# Some notes on Otocinclus



## Onoma1 (5 Oct 2019)

Otocinclus are a fish that were recommended to me as part of a ‘clean up crew’ and seem to be one of the ‘must have’ fish for aquascapers. On searching through the web for more information about them I noticed the lack of scientific evidence on how to care for, breed or manage these fish.


I started to put together some rough notes to help me and though they may be of interest to others.  My summary points are below followed by the evidence gathered so far. I am not a biologist (this is probably self-evident). I would welcome any corrections of views on my analysis.



20 species currently identified.  Many species are differentiated only under close scrutiny. There is a strong possibility of misclassification by non-expert.
The latest figures that I could find indicated vast numbers of these fish being caught and exported. In 2003 457735 Otocinclus flexilis and 331535 Otocinclus affinis were exported from the Amazon Basin at an average price .of 006 US Dollars per fish.  I noted that most for sale in the UK are currently Otocinclus affinis, although pictures of the fish for sale labelled affinis seemed to show a different species. This raises questions about overfishing and sustainability.
There is a strong likelihood that patterns of small-scale regional species endemism (that they will be unique to a particular area) and adaptation to these local environments.
They are found across the Amazon basin, however, are localised and found in very large volumes. The areas in which they live are under intense pressure from human activity.
There is a mimetic relationship between Corydoras diphyes and Otocinclus mimulus and _Otocinclus_ _flexilis and Corydoras paleatus_ this may be a form of adaptation.
They are diurnal.
Otocinclus _affinis uses its _stomach as a respiratory organ with suggestions that this is a evolunatory adaption to allow survival in periods when food resources are reduced and there are periods of hypoxia – dry season when low oxygen levels in the water.
The typical types of habitat are small rivers and streams, shaded blackwater, streams with turbidity, streams with clear highly oxygenated water. I found this slightly contradictory and assume the difference suggests seasonal variation in turbidity. It doesn't, however, suggest a densely planted environment.
They are referred to as herbivores based on the physical structure of the intestine and stomach. Conclusions seem to have been drawn using dissection not observation of behaviour. It is noticeable that catfish with similar characteristics eat invertebrates and moribund fish flesh.  My view on this that aquarists have observed them eating bloodworms and Repashy Soilent Green (containing insect protein).  Acclimatisation of Otocinclus flexilis was facilitated by feeding frozen bloodworms. Therefore, either they are not pure herbivores or different species have different requirements. Equally, flexibility of eating habits has been noted as a potential rationale for their large numbers within environments under intense human pressure which have experienced significant changes.
Little behaviour or reproductive information seems to be available. I noted that most of the papers seemed to deal with dissection and analysis of dead fish and extrapolating from this with only a few more recent papers focusing on behaviour. They rarely breed in captivity.
The mature size of Otocinclus Vittatus varies but averaged at 18.7 mm for females and 20.1 mm with a variation of between 10.5 to 41.25 mm. Breeding behaviour correlated with peak river flows but not rainfall. Extrapolating from this may suggest that techniques such as adding further RO water or colder water to simulate rainwater in the hope that this stimulates breeding (used with Tetras) possibly won’t work.
They show, marked reproductive seasonality therefore wide seasonal variation in day length and temperature may stimulate breeding behaviour.

*How many species?*

In 1997 Schaefer identified 13 species within the genus Otocinlcus. By 2017 Delapieve et., al. note that this had risen to 20 types of Otocinclus with a new related genus Leptotocinclus which contains two species:


