Field of Science

The Model Tetrahymenidans

Ciliates have long been one of the most (if not the most) confidently recognised groups of unicellular eukaryotes owing to their distinctive array of features, in particular locomotion by means of more or less dense tracts of small cilia that often run the length of the organism. And of all ciliates, perhaps none have been more extensively studied than species of the genus Tetrahymena such as T. thermophila. Being easily cultured in the laboratory, Tetrahymena species have become model organisms for the study of a great many genetic and cellular systems such as cell division and gene function. At least two Nobel prizes have been awarded for work based on Tetrahymena that established the functions of telomeres and ribozymes. But Tetrahymena is just one genus of larger group of ciliates, the Tetrahymenida.

Tetrahymena thermophila, from Robinson 2006.

In general, tetrahymenidans are more or less 'typical'-looking ciliates with an ovoid body form and a well-developed 'mouth' at one end. The name Tetrahymena, meaning 'four membranes', refers to the presence of four membrane-like structures inside the oral cavity, a larger, ciliated undulating membrane on the left and three membranelles (formed from polykinetids, complex arrays of cilia and associated basal bodies and fibrils). Most tetrahymenidans possess some variation of this arrangement with the exception of Curimostoma, a genus of parasites of freshwater flatworms and molluscs that lack oral structures (Lynn & Small 2002). Life cycles may contain a number of morphologically differentiated stages. A more mobile theront stage will seek out food sources then transform into a feeding trophont. Mature trophonts may divide asexually or reproduce through conjugation. Cellular multiplication often involves successive divisions so a single parent cell may give rise to four daughter cells. In a number of species, resistant resting cysts may form under adverse conditions.

Glaucoma scintillans, another well-studied tetrahymenidan, copyright Proyecto Agua.

Tetrahymenidans are also ecologically diverse, occupying a range of freshwater habitats. They may be free-living, feeding on bacteria, or they may be parasitic or histophagous, feeding on the tissues of invertebrates. Some species may switch between one or the other depending on circumstances. A few Tetrahymena species have even been cultured in the laboratory axenically: that is, absorbing nutrients directly from a culture broth without requiring a bacterial food supply. Recently, the first confirmed case of a tetrahymenidan containing endosymbiotic algae was described by Pitsch et al. (2016). The species Tetrahymena utriculariae inhabits the bladders of the carnivorous bladderwort Utricularia reflexa. Endosymbiotic green algae provide it with oxygen, allowing the ciliate to survive within the anoxic environment of the bladders.


Lynn, D. H., & E. B. Small. 2002. Phylum Ciliophora Doflein, 1901. In: Lee, J. J., G. F. Leedale & P. Bradbury (eds) An Illustrated Guide to the Protozoa: Organisms traditionally referred to as Protozoa, or newly discovered groups 2nd ed. vol. 1 pp. 371–656. Society of Protozoologists: Lawrence (Kansas).

Pitsch, G., L. Adamec, S. Dirren, F. Nitsche, K. Šimek, D. Sirová & T. Posch. 2016. The green Tetrahymena utriculariae n. sp. (Ciliophora, Oligohymenophorea) with its endosymbiotic algae (Micractinium sp.), living in traps of a carnivorous aquatic plant. Journal of Eukaryotic Microbiology 64: 322–335.

The Age of the Ceratites

The ammonites are unquestionably one of the most famous groups of fossil mollusks, indeed of fossil invertebrates in general. Even those who have little consciousness of the fossil world might be expected to have a vague mental picture of a coiled shell housing a squid-like beast. But ammonites are far from being the only group of shelled cephalopod known from the fossil record. And though ammonites may have dominated the marine environment during the Jurassic and Cretaceous periods, during the preceding Triassic period they were overshadowed by another such group, the ceratites.

Reconstruction of Ceratites spinosus, from Klug et al. (2007).

