Tuesday, June 22, 2010

The Leaping Blenny: A Fish Out Of Water

Using high speed video researchers have shown how a leaping blenny, Alticus arnoldorum (a fish), can thrive on land. The blennies use a twisting motion of their tail to spring forward. Essentially these fish curl their bodies into a C-Shape and then let fire. Typically, this is used as an escape response to avoid been eaten by a predator. But these leaping blennies have adjusted their biomechanics a little so they can use it to colonise intertidal areas. Intertidal means that area between low and high tides. In other words, these fish can, and do, live a substantial part of their lives out of water. 

Below is a lateral view of a leaping blenny, well, leaping.  

Below is a ventral view of the leaping blenny climbing up a upright piece of plexiglass. 


Monday, June 21, 2010

The Seahorse: A Perfect Dad

Here is a video I found over at Deep Sea News (check it out).  It shows amazing video of the seahorse, a fish. This fish is probably best known for its odd appearance almost looking like a dragon from a fairy tale. But did you know that the seahorse has a very unique reproduction strategy. The female places her eggs in the males brooding pouch where he then fertilizes the eggs and carries them for about two months until they are ready to be released. The male then cares for the young until they are ready to look after themselves. Ok so no dad is perfect and he may occasionally eat his children every now and then. But when you have a thousand of them who can blame him!!

So for all you fish geeks out there here is the reason why. Females spend twice as much energy generating the eggs than the males do incubating them. Because this is so energetically costly to the females it seems evolution has decided to give them a break, and the males incubate them instead. This means that females have more time to go and get pregnant all over again thus raising reproductive output. 


Saturday, June 19, 2010

The Burglar Alarm Hypothesis: The Role Of Bioluminescence

Anyone who has disturbed water at night, especially during a bloom, will have seen the intense bioluminescence produced (see picture above). But why this occurs has long been the subject of scientific query. Dinoflagellates are one planktonic group that bioluminesce, and this occurs due to deformation of their cell membrane caused by shear forces. This is often caused by intense water movement such as breaking waves or a predators swimming movements. One hypothesis is that this is a form of communication. This certainly seems to be the case when you consider that the light emitted by dinoflagellates has a maximum emission of around 475nm (blue-green), which produces light that is visible over long distances. 

The authors in this paper propose that bioluminescence from the dinoflagellates serves to attract predators to the grazer. This 'burglar alarm' hypothesis argues that dinoflagellates become less attractive to grazers by increasing the risk of predation for the grazer. In other words, if a planktivore eats these dinoflagellates they will shine big bright lights saying 'food here' for predators within the area. Thus, dinoflagellates would be expected to be eliminated from the grazers diet. 

Experiments to test this hypothesis were undertaken in glass jars containing dinoflagellates (those that bioluminesce, and those that don't), copepods (predators of dinoflagellates) and three-spined sticklebacks (predators of copepods). Thus, these experiments were able to directly test the predation rate on grazers, while feeding on dinoflagellates that either bioluminesce or don't. After 3.5 hrs both grazer and prey were removed from the jars, and the number of dinoflagellates remaining were counted. What they found was that the predation rate was almost doubled in the jars containing bioluminescent dinoflagellates. This shows that the mortality rates on copepods feeding on bioluminescent dinoflagellates increased, confirming the burglar alarm hypothesis. 

It is important to note that the sticklebacks used in these experiments were never exposed to the experimental conditions. Thus, the light emitted by the dinoflagellates is a cue used in nature. Using signals to attract predators is not unique to dinoflagellates. Fear screams produced by birds and mammals is thought to be used for the same purpose.

Abrahams, M., & Townsend, L. (1993). BIOLUMINESCENCE IN DINOFLAGELLATES: A TEST OF THE BURGLAR ALARM HYPOTHESIS Ecology, 74 (1), 258-260 : 10.2307/1939521

Wednesday, June 16, 2010

End Of Postdoctoral Stress

Every graduate student knows that behind any faculty position lies many years as a postdoctoral fellow. The big problem here is getting those postdoctoral positions, which itself is a bottleneck, unfortunately weeding out the unlucky many. This has formed the basis of my anxiety for the last few years since I handed in my PhD. I had a postdoctoral position, but only for a year. The constant worry of where that next job was coming from was hugely stressful. I spent a year as a fisheries scientific observer until I got my next position, and this was for one more year.

Last night I found out that I had finally been awarded a huge grant, which would provide my salary and research costs for the next three years. Obviously the amount of relief I am feeling is huge. I can finally plan my future for the next three years and actually feel settled. A lot of my work will be looking at the above fish. Can you guess what it is?


Monday, June 14, 2010

Saving Estuaries In Sri Lanka

Don't you just love a good news story. Well here is one. Over the past decade the northeast coastal district of Puttalam (Sri Lanka) has had decreasing fish catches. As a result the livelihood of the people living there is imperiled. The International Conservation Union (IUCN) has tackled this problem by training locals to cultivate aloe vera. This provides between $30-60 US to supplement their incomes. 

Conservationists say that the fisheries stocks collapsed because the mangroves were systematically destroyed, and in the process wiped out crucial nursery habitat for juvenile fish, crabs and prawns. IUCN is also educating the locals not to cut down any more mangroves with good results. Once they are engaged they realise the value of the estuary, and voluntarily conserve the ecosystem. 


Friday, June 11, 2010

BP Oil Will Kill Baby Fish

Louisiana's 3.5 million hectares of marshes and estuaries is teeming with life. This area contains far more species than that of the Everglades, Yellowstone Park, or the Rocky Mountains. This region contains major  nurseries for juvenile marine animals, and nearly everything that lives in the gulf is linked back to these estuaries. The natural capital of this area has been valued at around $1.3 trillion dollars due to the great contribution it makes to US fisheries.

These marshes are already devastated from hurricanes, canals built for the oil industry, as well as dikes. levees and channels that have altered the natural flow. However, now oil is about to further threaten life within this ecosystem and all the biodiversity it contains. At present huge populations of nesting birds are directly in the path of the incoming oil. This includes 400 pairs of brown pelicans, 8500 royal terns, 30000 sandwich terns, and 200 black skimmers.

Tuesday, June 1, 2010

Ciscoe die as Minnesota Lakes warm up.

Ciscoe, a prey species of gamefish such as lake trout, are experiencing die offs more frequently in recent years. This is likely to be caused by raised water lake temperatures and run off from surrounding areas that depletes the water of oxygen. Populations are significantly declining in some lakes. 

Some studies have predicted that the climate of Minnesota will become equivalent to Kansas in 85 years. For coldwater fish such as Ciscoe this is bad news since this would increase the die offs even more. 

For more on this story goto the StarTribune. Its very interesting reading the comments. Some good examples of ignorance about global warming.