Freshwater mussels are among the most threatened groups of aquatic animals in the world and face multiple threats including habitat modification, climate change, and altered water quality. Importantly as organisms, they have been shown to provide a range of ecosystem services, through biofiltration & nutrient recycling and indirectly, by acting as bio indicators. Bioindicators are living organisms ranging from microbes, through to complex animals, which are utilised to monitor of the health of the environment and any changes through time.
Carter’s freshwater mussel (Westralunio carteri) has long been recognised as the only species of freshwater mussel in south-western Australia. The species, like other freshwater mussels, has a complex life cycle including a parasitic larval stage which requires a freshwater fish host. The larvae, known as glochidia, are released in thick strands of mucus, and subsequently attach to a fish host (typically on the fin or gills of fish) for several weeks. During this time they metamorphose into the juvenile form prior to dropping off the fish host (Klunzinger et al., 2013). In 2018 this species was listed as ‘Vulnerable’ under the Environment Protection and Biodiversity Conservation Act 1999 (Commonwealth) and the Biodiversity Conservation Act 2016 (Western Australia). Research has identified that the species has undergone a 49% reduction in extent of occurrence due primarily to secondary salinization (Klunzinger et al., 2015). This declining trend has also been seen in a range of other freshwater mussel species from Mediterranean climate regions around the globe. They are now typically found within 50–100 km of coastal south-western Australia, and often occurs in greatest abundance in slower flowing waters where sediments are soft enough to allow the species to burrow. The species current range is between Gingin Brook in the north to the Kent, Goodga and Waychinicup Rivers in the South. Fascinatingly, however, recent research suggests that this individual species, may actually represent two/possibly three species/sub-species. DNA analysis suggests there are three evolutionary significant units, including western and southern lineages and a south-western subspecies (Klunzinger et al., 2021). This in turn may have significant conservation implications for the species. Despite the key role freshwater mussels play in the ecosystem, a number of key knowledge gaps remain, including for Carter's freshwater mussel. For example, what is the filtering capacity of this species? What are its tolerances to pollutants from urban, agricultural and industrial environments? There is always room for further research, particularly for threatened species, and through time, hopefully the answers will help conserve this iconic species. Links:
0 Comments
National Threatened Species Day happened just over the weekend on the 7th September 2019. The day marks the same date that the last known Thylacine (Tasmanian Tiger) died in captivity in Hobart Zoo in 1936 - although some still hold onto hope that it remains alive in the wilds of Tasmania. Over the weekend I had the pleasure of spending National Threatened Species Day out at the Tutanning Nature Reserve. The reserve is located in the Wheatbelt in the Shire of Pingelly, and is approximately 220 ha in size. A range of threatened species still call this reserve home, including the Woylie, Numbat, and Red-tailed Phascogale.
Although we had no luck observing Woylie, Numbat or Red-tailed Phascogale, during our time at the reserve we saw a range of fauna including the elusive Tammar Wallaby, Echidna, Ornate Crevice-dragon, and Western Spotted Frog (image below). Despite being in a nature reserve, we also came across signs showing exactly why so many of our species are threatened. We saw a large feral cat following a track in the reserve, came across fox scats throughout the reserve, and saw weed ingress at the edges of the reserve. Now the purpose of this short blog, was to highlight just a few of our threatened fauna (many of which the general public are unaware of). The list below are the species listed as "Critically Endangered" in just Western Australia (as of September 2018). This is the same conservation status as the Bornean Organutan, the Sumatran Rhinoceros, and the Western Lowland Gorilla. In addition to those listed below, an additional 58 fauna species are listed as Endangered (the same conservation status as the Bengal Tiger), and an additional 134 fauna species listed as Vulnerable (the same conservation status as the Giant Panda). Critically Endangered Mammals:
Critically Endangered Birds:
Critically Endangered Reptiles
Critically Endangered Amphibians
Critically Endangered Invertebrates
Despite how alarming this may sound, environmental awareness around the country is growing each year, and events such as the Threatened Species Bake Off are a great way to promote awareness of the risks facing our threatened species in Australia. So next year, why not look up your favourite threatened species, get baking and get your work place involved! The Bynoe's gecko (Heteronotia binoei) is endemic to Australia and occurs across much of the country including here in Western Australia (see image below - taken in the Pilbara in 2015). The species is irregularly patterned with spots and bands, but can be variable in appearance ranging from greys to reddish-browns. Bynoe's gecko is typically active at night and primarily terrestrial (as opposed to arboreal), feeding on a range of insects and other invertebrates.