The ceratites of the order Ceratitida (or suborder Ceratitina, depending on how you've tuned your rank-o-meter today) were close relatives of the ammonites, each deriving separately from an earlier cephalopod group known as the prolecanitids. The earliest forms regarded as ceratites appeared during the mid-Permian, though the exact dividing line between prolecanitid and ceratite seems to be somewhat arbitrary (as, indeed, is only to be expected with a well-known historical lineage). During the remainder of the Permian their diversity remained fairly subdued. When marine life was hit with the cataclysmic upheaval that was the end-Permian extinction, two lineages of ceratites managed to squeak through, together with a single other prolecanitid lineage that would give rise to the ammonites during the ensuing Triassic. With most of their competitors thus eliminated, ceratite diversity expanded rapidly.

Externally, the shells of ceratites and ammonites were very similar, and without knowing their evolutionary context one would be hard-pressed to tell one from the other. Most ceratite shells formed the typical flat spiral one associates with ammonoids, with different species being variously evolute (with successive coils lying alongside the previous one) to involute (outer coils overlapping and concealing the inner ones), and cross-sections varying from narrow and lenticular to broad and low (Arkell et al. 1957). One later Triassic family, the Choristoceratidae, had shells that began as an evolute coil but became uncoiled or straightened in later stages. Another Upper Triassic group, the Cochloceratidae, had turreted shells that might externally be mistaken for those of a gastropod.

Ceratites dorsoplanus, showing ceratitic sutures, copyright Hectonichus.

Internally, ceratites and ammonites often differed in the structure sutures, the lines formed by the join between the outer shell and the septa dividing the internal chambers. In ammonoids as a whole, the sutures are variously curved back and forth on the inside of the shell, with those parts of the suture going forwards (towards the shell opening) forming what are called saddles and those going backwards (away from the opening) forming lobes. In most ceratites, the sutures more or less form a pattern that is known (appropriately enough) as ceratitic: the saddles are simple and not future divided, but the lobes have multiple smaller digitations. In some later taxa, the sutures became goniatitic (with both saddles and lobes simple, secondarily similar to those found in earlier ammonoids) or ammonitic (with both saddles and lobes subdivided, the pattern more commonly associated with ammonites).

Our knowledge of the soft anatomy of ceratites remains limited. We know that they possessed an anaptychus (a leathery plate at the front of the body that may have functioned as an operculum, as I described in an earlier post). Known radulae have fairly simple, slender, undifferentiated teeth (Kruta et al. 2015) so they were probably micro-predators or planktivores in the manner of most ammonites. A black, bituminous layer sometimes preserved against the inside of the shell in the body cavity may represent the remains of the dorsal mantle. Similarity between this layer and the dorsal mantle of nautilids lead Klug et al. (2007) to infer the presence of a non-mineralised hood in ceratites, though I wonder how the presence of a hood would relate to an anaptychus. Conversely, Doguzhaeva et al. (2007) interpreted the black layer as the remains of ink from a ruptured ink sac.

Assemblage of Arcestes leiostracus, copyright Lubomír Klátil.

Ceratites were to remain the ecological upper hand throughout the course of the Triassic. Though ammonites (represented by the phylloceratidans) were not uncommon during this period, their diversity remained consistently lower. However, the end of the Triassic was marked by a spike in global temperatures and ocean acidification, generally regarded as connected to the volcanic rifting activity that marked the beginning of formation of the Atlantic Ocean (Arkhipkin & Laptikhovsky 2012). Of the two ammonoid lineages, only the ammonites survived into the Jurassic; the ceratites were wiped out. Whether some aspect of ammonite biology made them better suited to survive the stresses of global climate change, or whether their survival was a question of simple dumb luck, seems to be an open question. Nevertheless, with the ceratites out of the picture, the way was open for the ammonites to become the lords of the Mesozoic ocean.


Arkell, W. J., B. Kummel & C. W. Wright. 1957. Mesozoic Ammonoidea. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt L. Mollusca 4. Cephalopoda: Ammonoidea pp. L80–L465. Geological Society of America, and University of Kansas Press.

