| Return To Article List Fishmonger NewsletterFocus On Amazon PuffersSeptember, 2022 | |
| | Fish Store Construction is FINISHED!!!!! | You might have noticed that we have not had a newsletter released since April of this year. My apologies for that, but here at dansfish.com we’ve been preoccupied with finishing the construction of the new fish warehouse and moving our operations into our new space. For anyone who missed that journey, we documented it quite thoroughly on the Dans Fish Youtube and Instagram channels, so check that out if you are interested. Our friend Bob Steenfott made a couple of great videos, one detailing the finished system and the other detailing thousands of fish in the system. I’ve placed those vids directly below for those who might have missed them. | |  | Above is the video detailing the finished warehouse system. | | |  | Above is the video showing the fish in the new warehouse system. | | | | | | Featured Article | Deep Dive into Amazon Puffers | | Article by Dan Hodnett | This article is made possible by all of our wonderful dansfish.com customers. Thanks for your continued support!!!! | |  | | | Each type of freshwater puffer has different care requirements based on the niche it inhabits, so there is no one-size-fits-all care guide that works for this group of fish. Instead, each individual species deserves careful consideration. So, let's take a deep dive into the fascinating world of Colomesus asellus, a popular aquarium fish commonly known as the Amazon Puffer. But first, let's learn a bit about the natural history of puffers in general so we can better appreciate how unique our subject is. Fortunately, we know a lot about puffers. These fish have the smallest known genome of any vertebrate, making them ideal subjects for scientific research. This, combined with their unique anatomy and the deadly toxins embedded in their tissues, fascinates scholars resulting in ample study. |  | X-ray showing the skeletal structure of Columesus psittacus, the ancestor of the Amazon Puffer. Credit: Cesar Amaral et. al. | | There are currently about 187 species of puffers divided into 28 genera. The vast majority of these inhabit saltwater environments. However, over the millenia, a few species have migrated into freshwater environments. This type of "freshwater invasion" has occurred on at least 8 separate occasions. The original invaders subsequently differentiated into the diverse species of freshwater pufferfish we enjoy today. Depending on which scientist you listen to, the first puffers moved to freshwater between 20 and 78 million years ago. That's quite a time-spread and alone might not be a very helpful statistic. What is helpful is knowing that the invasion began in Southeast Asia, then later in Central Africa, and lastly in South America. | | |  | Amazon Puffer Family Tree. Credit: Chandhini Sathyajith et. al. | | Having only recently split from their ocean ancestors, the freshwater fish of the genus Colomesus are unique in their newness. There are 3 species in the genus. The oldest, Colomesus psittacus, differentiated from its ancestors about 12.9 million years ago. It remains in brackish and seawater environments along the shoreline, but two newer species, the recently described C. tocantinensis and the widespread C. asellus, left the salt and adapted to pure freshwater environments. These two species are the only freshwater puffers in South America. The largest one on record is around 5", but that is an outlier. They usually only grow to about 3". Here at dansfish.com, we've never seen them even close to 5". | The Amazon Puffer diverged from C. psittacus 2.5 - 7 million years ago, a recent occurrence in evolutionary time. Because the puffers in South America are relatively new arrivals on the freshwater scene, they have not had enough time to radiate into the variety of spectacular phenotypes found in Asia and Africa. Both South American freshwater species are striking in their similarities. The main differentiation is that C. asellus has small dermal flaps on its chin. These flaps are absent in C. tocantinensis. This difference is so small that they were considered the same species until 2013. |  | Unfortunately, there are no images of living Colomesus tocantinensis available, so we will have to settle for this image of the holotype specimen. Credit: Cesar Amaral et. al. | | While the natural range of Colomesus tocantinensis is restricted to the Rio Tocantis drainage, the Amazon Puffer is found throughout the Amazon basin in Brazil, Columbia, Peru, Ecuador, Guyana, and Venezuela. They are strong swimmers capable of handling the current in the main river channels. During the wet season these currents gain strength as the water level routinely rises over 30 feet, eventually flooding out into the forests surrounding the main river channels. Because fish with large natural ranges and extreme seasonal fluctuations encounter many different habitat challenges across their distribution, they tend to be hardy and adaptable. In our experience, Amazon Puffers are indeed hardy aquarium fish. |  | Yellow dots represent known Amazon Puffer collection locations. Credit: discoverlife.org | | Reproduction is tied to these vast seasonal changes. Amazon Puffers spawn in the "quantity over quality" fashion of their saltwater ancestors. Instead of laying a limited number of eggs and practicing brood care to ensure a quality hatch, our subjects scatter huge numbers of eggs and promptly abandon them. The resulting larvae are poorly developed in the way of planktonic saltwater fish larvae. Despite its popularity, this form of reproduction is difficult to simulate in aquaria. Despite its popularity among aquarists, the aquarium industry has yet to successfully culture C. asellus. All the fish in the trade are harvested from nature. | In one study of Amazon Puffer reproduction, Carlos Araujo-Lima and his cohorts attached a fine mesh seine net to a boat and trawled the Amazon River for puffer larvae over the course of a year. They found that 97.9% of larvae were found about 30 days after the beginning of the wet season. Because these larvae were congregated near the bank of the river at the mouth of side channels leading to floodplain lakes, it is thought that adults aggregate at those locations to spawn. The study found that as the wet season progressed and the water level continued to rise, the larvae were washed into floodplain lakes where they developed onto fry. As the water level dropped during the dry season, the young puffers were flushed back out into the main river channel to continue the cycle. | During the course of this study, the water temperature averaged 82.94 F, with little variation. It is important to note, however, that this data is from a single study in a very small part of the Amazon Puffer's natural range. This species experiences greater temperature fluctuations throughout its range and we've had no problems keeping them long term in our aquariums in temperatures ranging from 78F-84F. | |  | Amazon Puffer larvae. Credit: C. Araujo-Lima | | Many freshwater puffers are highly aggressive towards conspecifics. When kept in groups in an appropriately sized tank, Amazon Puffers enjoy each other's company. In nature, they are found in large aggregations. These are community minded fish that like being surrounded by their neighbors. In aquariums, they are best kept together in groups...the more the merrier. In addition, these fish are strong swimmers which appreciate open swimming space. It is important to keep both their gregarious nature and their desire to swim in mind when selecting the right sized aquarium for this species. They explore endlessly, so having lots of plants, decorations, and hardscape to scan will greatly enrich their lives. |  | Carinotetraodon irrubenesco, the Red Eyed Red Tailed Puffer, is a small freshwater species that, in our experience, does not tolerate conspecifics. | | When we think of puffers, most aquarists think of molluskivores. However, Amazon Puffers are different. While they do eat a significant amount of shellfish, mollusks, usually in the form of snails, only account for 25% of the adult puffers' diet. In juveniles, the percentage drops to 6.42%. This is because Amazon Puffers don't have very large mouths and so their tooth plates can't handle hard snail shells until they are adults. Even adults can't tackle anything except small snails. This is why aquarists tend to smash their snails' shells before feeding them to these fish. | The majority of C. asellus's diet, 62.18%, is made up of insects. Of these, 48.63% consists of mayfly nymphs. Then come the aforementioned snails at 25%, followed by...wait for it...FISH SCALES! It turns out that Amazon Puffers are scale eaters. 8.16% of their diet is fish scales. This has important implications regarding their compatibility with other species in aquariums. They definitely can be kept successfully in a community aquarium long term. I've seen it work on several occasions. However, this species might not play nice in every situation. It could be that fast moving fish are not at risk but that slower moving benthic grazers are. Should some of your fishes' scales start disappearing, the puffers may need to be removed. | To round out their diet, these fish ingest small amounts of algae (0.34%), fish (0.06%), and plants (0.03%). However, it is more likely that the algae and plants are acquired from the stomachs of their prey or as bycatch while attacking their prey than as food items which is purposefully sought out. |  | Mayfly nymphs are the mainstay of an Amazon Puffer’s natural diet. Photo credit: Jon Sullivan | | Like other puffers, Amazon Puffers have a set of tooth plates, often referred to colloquially as their "teeth" or "beak," which is used to dispatch prey. Just like a rodent's teeth, these tooth plates grow continuously and must be constantly worn down or they will become so overgrown that the fish won't be able to feed. In the wild, puffers routinely wear down their teeth as they hunt. When C. asselus attacks, it grabs the prey item while simultaneously scraping its tooth plates against the rocks onto which the mayfly nymphs cling. Eating snails further wears down the tooth plates. | In the aquarium, we must provide opportunities for our puffers to wear down their