1.      Otocinclus affinis Steindachner, 1877;

2.      Otocinclus arnoldi Regan, 1909;

3.      Otocinclus batmani Lehmann, 2006;

4.      Otocinclus bororo Schaefer, 1997;

5.      Otocinclus caxarari Schaefer, 1997;

6.      Otocinclus cocama Reis, 2004;

7.      Otocinclus flexilis Cope, 1894;

8.      Otocinclus hasemani Steindachner, 1915;

9.      Otocinclus hoppei MirandaRibeiro, 1939;

10.  Otocinclus huaorani Schaefer, 1997;

11.  Otocinclus juruenae Ribeiro, Lehmann, 2016;

12.  Otocinclus macrospilus Eigenmann, Allen, 1942;

13.  Otocinclus mangaba Lehmann, Mayer, Reis, 2010;

14.  Otocinclus mariae Fowler, 1940;

15.  Otocinclus mimulus Axenrot, Kullander, 2003;

16.  Otocinclus mura Schaefer, 1997;

17.  Otocinclus tapirape Britto, Moreira, 2002;

18.  Otocinclus vestitus Cope, 1872;

19.  Otocinclus vittatus Regan, 1904;

20.  Otocinclus xakriaba Schaefer, 1997.


The new genus Leptotocinclus contains the species Leptotocinclus madeirae, . and Leptotocinclus ctenistus. Leptotocinclus is from the Greek leptos, meaning fine, small, delicate, and Otocinclus, a genus of Hypoptopomatini.  (Delapieve et., al.2017).


Schaefer (1997) notes that many species are differentiated only under close scrutiny.


Below is a picture of a Otocindlus mariae (a male and fb emale) taken from Schaefer (1997)









Below is a picture of Otocinclus macrospilus both of which are female but caught in different locations







Schaefer (1997) argues that a strong likelihood that patterns of small-scale regional species endemism (that they will be unique to a particular area )


*Distribution*

Otocinclus Vittatus seem to be one of the more common fish found within the Amazon Basin. I take from  Claro-García  et., al. (2013) that while Otocinclus vittatus weren’t as widely distributed as some other types of fish they were found in very large volumes.


Claro-García  et., al. (2013) note that Otocinclus vittatus (20.4%) of fish caught.  In their paper they also in indicate that of the two areas surveyed the fish weren’t found in rio Purus basin but were found in six of the fifteen sample sites in the rio Acre basin. The three species Serrapinnus gr. microdon, Otocinclus vittatus and Hemigrammus ocellifer had a high dominance in the igarapés A (92%) and Pato (68.6%), igarapé Mapinguari (60.2%) and igarapé C (65%) respectively.


ANJOS et., al (2018)  The Juruá and Purus rivers, contribute significantly for exports, mainly of species of Callichthydae (Corydoras spp.) and Loricariidae (Otocinclus spp.).


Otocinclus tapirape are found in the headwater streams (HS), rivers (R) and headwater streams and rivers (HS/R) of the upper section of the Tocantins–Araguaia River basin (de Carvalho  2018)


*Behaviour*

Axenrot, and Kullander (2003) note the memetic relationship between Corydoras diphyes and Otocinclus mimulus. A similar memetic relationship was noted in planet catfish between Otocinclus flexilis and Corydoras paleatus https://www.planetcatfish.com/common/species.php?species_id=1350


Satora et., al., (2019) notes that Otocinclus _affinis uses its _ stomach as a respiratory organ in essence becoming air breathing.  They notes that it is supposed that this species uses respiratory stomach only during dry season, when severe competition for limited food resources takes place and there are periods of period of hypoxia.


*Habitat*

Delapieve et., al. note that there collecting localities for Leptotocinclus are blackwater creeks and small rivers with a sandy bottoms

Mas, Alvarenga and Scarabotti (2019)  note that O. arnoldi avoid major channels

Schaefer (2017) note that they are “distributed throughout most of lowland tropical South America and are generally found in smaller-sized streams and along quiet, slow-moving margins of larger rivers. They are typically found in locations characterized by clear, well oxygenated water, moderate flow, and abundant structure provided in the form of emergent marginal macro- phytes, or more commonly, where broad-leaf grasses, such as Brachiaria purpurescens, grow along the stream bank and extend into the water”. (page 4)


Otocinclus Mimulus was collected by Axenrot, and Kullander. (2003) in small streams with turbid water, shadowed by dense forest. The bottom of the river was littered with leaf litter and tree branches. Submerse plants were found in quiet areas of the river.


Satora, (2019)  notes Otocinclus_ affinis_  is found in “..small streams and quiet slow-flowing margin rivers”.


*Feeding and Resilience*

I understand from the paper written by Claro-García and colleagues the areas in which they live are under intense pressure from human activity and the authors speculate that the success of this fish in this area relates to their ability to exploration these environment:  high reproductive capacity in different environments, resistance to environmental variations, presence of schools of fish or the effect of environmental changes caused by human activities.

Schaefer (1997) refers to them as herbivorous catfish and states provides three forms of evidence to substantiate this. The first two relate to long intestine is adaptive in maximizing the extraction of nutrients from grazed plant material and the second is the large, thick-walled stomachs that may contribute to mechanical grinding of plant tissues found in catfish. Finally, he/she states “I have never observed anything other than plant material in Otocinclus stomachs” (page 30).

