Parasitic wasps

Most parasitoids control the behaviour of a particular host to benefit in defensive strategies for their larvae which is exactly what this parasitic wasp (Cotesia glomerata) does. The wasp not only alters the behaviour of the host but also physical and psychological patterns. The wasp is able to manipulate the host’s ability to construct shelters with intentions focused primarily in protecting larvae of the wasp (Edmunds 1974).

C. glomerata is involved in a parasitic relationship with host caterpillars in which the wasp injects its larvae into. The larvae are then able to feed on the host’s blood, whilst maintaining an interest in keeping the host alive avoiding any vital organs. At around 12 days the larvae start to become highly active in which they have developed specialised teeth that can slice through the tough skin of the caterpillar. The combined mass of the larvae can account for over a third of the caterpillar’s weight. In order to complete the next stage of the wasp’s life cycle they egress from the caterpillar’s body. Prior to exiting, the larvae release a toxin that temporarily paralyses the host. Once the larvae have exited the host, they begin to spin silk cocoons which provide an adequate environment for their final stages of development. These larvae are subject to hyperparasitoids which are parasites that host on other species of parasite. In this particular case, other species of parasitic wasp are able to use the larvae as hosts in which another feature of this intriguing relationship kicks in (Tanaka and Ohsaki, 2006).

Figure 1. Photographer: Paul M (2006). Caterpillar of Pieris brassicae guarding the larvae of Cotesia glomerata.

The host is not killed in the process of the larvae exiting, instead its behaviour has changed and seems to help and protect the young larvae. The caterpillar spins an additional silk layer over the group of cocoons for added protection and camouflage to other parasitoids. The caterpillar tends to the cocoons in an attempt to ensure their survival in which it eventually starves itself to death (Karowe and Schoonhoven, 1992).

This relationship is an interesting example of parasitism on multiple levels, in which it alters its host’s physical, psychological and behavioural characteristics which ultimately benefit the wasp’s biological fitness and reproductive success.

Video with thanks to National Geographic 

https://www.youtube.com/watch?v=vMG-LWyNcAs

References:

Edmunds M (1974) Defence in animals. A survey of anti-predator defences. Longman, New York

KAROWE, D. & SCHOONHOVEN, L. 1992. Interactions among three trophic levels: the influence of host plant on performance of Pieris brassicae and its parasitoid, Cotesia glomerata. Entomologia experimentalis et applicata, 62, 241-251.

TANAKA, S. & OHSAKI, N. 2006. Behavioral manipulation of host caterpillars by the primary parasitoid wasp Cotesia glomerata (L.) to construct defensive webs against hyperparasitism. Ecological Research, 21, 570-577.

Figure 1. Paul M (2006). Caterpillar of Pieris brassicae guarding the larvae of Cotesia glomerata.

Ants and Acacias

The swollen thorn acacia (Acacia cornigera) is distributed throughout Central America entwined in an obligatory mutualistic relationship with a species of acacia ant (Pseudomyrmex ferruginea). Plant species that have colonies of ants living within the internal and external structures have been given the term myrmecophytes (Janzen, 1966). The acacia ant and plant provides essential benefits for each symbiont concerning protective and reproductive purposes.

The swollen thorn acacias acquire their name from key characteristic features including: enlarged stipular thorns, enlarged foliar nectaries, modified leaflet tips known as Beltian bodies which are consumed by the ants, and year round leaf production. It is to be noted that the obligate acacia ants are not species specific rather to the swollen acacia life form (Janzen, 1966). Initially a queen ant is attracted by a distinct odour and selects to nest inside the tree, specifically the hollow acacia horns. The queen then lays her eggs within the hollowed thorn whereby they hatch and become the first generation workers, the colony continues growing in size to adequately provide protection for the acacia from many insects and mammals that may wish to feed on the plant. The ants repel epiphytic vines by sectioning tendrils that come into contact with the acacia. A. cornigera provides sugar rich nectar from nectaries and beltian bodies which are collected and stored by the ants as a food resource for the ant larvae. The ants have also been known to remove small seedlings around the base of the acacia as potential competitors for sunlight and other essential resources (Risch et al., 1977).

