Their skin is breathtakingly complex, providing them with very useful benefits in nature. Indeed, they can change the appearance of their skin like : color, contrast, and even texture in less than a second both to hunt or not be hunted!
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Thanks to the chromatophores (pigment cells reflecting light) present in its skin, the cuttlefish can either hide or display bright colours to attract its prey at arms reach. Cuttlefish protect themselves from enemies by hiding in plain sight pretending to be a rock or blending in perfectly with a patch of sand.

Are cuttlefish dangerous ? 

Cuttlefish are totally harmless to Humans and usually quite inquisitive and friendly.
Not common in Thailand, the Flamboyant cuttlefish (Metasepia Pfefferi), is the only poisonous cuttlefish. But they do not sting or bite so you would have to eat it to endanger yourself...
This species is quite small, poor swimmer, it walks on the sand thanks to two tentacles and hunts by day. The base color of Flamboyant Cuttlefish is brown, allowing them to blend in with the sands that cover the ocean floor. Nevertheless, when they hunt or seek to attract a mate for reproduction, they are true to their name and their skin takes on the colors of fire or blazing trees. Indeed, it is covered with brown but also with dark red, yellow and purple...

​The most common cuttlefish we encounter when diving in the Andaman sea are Pharaoh cuttlefish (Sepia pharaonis) an inquisitive dive buddy!

Cheeky Cuttlefish playing lady-boy !

Surprisingly there are a lot more males than female cuttlefish (up to 11 males per female!). Which means mating is a highly competitive game for the males and the strongest individuals are ready to fight for it.

Smaller males have developed smarter techniques to get a chance…. When the male cuttlefish is wooing a lady, he often "cheats" by painting typical female patterns on one side of his body, seen by a rival male and sexy male colours on the side facing the female.

That trick cuts the aggressive behaviour of its larger rival (who only sees two females in front of him) and increases the chance for the cheeky cuttlefish to mate.

Just like Octopus can open jars, cuttlefish have proved their intelligence with this delayed gratification, if given the choice between a dead shrimp now or a live shrimp (their preference) in a minute, they will wait a minute for their favorite choice! We could say that they have more self control than most kids !

​1- Cuttlefish are fully developed before they have hatched and can even react and change color in reaction to something they see beyond their eggshell !

2- Cuttlefish have copper based blood making it green instead of the iron based red blood making up most other earth inhabitants

3- The color Sepia, comes from cuttlefish ! The sepia colored ink they send when they are scared was used as a writing ink before 

What do you know about their reproduction ?

The answer to this question: not much …. even by whale sharks specialists.
There are three different modes of reproduction among sharks and rays (oviparity, ovoviparity and viviparity) and 1 variant (asexual reproduction)...

​Oviparous species, like many other fish (as well as birds and reptiles), lay eggs. ​

Viviparous species give birth to live young, just like mammals: a placental links the developing embryo and its mother and feeds it in utero until its birth. 

Ovoviviparous species also give birth to live young but do not have a placenta linking mum and baby. The embryo first develops within an egg, gaining nutrients from the yolk, it then emerges from the egg whilst still inside the mother who gives birth

Asexual: leopard sharks held in an aquarium have given birth after years of captivity!!!

Only 21 baby whale sharks smaller than 1.5 m long have ever been sighted globally till this day, most were neonate captured as bycatch in fishing nets. 

The latest Whale shark baby was found on the 15th of March 2020 and was 60cm long. This is smaller than the largest embryo found inside "big Mamma" in 1995, meaning this pup is either a small newborn or even neonate. 

Given their size and swimming ability it is likely that the Philippine, Peru, India, Australia, Pakistan and Taiwan, where they were found, may be close to whale sharks nurseries !

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learn about adult whale sharks in this bespoke article:
​All about whale sharks
​And if you have something to add, feel free to leave us a comment below! 

"Naked branchia", (naked gills) is the etymology of the name that was given to them. This one is explained in particular by the morphology of the nudibranch. The word Nudibranch comes from the Latin nudus meaning "naked" and the Greek brankhia (βράγχια) meaning "gills", the nudibranch is therefore by that recognizable by the absence of shell used to protect its gills.

The sensory organs of nudibranchs, the rhinophores, allow them to distinguish the chemical particles present in the water, and more particularly smell from afar potential food sources, the pheromones of sexual partners or the presence of certain threats.