Schaefer (1997)  also notes that other loricariids are opportunist omnivores, known to feed on invertibrates and moribund fish flesh


Observation from aquarists points to a more omnivorous diet. Acclimatisation of Otocinclus flexilis, for example is facilitated by feeding frozen bloodworms https://www.aquaticrepublic.com/common/species.php?species_id=1350


Mention is made of Otocinclus eating macrophytes and aufwuchs. I could not find a recent paper which provides a definitive view on this.

*Collection*

Anjos et., al (2018)  noted that in 2003 90% of exports from the State of Brazil consisted of the following fish: Paracheirodon axelrodi, Petitella georgiae, Otocinclus flexilis, Carnegiella strigata, Hyphessobrycon socolofi, Otocinclus affinis, Corydoras reticulatus, Corydoras agassizii, Corydoras schwartzi, Corydoras julii e Peckoltia vittata


In 2003 457735 Otocinclus flexilis  and 331535 Otocinclus affinis  were exported from this area at an average price .of 006 US Dollars per fish  Anjos et., al (2018) 

"According to Procolombia, in 2012 Colombia received approximately US $7 million a year in otocinclus exports. Their data also says that between January and November of 2013, along with data of the Ministry of Trade, Industry and Tourism and the National Administrative Department of Statistics, Colombia exported US $7.9 million in ornamental fish which was an increase of 7% compared to 2012. The main destinations for these exports were Hong Kong, United States, Taiwan, Japan, Germany and China." http://www.dicyt.com/news/ornamental-fish-to-be-genetically-studied-due-to-overexploitation

*When are they mature and how can breeding be stimulated? *

In 1997 Schafer noted “…no published behavioral or reproductive information is available.”(page 21)

 He went on to argue that “ Aquarists who have successfully spawned various species of Otocinclus and Microlepidogaster have informed me of aspects of the courtship and reproductive behaviors. In the interspecific inter- actions prior to spawning, individual males embrace the female by coiling the trunk around that of the female” (page 21)

Periera and Suarez (2019) noted that in the wild maturity of Otocinclus  Vittatus estimated was 18.7 mm for females and 20.1 mm with a variation of between 10.5 to 41.25 mm.

Interestingly Periera and Suarez (2019) noted that breeding behaviour correlated with water level but not rainfall. Pereira and Suarez note that their reproductive peaks coinciding with peak river flows and speculate that this may be a strategy to colonize floodplain habitats.

Extrapolating from this may suggest that techniques such as adding further RO water or colder water to simulate rainwater in the hope that this stimulates breeding (used with Tetras) possibly won’t work. 


Mas, Alvarenga and Scarabotti (2019)  O. arnoldi, showed reproductive activity in spring and summer.


“..most species showed a marked reproductive seasonality, with reproductive activity concentrated in the warmer months of the summer. This strong reproductive seasonality is consistent with other studies of loricariids … and is coherent with the wide seasonal variation in day length and temperature in this subtropical system.”


*References*

Axenrot, Thomas E., and Sven O. Kullander. (2003) Corydoras diphyes (Siluriformes: Callichthyidae) and Otocinclus mimulus (Siluriformes: Loricariidae), two new species of catfishes from Paraguay, a case of mimetic association. _Ichthyological Exploration of Freshwaters_ 14.3  249-272.

Borzone Mas, D., Alvarenga, P.F. and Scarabotti, P.A., 2019. Ecological and phylogenetic determinants of life‐history patterns among Loricariidae. _Journal of Fish Biology_. (in press)

Claro-García A, Abrahão V, Vieira L, Jarduli L, Shibatta O (2013) Fishes (Osteichthyes: Actinopterygii) from igarapés of the rio Acre basin, Brazilian Amazon. Check List 9(6): 1410-1438.

Delapieve, M.L.S., Pablo Lehmann, A., Reis, R.E. (2017) An appraisal of the phylogenetic relationships of hypoptopomatini cascudinhos with description of two new genera and three new species (Siluriformes: Loricariidae) Neotropical Ichthyology, 15 (4)

de Carvalho, R.A. and Tejerina-Garro, F.L., 2018. Headwater–river gradient: trait-based approaches show functional dissimilarities among tropical fish assemblages. _Marine and Freshwater Research_, _69_(4), pp.574-584.

dos ANJOS, H.D.B., de Souza AMORIM, R.M., SIQUEIRA, J.A. and dos ANJOS, C.R., 2018. Exportação de peixes ornamentais do estado do Amazonas, Bacia Amazônica, Brasil. _Boletim do Instituto de Pesca_, _35_(2), pp.259-274.

