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Where Is The Gravid Spot On A Molly Fish? (With Pictures)

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I remember how worried I got when I saw that my molly was bloated, although I couldn’t find the gravid spot. In other words, I didn’t know if my molly fish was actually pregnant. In this article, I will discuss the location of the gravid spot on a molly fish and what it means if you can’t find it.

The gravid spot is located near the anal fin at the lower part of the molly fish’s abdomen. As it resembles the womb of the fish, the gravid spot will gradually expand into a triangular shape. The spot will darken and enlarge until the molly fish gives birth to living fry.

As we move forward, I will share some valuable pictures that illustrate the gravid spot on a molly fish. I will also tell you in which cases you won’t be able to find the gravid spot and what other signs may indicate that your molly is indeed pregnant.

Still curious? Feel free to check my complete guide on pregnant molly fish. There, I discussed how to care for pregnant mollies, how long they remain pregnant, how to identify signs of pregnancy, and a lot more.

Where Is The Gravid Spot On A Molly Fish?

The gravid spot is a common attribute of molly fish. However, many aquarists do not fully comprehend what it does, where they can find it, and what the absence of the gravid spot means. Fortunately, the gravid spot is one of the least complicated facets of a molly fish.

You can find the gravid spot near the anal fin of a female fish.[1] The position doesn’t change, regardless of the age of the fish. However, the size of the gravid spot will fluctuate over time.[2]

In fact, many aquarists use the size of the gravid spot to track the pregnancy of a molly fish. This is because the gravid spot will expand in response to the growth of the fry in the molly fish. A larger clutch of eggs translates into a more prominent gravid spot.

The gravid spot’s location doesn’t change because the gravid spot points to the womb of the molly fish. This mark looks like a random splash of color on the molly’s skin, but it actually correlates to an organ inside the fish.

Because the womb of a molly fish doesn’t change position, you can’t expect the gravid spot to change location either. It is worth noting that the gravid spot isn’t necessarily a spot. Instead, it is a dark smear that can take various shapes. Though, it usually is triangular.

This distinction matters because the gravid spot eventually develops smaller spots that confuse first-time aquarists. Those more minor spots are the fry’s eyes inside the molly fish. This further emphasizes that the gravid spot is an external marker pointing to the location of the womb inside the molly fish.

Why Can’t I Find The Gravid Spot On My Molly Fish?

Many aquarists can’t find the gravid spot, even though their molly fish seems pregnant. If that is your case, this is what you should consider:

1. The Pregnancy Is Still Too Early

The color confuses newcomers because they expect to see a dark spot near the anal fin of a pregnant molly. But that isn’t always the case. First of all, the gravid spot is a lighter color in many molly fish before they conceive.

Keep in mind that many fish have translucent skin.[4] This isn’t always obvious until they eat colored foods and their bodies undergo a temporary color change.

The gravid spot is more likely to take on orange or red tones, reflecting the organs inside the fish or the objects in the tank. When a male molly fertilizes the female, the eggs will develop into fry whose presence will block out the light, causing the gravid spot to take on a darker tone.

As the molly fish’s pregnancy progresses, it will swell. The creature’s skin will stretch, causing the gravid spot to expand even as it darkens. But that doesn’t happen immediately, as the gestation period of a molly fish can last up to 70 days.

In some cases, the gravid spot will develop a lighter tone despite the pregnancy progression. You can blame those rare transformations on environmental factors such as changes in the temperature and pH, stress, fluctuating lighting, etc.

Many aquarists argue that a lighter gravid spot in a pregnant molly fish signifies lighter or albino fry. In guppies (which are closely related to mollies), the gravid spot is orange/pink among pregnant yellow female fish.[5]

Regardless of the reasons, these developments are rarely a cause for concern, if ever. Though, if the gravid spot is slowly losing color, along with the rest of the fish, don’t be too surprised if your pregnant molly dies before it can give birth.

