Time for just a quick (albeit late) update on day 3 of the Benthic Ecology Meeting. The meeting wrapped up on Saturday and there were plenty of fantastic talks to finish the meeting on a high.
Cannibalising sea stars: Even though sea stars are often the poster child for marine science (just check out the 42nd Benthic Ecology Meeting logo), it appears they have a dark side too. Janie Wulff has researched this behaviour in Oreaster sea stars. These sea stars eat coral reef sponges and don’t really like seagrass sponges. However, they if they forage on the coral reef, they are more likely to get eaten by fish. So, due to the lack of good sponges in the seagrass, the seastars resort to eating each other. It seems they live by the motto “Eat or be Eaten”.
What unites snapping shrimp, naked moles and termites? It turns out they all have a similar social structure. All these animals are eusocial which means that they have cooperative brood care, division of labour and overlapping generations (think of bees and ants). But how does this occur? Solomon Chak showed that in snapping shrimp it is based on colonies of mostly males and a few immature females (like in naked moles and termites). This lets the queen dominate and produce all the young.
- Not all urchins have fish predators, therefore overfishing may not influence urchin barrens of these species (Jon Witman).
- Increased water temperatures can increase asexual (without sex) reproduction in an invasive anemone (Megan Flenniken).
- Asterias forbesi, a seastar, produces both small and large eggs. Larvae from the small eggs take longer to develop but the female can produce more small larvae than large (Holly Blackburn).
Day 2 commenced with a bang; two talks on reproductive strategies in the first session! Plus both talks were on crustaceans so I was thoroughly pleased. There were plenty of other talks throughout the day to keep me satisfied, so let’s get to it!
Male or female? That is the question! Snapping shrimp are known for being the eusocial species of the sea. Eusociality is a term describing species with a structured society (e.g. queens, workers) like bees or ants. Not all species of snapping shrimp are eusocial, yet all species do appear to have intersex individuals (individuals with male and female body parts). This finding is so recent that no-one knows why intersex individuals are favoured over separate sexes! So keep up with Bittnee Barris’ work to see if the mystery is solved.
Hannibal – Marine edition: I’m sure many of you have eaten lobster before, but have you ever though about what a lobster eats? Video footage recorded by Noah Oppenheim has captured adult lobsters red-handed … eating juvenile lobsters. Interestingly, this behaviour only occurred at nighttime – apparently they are only comfortable eating their own under the cover of darkness. However, I’m a little sceptical as to how often this actually happens in the wild. In Oppenheim’s study, the juvenile lobsters were tied down. If they could exhibit normal behaviour it seems unlikely that they would stay in open environments.
Tiny males, long penises & large hermaphrodites: You may have heard that barnacles have the longest penis to body ratio in the animal kingdom. What you may not know, is that some species are androdioecious. This means that the population is made up of tiny males and large hermaphrodites. According to Christine Ewers, the amount of males in the population may be related to food availability. It seems more manipulative studies are needed to substantiate this, but it’s an interesting system!
Quick research results:
- Small, natural changes in pH and temperature can increase the numbers of twins, triplets and even quadruplets in sand dollar offspring.
- Blue crabs move further upstream in droughts.
- A new study in Belize will follow the effect of a Marine Protected Area on corals, fish and invertebrates.
Today was a fantastic start to the Benthic Ecology Meeting in Savannah. In fact, I was pleasantly surprised by the standard of the talks. I should probably give my colleagues more credit! Here’s a quick rundown of my highlights.
Brightly Coloured Warning Signals? Contrary to popular believe, Joseph Pawlik suggests that marine species rarely exhibit warning colouration. On land, many animals display bright colours to tell predators that they are toxic. In the marine world this fact is just assumed, however there is barely any evidence to support this claim (I was surprised!). The only proven example I can think of is the flamboyant cuttlefish, so perhaps he’s right!
Irresistible Habitats – Marine Protected Areas (MPAs): According to a convincing experiment by Mark Hay, coral larvae and juvenile fish prefer MPA water over water from outside MPAs. This attraction seems to be driven by the absence of seaweed and the presence of adult coral cues. On the one hand, this shows that MPAs are desirable habitats for marine life, on the other, it suggests the MPAs might not help recruitment outside of MPAs.
Deforestation vs De-coral-ation: It’s pretty easy to see the effects of deforestation; just compare aerial images from past and present day. But seeing under the water is more difficult … until now! Brooke Gintert showed how zig-zag surveys using something as simple as a Go-Pro camera gives detailed and extremely useful information about coral reef cover. Check out a short video here.
Also, here are some other (not necessarily new) pieces of info that I learnt!