Arkhipkin, A. I., & V. V. Laptikhovsky. 2012. Impact of ocean acidification on plankton larvae as a cause of mass extinctions in ammonites and belemnites. Neues Jahrbuch für Geologie und Paläontologie—Abhandlungen 266 (1): 39–50.

Doguzhaeva, L. A., R. H. Mapes, H. Summesberger & H. Mutvei. 2007. The preservation of body tissues, shell, and mandibles in the ceratitid ammonoid Austrotrachyceras (Late Triassic), Austria. In: Landman, N. H., R. A. Davis & R. H. Mapes (eds) Cephalopods Past and Present: New Insights and Fresh Perspectives pp. 221–238. Springer.

Klug, C., M. Montenari, H. Schulz & M. Urlichs. 2007. Soft-tissue attachment of Middle Triassic Ceratitida from Germany. In: Landman, N. H., R. A. Davis & R. H. Mapes (eds) Cephalopods Past and Present: New Insights and Fresh Perspectives pp. 205–220. Springer.

Kruta, I., N. H. Landman & K. Tanabe. 2015. Ammonoid radula. In: Klug, C., et al. (eds) Ammonoid Paleobiology: From Anatomy to Ecology pp. 485–505. Springer: Dordrecht.

The Life and Times of Diaulomorpha

Diaulomorpha is a fairly typical genus of the diverse micro-wasp family Eulophidae. Like most other eulophids, members of this genus are slender with a relatively soft metasoma. The mesosoma, on the other hand, is tougher, weakly vaulted, and conspicuously reticulate dorsally. Members of the genus are known from Australasia and South America (Bouček 1988).

Body of female Diaulomorpha itea, from Bouček (1988).

Diaulomorpha species are parasitoids of insect larvae that live as miners in leaves. They are known to feed on both Lepidoptera and Hymenoptera larvae; it seems that it is not the identity of the host that attracts them but the lifestyle. They are multivoltine, that is they can go through multiple generations in the course of a year. The breeding cycle and behaviour of a Diaulomorpha species was described by Mazanec (1990) as a parasitoid of the jarrah leafminer Perthida glyphopa, a moth whose larvae attack the leaves of jarrah Eucalyptus marginata.

Mating between males and females occured after a brief courtship ritual in which the pair each extended their wings upwards and beat them up and down. Females located host larvae by running across the leaf surface and drumming the outside of prospective mines with their abdomen. They would then drill into the mine with their ovipositor, though of course the host larva would generally be trying to escape the wasp's attentions; a female might have to drill several holes before successfully piercing the caterpillar. The ovipositor would then be 'stirred' into the host to cause haemolymph and other fluids to leak out of its skin, and the wasp would feed on this fluid through the hole formed by the ovipositor. Egg laying would begin shortly after the wasp had finished feeding. Egg production was relatively slow, with only five or six eggs able to develop within the mother at a time, and the female wasp would lay through a newly created hole into the mine near the selected host. Usually only one egg would be laid in a mine but sometimes multiple eggs would be laid and the emerging larvae would share the host individual. After laying an egg, the female would tap around the laying hole with the tip of her metasoma, presumably depositing some chemical that would signal to other Diaulomorpha females that the mine had already been attacked. The host, meanwhile, would stop feeding after being stabbed with the female's ovipositor and would finally die after about a day and a half. It was around this time that the larva(e) would hatch and commence feeding on its remains.

Though healthy hosts would obviously be preferable, female Diaulomorpha were not above attacking hosts that had already died or had already been parasitised by other wasps. Such hosts were particularly likely to be attacked by young females that had not yet learnt to deal with the defensive actions of a healthy host. Deceased hosts could present a problem in that their bodily fluid pressure had been lost, and the female might have to stab them with her ovipositor several times before she had ingested enough fluid to begin laying. Pre-parasitised hosts were less of a problem as endoparasitic wasp larvae within the host would die after the Diaulomorpha's stab along with the host.

