and livers of pufferfish.<ref name="lin, et al. (2012)">{{cite journal |last1=Lin |first1=W.-F. |last2=Hwang |first2=D.-F. |title=Analysis of Poisoning Cases, Monitoring and Risk Warning for Marine Toxins (TTX, PSP and CTXs) in Taiwan |journal=藥物食品分析 |date=1 January 2012 |volume=20 |issue=4 |pages=763–771 |doi=10.6227/jfda.2012200404 |url=https://www.jfda-online.com/cgi/viewcontent.cgi?article=2045&context=journal |access-date=12 May 2024 |language=en}}</ref> These traits are anti-predator adaptations. The pufferfish's ability to inflate makes it difficult to swallow or bite, and the tetrodotoxin makes it unpalatable or even deadly for other fish. Biologists believe these adaptations evolved because of the slow swimming speeds of pufferfish.<ref name="Nat Geo Pufferfish">{{cite web |title=Pufferfish {{!}} National Geographic |url=https://www.nationalgeographic.com/animals/fish/facts/pufferfish |archive-url=https://web.archive.org/web/20210329180151/https://www.nationalgeographic.com/animals/fish/facts/pufferfish |archive-date=29 March 2021 |website=www.nationalgeograph.orc |publisher=National Geographic |access-date=28 May 2022 |language=en |date=12 March 2010}}</ref>

===Resemblance to ''Carinotetraodon imitator''=== ''Carinotetraodon imitator'' is a species of related pufferfish closely resembling dwarf pufferfish. They are of similar size, shape, patterns, and colouration. Both species are found within the same region and may be sympatric, possibly inhabiting the same waters. Until 1999, ''C. imitator'' was mistaken as the same species, and the two could be found together in aquaria and were widely available in the international aquarium trade, both sold as dwarf pufferfish. Dwarf pufferfish can be distinguished from their congener (a member of the same genus), as ''C. imitator'' have smaller, faint blotches compared to dwarf pufferfish, as well as greatly reduced body spination. Male dwarf pufferfish have a darker yellow colouration and an iridescent "eye wrinkle" not found in males of ''C. imitator''.<ref name="Britz 1999" />