A true nudibranch is carnivorous and it uses its very powerful jaw to grate its food. Each specie has its preferences but it feeds mainly on sponges, bryozoans, ascidians and hydras. Many nudis feeds on toxic animals and store the toxins in specialized cells as a smart defense mechanism...
​Some species are cannibals, they feed on other nudibranchs, exceptionally specimens of the same species if no other food is available.

Nudibranchs are hermaphrodites, which means that they have both a male and a female genital system.
When two nudibranchs meet, they put in contact with their genitals to exchange their male gametes, in order to fertilize their female gametes.
Thus, both will leave this encounter pregnant and give birth to baby nudibranchs doubling the Nudi Hatchlings! Smart.

The nudibranch has many powers, contraction of the body, retraction of the gills, "hedge hogging" of the papillae, secretion of toxic or acid substances, isn't he a superhero? It also has the ability to practice autotomy, that is to say that it can auto-amputee a part of the body which will regenerate itself afterwards. Just like lizard leave their tail behind, the nudibranch, will be ready to give up its branchial plumage, its rhinophore or a fragment of its mantle in order to save the essential part of its body. Small but smart !

Some species of nudibranchs have the ability to store photosynthetic algae inside their bodies. They only need to eat for the first few weeks of their life and once they have enough, the algae present in its tissue provides enough energy from the light for the both of them !​

Just like the land snails we know, nudibranchs leave a trail behind them.
​This trail is filled with chemicals and speaks a thousand words! It can tell other nudibranchs about nearby dangers or help a potential partner to find it !

Nudibranch are very slow animals, which is why they are nicknamed "sea slugs". But they are also clever ! they often live on or near their preys not to lose sight of them.

(CNN) A female Zebra Shark in an Australian aquarium has astounded scientists by producing live offspring asexually, three years after being separated from her long-term mate. [...] It is only the third documented case of a vertebrate of any species switching its reproductive strategy from sexual to asexual.
The shark had earlier reproduced after mating with a male, so it was shocking that it managed to lay fertilized eggs again after so many years without any sexual intercourse.
This asexual reproduction - which exist in other animals’ reproduction like spotted eagle ray and Colombian rainbow boa - had never been seen in sharks before now. Studies are ongoing to understand this phenomenon, but some scientists believe that it might be a natural adaptation to the lack of sexual partners.

Are Zebra Sharks dangerous? 

Zebra Sharks are non-aggressive, they can be easily approached when underwater. Divers visiting the Koh Bon Pinnacle or Koh Tachai in Thailand as well as North Twin in Myanmar have a good chance to meet one of these fascinating sharks.

How to approach them without disturbing them?!
​Zebra shark are relatively easy to approach but they will run away from you if you don't do it right!
Approach them from the side, where they can see you. Dont pass on top of them or approach them from behind, if you are in their "dead angle" they will swim away.

​​About the Zebra Shark conservation

Today, Zebra Sharks are endangered: humans are the driving factor that might drive extinction in the future. Usually, inshore fisheries use them for their meat, which is either salt-dried or fresh.  The traditional Chinese delicacy also uses Zebra Sharks, particularly its fins, for making shark fin soup, a delicacy in China.

Is Zebra shark a fish?

​All sharks are cartilaginous fish (their skeleton is made of soft cartilage, not bones). These fish all fall into the group of fish called the elasmobranchs (like rays).

ZEBRA SHARK CLASSIFICATION:
LATIN NAME: Stegostoma tigrinum (fasciatum)
FAMILY: Stegostomatidae
PHYLUM: Chordata
CLASS: Chondrichthyes

1- Nautilus moves by jet-propulsion by blowing out water through a siphon. Position of the siphon decides the direction of the nautilus: front, back, upward or descending. 

2- Nautilus has 90 tentacles, situated outside the shell to catch and manipulate their prey. 

3- Nautilus has a beak which cuts their food (crabs, shrimps and fish), just like other members of the octopus family.

But unlike other members of the family, nautilus has poor visual perception. Eyes can only recognise light from dull, their smell is over developed and used for hunting their preys.

4- Nautilus spends their day at depths and moves toward the shallow water to hunt when the sun goes down. 

Nautiluses mate only once a year. 75% of nautilus caught to be studied are male and only 25% are females. Researchers don't really know why. 