2. You Are Looking At A Male Molly Fish

Do not look for the gravid spot on the bodies of male mollies. You can only find it near the anal fins of female fish. Male and female mollies have a lot in common, so beginners confuse the two.

Female fish tend to swell during pregnancy. But if your male mollies are bloated, you could easily confuse their condition for pregnancy. That is especially true if they have dark marks near the anal fin, spots they can develop due to bruising, ammonia burns, and the like.

A vet can help you separate the genders. They know that male fish are larger with brighter colors, flat bodies, and a pronounced dorsal fin. Female fish have dull colors, rounder bodies, and a smaller dorsal fin. Male fish are more likely to chase females instead of the reverse.[3]

If you feel unsure about your molly’s gender, here is an excellent Youtube video that goes through the differences between the two:

Should I Be Worried If I Can’t Find The Gravid Spot?

Some people panic when they try and fail to locate the gravid spot near the anal fin. In some cases, their concerns are justified. In other situations, the panic is unnecessary. At the end of the day, you should expect to see the gravid spot near the anal fin of every female molly fish. 

People think that the gravid spot signifies pregnancy. In other words, it manifests when a female fish is pregnant, and then it disappears once the molly fish gives birth. But that is not true. 

The gravid spot is a sign of a molly’s gender. Every female molly has this mark. If you have experience with these creatures, and if you look hard enough, you can see the gravid spot on the bodies of some molly fish fry.

Guppies and other livebearers are the same. They tend to develop the mark within the first two weeks of their lives. Therefore, if you investigate your non-pregnant female mollies right now, you will see the gravid spot.

Pregnancy causes this mark to grow in size and for the colors to become more prominent. After the molly gives birth, the gravid spot doesn’t disappear. It will shrink in size, and the spot’s colors will become lighter and duller. But if you look for it, you will find it in the same place, near the fish’s backside.

If you can’t see the gravid spot, either you’re not looking hard enough, or the molly in question is male. Every female molly has a gravid spot, pregnant or not. That being said, the color of the fish will affect its visibility.

For instance, black mollies have black scales. Black sailfin and black lyretail mollies are even darker than standard black mollies. Therefore, if they have a dark gravid spot, you probably won’t see it.

Creamsicle sailfin lyretail mollies, on the other hand, have a white bottom, which means that the gravid spot will stand out. Dalmatian mollies have light colors, but their bodies are peppered with black spots, so you could easily confuse the gravid spot for one of those ordinary marks.[6]

A molly’s natural colors can easily camouflage the gravid spot. Fortunately, mollies have other signs of pregnancy. You don’t have to rely on the gravid spot.

What Other Signs Suggest That My Molly Fish Is Pregnant?

So the gravid spot indicates you’re looking at a female molly fish. And if the spot expands, the molly fish is likely pregnant. However, as noted above, it can be challenging to locate the gravid spot in some cases.

That is why I suggest that you look for additional signs that are typical for a pregnant molly fish. For example, you’ll notice that the fish’s belly gradually swells and takes on a rounded shape. Also, pregnant mollies spend most of their time hiding.

During pregnancy, you will also see that your molly becomes aggressive towards tankmates. In some cases, the female will even start chasing other males, which is why it is better to separate the pregnant molly from other fish. In addition, you’ll see an increase in appetite, except for the time when the fish is about to give birth.

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Conclusions

The gravid spot is located near the anal fin of a molly fish. This is one of the signs that your fish is a female and not a male. You can even find the gravid spot in non-pregnant molly fish. During pregnancy, the gravid spot will expand and go darker.

If you can’t see the gravid spot, but your molly seems bloated, you might be dealing with a sick male. However, it is also possible that your molly is in the early stages of pregnancy. Start by checking the gender of your fish.

References

  1. https://www.tankarium.com/pregnant-guppy/
  2. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0147711
  3. https://mrfishkeeper.com/molly-fish-gender/
  4. https://www.buildyouraquarium.com/pregnant-guppy/
  5. https://guppyfish.xyz/pregnant-guppies/
  6. https://petkeen.com/popular-types-of-molly-fish/