==Distribution and habitat==

thumb|Global distribution<ref>Based on the following sources: * {{cite journal |last1=Anupama |first1=K.M. |last2=Harikrishnan |first2=M. |title=Improved survival of Malabar puffer fish, ''Carinotetraodon travancoricus'' (Hora and Nair, 1941) in planted aquaria |journal=International Journal of Environmental Sciences |date=2015 |volume=6 |issue=1 |pages=138–144 |doi=10.6088/ijes.6016 |doi-broken-date=18 April 2026 |url=https://www.indianjournals.com/ijor.aspx?target=ijor:ijes&volume=6&issue=1&article=016 |issn=0976-4402}} * {{cite journal |last1=Hora |first1=S.L. |last2=Nair |first2=K.K. |title=New records of freshwater fish from Travancore. |journal=Records of the Indian Museum |date=1941 |volume=43 |pages=387–393 |url=https://archive.org/details/records-indian-museum-43-387-393/page/n4/mode/1up |access-date=4 May 2022}} * {{cite journal |last1=Raghavan |first1=R. |last2=Prasad |first2=G. |last3=Ali |first3=A.P.H. |last4=Pereira |first4=B. |title=Fish fauna of Chalakudy River, part of Western Ghats biodiversity hotspot, Kerala, India: patterns of distribution, threats and conservation needs |journal=Biodiversity and Conservation |date=2008 |volume=17 |issue=13 |pages=3119–3131|doi=10.1007/s10531-007-9293-0 |bibcode=2008BiCon..17.3119R |s2cid=7563806 }} * {{cite journal |last1=Biju, C.R. |first1=C.R. |last2=Thomas |first2=R.K. |last3=Ajithkumar |first3=C.R. |last4=George |first4=M.J. |title=Occurrence of ''Tetraodon travancoricus'' (Hora and Nair) in the Chalakudy, Periyar and Kechery rivers, Kerala |journal=Journal of the Bombay Natural History Society |date=1999 |volume=96 |issue=1 |page=161 |url=https://archive.org/details/biostor-151846/mode/1up |access-date=4 May 2022}} * {{cite journal |last1=Beevi |first1=K.S. Jameela |last2=Ramachandran |first2=A. |title=Checklist of freshwater fishes collected from Ernakulam District, Kerala, India |journal=Journal of Threatened Taxa |date=26 September 2009 |volume=1 |issue=9 |pages=493–494 |doi=10.11609/JoTT.o1559.493-4 |url=https://dyuthi.cusat.ac.in/xmlui/bitstream/handle/purl/4123/Checklist%20of%20freshwater%20fishes%20collectedfrom%20Ernakulam%20District%2c%20Kerala%2c%20India.pdf?sequence=1 |access-date=4 May 2022}} * {{cite journal |last1=Devi |first1=K.R. |last2=Indra |first2=T.J. |last3=Emiliyamma |first3=K. J. |title=On the Fish Collections from Kerala, Deposited in Southern Regional Station, Zoological Survey of India by NRM Stockholm |journal=Records of Zoological Survey of India |date=1996 |volume=95 |pages=3–4 |url=http://faunaofindia.nic.in/PDFVolumes/records/095/03-04/0129-0146.pdf |access-date=4 May 2022}} * {{cite journal |last1=Easa |first1=P.S. |last2=Basha |first2=C.C. |title=A Survey on the Habitat and Distribution of Stream Fishes in the Kerala part of Nilgiri Biosphere Reserve |journal=Kerala Forest Research Report |date=1995 |volume=104 |url=http://docs.kfri.res.in/KFRI-RR/KFRI-RR104.pdf |access-date=6 May 2022}} * {{cite journal |last1=Prasad |first1=G. |last2=Sabu |first2=K. |last3=Prathibhakumari |first3=P.V. |title=The first report of the Malabar puffer, ''Carinotetraodon travancoricus'' (Hora & Nair, 1941) from the Neyyar wildlife sanctuary with a note on its feeding habit and length-weight relationship |journal=Journal on New Biological Reports |date=2012 |volume=1 |issue=2 |pages=42–46 |url=https://researchtrend.net/jnbr/jnbr/VOL%201(2)%202012/3%20Prasad%20et%20al,%202012.pdf |access-date=6 May 2022 |issn=2319-1104}} * {{cite journal |last1=Bijukumar |first1=A. |last2=Philip |first2=Siby |last3=Ali |first3=Anvar |last4=Sushama |first4=S. |last5=Raghavan |first5=Rajeev |title=Fishes of River Bharathapuzha, Kerala, India: diversity, distribution, threats and conservation |journal=Journal of Threatened Taxa |date=26 November 2013 |volume=5 |issue=15 |pages=4979–4993 |doi=10.11609/JoTT.o3640.4979-93|doi-access=free }} * {{cite journal |last1=Easa |first1=P.S. |last2=Shaji |first2=C.P. |title=Freshwater fish diversity in Kera a part of the Nilgiri Biosphere Reserve |journal=Current Science |date=1997 |volume=73 |issue=2 |pages=180–182}}</ref>