5 – Nautiluses are true living fossils. They have been roaming the oceans for nearly 500 million years, with almost no changes in their appearance since they first evolved. Their iconic spiral shell, their way of life, and their unique biological features have remained remarkably stable throughout geological history.

To put their age into perspective, nautiluses were already thriving 265 million years before the first dinosaurs appeared. These ancient creatures have survived multiple mass extinctions that wiped out countless other species, yet they continued to glide through the oceans with their timeless spiral shells. Today, they still drift gracefully through the deep, silent witnesses of an ancient world that existed long before mammals, birds, or even most fish as we know them.

Despite their prehistoric origins, nautiluses remain surprisingly resilient. They have a long life expectancy, often living over 15 years in the wild—a remarkable lifespan for a marine invertebrate. Their slow, steady pace of life and their ability to adapt to deep, stable environments have contributed to their persistence through Earth’s most chaotic eras. Nautiluses are, in every sense, living relics of our planet’s distant past—beautiful, mysterious, and enduring.

6- A couple of nautiluses may have sex for up to 30 hours at a time... During intercourse, males often bite females on the mantle which will leave a mark on his partner’s shell.
Some male nautiluses attempt to mate with any object that that seems to have similar shape and size as an other nautilus, and this without making any difference between male or female.

The reason I wrote this blog post is because we first came across this little fellow while diving Myanmar in 2017 but I just updated this article since our last sighting was in March 2021 in the Similans and we now have a few nice photos to add to this blogpost! :)
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After some research, we found out that this weird creature is called paper nautilus or argonauts.
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We apparently encountered a female Argonaut as male are 10 times smaller (rarely passing the size of 2cm) and dont have a shell.

Little is known about these creatures but I found these few facts  interesting enough to share!

One of the male's arm serves as a penis and is snapped off his body during sex to inseminate the female. The arms then remains inside the female body.
The female then secretes the papery shell with the tips of two tentacles. She lays her eggs inside the paper shell before using it as a house for herself. 

​But the real cool fact about argonauts is their BCD (buoyancy control device).
they are the only creature known to trap air bubble from the surface.
They swim to the surface, suck in some air from small vents on the top of their (non-compartmented) shells, close the holes with a tentacle before turning upside down and pushing themselves below the surface where they reach neutral buoyancy.
​They can then swim effortlessly and weightless!

Have you ever encountered weirder octopus?

This type of octopus can be found in the tropical and temperate waters of the the Eastern Atlantic, Mediterranean sea, the Pacific ocean and the coast of Africa.
It prefers shallow rocky bottoms or coastal coral reef in depths above 200m. Octopi will find themselves a shelter where they can minimize exposure and stay safe but will come out, mostly at night, to hunt. They usually move by crawling along the sea floor where it can protect its belly. They are also known to swim using a type of jet mechanism found in its mantle cavity. 

Octopi are solitary creatures with short life spans. They spend most of their young life eating and growing until they reach sexual maturity. At this time, they will metabolize muscle mass to make sperm and eggs and search for a mate. 
Mating can be very dangerous for the male. A female doesn't often refuse a male's advances but it is not uncommon for the female to change her mind and eat the male. To address this problem, males have a specially adapted mating arm that can deliver sperm into the female's mantle cavity from a safe distance.
The female will lay between 100 000 to 500 000 eggs which she will very rarely leave unattended for her 4-5 month brooding.  She will even stop eating to take care of them and will die shortly after they hatch. 

Studies show that they are extremely clever and resourceful. They have a much more complex nervous system than other mammals and most of their 500 million neurons are found in their arms. The have been taught to navigate mazes, problem solve and recognize visual clues to find the best way to get to a reward. Don't under estimate them !

​       Although they are small, they have developed some very industrious techniques to protect themselves. Many nudibranchs display bright colours for a multitude of reasons. Some practice what’s called aposematism which is colouration to suggest to predators that they aren’t tasty or can be toxic. This is a technique used by the Phylidiidae family that we often see in the Indo-Pacific.

Along with other types of seahorse, pipefish and seadragons, the tiger tail seahorse belongs to the Syngathidae family. They can grow up to 18.7 cm and have a lifespan of 1-5 years.
They can sport different patterns but the most commonly seen is alternating yellow and black.