What is your favorite type of plastic to eat?

Oh are you going to tell me you don’t eat plastic? Unfortunately, there’s a real good chance that isn’t true. Let me tell you about this study by The University of Queensland, you might want to sit down for this. 

They looked at tissue samples of a variety of different species- 10 oysters, 10 farmed tiger prawns, 10 wild squid, five wild blue crab and 10 wild sardines. They found plastic in 100% of the samples they looked at. 

Of all the species they looked at they found Sardines had the highest amount of plastic. 

The study’s lead author said this “Considering an average serving, a seafood eater could be exposed to approximately 0.7mg of plastic when ingesting an average serving of oysters or squid, and up to 30mg of plastic when eating sardines, respectively …. For comparison, 30mg is the average weight of a grain of rice."

Now before you say “I don’t eat seafood, so I don’t have to worry.” If micro plastics have gotten into the tissues of sessile organisms that live on the bottom of the ocean, don’t for a second think they haven’t infiltrated our land based foods systems as well. 

To Read the full paper: https://pubs.acs.org/doi/pdf/10.1021/acs.est.0c02337

Microplastic Trapping Corals

Which of these catches more plastic particles- sand beds, coral reefs, sea grass beds, or macro-algae?

A study released last month by Jaco C. de Smit et al. looked at how different nearshore habitats trap and collect micro plastics.

They looked how sand/ sediment bed, sea grass, macro algae, and Stylophora (coral) were able to trap 2 different sizes of micro-plastics- 2.5mm and .5 mm.

What they found is that habitats with more complex structures trapped a higher amount of micro-plastics, but the area which trapped the most micro plastics was the sediment, which trapped 1 to 2 times more than any of the other areas.

The reason they believe this happened is because of the near-bed turbulent kinetic energy which is a contributing factor to sediment trapping.

Of the 2 different sizes of microplastics that were trapped, the .5mm particles seemed to be trapped more frequently than the 2.5 mm particles.

We already know micro-plastics are an issue, why does study this matter?

Nearshore ecosystems, like sea grass beds and coral reefs are hugely productive ecosystems and act as nurseries for many species of fish and sharks. According to this study they have large capacity for sequestering plastic. With these areas that are used by animals in vulnerable life stages, being inundated with micro plastics, it is much easier for them to get ingested and cause issues starting from early on. If the inhabitants of these area start to have issues, so too with the areas themselves.

To read their full article search here.

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

Can Stingrays Hear Sound?

Southern Stingray Photo by Hilary Jaffe

In 2019, Mickle et. al studied 20 different Southern stingrays (Hypanus americanus) in the waters surrounding the Bimini Biological Field Station. They placed underwater speakers in the pen with the stingrays and using a Sony Walkman, they played 5 different low frequency tones.

The 9 males and 11 females were tested individually and were exposed to 5 sound frequencies- 50Hz, 90Hz, 200Hz, 500Hz, and 1000HZ. Using a hydrophone they measured the sound level (in decibels) at 27 different locations inside the stingray’s enclosures.

Since a sound threshold for the rays was previously unknown, they started with 140dB , then depending on the stingray’s swimming behavior** , the sound was increased or decreased by 10dB or 5dB respectively making the levels tested- 130dB, 135 dB, 140dB, 150dB, and 160 dB.

What they found was both male and female stingrays exhibited behavioral differences. The average tone males responded to was 160dB while females responded more to 140dB.

With regard to frequency, males swimming activity increased at 50Hz, 90Hz, 200Hz, and 500 Hz and the females increased their activity at 50Hz, 90Hz, 200Hz, and 1000Hz.

The study looked at the following stingray behaviors- surface breaches, time spent resting, and side-swimming. Both males and females had significant increases in breaching events at 50 Hz, 90 Hz, and 200Hz. Resting rates for males and females decreased at 50Hz, 90Hz, and 200Hz and 50Hz, 90 Hz, 200Hz, and 500Hz respectively. At frequencies of 50Hz, 90 Hz, 200Hz, and 500Hz, both males and females showed increased rates of side-swimming.

If you would like to read their full article, you can find it here.

Mickle, Megan F et al. “Field assessment of behavioural responses of southern stingrays (Hypanus americanus) to acoustic stimuli.” Royal Society open science vol. 7,1 191544. 22 Jan. 2020, doi:10.1098/rsos.191544

** Animal trainers use similar observation to determine their animals level of enrichment and engagement.

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>.