When it comes to breeding biology, this is where this gecko gets really interesting. Some populations are diploid (two sets of chromosomes) consisting of both males and females, which reproduce sexually with females laying eggs from September to January. However, other populations are only female and are triploid (three sets of chromosomes). These all female populations reproduce asexually without the need for males, resulting in genetic clones. This process is known as parthenogenesis, from the Greek parthenos, meaning virgin, and genesis meaning creation. Now although parthenogenesis is not uncommon globally, Bynoe's gecko is one of the only known species of Australian reptile to reproduce through this process (a skink that undergoes parthenogenesis has also been identified in Central Australia). The parthenogenic populations are typically found in the Central and Western deserts of Australia, however, interestingly these populations often overlap with the diploid populations. Research by Mortiz (1989) helped shed light on this, as it was observed that the triploid parthenogenic populations arose from a hydridisation event between two genetically distinct populations of Bynoe's gecko. Now despite reproducing asexually the genetic diversity in the all female populations is higher than most parthenogenic reptiles. It has been suggested that this may be explained through multiple hydridisation events. More recent research by Kearney et al. (2005) has also shed some light on the abilities of these all female populations. The findings suggest these populations appear to be the "wonder women" of the gecko world. In terms of oxygen consumption rates, endurance and aerobic speeds, the parthenogenic all female populations out-compete the sexually reproducing populations by up to 50%. Although they appear to have a competitive advantage over their sexually reproducing counterparts, they are not invincible. The all female populations have been documented to suffer from higher deformity rates than their sexually reproducing counterparts and are more susceptible to infestation from parasitic mites. So although they can keep the population ticking over without males, the lack of genetic mixing in the population comes at a cost. Further reading & resources
The Slender tree frog is a small species reaching a maximum size of approximately 4.5 cm. It's colour can vary widely from bright green to more of a pale fawn/tan (like the ones pictured above and at the end of the article). The species is quite widespread within the south-west of WA and can be found in a range of habitats including urban gardens (the top image was taken in our native garden).
The Slender tree frog's scientific name is Litoria adelaidensis, yet despite its specific name it is found in the south-west of Western Australia near Perth. The Museum of WA website describes its etymology as "Named in error after Adelaide, South Australia, where this species does not occur." In fact, it is ONLY found in the south-west of Western Australia and has no close relatives anywhere in Australia. It is thought to descend from an ancient lineage when Australia was far wetter than our current climate. So luckily for us here in Perth we have this amazing species right on our door step ... unlucky Adelaide. The species is classed as "insectivorous" but also feed on spiders & worms. We regularly have resident slender tree frogs in our veggie patch (see images at the bottom) and think they could be the reason behind our successful harvest. We use no chemicals/pesticides on our veggies, yet never have a problem with pest insects. Although I haven't actually witnessed any predation of insects by the frogs in our veggie patch, they have certainly made a home for themselves and it seems a logical conclusion. The species is listed as Least Concern under the IUCN Redlist and although widespread it still faces threats. One major threat facing the species is the chytrid fungus which was detected in the species at Lake Gwelup. The chytrid fungus has been implicated in widespread extinctions and die-offs of frogs across the globe, with the first frogs dying from the disease in Australia discovered in 1993. The fungus invades the surface of the frogs skin resulting in loss of electrolytes and impacting its osmotic balance. The fungus has already been implicated in the extinction of four species in Australia, however, further research is needed into the remaining species including the Slender tree frog to better understand how the disease is impacting populations and how to potentially cure the disease. Further reading:
The Western Pygmy Perch (Nannoperca vittata) is a small species (up to 8cm TL) of freshwater fish found only in the south-west of Western Australia. Within the south-west however the species is relatively widespread and abundant, found in lakes, streams, rivers & swamps. Despite this, the species still faces many threats, including climate change, secondary salinisation, and invasive species (the introduced Eastern Gambusia is known to fin-nip pygmy perch). Thankfully the ecosystem services this species provides (such as mosquito control) has been recognised and local councils and other groups are helping reintroduce the species into wetlands across the south-west. Despite these efforts, how much do we really know about the Western Pygmy Perch? And are we managing just one species, or are there actually several cryptic species? Research by Buckley et al. (2018) used genomic data and modelling techniques to explore how the pygmy perches of Australia have evolved, including how during Australia's less arid past the east and west coast were connected with waterways allowing the species to disperse. An unexpected find from this study however was that there may potentially be up to 3 distinct species/lineages within the traditionally recognised Western Pygmy Perch. To highlight why these may actually be distinct species, the authors documented that the level of divergence between these N. vittata lineages is similar to that between N. vittata and the Little Pygmy Perch (Nannoperca pygmaea). Now the Little Pygmy Perch itself was only discovered in 2009 and named in 2013; up until then it was likely being misidentified as the Western Pygmy Perch. Research since its identification has continued to increase the understanding of the species, including the discovery of new populations. If the Little Pygmy Perch went unnamed for so long, is it possible that there are in fact more distinct cryptic species in the south west? The region is already a hot-spot for endemism, with 9 of the 11 native freshwater fish found no where else. Should these numbers actually be 11 of 13? Only time and more solid scientific research with larger sample sizes etc. will tell. With the discovery of 20 new species in the Kimberley in the last few years, and now the potential for three more in the south-west it is an exciting time for freshwater fish science in Western Australia. Did you know? The Western Pygmy Perch can also be purchased for aquariums and ponds (like this little one we had in our home aquarium). They can co-inhabit ponds with frogs and are great at controlling mosquito larvae! Further reading & resources:
Here in Western Australia, when the word possum is mentioned, thoughts immediately go to our common brushtail possums, or the critically endangered Western ringtail possum. Lesser known to the public are the pygmy possums of Australia, such as the Western Pygmy Possum (pictured at the end of the article - photo taken at Perup, Western Australia).