Mazarec (1990) found parasitism levels by Diaulomorpha within the host population to be low. What is more, as host populations increased the level of parasitism would plateau, so the proportion of parasitised hosts was far lower in dense host populations. This presumably resulted from the wasp's low rate of egg production: as host populations increased, the population of wasps did not keep up with it. As such, the role of Diaulomorpha in pest control is probably limited.


Bouček, Z. 1988. Australasian Chalcidoidea (Hymenoptera): A biosystematic revision of genera of fourteen families, with a reclassification of species. CAB International: Wallingford (UK).

Mazanec, Z. 1990. The immature stages and life history of Diaulomorpha sp. (Hymenoptera: Eulophidae), a parasitoid of Perthida glyphopa Common (Lepidoptera: Incurvariidae). Journal of the Australian Entomological Society 29: 147–159.

The Mirines

Every profession has its quirks, tricks of the trade that are difficult to learn and appreciate except through direct experience. One quirk of entomology is that specimens of each distinct type of insect will have their own nuances for the best method to preserve and present them. And there are some particular types of insect that can be particularly challenging in that regard. Which is a roundabout way of saying: I am not a great fan of mirids.

Green mirid Creontiades dilutus, copyright CSIRO.

Mirids are the largest recognised family of the true bugs in the Heteroptera, with over 11,000 species known worldwide and presumably many more remaining undescribed. They can be distinguished from most (though not, it should be stressed, all) other bug families by the presence of the cuneus, a distinct cross-fold near the outer tip of the hemelytron (the toughened basal part of the fore wing). Most mirids can be further recognised by the absence of ocelli. They are mostly smaller bugs, generally somewhat soft-bodied, and mostly plant feeders though there are some notable exceptions. They also (and this is the reason why they have sometimes been the object of my animus in the past) have a tendency to be what I can only describe as weirdly flimsy. Most insect specimens, at least while stil fresh and relaxed, hold together reasonably well when subject to basic handling. Mirids, on the other hand, will throw off legs if you so much as look at them too hard.

An ant-mimicking mirid, Dacerla inflata, copyright Judy Gallagher.

Mirids are divided between several subfamilies, with the type subfamily Mirinae including well over 4000 species (Kim & Jung 2019). Mirines tend to be relatively large compared to other mirids (up to a bit over half a centimetre in length) and are characterised by features of the genitalia, together with a pair of lamellate, divergent parempodia (fleshy structures that may help in gripping onto things) at the end of the legs between the claws. Other notable features (shared with the closely related Deraeocorinae) include a deeply punctate pronotum, and a relatively long beak that extends beyond the mid coxae at rest. Several species of Mirinae are notable pests. The green mirid Creontiades dilutus is one of the more significant bug pests of crops in Australia, attacking a wide range of hosts including cotton, stone fruit, potatoes, legumes and many more (Malipatil & Cassis 1997). It generally feeds from growing points, killing new buds and inhibiting the production of flowers and new growth. Other polyphagous pests causing similar damage include the tarnished plant bugs of the genus Lygus, whose vernacular name is somewhat self-explanatory, and the alfalfa bug Adelphocoris lineolatus.

Tarnished plant bug Lygus pratensis, copyright Hectonichus.

Six tribes have been recognised within the Mirinae, distinguished by their overall habitus. The Mirini, the largest tribe, have a more or less ovoid body shape with a distinct, raised pronotal collar and opaque hemelytra. The Hyalopeplini have a similar body shape to Mirini but transparent hemelytra. The Restheniini have a reduced evaporative area on the abdomen. The Stenodemini and Mecistoscelini are long and slender with long appendages, with the head directed forward in the Stenodemini. The Herdoniini are ant mimics, presumably for defence from predators. The appearance of an ant waist is achieved by a narrowing of the mirid's own body and wings, and/or an appropriately placed white triangular marking across the hemelytron. Despite the superficial distinctiveness of the tribes, however, a phylogenetic study of the Mirinae by Kim & Jung (2019) found at least two of them to be paraphyletic, with Mecistoscelini being nested within Stenodemini, and Hyalopeplini and Restheniini within Mirini. The affinities of the Herdoniini, unsampled by Kim & Jung, remain to be established.


