Giant Sea Scorpion!

We usually think of invertebrates as small animals, and arthropods in particular as being limited by the structural engineering of an exoskeleton, which is less capable of supporting large body sizes than an endoskeleton. A new fossil discovery however should creep out anyone who thinks that crabs and lobsters are already bigger than a decent invertebrate should be.

From a 43 cm long claw of the fossil eurypterid (sea scorpion) species Jaekelopterus rhenaniae found in Germany, researchers extrapolated the length of the animal's body to be between 233 to 259 cm, using claw size to body length ratios from other sea scorpinons. Eurypterids are members of the extinct subclass Eurypterida within the class Merostomata of the subphylum Chelicerata, i.e. they were chelicerates (like spiders and scorpions) most closely related to the horseshoe crabs.

Eurypterids were aquatic and the buoyancy conferred by water may help explain structurally their large size, but what about the problem of gaseous diffusion to tissues? They presumably had an open circulatory system like other arthropods which is less efficient than the closed circulation of vertebrates. The authors hypothesise that the higher oxygen levels in the atmosphere in the past could have helped them attain their large size, or that it was driven by an evolutionary arms race with their prey.

Some questions to think about:

• Why is extrapolation using data from other sea scorpions a valid means of predicting the body length of the animal from only its claw?
  
• Among the extant (still living) chelicerates, how do the methods of gas exchange differ between the aquatic and terrestrial groups?
  
• What can we infer about its mode of feeding and possible prey?
  
• How can we explain why such giant arthropods are no longer extant today?
  

Bacterial Biofilms

This recent article in PLoS Biology gives a very readable review of bacterial biofilms and the kinds of problems they pose in medical settings. A familiar example of a bacterial biofilm is plaque on our teeth. Bacteria, when they reach a certain critical density on a surface, begin to aggregate and secrete a slimy polymeric matrix which aids further establishment and eventually builds up to a complex structure with channels and pores through which fluid can flow, carrying in nutrients and carrying away waste materials.

A few interesting points to think about:

• The means by which the bacteria detect the critical population density needed to form biofilms is called quorum sensing. How does it work?
  
• Previously it was thought that the slimy matrix protected bacteria by preventing them from being engulfed or attacked by other cells or substances, but the matrix has to be permeable to most substances because waste and nutrients must reach the bacteria. So how do they defend themselves?
  
• Biofilms usually form on surfaces over which there is regular fluid flow. Why would the biofilm growth form be advantageous?
  
• Bacteria living in biofilms reproduce at a slower rate than free living ones. How might this be understood by analogy to life-history trait selection in r- and K-selective environments?
  

Going or gone?

The Yangtze fresh water dolphin (or Baiji 白鱀豚 in Chinese) was recently declared to be extinct after a survey expedition failed to spot any of the species. but faint hope was stirred when the animal in video footage of a sighting was identified as this species.

Nonetheless, researchers still consider the species as functionally extinct. Hopefully, the Yangtze finless porpoise will not follow in the Baiji's fate. Personally, I think that the finless porpoise has a better chance due to its "cuteness factor."

See this video at current.com.

Fungal Endophytes

Is a leaf all that it seems to be -- just a leaf? It turns out that fungal endophytes - fungi that live inside plants without harming them - are common and to be found in almost all leaves of tropical forest plants. It seems that the more we learn about organisms and their interactions, the more the idea of the 'free living organism' turns out to be a big lie! Not only are all organisms dependent upon others in obvious ways such as for food and nutrient cycling, but virtually all macroscopic creatures seem to have microscopic organisms living in them too (and frequently even the microscopic ones are hosts to yet smaller ones.)

We commonly understand fungi to adopt a saprobiontic lifestyle, acting as decomposers in the soil, in wood, in leaf litter, or perhaps as pathogens and parasites such as rusts and smuts. But the diversity of these lifestyles may be matched by the diversity of fungal endophytes, which live in the leaf tissues of plants without showing any symptoms or substantially impairing host productivity. They offer benefits to their hosts' fitness, such as preventing pathogenic infection, and possibly making leaves less palatable to herbivores. At the same time the leaves offer a substrate for the fungi to grow upon and provide food substances for their growth and reproduction. Most of these endophytes are transmitted horizontally rather than vertically, though the most well-studied case, that of grass endophytic fungi, are vertically transmitted.

Check out the webpage of Betsy Arnold from the University of Arizona. Her lab does a lot of work on fungal endophyte diversity and interactions with their host plants. Their diversity is still barely understood, especially in the tropics, and culture methods are relatively simple. This could be a pretty cool project for those of you living in places where the leaves aren't all falling off the trees!

GM foods are ubiquitous

Almost all the varieties of rice grown in Southeast Asia are genetically modified. A conspiracy by governments and biotech firms to reap big bucks while penalising ignorant consumers and poor farmers? No. They have been 'modified' by "accidentally as the result of mutations, chromosomal recombinations, translocations of pieces of DNA and even deletions of sections of DNA. This rice is consumed everywhere without the requirement of any laboratory tests," as this article rightly points out. Are GM foods the enemy, as some organic food advocates say that they are, or is this moralising about GM foods costing lives which could be saved by improved crop yields?

A rare nut

So, the other day we were at the East Coast Park beach playing with the sand when Josh picks up a "brain", well a hard fruit the size of a lime that look much like a brain. It took me a while before I did a double take and realised, my goodness, he had picked up a rare legume... a legume is the fruit of a member of the bean family.. That family of plants basically contains the peanut, soya beans, rain trees, in essence anything that has a pod, to be more accurate, a legume. the legume is a fruit that has 2 valves that will split along a line and reveal beans, which essentially are seeds. A pod is more layman and can be applied loosely to other fruits.

Anyway, what josh had picked up was a rare native of Singapore called Cynometra ramiflora L. var. ramiflora, its an inhabitant of back mangroves, which basically means, somewhere behind the mangroves where the ground isn't so muddy anymore and resembles an inland forest.

Why rare? When I revised the group for the Flora of Singapore, I listed it as "probably extinct", following a previous status accorded to it by other botanists. After a few years, someone else spotted it along one of the offshore islands and so it became extant in Singapore with at least one or two mature individual. So it was really great that a few more years later, Josh simply picked up the legume from the strand line along the east coast park beach.


Here's Josh presenting the rare legume. He had inadvertently picked it up and brought it to the at first unappreciative local authority on the Caesalpinioid legumes of Singapore.


This is Matt contemplating the size of the fruit. Its hard and corky so definitely buoyant. I am not sure where it came from though but at least it is here.

I looked around the strand line for more of the fruit and found another. How serendipitous.


Here's my botanical illustration of the species, from Loo, A.H.B. & H.T.W. Tan, 1997. The Angiosperm Flora of Singapore Part 6 --Caesalpiniaceae. Gardens' Bulletin, Singapore, 49: 55–106.