The acacia ant colonies are continuously increasing in size until a population of over 4000 exists which takes a minimum of three years to establish. In recent experiments it has been shown that an acacia plant will become subject to large amounts of damage from herbivorous behaviour if the pair are separated (Hölldobler, 1990). The benefits each receive from the relationship are essential to each symbionts survival and success.

 Video with thanks to National Geographic

https://www.youtube.com/watch?v=Xm2qdxVVRm4

References:

HÖLLDOBLER, B. 1990. The ants, Harvard University Press.

JANZEN, D. H. 1966. Coevolution of mutualism between ants and acacias in Central America. Evolution, 249-275. 

RISCH, S., MCCLURE, M., VANDERMEER, J. & WALTZ, S. 1977. Mutualism between Three Species of Tropical Piper (Piperaceae) and Their Ant Inhabitants. American Midland Naturalist, 98, 433-444.

Rajah Pitcher Plant and Tree Shrew

A recently discovered mutualistic relationship exists between 3 species of Nepenthes genus carnivorous pitcher plants and the mountain treeshrew (Tupaia montana). In this blog I will focus specifically on the Rajah Pitcher Plant (Nepenthes rajah) and the mountain treeshrew which are located and endemic to the tropical regions of Borneo (Greenwood et al., 2011).  

These pitchers are distributed in nutrient deficient substrates in which its acquisition of essential nutrients such as nitrogen and phosphorus cannot be sourced via the typically method seen in most species of plants. These three species have shown to dominate the specialized acquisition of nutrients away from the typical arthropod trapping strategies (Moran et al., 2003). Each have developed certain attributes which specifically attract the montane treeshrew in the rather unusual mutualistic relationship in which the treeshrew defecates into the Nepenthes’ pitchers. The treeshrew does this whilst visiting the pitchers to access the delicious secretions from the strategically positioned pitchers lids which is rich in carbohydrates (Greenwood et al., 2011). The Rajah Pitcher has had some interesting studies conducted investigating the pitcher geometry. It was found that the distance from the front of the pitchers digestive organ to the secretionary glands is exactly that of the treeshrews head to body length. The only way for the treeshrew to access the delicious secretions is to orientate its self so its rear is hovering above the pitchers mouth in which it defecates into as a marking of feeding territory (Walker, 2010).

Figure 1. Photographer: Chien Lee (2011) Rajah pitcher plant (Nepenthes rajah) with Mountain Treeshrew (Tupaia montana). 

A study conducted by Greenwood, et at. 2011, indicated that more than one species of mammal visits the pitchers. A small number of mammals visit the N. rajah during daylight and night periods with the treeshrew only visiting in daylight hours whilst a small rat species (Rattus baleunsis) was seen to visit both during nocturnal and diurnal hours. It was found that sugar concentrations of the secretions do not significantly differ in neither day nor night period suggesting that multidirectional resource-based mutualism between a mammal and a carnivorous plant which is the second known example discovered. It was also discovered the N. rajah is the first species of the Nepenthes species to benefit from nocturnal and diurnal mammalian faecal input (Greenwood et al., 2011).

T. montana is also known to display a relatively simply intestinal morphology which results in moderately short digestion tract and passage time which causes the treeshrews to regularly defecate in time periods no longer than one hour which is largely beneficial for N. rajah (Emmons, 2000). The down side to this is that the nutrient extraction within the treeshrew through the intestinal tract is low and causes an increase in nutrient content in the excreted in the scats. This is suggested to be the reason they visit these pitchers so vigorously to supplement their diet and gain the essential nutrients they require (Clarke et al., 2009).

A very interesting relationship exists between these two symbionts with a large amount of room for further scientific investigation to uncover more of the unusual mutualism and the benefits each receive. The below video shows a treeshrew accessing secretions from N. rajah and depositing excrement.

Video with thanks to BBC Earth 

https://www.youtube.com/watch?v=TwL7K_loRjM

References:

CLARKE, C. M., BAUER, U., CH'IEN, C. L., TUEN, A. A., REMBOLD, K. & MORAN, J. A. 2009. Tree shrew lavatories: a novel nitrogen sequestration strategy in a tropical pitcher plant. Biology Letters, 5, 632-635.

EMMONS, L. 2000. Tupai: a field study of Bornean treeshrews, Univ of California Press.

