I Am Back

What can I say in my pitiful defence? This Blog site has languished in the nether regions of the internet for quite some time now. It has been a strange few years which do not need to be gone in to here. But for the last year and slightly more I have been working in China. One of my positions is the vice curator of what I reckon is the only Cordyceps museum in the World. I am now back to doing what I have always enjoyed doing and that is hunting for Cordyceps in the forest, isolating them and staring down a microscope at them. Oh, and in this day and age of course tearing out chunks of their DNA to see how they relate to each other.

Aleyrodidae as a source of nutrients for fungi. Are they really?

It is well known that aleyrodids are hosts to a wide variety of insect fungi. Some of the earliest attempts at biological control were in the early 1900s when Aschersonia and others were tested as control agents for citrus whitefly. Work at the Florida University Agricultural Experimental Station over a period of 15-20 years looked at the possible use of these 'friendly fungi'. Sadly by the 1920s attention had switched to the use of chemical means which were quicker and more reliable and cheaper. Interest in Aschersonia went into decline until the mid 80s when the Dutch company Koppert started looking at the use of Aschersonia against glasshouse whitefly pests.

I have studied Aschersonia-Hypocrella for over 20 years and one matter has always intrigued me. A typical whitefly larva is less than 3 mm and is so very dorso-ventrally flattened that it barely reaches 0.1 mm thick. And yet.... After it has been killed by Aschersonia the resulting fruitbody can be 4-5 mm diameter and 1-2 mm high. That is a large volume of fungus to emerge from such a small host.

Figure One - Aleyrodid host infected with Aschersonia luteabadia

It is almost certain that the fungus, once it has killed its host, continues to get nutrients from the plant on which the host was feeding. Fig. 1 shows an aleyrodid larva with the stroma of Aschersonia luteabadia developing over it. The traditionally accepted development is that the abdomen of an insect/spider host is overcome first and only later the thorax. But in Fig. 1 the abdominal segments are still visible while the yellow stroma has grown over the thorax/head region.

After death the stylet of the aleyrodid must still be stuck in the phloem of the host plant. Phloem sap will continue to pump up that stylet thanks to phloem pressure. Phloem sap is a rich source of nutrients - sugars, hormones, minerals etc. All useful for a still-developing Aschersonia-Hypocrella.

Figure Two - Aschersonia confluens with sticky droplet

In March 2005 Rung and I were doing a survey in the south of Thailand and came across Aschersonia confluens in big numbers. It was early in the morning and what struck me was the numbers of specimens that had little droplets on the developing stromas. Fig. 2 is slightly out of focus for the stroma but shows a glistening drop of liquid. It was viscous and when I tasted it it was sweet. My conclusion was that this was a droplet of phloem sap that had been pumped up the stylet of the now-dead aleyrodid.

Gary Samuels and myself drew attention to this phenomenon in 1998 when we were discussing the large stroma  Hypocrella species on bamboo scale insects. At that time we assumed the fungus kept the host alive while it continued to grow over it. Much liked Septobasidium. I think, now, it is more likely the host is killed and it is only the stylet that continues to provide nutrients for the fungus host.

Cordyceps tuberculata on adult moth - Trashiyangtse, Bhutan

Cordyceps tuberculata on adult moth

This is Cordyceps tuberculata on an adult moth from Trashiyangtse in the far east of Bhutan. A 570 km drive from the base in Thimphu took three days of driving to get to the Bumderling Wildlife Sanctuary. Usually this is only found in the anamorph state - Akanthomyces pistilariiformis. occasionally there may be a few perithecia present. This specimen has plenty of perithecia present as cream yellow conical structures. The Akanthomyces anamorph was on the synnemata. This moth is about 40-50 mm long. It always amazes me that the fungus can start to grow out from the moth and cement it to the underside of a leaf after the moth has come to rest but before it has died.

What is Cordyceps sinensis?

Cordyceps sinensis is the old name for a fungus that is now correctly called Ophiocordyceps sinensis. It was named originally by Berkeley in 1843 (although it had been known in Europe for about 100 years previously) and was placed in the genus Sphaeria as Sphaeria sinensis. The material had been collected from a market in Canton (Guangdong) and was passed on to the Linnaean Society who in turn passed the material to Berkeley. When Berkeley named the fungus he recognised its origin as China – hence sinensis. This is a pity because it was not possible to determine where it came from once it ended up in the Canton market thousands of miles from where we now the species does grow. The type material is still contained in the herbarium at Kew Gardens.

Since its original naming the genus has been changed a few times. Sphaeria is a genus that is not now accepted. It rapidly became a catch-all genus. With such confusion it became easier to put species originally named in Sphaeria into other genera that were well described and well-known. Consequently, Saccardo transferred Berkeley's fungus from Sphaeria to Cordyceps in 1878 and there it happily remained for ca. 130 years.

Why couldn't it stay in Cordyceps? As with Sphaeria, Cordyceps was becoming unwieldy although it was rapidly recognised as a pathogen of insects, other invertebrates (especially spiders) and of other fungi. It became convenient to lump many species into this one genus. A few attempts were made to sub-divide the genus (notably by Yosio Kobayasi in Japan from the 1930s to 1980s) but no real effort was made to break the genus up. One exception was Tom Petch who named several species to a new genus which he called Ophiocordyceps. The type species of Cordyceps produces extremely long thread-like ascospores that break into typically 128 part-spores^[1]. By contrast, the type species of Petch's Ophiocordyceps had ascospores that were long (although not thread-like) but significantly did not divide into part-spores on release. They remained whole. This genus was not widely accepted by contemporaries of Petch (namely Yosio Kobayasi and Edwin Mains) and faded into obscurity.