Although closely related to marine pufferfish, they are not found in salt water, and reports to the contrary are based on misidentification.<ref>{{cite book |last1=Schäfer |first1=Frank |title=Brackish-water Fishes: All about Species, Care and Breeding |date=2005 |publisher=A.C.S. |isbn=978-3-936027-82-2 |page=34}}</ref> Dwarf pufferfish are one of only 27 known species of Tetraodontidae adapted to freshwater.<ref name="Doi 2015">{{cite journal |last1=Doi |first1=Hiroyuki |last2=Sakai |first2=Harumi |last3=Yamanoue |first3=Yusuke |last4=Sonoyama |first4=Takayuki |last5=Ishibashi |first5=Toshiaki |title=Spawning of eight Southeast Asian brackish and freshwater puffers of the genera ''Tetraodon'' and ''Carinotetraodon'' in captivity |journal=Fisheries Science |date=March 2015 |volume=81 |issue=2 |pages=291–299 |doi=10.1007/s12562-014-0842-7|bibcode=2015FisSc..81..291D |s2cid=255616157 }}</ref> They are a potamodromous species,<ref>{{cite book |last1=Reid |first1=Klaus |title=Global Register of Migratory Species: From Global to Regional Scales: Final Report of the R&D-Projekt 808 05 081 |date=2004 |publisher=Federal Agency for Nature Conservation |isbn=978-3-7843-3845-3 |page=308}}</ref> meaning they migrate within freshwater river systems,<ref>{{cite report |last1=Gopalakrishnan |first1=Omkar |last2=Riede |first2=Klaus |title=Some observations on fish migration, with emphasis on tropical waters |date=2004 |publisher=Federal Agency for Nature Conservation |doi=10.13140/RG.2.1.5099.0969 |url=https://www.researchgate.net/publication/301867148 |access-date=12 October 2023}}</ref> and are endemic to rivers, lakes, and estuaries<ref name="Sabu 2012" /> in Kerala and southern Karnataka in the Western Ghats of Peninsular India.<ref name="iucn status 19 November 2021" /><ref name="Easa 1995" /><ref name="Devi 2000">{{cite journal |last1=Devi |first1=K.R. |last2=Indra |first2=T.J. |last3=Raghunathan |first3=M.B. |title=On a report of ''Tetraodon'' (''Monotretus'') ''travancoricus'', from south Kanara, Karnataka, India |journal=Journal of the Bombay Natural History Society |date=2000 |volume=97 |issue=3 |pages=441–443 |url=https://archive.org/details/biostor-151657/mode/2up |access-date=4 May 2022}}</ref> They can be found in waters with a pH of 7.5–8.3 and temperatures of {{convert|22–28|C|F|abbr=on}}.<ref name=fishbase/> Inhabiting heavily vegetated waters with beds of gravel and rock or clay loam with silt and sand,<ref name="Sabu 2012" /> the species is reported from 13 rivers in Kerala,<ref name="Anupama 2015" /> lakes such as Vembanad,<ref name="Devi 1996">{{cite journal |last1=Devi |first1=K.R. |last2=Indra |first2=T.J. |last3=Emiliyamma |first3=K. J. |title=On the Fish Collections from Kerala, Deposited in Southern Regional Station, Zoological Survey of India by NRM Stockholm |journal=Records of Zoological Survey of India |date=1996 |volume=95 |pages=3–4 |url=http://faunaofindia.nic.in/PDFVolumes/records/095/03-04/0129-0146.pdf |access-date=4 May 2022}}</ref> the Nilambur harbours,<ref name="Easa 1995">{{cite journal |last1=Easa |first1=P.S. |last2=Basha |first2=C.C. |title=A Survey on the Habitat and Distribution of Stream Fishes in the Kerala part of Nilgiri Biosphere Reserve |journal=Kerala Forest Research Report |date=1995 |volume=104 |url=http://docs.kfri.res.in/KFRI-RR/KFRI-RR104.pdf |access-date=6 May 2022}}</ref> and Kallar Stream, part of the Neyyar Wildlife Sanctuary.<ref name="Sabu 2012">{{cite journal |last1=Prasad |first1=G. |last2=Sabu |first2=K. |last3=Prathibhakumari |first3=P.V. |title=The first report of the Malabar puffer, ''Carinotetraodon travancoricus'' (Hora & Nair, 1941) from the Neyyar wildlife sanctuary with a note on its feeding habit and length-weight relationship |journal=Journal on New Biological Reports |date=2012 |volume=1 |issue=2 |pages=42–46 |url=https://researchtrend.net/jnbr/jnbr/VOL%201(2)%202012/3%20Prasad%20et%20al,%202012.pdf |access-date=6 May 2022 |issn=2319-1104 |archive-date=13 July 2020 |archive-url=https://web.archive.org/web/20200713012131/https://www.researchtrend.net/jnbr/jnbr/VOL%201(2)%202012/3%20Prasad%20et%20al,%202012.pdf }}</ref> They have been reported as rare in Bharathapuzha<ref name="Bijukumar 2013">{{cite journal |last1=Bijukumar |first1=A. |last2=Philip |first2=Siby |last3=Ali |first3=Anvar |last4=Sushama |first4=S. |last5=Raghavan |first5=Rajeev |title=Fishes of River Bharathapuzha, Kerala, India: diversity, distribution, threats and conservation |journal=Journal of Threatened Taxa |date=26 November 2013 |volume=5 |issue=15 |pages=4979–4993 |doi=10.11609/JoTT.o3640.4979-93|doi-access=free }}</ref> and the Nilgiri Biosphere Reserve.<ref name="Easa 1997">{{cite journal |last1=Easa |first1=P.S. |last2=Shaji |first2=C.P. |title=Freshwater fish diversity in Kera a part of the Nilgiri Biosphere Reserve |journal=Current Science |date=1997 |volume=73 |issue=2 |pages=180–182|url=https://currentscience.ac.in/Volumes/73/02/0180.pdf}}</ref> The species was also found in inundated brickyards in Puthukkad,<ref name="Biju 1999">{{cite journal |last1=Biju, C.R. |first1=C.R. |last2=Thomas |first2=R.K. |last3=Ajithkumar |first3=C.R. |last4=George |first4=M.J. |title=Occurrence of ''Tetraodon travancoricus'' (Hora and Nair) in the Chalakudy, Periyar and Kechery rivers, Kerala |journal=Journal of the Bombay Natural History Society |date=1999 |volume=96 |issue=1 |page=161 |url=https://archive.org/details/biostor-151846/mode/1up |access-date=4 May 2022}}</ref> as well as ditches, ponds, irrigation channels, and artificial tanks or abandoned water bodies in paddy fields. Their presence in small, isolated water bodies is likely due to unintentional dispersal by waterfowl.<ref name="Gopi 2007">{{cite journal |last1=Gopi |first1=K.C. |last2=Radhakrishnan |first2=C. |title=Waterbird-Mediated Chance-Dispersal of Fishes: A Natural Process of Affecting Range of Distribution and Biogeography of Fishes |journal=Records of the Zoological Survey of India |date=2007 |volume=108 |issue=1 |pages=19–31 |doi=10.26515/rzsi/v107/i1/2007/159160 |s2cid=201600208 |url=http://faunaofindia.nic.in/PDFVolumes/records/107/01/0019-0031.pdf |access-date=6 May 2022}}</ref>