Kim, J., & S. Jung. 2019. Phylogeny of the plant bug subfamily Mirinae (Hemiptera: Heteroptera: Cimicomorpha: Miridae) based on total evidence analysis. Systematic Entomology 44: 686–698.

Malipatil, M. B., & G. Cassis. 1997. Taxonomic review of Creontiades Distant in Australia (Hemiptera: Miridae: Mirinae). Australian Journal of Entomology 36: 1–13.

The Concilitergans: Sitting Next to Trilobites

The last few decades have seen a vast increase in our understanding of life during the early Cambrian. Long one of the most famous groups of invertebrates of the Palaeozoic, the trilobites are now known to have shared their early environment with a number of related lineages that bore some resemblance in overall appearance but lacked their mineralisation of the exoskeleton. One such group was labelled by Hou & Bergström (1997) as the Conciliterga.

Reconstruction of the concilitergan Kuamaia lata from Hou & Bergström (1997). Note that the reconstructed appearance of the eyes is probably erroneous, as explained below.

Concilitergans are a group of flattened marine arthropods known from the early and middle Cambrian of a number of parts of the world, including North America, China and Australia. Most species were ovoid in shape (like a typical trilobite), tapering somewhat towards the rear and often ending in a point. An Australian species, Australimicola spriggi, was more elongate in form and ended in a pair of terminal spines. Some were quite sizable; one species, Tegopelte gigas, reached nearly a foot in length and was one of the largest known animals of its time. Concilitergans also resembled trilobites in possessing a more or less semi-circular head shield followed by a series of regular segments and often a final larger pygidial segment. Towards the front of the body, the segment boundaries were anteriorly reflexed (Paterson et al. 2012). In a number of species, the body segmentation was more prominent medially than laterally with the tergites overlapping slightly down the mid-line but not along the edges. A pair of antennae arose from the underside of the head near the front. In most species, with the exception of Australimicola, a pair of prominent teardrop-shaped bulges was also present dorsally near the front of the head. These bulges were interpreted as a pair of dorsal eyes by Hou & Bergström (1997) but re-interpreted by Edgecombe & Ramsköld (1999) as raised areas of the exoskeleton that provided accomodation for the actual eyes located on the underside of the head.

Reconstruction of Tegopelte gigas, copyright Marianne Collins.

Phylogenetic analyses have confirmed a close relationship between concilitergans and trilobites (Edgecombe & Ramsköld 1999) and the two groups probably resembled each other in life-style. With their ovoid shape, flattened body and down-cast eyes, concilitergans were also not dissimilar in overall conformation to modern cockroaches and a comparison is tempting. Study of trackways attributed to Tegopelte, owing to their size and structure, indicated that it mostly walked with a slow, low gait but was also capable of adopting a higher, faster gait for quickly skimming across the sediment surface (Minter et al. 2012). It should be noted that while news reports on the latter study (like this one) repeatedly refer to Tegopelte as a predator, the original paper consistently describes it as a "predator or scavenger". One can imagine concilitergans crawling along the sea-bed, picking up fragments of organic matter and scavenging on the remains of the less fortunate. Eventually, though, their lack of armament compared to their longer-surviving allies might have been their downfall as they were less prepared to deal with the diversification of active predators as the Cambrian progressed.


Edgecombe, G. D., & L. Ramsköld. 1999. Relationships of Cambrian Arachnata and the systematic position of Trilobita. Journal of Paleontology 73 (2): 263–287.

Hou X. & J. Bergström. 1997. Arthropods of the Lower Cambrian Chengjiang fauna, southwest China. Fossils and Strata 45: 1–116.