tooth plates. This can be done by rotating crushed snails into the diet. Here at dansfish.com, we find that Repashy gel foods into which crushed oyster shells have been embedded helps with puffer "tooth maintenance." Crushed oyster shells are commercially produced as chicken grit and can be purchased cheaply at livestock supply stores. To embed them in the Repashy, mix the Repashy powder with hot water as per usual, but stir the crushed oyster shell into the slurry so that when the Repashy hardens, it has bits of oyster shell throughout. When this is fed to the Amazon Puffers, they will wear down their teeth on the oyster shell as they feed on the Repashy mixture. It takes a week or so of training to get the puffers to accept this Repashy/oyster shell mix, but, once they do, their tooth plates will be simple to maintain. | |  | Above is a video showing how we make our Repashy with Oyster Shell here at dansfish.com . | | Amazon Puffers are eager feeders and can be trained to eat dry, gel, frozen, and live foods. We rotate the Repashy into the diet and feed it every third feeding or so. Other readily accepted foods include Hikari Vibra Bites, frozen blood worms, frozen mysis shrimp, frozen brine shrimp, live scuds, live cherry shrimp, and crushed snails. Rotating a variety of foods into their diet helps ensure our puffers get all the nutrition and enrichment they need. | Puffers are deadly to humans if ingested. Fugu, a Japanese delicacy prepared from the flesh of the Fugu Puffer, is famous for being deadly if it is not properly prepared. There are two types of toxins in pufferfish: Tetrodotoxin and saxitoxin. Neither compound is produced by the puffer itself. Instead, these toxins are created by bacteria, cyanobacteria, protists, and algae. Small quantities of these toxins get passed up the food chain. Most animals excrete these compounds before they can build to harmful levels, but Puffers have the ability to retain these compounds and concentrate them. Amazon puffers store concentrated saxitoxin in their skin and other tissues, especially their gonads. Saxitoxin is a potent neurotoxin which cuts off the nerve cells’ ability to transmit signals, causing paralysis and death. A dose of 0.57mg, or about 1/8 of a medium sized grain of rice, is lethal to humans. However, you can still keep puffers safely as pets because these toxins have to be ingested to be of any concern. |  | Freshwater cyanobacteria produce the saxitoxin which make Amazon Puffers deadly to eat. Photo credit: Silviapvadi's Blog | | So, I guess the takeaway is don't eat your pet puffer, and all should be fine. | If you have any questions about this article, join us for our weekly livestream Wednesdays at 9pm EST on the Dans Fish Youtube channel at this link: https://www.youtube.com/c/DansFish/featured | | | Article References
Amaral, Cesar & Brito, Paulo & Silva, Dayse & Carvalho, Elizeu. (2013). A New Cryptic Species of South American Freshwater Pufferfish of the Genus Colomesus (Tetraodontidae), Based on Both Morphology and DNA Data. PloS one. 8. e74397. 10.1371/journal.pone.0074397. Araujo-Lima, C A et al. “Drift of Colomesus asellus ( Teleostei : Tetraodontidae ) larvae in the Amazon river.” (1994). Bartolette, Renata & Rosa, Daniela & Beserra, Danielle & Soares, Bruno & Albrecht, Míriam & Brito, Marcelo. (2018). Seasonal and ontogenetic diet patterns of the freshwater pufferfish Colomesus asellus (Müller & Troschel, 1849) in the upper-middle Tocantins River. Acta Scientiarum Biological Sciences. 40. 10.4025/actascibiolsci.v40i1.35282. discoverlife.org via fishbase.org: https://www.discoverlife.org/mp/20q?search=Colomesus+asellus&btxt=FishBase&burl=http://www.fishbase.org/Summary/SpeciesSummary.php:;q:;id:;e:;51376&b=FB51376&btxt=FishBase&burl=www.fishbase.org/Summary/SpeciesSummary.php?id=51376 September 2, 2022. Oliveira, Joacir Stolarz et al. “Toxicity and toxin identification in Colomesus asellus, an Amazonian (Brazil) freshwater puffer fish.” Toxicon : official journal of the International Society on Toxinology 48 1 (2006): 55-63. Santini, F et al. “Do habitat shifts drive diversification in teleost fishes? An example from the pufferfishes (Tetraodontidae).” Journal of evolutionary biology vol. 26,5 (2013): 1003-18. doi:10.1111/jeb.12112 Sathyajith, C., Yamanoue, Y., Yokobori, SI. et al. Mitogenome analysis of dwarf pufferfish (Carinotetraodon travancoricus) endemic to southwest India and its implications in the phylogeny of Tetraodontidae. J Genet 98, 105 (2019). https://doi.org/10.1007/s12041-019-1151-9 seriouslyfish.com https://www.seriouslyfish.com/species/colomesus-asellus/#:~:text=Tetraodontids%20are%20commonly%20referred%20to,is%20removed%20from%20the%20water. June 5, 2022. Yamanoue, Yusuke et al. “Multiple invasions into freshwater by pufferfishes (teleostei: tetraodontidae): a mitogenomic perspective.” PloS one vol. 6,2 e17410. 25 Feb. 2011, doi:10.1371/journal.pone.0017410 | | | | | | | Here are some of our current favorites at dansfish.com at the moment |  | Empire Gudgeon (Hypseleotris compressa) | | |  | | |  | | |  | | |  | | |  | | |  | | |  | | | | |
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