===Conservation status=== Several researchers have considered the species endangered, though with no rationale provided.<ref name="Dahanukar 2003">{{cite journal |last1=Dahanukar |first1=Neelesh |last2=Raut |first2=Rupesh |last3=Bhat |first3=Anuradha |title=Distribution, endemism and threat status of freshwater fishes in the Western Ghats of India |journal=Journal of Biogeography |date=22 December 2003 |volume=31 |pages=123–136 |doi=10.1046/j.0305-0270.2003.01016.x |s2cid=83574801 |url=http://wgbis.ces.iisc.ernet.in/biodiversity/sahyadri_enews/newsletter/issue53/bibliography/211-distribution-endemism-and-threat-status.pdf}}</ref><ref>{{cite journal |last1=Thomas |first1=K. |last2=George |first2=M. |last3=Biju |first3=C. |title=Freshwater Fishes of Southern Kerala with Notes on the Distribution of Endemic and Endangered Species |journal=Journal of the Bombay Natural History Society |date=April 2002 |volume=99 |issue=1 |pages=47–53 |url=https://archive.org/details/biostor-152184/mode/2up |access-date=4 May 2022}}</ref><ref name="Raghavan 2008">{{cite journal |last1=Raghavan |first1=R. |last2=Prasad |first2=G. |last3=Ali |first3=A.P.H. |last4=Pereira |first4=B. |title=Fish fauna of Chalakudy River, part of Western Ghats biodiversity hotspot, Kerala, India: patterns of distribution, threats and conservation needs |journal=Biodiversity and Conservation |date=2008 |volume=17 |issue=13 |pages=3119–3131|doi=10.1007/s10531-007-9293-0 |bibcode=2008BiCon..17.3119R |s2cid=7563806 }}</ref> The dwarf pufferfish is officially classified as vulnerable on the IUCN Red List due to declining populations because of damming, indiscriminate deforestation for agriculture, pollution from wastewater, and, primarily, overfishing for the aquarium trade.<ref name="iucn status 19 November 2021" /><ref name="Anupama 2015" /> In 2010, some researchers estimated that the population would decline by 30–40% from 2005 to 2015,<ref name="iucn status 19 November 2021" /><ref name="Dahanukar 2003" /> while others estimated it had already declined by the same amount between 2005 and 2010.<ref>{{cite journal |last1=Kurup |first1=B.M. |last2=Manojkumar |first2=T.G. |title=Central Marine Fisheries Research Institute |journal=Indian Journal of Fisheries |date=2010 |volume=57 |issue=1 |pages=81–85 |publisher=Central Marine Fisheries Research Institute |location=India |issn=0970-6011}}</ref>