- Sponges may increase chemical defenses in response to getting eaten.
- Amphipods navigate using polarised light.
- Sea hares eat less when danger is increased.
- Bacteria growths can indicate health of marine environments near fish aquaculture.
- Ocean acidification affects crab larvae development time, growth of spines and number of larvae hatched.
Video copyright A. Franklin – not to be used without permission
Dumpling squid are as cute as their name suggests. But don’t let their looks deceive you, they’re feisty little buggers in the bedroom. Mating is long, rough and regular. Males roughly grasp any passing female and begin pumping water into her mantle cavity (the mantle is the part you eat). Why he does this is not yet known, but it’s likely that he is attempting to remove other males’ sperm. He then transfers the female about 20 little packets of sperm known as spermatophores. He slowly positions these inside the female, and, when he’s done (up to three hours later), he forcefully throws her off!
My Masters research investigated the costs of this mating ritual. I found that males and females are knackered after such a long copulation. They also stare death in the face and mate despite the chance that they will be eaten. However, if we ignore predation risk, mating actually doesn’t reduce female lifespan when she mates with more than one male. Perhaps that’s why females have been known to have up to 7 male partners in their short lifespan (<1 year)!
Mantis shrimp egg mass (c) Amanda Franklin
I know I haven’t mentioned my research yet (stay tuned!), but an exciting event happened this week that I wanted to share: one mantis shrimp laid eggs! I haven’t counted them yet but there appear to be about 100 eggs, all about half a millimetre wide. They are greenish, yellowish and joined together in a big jelly-like blob.
Mantis shrimp holding egg mass (c) Amanda Franklin
Mantis shrimps are caring mothers in that they never let the eggs out of their sight and will even stop eating whilst tending to eggs. This is a long time without food because the eggs can take up to 30 days to hatch! Mothers will ensure every egg receives adequate oxygen by rotating and fanning the egg mass and keep the eggs in their cavities, away from predators. When the eggs hatch a tiny mantis shrimp larvae pops out. The larvae may stay in the cavity for a few days before emerging into the open ocean. Here, their two goals are to eat and not be eaten. Eventually they will settle to the sea floor, find their own cavity to live in and start the process again!
Unfortunately I do not think the eggs this female laid are fertile. She hasn’t been in contact with a male in the lab and she recently moulted, which means she would have lost any stored sperm. Nonetheless, it is exciting to see a different stage of the mantis shrimp life cycle!
Check out my other mantis shrimp post, “Eye Sea You”.
(c) David Paul Museum Victoria
“Salty Sex” started with renewable penises, a hard act to follow, but I think parasitic testicles are up to the challenge. Anglerfish are fearsome looking creatures found in the deepest of seas. Their mouths are lined with hundreds of needle sharp teeth that can easily slice through prey up to twice as large as the anglerfish! They are named for the glowing lure in front of their heads used to attract innocent prey. However, what you may not realise is that I am describing only the female anglerfish.
Males, on the other hand, are almost cute.They are tiny fish with huge eyes. These help them to achieve their one goal: to find a female. This is literally their only goal; they do not eat, they do not compete against each other, they just search for females. And it is when they find a female that it gets interesting.
The gallant male will sacrifice himself to provide the female with sperm. Using his pincer like teeth, he latches on to the gigantic female. Their skin fuses and the male is now permanently reliant on the female for nutrients. He is a parasite. Effectively he is a parasitic testicle as his sole function is to provide the female with sperm.
This strategy is probably very effective because the female will have access to sperm whenever she needs. What a way to reproduce!
More Info? Try here
(c) Andreas Trepte
So I am a little bit slow on this one, but old news can still be good news!
A couple of weeks back at the AAAS conference in Boston, Dr Phillip Messersmithannounced a scientific breakthrough. He and his colleagues have developed a glue which could have a huge range of medical applications. Now why am I telling you this? This is supposed to be a marine blog. Well, the glue is based on a compound that marine mussels produce!
If you have ever been to the beach and walked through the rock pools, chances are you will have seen some mussels. If you’re anything like me, you might have tried to pull them off the rocks to get a better look. Now this is not necessarily an easy task, they hold on tight! Their strong grip helps them to stay in place despite the pounding waves.
So, how do they do this? The mussel uses string-like structures called ‘byssal threads’ to attach to the rocks. These threads are covered in a sticky goo which can glue to the rocks despite the presence of water. It is components of this goo, that have been used to make a glue suitable for medical uses.
Current research has involved using the glue to seal up holes in the fetal membrane of rabbits. This improves their chance of survival by 20%! Messersmith and colleagues hope that this glue will be able to help repair the birth defect spina bifida.