Blue Nation Baja

A Fantastic Voyage: Loreto’s sea life through the microscope

Loreto is renowned by its wide biodiversity and rich marine life. As a matter of fact, it is the most biodiverse spot in the entire BCS when it comes to invertebrates. This wide kingdom includes corals, molluscs, crustaceans, echinoderms (starfishes, sea urchins…) etc.

New divers often focus on schools of fish and big life, like the eagle rays, sea lions, sharks etc. We can not blame them, they are great to see, and also, kinda straightforward ain’t it? You just float out there and see life just pass by. It’s spectacular and low-effort. WHY wouldn’t we like it?

But, Alas! Some of the craziest stuff and some of the rarest things only happen in the microscopic level (well, we actually call it macroscopic, because you can see it with your eyes in comparison with the real tiny stuff….but a dolphin is technically macroscopic too isn’t it?) The world of the tiny is paradoxically HUGE. As a matter of fact it’s so huge there are dozens if not hundreds of things you might see once and once only in your lifetime, but they will keep happening to you during your entire diving career….It might sound counterintuitive but think about it: for a constant flow of unique encounters happening to a diver, the amount of rare, diverse and cryptic animals must be huge! Of course, the usual suspects will be there for you as well.

Follow us in this brief but amazing trip around the tiniest beings of the Loreto National Park. Let’s shrink ourselves and see these mini-wonders eye to eye like if it were the Fantastic Voyage novel from Isaac Asimov, only in this case, brought to you by our friends Mary & Chris, fantastic divers and photographers. You can click on any picture to enlarge it. Do it you fools!

All pictures in this post belong to these beautiful individuals with macro-hearts!


Introducing the Nudibranchs

Oh boy, what can we say about this fellas? Let’s start by saying that its name comes from the latin Nudi (naked) and Branchs (gills), the Naked-Gills! So yes, these flamboyant sea slugs have their gills exposed, something widely considered wildly dangerous in the marine realm. Vital, blood-rich organs being waved freely for everyone to see (and nibble on)? The marine consensus is clear about it: not a good idea.

But these guys know what they are doing. Initially, all molluscs had a shell that protected them and their vital organs. Think about the snails for instance. But there was a point that these slugs thought “yeah, screw this carry-my-heavy-house with me all the time. So exhausting!” and then they decided to become pretty toxic and unedable. See those pretty colors? Yeah, that is a warning for the fish. They are quite literally the jalapeños of the sea.

I give bad digestions. Do not eat

But there is this thing with evolution: there will be always somebody evolving faster than you. As a matter of fact, there are some nudibranchs that CAN eat other nudibranchs. They are cannibals! So yes, nudis are one of the few things that can eat nudis. Oh, the irony!

The best example is the Tiger nudibranch, a behemoth that can grow up to 30cm and literally engulf its prey whole. That guy doesn’t mind spicy food. Nice.

Tiger nudi chasing its meal. It’s like a reverse UBER Eats

But most nudis are pacifists. They just like to roam the sea floor minding their own business just being selflessly toxic. While not being chased by the Tiger, nudis just chill and graze on hydroids for most of their day. Hydroids tend to be stingy, a perfect diet for a toxic creature.

They come in all designs and colours. The diversity is so vast and the colors so bright that some have called them the “drag-queens” of the mollusc kingdom. This statement might be more accurate than you think, as nudis do not identify with an specific  gender and quite often they swop sexes. They are all hermafrodites and gender-fluid when it comes to mating. So modern and progressive of them! To be honest, when they mate they sort of fight to see who will become the male of the relationship, but I’m sure they take it as some sort of role-playing and nothing patriarchial at all. They are beyond that.

In spring time, they start laying eggs that always look like a colorful and ethereal spiral. They are cute even at giving birth.

A nudi doing the downward facing dog  yoga position.

A Marislae nudi just nudiing about

A handsome Agassizi nudi

A Tambja abdere nudi looking at a hydroid with glotony. Just look at it!

Grow, grow spicey and conquer the world my children!

The odd ones we found this time

There are literally dozens of species of sea slugs but 90% of them belong to a handful of different types that we see very often. After years of diving in Loreto, we keep finding some rare ones. Some are just rare or seasonal, but some others we might have seen only a few times in thousands of dives. Makes you wonder how they find each other. No wonder they must be hermafrodite, imagine looking for an entire year to find a mate only to find out it’s just another dude like you.

A rare ringed flatworm. Normally non toxic, but they mimic the colours of toxic nudis to deceive their predators

A not-so-flat worm. Normally spotted at night more often.

A super-rare and slimy nudi, yet to be identified.

This is an Eolid. A very elusive type of nudi that has its “ceratas” (gills) spread along the sides of the body (usually)

An “spanish shawl” nudi that belongs to the flabellina family. More common in the colder Pacific waters.


Snails are also molluscs, like the nudibranchs, but they carry a shell as we mentioned before. Their strategies are a bit different. They rely more on camouflage and other defensive mechanisms that go far beyond as shrinking back into the shell.

The Mushroom snail feeds exclusively on yellow sponges so it decided being yellow itself would be a good idea. And it is, you won’t see these guys unless you know what you are looking for. Their shell is not particularly a tough one, or big, but given that their underside is protected against the sponge (or rock) and that besides being yellow their shell camouflages nicely with algae growth, they are pretty confident being out there munching sponges away.