==Diet and behaviour== Dwarf pufferfish are euryphagous carnivores in that they consume a wide variety of animals. Dwarf pufferfish favour insect larvae but will rely on crustaceans and annelids as alternate feed when the availability of preferable prey decreases.<ref name="Renjithkumar 2020" /> Their diet in the wild mainly consists of small animals such as water fleas, rotifers, copepods, and seed shrimp, and aquatic larvae such as those of Odonata, Hemiptera, mayflies, and flies, with some amounts of plant matter, largely diatoms and green algae.<ref name="Sabu 2012" /><ref name="Renjithkumar 2020" /> Sand and detritus, presumably ingested by mistake when feeding on small, bottom-dwelling animals, have also been found in their gut.<ref name="Sabu 2012" /><ref name="Renjithkumar 2020" />

left|thumb|Dwarf pufferfish shoaling in the wild, seen from above|alt=Several wild dwarf pufferfish are viewed from above in yellowish water In captivity, dwarf pufferfish benefit from a varied diet and will eat small freshwater snails, shrimps, as well as foods like frozen mussel meat or other frozen shellfish. They will also readily eat live foods such as red and white mosquito larvae and other small animals they would predate in the wild.<ref>{{cite web |last1=Schäfer |first1=Frank |title=''Carinotetraodon travancoricus'' |url=https://www.aquariumglaser.de/en/27-puffers/carinotetraodon-travancoricus-2/ |website=www.aquariumglaser.de |publisher=Aquarium Glaser GmbH |access-date=14 October 2023 |archive-url=https://web.archive.org/web/20231014181436/https://www.aquariumglaser.de/en/27-puffers/carinotetraodon-travancoricus-2/ |archive-date=14 October 2023 |date=20 November 2020}}</ref> Dwarf pufferfish are commonly associated with plants in the genus Cabomba, and the presence of these plants has been shown to reduce mortality among captive specimens.<ref name="Anupama 2015">{{cite journal |last1=Anupama |first1=K.M. |last2=Harikrishnan |first2=M. |title=Improved survival of Malabar puffer fish, ''Carinotetraodon travancoricus'' (Hora and Nair, 1941) in planted aquaria |journal=International Journal of Environmental Sciences |date=2015 |volume=6 |issue=1 |pages=138–144 |doi=10.6088/ijes.6016 |doi-broken-date=18 April 2026 |url=https://www.indianjournals.com/ijor.aspx?target=ijor:ijes&volume=6&issue=1&article=016 |issn=0976-4402}}</ref>

