Fish Traveling Via Duck Poo

Male and Female Mallard Duck. Photo by MDC Staff, courtesy Missouri Department of Conservation.

What ways can fish eggs be spread? You thought I was talking about different crackers to use with caviar didn’t you?

In your biology courses, you may have learned there are many different ways seeds, invertebrates, and even larvae of insects are able to disperse over large ranges and to unexpected locations, but can the same be said for fish eggs?

Up until recently the answer to that was no (with the exception of Killifishes), however a paper released in July 2020 by Adam Lovas-Kiss et al. learned something interesting when it comes to waterfowl.

Mallard ducks, a migratory waterfowl, already known for their ability to disperse both aquatic and terrestrial plants were chosen to use in the study and due to their similarity to most teleost fish, researchers chose to use 2 types of fertilized carp eggs- Common Carp and Prussian Carp.

The ducks were individually housed and were each force fed the fertilized eggs (Common Carp in the first experiment and Prussian Carp in the second). After the eggs were ingested, their feces were collected after 1,2,4,6,8,12, and 24 hours.

After the feces were soaked in river water and each sample sifted through this is what they collected:

.2% (8) of the Common Carp eggs

.25% (10) of the Prussian Carp eggs

All but 1 of which, were recovered from the feces within the first hour after ingestion, with the outlier egg being recovered between 4 and 6 hours after ingestion.

Of all the eggs that passed through the Mallards’ digestive systems, 2 Prussian Carp eggs hatched and 1 Common Carp egg hatched! The males passed more eggs than females (15 to 3) and only the eggs passed by the males hatched after they were recovered. It should be noted that all of the hatched fish, both those in the control group and those ingested by the ducks eventually died of fungal infections.

These findings open up and invite many future studies that could look at the traits of fish as well as other waterfowl and their ability to act as a means of dispersal for embryonic fish.

Experimental evidence of dispersal of invasive cyprinid eggs inside migratory waterfowl

Ádám Lovas-Kiss, Orsolya Vincze, Viktor Löki, Felícia Pallér-Kapusi, Béla Halasi-Kovács, Gyula Kovács, Andy J. Green, Balázs András Lukács

Proceedings of the National Academy of Sciences Jul 2020, 117 (27) 15397-15399; DOI: 10.1073/pnas.2004805117

Newly Discovered Fish!

Image courtesy of - https://www.vectorstock.com/royalty-free-vector

Lesley de Souza lead author, conservation scientist, and ichthyologist had the honor of describing 6 new species of catfish found in the Amazon and Orinoco River Basins.

The newly discovered fish are all part of the genus commonly known as Bristlenose catfish, just like plecos commonly kept in freshwater aquariums. De Souza described them as having tentacles on their snouts and spines sticking out of their heads.

The purpose of the spines is to help them protect themselves and their nests. The tentacles however, are there to persuade females they will be good Dad’s as the males are the ones who look over the next and guard the fry.

These fish were found in the “clear fast flowing rivers and streams” in Northeastern South America, but there are many species of fish that have yet to be discovered.

Dr. De Souza is excited and hopeful, as “describing a new species is an opportunity for conservation action. For example, Ancistrus kellerae is one of the new species described and is only found in the highlands of Guyana, in one area, likely making it endemic. With the impending threats to its watershed from gold mining, maybe its status as an endemic species will help to protect the ecosystem.”

Anyone can make a difference in their local aquatic ecosystem. Lesley recommends getting involved with local initiatives you are passionate about. She encourages us to make sure we’re familiar with native fauna as well as potential threats to the area, and most importantly, she encourages people to get out and enjoy the rivers and natural areas nearby.

Thank you so much to Dr. Lesley de Souza for sharing your passion about these fish and their ecosystems.

Source - Field Museum. "Six new species of hideously adorable tentacle-nosed catfish discovered in Amazon: Tentacles 'catfish' potential mates into picking the best father." ScienceDaily. ScienceDaily, 6 February 2019. <www.sciencedaily.com/releases/2019/02/190206200401.htm>.