The Western Pygmy Possum (Cercartetus concinnus) is a small, largely nectarivorous marsupial, found across much of southern Australia including south-western Australia (which is also a biodiversity hotspot!). Despite being relatively widespread, populations are still poorly understood, and new discoveries in recent years suggest they may be found in more places than we know. They are a cryptic, nocturnal, and small species of marsupial growing to only around 13 g, and inhabit rather dense woodland, heath and forests, making the study and identification of these animals difficult. Despite this, they have attracted the attention of the scientific world, with one area of interest being their ability to enter an almost hibernation like state, called torpor. Torpor itself is a decrease in physiological activity of an animal usually in response to a reduction in ambient temperature, and/or food availability. Unlike hibernation however, many animals, including the Western Pygmy Possum utilise torpor throughout various seasons, not just during winter. Turner & Geiser (2017) utilised laboratory studies to better understand the drivers of torpor in the pygmy possum. Although food availability is often seen as a driver to enter torpor, Turner & Geiser (2017) found that photoperiod (day-length) may have been a more important environmental cue, and that Western Pygmy Possums may undertake torpor as part of their everyday energy budgeting regardless of food availability. So it seems, just like us, the Western Pygmy Possum love a good snooze! Further reading
By Diana Prada PhD Candidate School of Veterinary and Life Sciences Murdoch University [email protected] Bats are amazing creatures as they are the only mammals capable of true flight. Unlike flying foxes, microbats eat only insects and use echolocation to find their prey and navigate their surroundings. They emit a high-frequency call, listen for the echo and depending on how quickly they hear it back; they can tell the distance to objects. The fact that they are small, nocturnal and, most of their calls are non-audible to the human ear, make them secretive, and easily missed. These may be some of the reasons many people are unaware that we have these creatures living in the forest and cities of the South West of Western Australia. I am bat obsessed. I have been studying microbats for the last couple of years. I often find myself looking for them in the summer evenings. Dusk is prime bat time. There are 13 species of microbats in the South West Botanical Province, my region of interest. The southern forest bat (Vespadelus regulus) is the smallest of them all (top image). It weighs 5 gr, as much as an A4 piece of paper and his body hardly the length of a thumb. The white striped free-tail bat (Austronomus australis) is the largest at around 40gr (see image below), it is as long as an adult’s hand, it has white markings along the inside of its torso, and the "click, click" of its call can be easily heard at night. The most special of all bats in the region is the false western pipistrelle (Falsistrellus mackenziei) (image at end of blog). This species is unique as it is only found in the Jarrah forest of the South West of WA, and it weighs about 20gr. As remarkable as they are, we know very little about microbats of the South West of WA. Since they are capable of flight, we assume that they can cover long distances. However, we do not know this for sure. We also do not know whether females and males disperse at equal rates and we hardly know of health conditions that may affect their persistence. I am using DNA based technologies to address these questions. By looking at different parts of their genetic make-up, and comparing different populations, there is a lot we can tell about bats. We can determine whether the lack of natural vegetation is interfering with their capacity to travel between forest patches or whether they prefer to find a mating partner within their region or further afield. For those interested in spotting bats, you can look for them near dams or lakes. At times, you may see them hunting insects near street lights. Near Perth, Dwellingup and Dryandra are great places for bat spotting. In Dwellingup, bats can be easily seen flying between the lights in the town's private campground, and in Dryandra you will need to stand by one of their many dams. If you are lucky, you may even be able to see a numbat during the daytime. Further reading:
Note - All photos in this article belong to Diana Prada Australia is blessed with both an incredible terrestrial environment and a beautiful marine environment. One of the biggest (quite literally) tourist attractions in Western Australia is the opportunity to swim with whale sharks (Rhincodon typus) off the Ningaloo coast in Exmouth and Coral Bay. These magnificent creatures can reach a total length greater than 12 m (reports of up to 18 m), making them the worlds largest extant fish. Despite its immense size the species predominantly feeds on some of the smallest organisms in existence, plankton. The species is currently listed as Endangered (IUCN Redlist) and while protected in many parts of the globe, it is still hunted for its meat, fins for shark fin soup and oils (including for fish oil!).