Minter, N. J., M. G. Mángano & J.-B. Caron. 2012. Skimming the surface with Burgess Shale arthropod locomotion. Proceedings of the Royal Society of London Series B—Biological Sciences 279: 1613–1620.

Paterson, J. R., D. C. García-Bellido & G. D. Edgecombe. 2012. New artiopodan arthropods from the Early Cambrian Emu Bay Shale Konservat-Lagerstätte of South Australia. Journal of Paleontology 86 (2): 340–357.


The reefs of the Indo-west Pacific Oceans are one of the most species-rich regions of the entire marine environment. A complex geological history and high geographical complexity have contributed to drive speciation, resulting in a number of local radiations. One such radiation is the tuskfishes of the genus Choerodon.

Orange-dotted tuskfish Choerodon anchorago, copyright Bernard Dupont.

Choerodon is a genus of the wrasse family Labridae, most diverse around the islands of south-east Asia and northern Australasia where they inhabit coastal reefs or sea-grass beds. A revision of the genus by Gomon (2017) recognised 27 species, varying in size from a little over ten centimetres in length to half a metre or more. LIke other members of the wrasse family, they are often brightly coloured, with juveniles in particular of a number of species being patterned with bold vertical stripes. The vernacular name of 'tuskfish', as well as the zoological name of the genus (which translates as 'pig-tooth'), refers to the possesion of a pair of prominent, protruding incisors at the front of each of the upper and lower jaws. Other characteristic features of Choerodon include a dorsal fin with twelve spiny rays and eight soft rays, or thirteen spines and seven soft rays, and a lack of scales on the lower part of the cheek and lower jaw. Choerodon species, like most other wrasses, are protogynous hermaphrodites, starting their lives as females before eventually transforming into males.

Baldchin groper Choerodon rubescens, copyright Katherine Cure.

Diet-wise, tuskfishes are predators, feeding on animals such as crustaceans or mollusks. Larger species may even take other vertebrates. A kind of tool use has been observed for the genus, with difficult prey such as clams (Jones et al. 2011) or young turtles (Harborne & Tholan 2016) being grasped in the mouth and hammered against rocks to subdue them and/or break open shells. Multiple species of tuskfish may be found in close proximity though they will often differ in their preferred habitat. A study of five Choerodon species found around Shark Bay in Western Australia by Fairclough et al. (2008) found that the baldchin groper C. rubescens was found only on exposed marine reefs whereas the other four species preferred more sheltered habitats further inside the bay. The blue tuskfish C. cyanodus and blackspot tuskfish C. schoenleinii were both found in a range of habitats in this region but C. cyanodus was most abundant along rocky shores whereas C. schoenleinii preferred coral reefs (C. schoenleinii also differed from other species in the region in constructing burrows at the base of reefs that it used as a retreat). The purple tuskfish C. cephalotes was almost exclusively found among seagrass meadows. Finally, the bluespotted tuskfish C. cauteroma spent the early part of its life among seagrasses but moved onto reefs as it matured to adulthood.

Tuskfish and other wrasses are highly prized as eating fishes. However, it would be remiss to refer to the reefs of the Indo-west Pacific without mentioning that many of them are highly endangered. Heavy fishing, often using destructive methods, have combined with the effects of changing climate to cause a dramatic reduction in reef cover in recent decades. Should the decline continue at current rates, the lives of millions of people stand to be dangerously impacted.


Fairclough, D. V., K. R. Clarke, F. J. Valesini & I. C. Potter. 2008. Habitat partitioning by five congeneric and abundant Choerodon species (Labridae) in a large subtropical marine embayment. Estuarine, Coastal and Shelf Science 77: 446–456.

Gomon, M. F. 2017. A review of the tuskfishes, genus Choerodon (Labridae, Perciformes), with descriptions of three new species. Memoirs of Museum Victoria 76: 1–111.