The Anette’s cowry is a different story. They are more related to the conchs than to the latter, with a twist. Their shell is tough and normally it dwells under rocks, but they have a secret weapon: when exposed, they stretch their mantle over their shells and form colorful spikes, a clear warning of toxicity. The mantle is displayed until the cowry finds a new shelter. If having a shell is like wearing a helmet when you ride your bike, this special mantle would be like pointing a gun to the traffic as you go. Some next level reef rage.

Mushroom snail reflecting about the futility of existence, probably

Annete’s cowry going full bershek


Technically called “Pancrustaceans” now. Biologists were bored, got together a few years back and decided that crustaceans will now be related to insects and put them together in the same sack, effectively making shrimps the cockroaches of the sea. Thanks guys.

This is a super diverse group of animals and to be honest, we had to select which to show you here. It was tough! Although technically invertebrates, crustaceans carry their skeleton outside rather than inside. So they are hard and crunchy instead of squishy like us, humans. They put the “crust” in crustacean! *ba-dam-tss*

There are thousands of shrimps and crabs in every dive, but they are usually the prizes of experienced divers that know how to find them and how to make them stay still. Which they don’t often. If you ever tried to take a picture of an ant you would understand what I mean. But because this, they are rewarding finds and almost every week we found ourselves trying to identify an species we never seen before. Very often we do not succeed. Not even the biologists can be sure. They are that diverse.

Shrimps and crabs have developed all sort of mechanisms to stay safe. Some, like the Black Coral Shrimp or the Majidae crab are masters of disguise. The former evolved to look exactly like a coral polyp, where they live, the latter can grow a shell that can resemble sand grains, algae or a mix of both, besides growing real algae on top. You won’t be seeing them unless they move. You are the T-Rex of the seas to them.

Other crabs, like the Trapezium crab lives deep within stony coral heads, between the mess of its branches. The branch mess makes it really hard for predators to catch them, and the crabs don’t really need to venture out often. Other animals, like coral shrimps and arrow crabs have adopted the same strategy and live shoulder to shoulder with the Trapezium crabs.

Other crabs are lured by the vastness of the ocean and venture outside and wander. Being a small crab in the open was catalogued as one of the “Top 5 most suicidal things” by Forbes magazine in 2020, and the crab community heed the warning. The iconic Janaria mirabilis, or staghorn coral hermit crab, has found a practical way of quenching its travel thirst: it grows a coral in its housing shell. It’s a fully symbiotic relationship. The crab gets protection from the hard coral and the coral has a transportation mean to expand is feeding chances.

Pocillopora coral shrimp (foreground) and arrow shrimp photobombing the shot (back)

Staghorn crab backpacking like a champ

Black coral shrimp. Why is it yellow then?

Majidae crab staying veeery still

Trapezium crab wondering how you got in here

some surprises

During the week when Chris and Mary were taking this pictures, we had some very rare encounters. Some of them filled me with joy as some of these creatures I only had seen a few times in thousands of dives.

From the least rare to the most rare:

The always elusive Snapping shrimp is considered a rare sighting although they are technically one of the most abundant shrimps out there. The hide so well and are so fast that the first one to see one is the last one as well. But they are out there. Have you ever wondered what was that ever present “choco krispies” sound underwater? Yeah, those are mostly pistol shrimps snapping.

If you manage to see one that doesn’t move, snap a picture quick! Their most emblematic feature is one supersized claw that they use for defense and attack. They can “snap” it and stun prey and hurt predators (or your finger).

The Mantis shrimp is like the most iconic shrimp out there. Divers love them because they are colorful, weird and very interactive. For real, you can see the animal thinking as it looks at you. They have big eyes that they can move so you can see it looking at you, they move in a more “human manner” in the way that you can see when they are being curious, cautious or they are fleeing.  They are called “mantis” because the way they have their front legs bent.

Then we found the extremely rare Cortez Barrel shrimp. It takes its name from the barrel shape of its body. This is hands down my favorite shrimp. It is so ornamented and beautiful, but also so fun to watch. Like most cleaning shrimps (shrimps that groom other bigger fish), they can dance. Yes, the shrimp has moves and it uses them to communicate other fish that he is ready to clean. No words can describe how they move, but maybe “bumble booty shake” gets close.

And then there was The Shrimp. A shrimp I’ve never seen before. It was extremely small, like maybe 2-3 mm, very still and very pretty. It lived between sand and shell grains on a rock with sponges and tunicates. Until this day we are not able to identify it. Not in any books that we know and the biologists don’t know either. Call it like what you want, you are not gonna see it again in your entire life. The guy is a ghost. May the ocean currents bring you joy, mysterious shrimp. Until we meet again.

Cortez Barrel Shrimp. Shame pictures can’t dance

The Shrimp. It looked at me, I looked at him, instant connection. This guy is from now on my spirit animal, my “spectro patronus”

A napping Snapping shrimp

Mantis shrimp

Mary and Chris have taken such beautiful pictures. I have left so many out of this article, enough for a second one. I do hope you enjoyed it as much as I did writing it. It was an incredible week of discovery filled with so many great tiny critters. Macro is an ever rewarding way of diving, one that never ends and keeps surprising you over the years, more than any school of fish and whalesharks.

Happy bubbles everyone!