Dwarf pufferfish are a slow-swimming,<ref name="Gopi 2007" /> demersal (bottom-dwelling) species.<ref name=fishbase/> Unlike many pufferfish species, which are primarily solitary and potentially aggressive or territorial between conspecifics (members of the same species),<ref>{{cite magazine |last1=Monks |first1=Neale |date=December 2007 |title=In Search of the Peaceful Puffer |url=https://www.tfhmagazine.com/articles/freshwater/in-search-of-the-peaceful-puffer |website=tfhmagazine.com |publisher=TFH Magazine |access-date=6 May 2022 |language=en}}</ref> dwarf pufferfish are found in large shoals, occasionally consisting of hundreds of individuals.<ref name="Biju 1999" /> They are found mainly during the summer months of January to May and rarely during the rainy season.<ref name="Biju 1999" /> Shoaling fish experience stress or weight loss when kept in solitude or in groups too small.<ref>{{cite journal |last1=Pagnussat |first1=Natália |last2=Piato |first2=Angelo L. |last3=Schaefer |first3=Isabel C. |last4=Blank |first4=Martina |last5=Tamborski |first5=Angélica R. |last6=Guerim |first6=Laura D. |last7=Bonan |first7=Carla D. |last8=Vianna |first8=Mônica R.M. |last9=Lara |first9=Diogo R. |title=One for All and All for One: The Importance of Shoaling on Behavioral and Stress Responses in Zebrafish |journal=Zebrafish |date=September 2013 |volume=10 |issue=3 |pages=338–342 |doi=10.1089/zeb.2013.0867|pmid=23802189 }}</ref><ref>{{cite book |title=Coral fish stress out if separated from 'shoal-mates' |url=https://link.gale.com/apps/doc/A510692129/STND?u=wikipedia&sid=ebsco&xid=5f2b57d0 |access-date=13 May 2022 |publisher=Manila Bulletin Publishing Corp. |date=22 September 2016}}</ref> {{clear}}

==Reproduction== In the wild, males with ripe gonads have been found during all months of the year but December and January, with the peak spawning period extending from May to August, concurring with the South-West monsoon period.<ref name="Anupama 2019">{{cite journal |last1=Anupama |first1=K.M. |last2=Hari Sankar |first2=H.S. |last3=Rithin Raj |first3=M. |last4=Harikrishnan |first4=M. |title=Reproductive Biology of Malabar Pufferfish ''Carinotetraodon travancoricus'' (Tetraodontidae) |journal=Journal of Ichthyology |date=July 2019 |volume=59 |issue=4 |pages=545–554 |doi=10.1134/S0032945219040027 |bibcode=2019JIch...59..545A |s2cid=201714471 |url=https://www.researchgate.net/publication/335583238 |access-date=6 May 2022 |issn=0032-9452}}</ref> Within the Pamba River, the minimum size at which half the population becomes sexually mature is approximately {{convert|1.83|cm|in|abbr=on}}. Environmental and dietary conditions may influence the maturation rate of individuals.<ref name="Anupama 2019" />

thumb|Juvenile|alt=Left-side view of a juvenile against a blank background. The mid-dorsal and mid-ventral skin ridges of males become brown in colour during the spawning season. The belly of the female will swell, and the courting male will frequently chase the female and nibble at its belly. The female will then search for a suitable location to spawn while the male chases away other males.<ref name="Doi 2015" /> In the aquarium, dwarf pufferfish are often plant-spawners, laying eggs in plants, including java moss, or on the substrate hidden within plants.<ref name="Chris 2003" /> A female will scatter approximately 1–5 eggs, {{convert|1.43|mm|in|abbr=on}} in mean diameter. The eggs are adhesive and appear transparent and round, with a mass of small oil globules. After laying, the eggs are then fertilized externally by the male.<ref name="Doi 2015" /> Spawning has been observed in the evening, with the female resting on the spawning site and the male slowly approaching. After spawning, both fish will leave the site. The male will then quickly return to guard the eggs.<ref name="Doi 2015" /> Sneaking ejaculation by other males has also been observed.<ref name="Doi 2015" /> The pair may spawn multiple times in 1–4 day intervals.<ref name="Doi 2015" />