GREENWOOD, M., CLARKE, C., CH'IEN, C. L., GUNSALAM, A. & CLARKE, R. H. 2011. A unique resource mutualism between the giant Bornean pitcher plant, Nepenthes rajah, and members of a small mammal community. PLoS One, 6, e21114.

MORAN, J. A., CLARKE, C. M. & HAWKINS, B. J. 2003. From carnivore to detritivore? Isotopic evidence for leaf litter utilization by the tropical pitcher plant Nepenthes ampullaria. International Journal of Plant Sciences, 164, 635-639.

WALKER, M. 2010 Giant meat – eating plants prefer to eat tree shrew poo. BBC Earth news. Retrieved from http://news.bbc.co.uk/earth/hi/earth_news/newsid_8552000/8552157.stm on 29/05/2015

Figure 1. Chien Lee (2011) Rajah pitcher plant (Nepenthes rajah) with Mountain Treeshrew (Tupaia montana). 

Clown Fish and Anemone

The famously known clownfish and anemone are a classic example of an obligatory mutualistic relationship. 10 species of anemone coexists with the 26 species of tropical clownfish. Within this only select pairs of anemone and clownfish are compatible; some species specific (Fautin, 1991). The individuals involved in the mutualistic relationships are known as obligatory symbionts which means they are highly dependent on each other; for a variety of beneficial reason including protection from predators, exchange of nutrients and protection from nematocyst strikes from the anemone (Fautin, 1991).

Figure 1. Photographer: Samuel Chow (2007). Clownfish protected by tentacles of anemone in obligatory mutualistic relationship.

This relationship is exclusively observed in shallow waters of the tropical Indo-Pacific, typically on or near coral reefs. In nearly all cases, an individual sea anemone or a cluster of contiguous ones is inhabited by an adult pair of anemone fish and, depending on the species of fish, in some cases by one or more juveniles (Dunn, 1981). Reproductive behaviour is constituted by both parental figures, though predominantly male orientated. The eggs are laid on the substratum beside the anemone, and whereby the male regularly exercises mouthing and fanning the eggs to keep them clean and supplying constant oxygenated water; he also removes the unfertilised eggs from the clutch to further increase the success rate of the incubating young (Allen, 1972):(Dhaneesh et al., 2009).

Anemones possess tentacles that are covered in nematocysts which are characteristic to scyphozoan and other cnidarians. Nematocyst strikes from the anemone paralyse almost any small marine organisms that comes into contact with the tentacles. They are spear like stingers that when mechanically or chemically stimulated fire and penetrate into a foreign object and release a paralysing toxin into the blood stream of the organism; the anemone is then able to digest the food (Nematocyst, 2015). Some fish try to feed on the nutrient rich tentacles of the anemone in which the clown fish’s aggression and territorial behaviour warns them off and if that fails they risk being stung by the nematocysts (Fautin, 1991).

Figure 2. Author: unknown. Firing of a nematocyst used by cnidarians for feeding

Clownfish are believed to be protected by a mucus coating produced that prevents nematocysts strikes against them. Some studies have suggested the protective feature can be of various nature including: innate, acquired or both. Some species of clownfish are suggested to be innately protected by the mucus before ever coming into contact with the anemone while other species are suggested to have an acquired mode of protection. This is seen in the behaviour of the clownfish by repeated brushing through the tentacles of the anemone to acclimate to the host before clownfish can move freely throughout the anemone. The clownfish then acquires antigens that act as a chemical camouflage preventing the nematocysts from firing (Fautin, 1991).

The anemone and clownfish actively participate in the mutualistic relationship as obligatory symbionts providing essential and beneficial natural services for each individual.

References:

ALLEN, G. R. 1972. The Anemonefishes: their Classification and Biology     (Neptune City, N. J., T. F. H. Publ., Inc. Ltd.).

DHANEESH, K., KUMAR, T. A. & SHUNMUGARAJ, T. 2009. Embryonic development of percula clownfish, Amphiprion percula (Lacepede, 1802). Middle-East J. Sci. Res, 4, 84-89.

