Science Experiment

The Pangasius Fish

Vidheha’s narrative

You can't believe how much fun science is at school. 

We brought the table. Then we brought the fish. Fish’s teeth were many. The teeth were like a zipper. The fish was gray on the top and white on the bottom. We cut the fish from its belly. We saw the gonads, intestines, and liver. The fish had four barbals.

Science Report by Utkrishta Mulmi

Suprit and Sanket getting comfortable touching the fish. Snighda's already a veteran.

We have been doing fish dissections over the past 3 years, ever since I have been at Evolution School. We have done the catfish, the common carp, grass carp, piranha, and rohu. This time we were doing another fish dissection. This time it was the Pangasius fish we were going to look at.

The teeth were like a zipper, says Vidheha to Utu.

Our Objectives were to

-          Desk review the specimen

-          Observe external physiology

-          Conduct dissection

-          Observe the internal anatomy

-          Document, visualize, report and publish

Practicing smiling, Aarambha.

Desk review

Where we started research, we found about five types of fishes called the Jal Kapoor in Nepal. So it was hard to determine the particular information we were seeking. I got the fish species wrong a couple of times so we changed the search to fish farming in Nepal and at last got the samples of fish we wanted.

Chuntu is 3 and she is thrilled, so are Bishes, Amulya and everyone else.

Last time too, we were told that a fish that we were going to study was fresh water so we assumed that we had a pacu fish on our hands. Very similar to the piranha, it has human like teeth. Its mouth was closed as we studied the external physiology and when Pallav sir tried to open its mouth so we could look at the teeth, one of them cut into his hand through the surgical gloves. We found out that it was not a pacu at all, it was a large piranha we had on our hands. So after that anecdote, here we go, we did find the right species related information.

Suprit thinks the fish looks like a bird of some sort :)! Wait until you are 5 years older, keeping this one in stock.

Common name/ Local name: Jal Kapoor

Scientific name: Pangasius Sannitwongsei

Kingdom: Animalia

Phylum: Chordata

Class: Actinopterygii

Order: Siluriformes

Family: Pangasiidae

Genus: Pangasius

We are about to start, no scalpel this time, Sabita in the kitchen does NOT want science equipment touching the fishy.

External physiology

Initially, we look at the overall fish. As Vidheha has said above, we prepared our tables, cutting tools, and other required material. We settled the seating and lay the specimen in front of us. We measured it, observed its colors, different parts, and documented our learning. The objective were to learn as much as possible about the specimen from the outside.

Fish face me.

1.      The Pangasius specimen that we had was:

-          1.5 kilograms

-          About 18 inches long

-          About 8 inches wide

2.      It had 8 fins: the dorsal fin, pectoral fins (2), pelvic fins (2), adipose fin, anal fin and the caudal or the tail fin.

3.      It had no scales which was weird because all fish we had done, except the catfish, had many many scales (After we study the fish, we eat it J so we have to clean the scales. It is a hassle getting rid of the scales, I can tell you by experience).

4.      The teeth were tiny and serrated. They were so small that I couldn’t even see them clearly.

5.      The tail fin was smooth and not that boney.

6.      It was white on the belly, with pink edges. It was grey on the side darkening to almost black on the top.

7.      It had two maxillary barbals, like moustaches, on two sides and two extensions called mandibulary barbal, like the beard, below the chin.

8.      It had four nostrils, a pinkish eye.

9.      It had a pinkish round anal outlet.

10.  It had a clear lateral lines on both sides which, when felt, did not have a groove.

11.  The gill coverings were stronger than on rohu and other pieces and they were not as red as on common carp, grass carp, piranha and other fishes that we have studied.

Here are the pelvic fins and the anal area, Bishes knows his fish.

Dissection

During dissection, we cut open the specimen. The process is sometimes difficult due to presence of bone and other material such as tough tissue. The objective is to reach inside the specimen doing as little damage as possible so we can observe the internal anatomy.

1.      Pallav sir cut the fins except the caudal fin and we identified and felt the fins.

2.      Then he cut a small line along the anus to the area below the gills.

3.      Then we pulled the innards like the gonads, intestines, liver, gall bladder, heart, stomach, the deflated air bladder out.

4.      We all got to feel the organs and they felt slimy and squishy.

5.      I already had researched the external and internal parts of the fish, I told the others the names of the organs and what they do.

Aarambha and Snighda about to feel the teeth as Vidheha and Sanket watch on.

Internal anatomy

After we dissected the fish we could see its insides. We took a class on its internal anatomy. We observed and touched the internal organs and we tried to identify what part is which from a picture of the fish. Sometimes we got the organs mixed up, like I’m was sure this fish had a heart and a kidney but we just didn’t see them.

1.       The pangasius had a thick layer of fat covering its innards.

2.       The first things we saw were the intestines and gonads.

3.       We thought that the gonads were eggs or fat or some kind of growth as we had never seen the gonads so prominently in any other fish we dissected.

4.       We saw very clearly the blood vessels that are attached to the intestines. They absorb the nutrition that has been processed and take it through the blood stream to the rest of the body we were told.

5.       We saw the liver and the gall bladder.

6.       There was a hard item and I was not sure if it was the heart or the stomach. I could have connected the organ to the intestines to make sure, but I didn’t.

7.       We didn’t see the kidney and the urinary bladder.

8.       We didn’t cut the head as the bone was very hard so we couldn’t  see the brain.­

That is ze intestines says Utu Man. Bishes knows fish liver. Shila knows now that fish, especially the pangasius has gonads!

Documentation, Visualization, Reporting, Publishing

We documented the information we had about the species we were dissecting and we compared the information to the live specimen. We took photos of the specimen’s parts so we could identify them and use them to compare with other pictures we took in the past or the future. We made a report on the experiment and we published it on our blogsite as well as other social media sites.

Learning

We saw a lot of things that we didn’t see in other species of fish that we dissected.

1.      This fish did not have scales, I thought all fish had scales.

2.      When we cut the fish we saw these tiny white-yellow rice-like objects and we didn’t know what they were. They were apparently gonads. We hadn’t seen such prominent gonads in any other fish.

3.      This fish had lots of fat so it was very healthy.

4.      This was a species of catfish and it was the second catfish species that we dissected.

5.      The fish’s teeth were like tiny serrated spikes, they were so small it looked like it had none.

6.      We didn’t see some organs like the stomach heart and kidney.

To begin with, when we did experiments, we started off with just taking pictures. They were put up in Facebook to share and to save. Later we started writing 100-word blogs in our science copy books with appropriate sketches. However, they remained in the copy book and after a while were hard to access and no one else really could share them with us.

After that we started publishing  them in the school blog page where we can go and access the reports. For example, after we do this fish, we will do the same species as well as others. If we have this report online with photographic and sketch samples, it will be so much easier next time. We can learn from our mistakes and increase our store of knowledge.

We are starting to make better reports like this one but we need to improve on them by studying other samples.