Eggs hatch after five days at {{convert|27|C|F|abbr=on}}, with larvae and fry in captivity initially fed infusoria, ''Brachionus'' (a genus of rotifers), frozen bloodworms, and brine shrimp when they are a week old.<ref name="Chris 2003">{{Cite book |last=Ralph |first=Chris |year=2003 |title=Practical Fishkeeping: Pufferfish |page=61 |publisher=Ringpress |isbn=1-86054-233-6}}</ref><ref name="Doi 2015" /> There is little information on what the larvae eat in the wild.<ref name="Ebert" /> Hatched larvae are a mean of {{convert|3.15|mm|in|abbr=on}} total length, with eyes incompletely developed and the body a red-brown. The yolk sac is consumed in four days, and the larvae commence swimming after six days, at which point their eyes are completely developed.<ref name="Doi 2015" />

There is no information available on the lifespans of these fish in the wild, but aquarists report specimens live for approximately five years in captivity.<ref name="Hellweg 2007" />

==Association with humans== When first described in 1941, K. Nair noted that dwarf pufferfish were a favourite of children, who would catch and use the fish as playthings.<ref name="Hora 1941" /> They were regarded as "frog tadpoles" by local fishermen<ref name="Biju 1999" /> and otherwise given little consideration. They are of no interest to fisheries,<ref name="Jhingran 1991">{{cite book |last1=Talwar |first1=P. K. |last2=Jhingran |first2=A.G. |title=Inland fishes of India and adjacent countries |date=1991 |publisher=Oxford & IBH Pub. Co |location=New Delhi |isbn=978-81-204-0639-1}}</ref> are not a food fish, and are only valued as ornamental fish in aquaria.<ref>{{cite book |last1=Ponniah |first1=A.G. |last2=Gopalakrishnan |first2=A. |title=Endemic fish diversity of Western Ghats |date=2000 |publisher=National Bureau of Fish Genetic Resources |location=Lucknow, India |isbn=81-901014-2-0 |pages=13–32 |url=https://eprints.cmfri.org.in/12661/1/Gopalakrishnan_2000_Endemic%20Diversity%20of%20the%20Western%20Ghats.pdf |access-date=5 May 2022}}</ref><ref name="iucn status 19 November 2021" /> Dwarf pufferfish have become popular as aquarium fish thanks to their attractive colours, small size, "puppy dog eyes", and relative ease of maintenance.<ref name="Ebert" /><ref name="Renjithkumar 2020">{{cite journal |last1=Renjithkumar |first1=C.R. |last2=Roshni |first2=K. |last3=Ranjeet |first3=K. |title=Feeding ecology of the endemic freshwater puffer fish ''Carinotetradon travancoricus'' (Hora & Nair, 1941) in Western Ghats hotspot, India |journal=International Journal of Aquatic Biology |date=24 September 2020 |volume=8 |issue=5 |pages=300–310 |doi=10.22034/ijab.v8i5.922}}</ref> The dwarf pufferfish is also one of the few aquarium fish to regularly eat small, live snails and thus can be helpful in controlling snail populations.<ref name="Anna Mercy 1999">{{cite book |last1=Anna Mercy |first1=T.V. |last2=Gopalakrishnan |first2=A. |last3=Kapoor |first3=D. |last4=Lakra |first4=W.S. |title=Ornamental fishes of the Western Ghats of India |date=2007 |publisher=National Bureau of Fish Genetic Resources |location=Lucknow |isbn=978-81-902951-8-5 |pages=227–228}}</ref> {{clear}}

==References== {{Reflist}}

==External links== {{Commons category|Carinotetraodon travancoricus}} * [http://www.pufferfishenthusiastsworldwide.com/post/c-travancoricus Pufferfish Enthusiasts Worldwide Dwarf Pufferfish Care Sheet]

{{Taxonbar|from=Q175560}}

Category:Carinotetraodon Category:Fishkeeping Category:Fish described in 1941 Category:Taxa named by Sunder Lal Hora Category:Endemic fauna of the Western Ghats Category:Freshwater fish of India Category:Species that are or were threatened by the pet trade Category:Species that are or were threatened by agricultural development Category:Species that are or were threatened by urbanization Category:Species that are or were threatened by damming Category:Species that are or were threatened by deforestation