Fast forward to the present. Importantly, the last 20+ years has seen a revolution in how we look at taxonomy - whether it be that of a humble bacterium or of a blue whale. Whereas, in the past, relationships were based on shared characteristics the advent of molecular phylogenetics has brought a powerful tool to bear upon taxonomy. Molecular methods can therefore show that there is only a 2% difference between human DNA and our nearest relatives the chimpanzee and bonobo. Within the human species there is only a 0.1% difference in the DNA of all humans.

The same techniques apply to fungi. The type species of Cordyceps is Cordyceps militaris. It was the first species named for what is now recognised as Cordyceps. It therefore stands as the basis by which all other 'Cordyceps' must be compared. A major study was published in 2007 (I was one of the authors) that looked at a wide and representative range of species that had previously been considered to be Cordyceps as well as related species of other insect fungi^[2]. Our study showed that Cordyceps fell into four distinct groups that were spread across three different families. Effectively, three new genera had to be found for the species that did not group closely with Cordyceps militaris. Two new genera were named in the study – Elaphocordyceps and Metacordyceps. One group included Cordyceps sinensis and one of the species that Petch had used to create Ophiocordyceps – Cordyceps unilateralis. As a result, Ophiocordyceps was resurrected and the Chinese Cordyceps became the Chinese Ophiocordyceps. By current thinking (but who is to say this will not change in the future) Petch was right whilst Kobayasi and Mains were wrong.

So, as noted at the beginning Cordyceps sinensis is more correctly called Ophiocordyceps sinensis. It will take time for this name to be used widely although it is catching on. Even I still refer to Cordyceps sinensis when talking generally.

References:

[1] Hywel-Jones, N.L. (2002). Multiples of eight in Cordyceps ascospores. Mycological Research 106: 2-3.

[2] Sung, G-H., Hywel-Jones, N.L. Sung, J-M, Luangsa-ard, J.J., Shrestha, B. & Spatafora, J.W. (2007). Phylogenetic classification of Cordyceps and the clavicipitaceous fungi. Studies in Mycology 57: 5-59.

A new challenge

Sadly the Bhutan venture failed. [NOTE: Anyone interested in working in Bhutan and/or doing business there is welcome to contact me privately. I will happily discuss the pros and cons.] After four interesting years living in Bhutan I moved back to Thailand in July of 2013. Since then I have been quietly working away on the start of a new project. And I now feel I can talk about this project.

A new start-up company contacted me out of the blue as they wanted to grow Cordyceps militaris for the nutraceuticals market. Luckily for me (since Thailand is my home base) the company is Thai. Last month, in spite of the political troubles, the work permit was sorted out and things are beginning to move forward. Over the next few months we will build lab facilities at the Science Park (Rangsit) where I used to be based. How ironic that I will be based across the car park from where I used to work. Not quite full circle.

Ophiocordyceps sinensis and Cordyceps militaris in Traditional Medicine

There are several hundred species (anamorph and teleomorph) of insect fungi belonging to the order Hypocreales around the World. It would seem they are present from sea level to at least 5500-6000 metres and around the world apart from the extreme polar regions (Arctic and Antarctic). And yet there are only a small few that have been used by man before the modern era. And mostly in what we like to call traditional medicine.

Of course, Ophiocordyceps sinensis is the superstar. But there is also Cordyceps militaris and others such as Isaria tenuipes and Isaria cicadae (whatever these latter two really are). There are also anecdotal references to Cordyceps being used in Australia, New Zealand and Papua New Guinea.

While Ophiocordyceps sinensis has a restricted distribution (the Himalayan Plateau) Cordyceps militaris has a distribution around the whole northern temperate region. It was originally described from Denmark but is now known throughout Europe, Russia, Korea, Japan and North America. For me these are the reliable records. There are other records from around the World that need to be confirmed for sure!

But interestingly, it only became a component of traditional medicines in north eastern Asian medicine (ie China, Japan and Korea). Before the advent of pharmaceutical medicine the west also had a strong tradition of medicine from the land. But for some reason Cordyceps militaris was overlooked in spite of its widespread distribution in Europe. I wonder why!

Isaria cicadae and traditional medicine

My work appears to be drifting further away from insect-fungus biodiversity research and more towards their uses in traditional medicine. Of course the most famous of these beasties is Ophiocordyceps sinensis. Followed closely by the original insect-fungus Cordyceps militaris. But there are others also. One that has been popping up in various searches I have made is Isaria cicadae. This was first described from South America (Brazil) and then transferred to Cordyceps. From the early 70s it was placed in Paecilomyces. Any internet searches need to consider all three genera Cordyceps, Isaria and Paecilomyces.

But the question needs to be raised. What is Isaria cicadae? Since a fungus under this name is featured in Traditional Asian Medicine it is important to get the scientific name right. Isaria cicadae was named from a very brief description lacking many of the features we would consider important today. Quite simply I do not believe that what Miquel described from Brazil almost 200 years ago is the same as what is being called Cordyceps/Isaria/Paecilomyces cicadae today in East Asia.

Insect-fungi are becoming increasingly popular in traditional medicine. And it is increasingly important that we know exactly what it is that we are working with.