PEREIRA, M. J.  and  SUAREZ, Y. R.. Reproductive ecology of Otocinclus vittatus (Regan, 1904) in the Pantanal floodplain, upper Paraguay River basin._ Braz. J. Biol._ [online]. 2019, vol.79, n.4 [cited  2019-10-04], pp.735-741. Available from: <http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1519-69842019000400735&lng=en&nrm=iso>.  Epub Nov 23, 2018.

Satora, L., Kozioł, K., Waldman, W., & Mytych, J. (2019). Differential expression of epidermal growth factor receptor (EGFR) in stomach and diverticulum of Otocinclus affinis (Steindachner, 1877) as a potential element of the epithelium remodeling mechanism. _Acta histochemica_, _121_(2), 151-155.

Schaefer, Scott A. (2017) “The Neotropical Cascudinhos: Systematics and Biogeography of the Otocinclus Catfishes (Siluriformes: Loricariidae).” _Proceedings of the Academy of Natural Sciences of Philadelphia_, vol. 148, pp. 1–120


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## Gaina (5 Oct 2019)

For anyone looking for information on just about any species, I can recommend a great YouTuber, Rachel O'Leary.  She breeds and sells fish for a living and does brilliant 'species spotlight' videos. She's highly knowledgeable and makes the information on keeping various species very accessible.

Go to her channel, select the 'species spotlight' playlist (there are a lot of videos!) and find the one for Otocinclus.


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## alto (5 Oct 2019)

Onoma1 said:


> The latest figures that I could find indicated vast numbers of these fish being caught and exported. In 2003 457735 Otocinclus flexilis and 331535 Otocinclus affinis were exported from the Amazon Basin at an average price .of 006 US Dollars per fish. I noted that most for sale in the UK are currently Otocinclus affinis, although pictures of the fish for sale labelled affinis seemed to show a different species. This raises questions about overfishing and sustainability.


That is 16 year old data 
Otocinclus have increased substantially in export price and thus wholesale prices
O affinis has likely never been exported except as a bycatch 

There are some online videos of SA export facilities


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## Onoma1 (6 Oct 2019)

alto said:


> That is 16 year old data
> Otocinclus have increased substantially in export price and thus wholesale prices
> O affinis has likely never been exported except as a bycatch
> 
> There are some online videos of SA export facilities


The paper the figures were derived from was published in 2018. It indicates with nine other species affinis and flexillis accounted for 90% of fish exported by volume in 2003. I had the impression they were targeted and the figures indicated most were exported to countries other than the UK - where there seems to have been a demand. What seems to be of concern / interesting is that based on what is available to buy this profile of export seems to have shifted.  Which begs the question of why has it changed?

I couldn't however find any more recent figures ...if anyone knows of a source could you post it here and I will amend the first post.


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## Onoma1 (6 Oct 2019)

Gaina said:


> For anyone looking for information on just about any species, I can recommend a great YouTuber, Rachel O'Leary.  She breeds and sells fish for a living and does brilliant 'species spotlight' videos. She's highly knowledgeable and makes the information on keeping various species very accessible.
> 
> Go to her channel, select the 'species spotlight' playlist (there are a lot of videos!) and find the one for Otocinclus.


The video from Rachael is very informative (like you I enjoy her videos), I do need to add in links to some of the more interesting resources. I have the feeling that some of the aquarists know more about the fish that they care for and observe than many of the scientists who seem to rely on disection of dead fish!


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## Gaina (6 Oct 2019)

Onoma1 said:


> The video from Rachael is very informative (like you I enjoy her videos), I do need to add in links to some of the more interesting resources. I have the feeling that some of the aquarists know more about the fish that they care for and observe than many of the scientists who seem to rely on disection of dead fish!



That's what I like about keeping fish, it often throws up surprises you can only discover by actually getting your hands dirty.


