Marine Vertebrates

The tip of the barb is the sharpest part of the structure and allows the animal to impale predators.

Although some ray species do not have stingers there is a large portion of the group that have them. These structures are not used to hunt for prey but rather as a way to defend themselves from predators. Occasionally people have interactions where they are stabbed by them and it can be a serious situation.

 

The manta ray (left) is a species that is well known and is absent of a barb. The barb is commonly located at the base or close to the base of the tail (right)

Back in April of 2015 I had an interaction with a bat ray where I was stung in the arm. The initial pain was brief and my adrenaline began to kick in. I asked my friend to take the barb out immediately and thinking about it I may have wanted to keep it in. When thinking about the barb it’s in the shape of a Christmas tree almost. The barb has a sharp point in the top and it’s followed by a series of serrations facing the opposite side of the initial point and taking it out could do more damage than leaving it in, but I was in survival mode and I wanted it out of my body.

 

This is an image showing the anatomy barbs come in. The darker sections labeled with the number 1 is where the venom glands are located. The number 2

For this post I wanted to look at a barb under the SEM from the same species that stung me and get an appreciation for this defense mechanism. As seen in the second and third picture there are variations in shape and size and it helps with species identification if that is wall that you have to work with. In my ichthyology class we dissected bat rays, where I collected one of the barbs. I also used the Oblique analysis tool to get a three dimensional image of the barb. Can you tell where the venom gland would be located on the barb in relation to picture 3?

 

 

These are the images of the barb that specifically focuses on the serrations. The serrations on this structure help the ray increase its capacity of damage if the barb is pulled out.

 

 

 

 

Image sources in order starting from the top:

MLML

http://divetrip.com/quintana_roo_report.php

https://web.csulb.edu/labs/sharklab/public/stingrays.html

http://www.fishing-headquarters.com/stingrays-scorned-saltwater-species/

https://www.vapaguide.info/page/25

MLML

MLML

 

On the first day of our Scanning Electron Microscopy class our instructor asked if we would like to prepare a sample for the following week. I initially didn’t have a clue on what I wanted to use because I had not prepared any sample of my own to go through the process to be prepped for the SEM. While I was waiting and thinking about what I wanted to use, I realized that I had a pair of otoliths in my backpack. These otoliths were collected from a rock fish during a series NOAA surveys conducted off the West Coast of the U.S. I had them as mementos of the trip I was on and forgot about them for a couple of months and I thought this would be a great opportunity to look at one of them under a high powered microscope.

Otoliths are boney structures located behind the brain of fish and come in different shapes and sizes. Otoliths are not found in cartilaginous fish like sharks, skates, rays and chimaeras and are predominantly in bony fishes. These hard structures are made of calcium carbonate and aid fish in detecting balancing, and directional movement. Scientist can use these structures to identify species, calculate growth rates, and determine the age of the fish. This is made possible because during the lifespan of these fish proteins and calcium carbonate layer on top of each other annually.

(Picture 1) A comparison in size of an otolith and a penny. Although it’s coated in a thin layer of gold you can see the distinct bands that surround the otolith. These distinct dark “rings” are made of calcium carbonate and proteins, are commonly used to age fishes. This technique is analogous to counting the rings of a tree to determine the age but I was curious to see if there was physical difference between the bands or if it is just a difference in color. When we actually looked at the otolith it almost looked like the surface of a planet. Some areas of the otolith looked like canyons and it was interesting seeing how distinct the bands looked compared to the lighter areas of the otolith. When we looked even closer it seemed that there was a courser texture in the bands than areas without it and the structures were smaller. I thought it was an interesting thing to see not only that there is a color difference but a physical difference in a micro scale.

(Picture 2) A first glance at the surface of the otolith where distinct banding paterns are easily seen. The box is a lead-in to pictures 3&4 where we get a deeper understandig of the physical aspects of the bands.

(Picture 3) The physical differences between the darker band and the lighter bands. The red box leads into the physical aspect of the smaller calcium carbonate structures in Picture 4.

(Picture 4) The structures in the band almost mirror the structures on the light side but are smaller and more compact.