Harborne, A. R., & B. A. Tholan. 2016. Tool use by Choerodon cyanodus when handling vertebrate prey. Coral Reefs 35: 1069.

Jones, A. M., C. Brown & S. Gardner. 2011. Tool use in the tuskfish Choerodon schoenleinii? Coral Reefs 30 (3): 865.

Australasian Mistletoes

Australia is home to a fair diversity of parasitic mistletoes, nearly ninety species in all. In a previous post, I described one of our most remarkable species, the terrestrial Nuytsia floribunda. But, of course, the remaining species occupy the more typical aerial mistletoe habitat, growing directly attached to the branches and trunk of their host. And within Australia, the most diverse mistletoe genus is Amyema.

Amyema pendula growing on Acacia, copyright Groogle.

Species of Amyema are found in southeast Asia, Australia, and islands of the Pacific as far east as Samoa. A revision of the genus by Barlow (1992) recognised 92 species with the greatest diversity in the Philippines, Australia and New Guinea. They are found in a range of habitats, from wet rainforests to arid woodlands. Some species (particularly in arid habitats) grow from a single central haustorium (the structure by which a parasitic plant attaches to and draws nutrients from its host); others (particularly rainforest species) produce numerous haustoria from runners stretching along the outside of the host. Most rainforest species tend to have low host specificity but those growin in arid habitats may be more likely to restrict themselves to a small number of host species. Those species which restrict themselves to a single host may have leaves closely resembling that host, making them difficult to spot within the host canopy.

Amyema species are mostly characterised by their flowers which are typical borne in triads with the triads often then being clustered in loose umbels. In some species, the triads are reduced to pairs or single flowers. The flowers themselves are bird-pollinated and have four to six long petals that are generally separated right to the base, at most forming only a very short tube at the base of the flower. The flowers are hermaphroditic though a study of some Australian species by Bernhardt et al. (1980) found a tendency for anthers to mature before the stigma, presumably to prevent self-pollination.

Flowers of Amyema miquelii, copyright Kevin Thiele.

Not surprisingly, attention on mistletoes in Australia has commonly been focused on their effect on host trees. Mistletoe infestations may be heavy and have commonly been blamed for tree mortalities. However, one might legitimately question whether mistletoes themselves cause fatalities: does mistletoe infestation cause a host tree to become unhealthy, or are unhealthy trees more vulnerable to infestation by mistletoes? A study by Reid et al. (1992) on Amyema preissii infesting Acacia victoriae found that, though there was a relationship between mistletoe volume and host mortality, they were unable to demonstrate that mistletoe removal improved host survival. Conversely, such a positive effect was found by Reid et al. (1994) for removal of Amyema miquelii growing on two Eucalyptus species (the methods of this latter study also include the great line, "the highest mistletoes had to be shot down with a .22 rifle"). However, the authors remained conservative when it came to advocating mistletoe removal. Not only do a number of native birds and other animals depend on mistletoes for food and nesting sites, mistletoe removal can be an expensive process and may not itself be devoid of adverse effects on the host tree. Where rates of infestation are not extreme, it may still be better to just live and let live.


Barlow, B. A. 1992. Conspectus of the genus Amyema Tieghem (Loranthaceae). Blumea 36: 293–381.

Bernhardt, P., R. B. Knox & D. M. Calder. 1980. Floral biology and self-incompatibility in some Australian mistletoes of the genus Amyema (Loranthaceae). Australian Journal of Botany 28: 437–451.

Reid, N., D. M. Stafford Smith & W. N. Venables. 1992. Effect of mistletoes (Amyema preissii) on host (Acacia victoriae) survival. Australian Journal of Ecology 17: 219–222.

Reid, N., Z. Yan & J. Fittler. 1994. Impact of mistletoes (Amyema miquelii) on host (Eucalyptus blakelyi and Eucalyptus melliodora) survival and growth in temperate Australia. Forest Ecology and Management 70: 55–65.