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## Finn (6 Oct 2019)

Great job collecting all this info. Regarding breeding - I think it's important to note that the rainfall season starts right after very punishing prolonged droughts. During this time, river systems diminish greatly in size and flow, and water quality plummets. Fish that were cut off from the wet season river systems during this drought period become completely restricted to diminishing ponds of opaque green water which become progressively filled with dead and dying fish - most of these ponds become feeding hotspots for caiman, turtles and birds and are predominately exterminated, however I imagine some water bodies may be large enough to protect some survivors to the start of the rainfall season. This is entirely speculative but I feel it would make sense that they have the capacity for opportunistic carnivorous behaviour given that this die-off is a major seasonal event of their ecosystem even in the river systems, and could not only enable Otocinclus to survive the deleterious conditions but perhaps even give them a mating advantage with a high protein diet required for gamete production. This documentary on the seasonality of their locale (and the effect on the aquatic life), by Ivan Mikolji on youtube is extremely informative. One peculiarity of this genus is just how extraordinarily fecund they seem to be in nature, compared to how difficult it is to stimulate to breed in the aquarium, and I have a hunch that it's likely because the prolonged stress of the drought season simply isn't experienced in correctly maintained aquarium scenarios - not necessarily a bad thing though when taking the fishes quality of life into consideration.


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## zozo (6 Oct 2019)

Nice read! Thank you. Funny is I lately did setup a tank containing 8 Otocinclus and 10 Pygmy Cory's and I also noticed the Mimetic relation they have. At least its the Cory schooling with the Oto's and mimic their behavior. For example, the Oto sticks to the glass going up and down and 2 Cory's following the Oto around doing the exact same thing.

I've had Pygmy cory's in the past and also noticed mimetic behavior with other fish sp. Like schooling around for a while with Ember Tetras.  They are absolutely lovely little fish, like little monkies having fun mimicking others.

There also is a video on U tube where Oto's are caught in the wild. It is in a stagnant green and muddy puddle, leftover from the flooding season. They are scooped with 1000'nds in one scoop. It is said, the puddle will evaporate and dry out soon and if the fish in it are not caught they will die anyway..Here it is


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## tam (6 Oct 2019)

zozo said:


> Nice read! Thank you. Funny is I lately did setup a tank containing 8 Otocinclus and 10 Pygmy Cory's and I also noticed the Mimetic relation they have. At least its the Cory schooling with the Oto's and mimic their behavior. For example, the Oto sticks to the glass going up and down and 2 Cory's following the Oto around doing the exact same thing.



My habrosus corys and otos do the same. I have a otos specie(s) with a tail spot like the habrosus so I have to look twice sometimes to work out which is which. They often shoal with each other. I've read before somewhere that cory spawning can trigger otos. My otos sometimes look to be carrying yellow eggs but I've never seen them actually spawn.


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## zozo (6 Oct 2019)

Dropping temps seems to do the trick with read..I remember reading at 19°C.. It mimics the rain/flood season, there the new fresh rain/mountain stream waters significantly dropping temps signaling spring and spawn time.

I've read people have gone so far even with spraying installations to mimic rain and turbidity in the corry breeding tank. Spraying cooler water and letting the temps drop.


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## Steve Buce (6 Oct 2019)

Nice write up


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## tam (6 Oct 2019)

I've some 7 week old baby corys after dropping the temp a couple of degrees at a water change, but the otos didn't follow suit. I suppose I could break out the watering can and make rain. 

I do wonder if I've got enough males/females of the same species though, as they were added in a couple of batches. I've had trouble finding information on telling different oto species apart and often the photos don't match the species write ups.


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## Matt @ ScapeEasy (7 Oct 2019)

All this talk of rain simulation reminds me of one of my favourite vids of all time ... get yourself a brew and watch this...


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## BrysonZheng (7 Oct 2019)

I can attest to the meat eating aspects in O. macrospilus. I used to have a group of ten and when I fed the tank, they would all take bribe shrimp and eat them!


Sent from my iPhone using Tapatalk


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## Matt @ ScapeEasy (8 Oct 2019)

I also had some in a dwarf puffer tank and they enjoyed the bloodworm too.


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## jaypeecee (12 Nov 2019)

Gaina said:


> For anyone looking for information on just about any species, I can recommend a great YouTuber, Rachel O'Leary.



And, please don't forget about the following resource:

https://www.seriouslyfish.com

And, if I could add one observation, my Otocinclus are most active when the tank light has gone off.

JPC


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