Shark Babies!

So things have been a bit quiet for me lately since I’ve been a bit sick but that doesn’t mean nothing cools been happening.

Recently, we took the interns out to take part in a citizen science project studying the breeding patterns of small sharks and skates found along the coastal waters here. Specifically we were down on the beach collecting their egg casings. The project is being run by Whale Coast Conservation. It covers around thirty different beaches on the Western Cape of South Africa. Anyone can take part in collections  and the idea is that after two years, the pooled data will hopefully help us understand if certain species of egg laying shark breed at certain times of the year, and if they favor particular areas(Head to http://www.whalecoastconservation.org.za to find out more). This has obvious benefits for targeting conservation efforts. It also happens to make for a great afternoon out

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But Back to the Sharks

Roughly 25% of know shark species lay eggs. But they dont look anything like what you’d imagine an egg to be, Here is an example.

Image result for shark eggs

This is just one example of the weird and wonderful shapes out there.  The Port Jackson Shark, found in South Australia has corkscrew shaped eggs. There are others that look like leafy fronds, some that look like they have a tangled mess of string protruding from one or both ends and a wide array of other strange shapes. They don’t even feel like your typical chicken egg. They aren’t hard and easily smashed but instead have more of a tough leathery shell. But this all begs the question…

Why?

Well to answer that you need to think about the environment they’ve evolved in. When a chicken for example lays an egg, that egg will more or less stay in the same spot unless moved by someone else. Its not like a strong gust of wind will blow it away. The problem a chicken egg faces is air. Its pretty dry biologically speaking and an embryo needs to stay wet, so a thick, hard shell make sense from a protection point of view. But lets apply the same thinking to sharks. They live in a wet environment so they don’t need to invest in the extra protection of a rigid egg case. But more importantly, that gust of wind analogy suddenly has serious consequences in water. A strong water current could easily pick up a light shark egg and carry it far away. If that happened, the new born shark might find itself far from home and unable to survive. Thats where those weird shapes come in, they create ways for shark eggs to get caught on rocks, seaweed or anything else that might keep it in place.

Shark Eggs

So thats all for this post. As always, feel free to comment or ask questions, and most importantly share it around. Next week I should hopefully have some ROV dives to share!

Tomasz Pedlow

Lovely Limpets

Hi everyone!

So sorry to say it but I wont be jumping into shark science just yet. For my first day of field specialist training I was doing some inter-tidal surveys with the new interns to watch how a more experienced field specialist teaches it.

For those who don’t know the inter-tidal zone is basically that area where the land meets the sea, its an area where a heap of marine creatures live and its an area that can be very reactive to changes in climate, water quality and anthropogenic impacts.

As it turns out inter-tidal zone of Mossel Bay is  in a particularly interesting area because of two large oceanic currents. The Agulhas current comes down the coast from the east and brings warm water. The Benguela current comes from the south bringing cold waters up the west coast of Africa. Mossel Bay sits smack dab in the middle. What this means is that while warm water environments typically have high species diversity but low abundance and cold water environments typically have low species diversity but high abundance. Mossel Bay gets the best of both worlds.

But back to the surveys, we were basically being kids exploring rock pools. But with the crucial distinction that we were writing down everything so it counts as science. What we did was lay out a long rope, then starting at the low tide mark, place a 1m x 1m square on the ground every 2.5m and count all the critters that we found inside.

This may not sound as fun as getting up close with Great whites but its incredibly interesting. In my case, I was particularly amazed by the limpets.

But whats that you ask?

A limpets a type of gastropod. Imagine a snail, except instead of living in a swirly shell, imagine it lives under a dome shell and you’re in the ball park. They look like this.

Image result for Limpets

They spend their lives clinging to rocks in rock pools all around the world and while they look pretty mundane, they’re actually incredible!

Exhibit A: The Brown Limpet

brown limpet

Looks pretty dull, but this little guy can paralyze a starfish! Starfish living in these rock pools eat lots of things including some types of limpet. They manage to get under their shell and flip them over to feast on the unprotected underside. But this limpet carries a special toxin, and when the starfish makes contact with its flesh, it gets paralyzed while the limpet gets to make a sneaky getaway.

Exhibit B: The Star Limpet

 

Star Limpet

I figured these guys needed a little highlighting as they have a tendency to blend into the background a bit. Whats cool about star limpets is these two are actually separated for a very good reason, they’re ultra territorial.

This is because star limpets actually tend a garden or algae all around them. You can see it fairly clearly with the limpet at the top of the photo. It cultivates and maintains an algae crop that it can feed from and if any star limpet dares enter its territory, there’ll be hell to pay! If a territory is invaded, the limpets will fight each other, trying to get their shell over the edge of the other before sucking onto the rock to crunch down on their opponents shell. Hopefully the snail on that top limpets rock is quick enough to escape!

Exhibit C. The Shield Limpet

20180503_093629So there is a fun story about these ones. Back when I interned with Oceans Research last year, during one of the inter-tidal survey sessions, one of the field specialists made an offer to me and a friend. “If you can pull that limpet off the rock, I’ll give you my van” he said. With our heads filled with visions of cheap trips up and down the coast on the weekends, we spent longer then I’d care to admit trying to win the van. I only found out on Thursday just how safe a bet that was for the field specialist when he pointed these out to me.

 

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What I had thought were random markings on the rocks were actually grooves created by shield limpets shuffling around, and then suctioning onto the rock. With that kind of power I finally understood why we never had a shot at the van.

So there you have it

Hopefully you have a new found appreciation for these weird and wonderful critters, feel free to post questions in the comments sections and stay tuned for me next week!

 

 

Tom’s doing a Science!

Hi All,

Welcome to Ocean Minded. I’m going to use this to share some of the awesome science I’ll be doing out here in South Africa over the next four months. My time with Oceans Research is going to cover a wide variety of marine science including catching and tagging small sharks, collecting data on great whites monitoring dolphins (and possibly tagging them with drones), Intertidal surveys and ROV dives.

Check it out, share it around, comment and ask questions,learn stuff and most importantly, enjoy!