DUNN, D. F. 1981. The Clownfish Sea Anemones: Stichodactylidae (Coelenterata: Actiniaria) and Other Sea Anemones Symbiotic with Pomacentrid Fishes. Transactions of the American Philosophical Society, 71, 3-115.

FAUTIN, D. G. 1991. The anemonefish symbiosis: what is known and what is not.

NEMATOCYST. 2015. Encyclopædia Britannica Online. Retrieved 29 May, 2015, from http://www.britannica.com/EBchecked/topic/408444/nematocyst.

Figure 1. Samuel Chow (2007). Clownfish protected by tentacles of anemone in obligatory mutualistic relationship. Retrieved from http://www.asknature.org/strategy/fb410d8500af30a5daf5b647954b7fa5#menuPopup, on 29/05/2015.

Figure 2. Author:unknown (n.d) Firing of a nematocyst used by cnidarians for feeding. Retrieved from http://reefworks.co.uk/wp-content/uploads/2011/10/nematocysts-glow-small.jpg, on 29/05/2015

Cleaners of the blue

The bluestreak cleaner wrasse (L. dimidiatus) from the Labridae family shares mutualistic relationships with a vast number of larger marine species, specialising on crustacean ectoparasites and mucus. Vastly distributed throughout shallow reef systems occupying cleaning stations associated with formations such as coral heads and between two outcrops. This species of cleaner wrasse is distributed throughout the Indo-Pacific from southern and eastern Africa to the Tuamotus in the south Pacific, also from southern Japan to the Great Barrier Reef and south-western Australia (Losey, 1972)

Coral reefs are one of the most species rich environments on earth, they provide protection and habitat for a diverse range of sea life ranging from large migratory mammals to small crustaceans, also a large amount of bacteria and algae species. Cleaner wrasse encourage diversity within a coral reef ecosystem by providing beneficial cleaning stations, typically occupied by a group of youths, a pair of adults, or a group of females accompanied by a dominant male. The cleaners greet the clients with an up and down motion of the rear end and the fish respond by opening their mouths or exposing the area they wish cleaned for example flaring their gills. In a recent experiment conducted on the effect that cleaner wrasse have on coral reef communities it was found that resident fish species were 37 % less abundant and 23 % reduced species richness per reef when cleaner wrasse were removed. The investigation also showed lower growth rate and survivorship among fish species within the community (Waldie et al., 2011).

A bluestreak fangblenny (Plagiotremus rhinorhynchos) has taken advantage of the juvenile cleaner wrasse appearance to gain access to food, with a single blue strip down the lateral surface of the fish. The fangblenny is found lurking around cleaning stations mimicking the appearance and behaviour of the bluestreak cleaner wrasse, when in striking range they ambush and use their fangs to tears pieces of flesh from client fish. They are able to change their appearance accordingly and can be found in locations that cleaners have not settled and occupy small crevasses and strike at shoals when they swim by. These mimics have shown to reduce the number of clients that enter the cleaning station which inevitably affects the feeding habits and behaviour of the cleaner wrasse (Côté and Cheney, 2005).

Figure 1.0 Difference in species. Top: Bluestreak cleaner wrasse. Bottom: Bluestreak fangblenny

The crucial health benefits these cleaner wrasse provide in the mutualistic relationship are very important in helping maintain species diversity and richness in coral reef communities where a range of larger species regularly visit. The bluestreak cleaner wrasse is not the only species of cleaner fish that partakes in this mutualistic relationship, though is one of the better known examples of cleaners in the marine environment.

References:

CÔTÉ, I. M. & CHENEY, K. L. 2005. Animal mimicry: Choosing when to be a cleaner-fish mimic. Nature, 433, 211-212.

LOSEY, G. S., JR. 1972. The Ecological Importance of Cleaning Symbiosis. Copeia, 1972, 820-833.

WALDIE, P. A., BLOMBERG, S. P., CHENEY, K. L., GOLDIZEN, A. W. & GRUTTER, A. S. 2011. Long-term effects of the cleaner fish Labroides dimidiatus on coral reef fish communities. PLoS one, 6, e21201.

Figure 1. Difference in species of cleaner and mimic. (n.d) Available from http://ed101.bu.edu/StudentDoc/Archives/fall05/edwardsk/blueblenny.html. Retrieved on 03/05/2015