Thankfully for us in Australia the species resides year-round in Ningaloo, with yearly congregations coinciding with coral spawning causing a boom in numbers between March and September. This is the peak tourist season for swimming with the whale sharks! We had the pleasure of undertaking one of these tours in 2017 with Coral Bay Eco Tours in which we managed to swim with not one, but two whale sharks (the picture at the top of the article is one we had the pleasure of taking during our swim). The tour was run exceptionally well and although they want everyone to get the best experience (which we did!), the welfare of the animals comes first. All swimmers were advised of required distances to remain from the animal prior to each swim and the tour guides and camera crew in the water with us ensured these were adhered to. I would highly recommend this tour and this company and can't wait to revisit again some day soon. Now how can swimming with the whale sharks benefit the species? Well aside from the obvious economical benefit from tourism - meaning the area and the species is more likely to be protected, photos taken by everyday people on these tours are also being used to help further understand these creatures. The whale shark citizen science project allows anyone, any where in the world, to upload photos of their encounters with whale sharks. Researchers then use technology similar to technology which studies the stars in the night sky, to identify individual whale sharks and store them into the database. Through being able to identify each individual through its unique patterning, researchers are able to unlock some of the secrets of the whale shark, such as habitat use, migration, growth rates etc. If you have had the pleasure of seeing a whale shark in the wild and managed to grab a photo alongside it, why not head over and submit your photo now to do your part in helping conserve these amazing creatures! Did you know? Although not as common in Australian waters, the second largest fish in the world, the basking shark, also adopts the method of filter feeding! Within Australian, it would be rare to find someone who does not know of the Wedge-tailed eagle, and rightly so with it being Australia's largest bird of prey. However, jump down just one spot to the second largest bird of prey that shares the skies above our great country and many people are unaware of this species, the White-bellied sea eagle, Haliaeetus leucogaster. The species is a large raptor that can reach up to 4.2 kg for females and 3.7 kg for males with a wingspan up to 220 cm. The plumage of the adult birds is largely white and grey with the head, breast and belly being white (hence the name). Juveniles differ quite markedly from the adults, with more mixed patterning of brown and cream plumage on the underside (see image of a juvenile below - taken on Faure Island, Western Australia). The juveniles colouration gradually transitions until they acquire the full adult plumage usually by their fourth year.
The White-bellied sea eagle is widespread around Australia (generally located not far from the coast) but is not without threats. The species is listed on the Marine species list under the EPBC Act, Vulnerable in New South Wales and Tasmania, Threatened in Victoria, and Endangered in South Australia. Threats present for the White-bellied sea eagle include indirect/secondary poisoning, shooting, wind turbine collisions and electrocution, competition with the Wedge-tailed eagle, & degrading water quality in inland waterways, however, the two major threats for the species are loss of habitat, and disturbance of nesting pairs through human activity. A study published in 2011 by Dennis et al. explored the potential impacts of humans on the nesting success of White-bellied sea eagles. Territories were assigned categories based on the disturbance levels, with productivity data (e.g. eggs produced, young fledged, nesting failures) assessed between the various categories of disturbance. Territories that were rated as high-disturbance produced less eggs than those in low-disturbance areas, 65% active compared to 79% respectively. Of these active nests success rates were also alarmingly different, with only 54% of active nests in high-disturbance areas being successful, compared to 87% within the low-disturbance areas. The frequency of this success also varied with high-disturbance areas only being successful every 2.9 years compared to every 1.5 years in low-disturbance areas. Several management recommendations have been published in various reports, including the protection of habitat on public land, identifying nesting sites prior to development including clearing of land or forestry operations, identifying human causes of breeding failure and implementing mitigation against these, further research into the diet of the species due to the potential for heavy metal accumulation, and implementing buffer zones for nesting sites. As individuals we can also take steps to minimise our impact, by following ethical guidelines set out by Birdlife Australia - see excerpt below. "... ‘nesting birds’ is defined as the period from the start of nest building, through egg-laying, incubation and rearing of the chicks until the last young bird in a nest has fledged. A fledgling (whether it be an atricial or precocial chick – these terms are described elsewhere) is described as any young bird that has left the nest permanently.Photographers MUST keep an appropriate distance from nesting birds. Nesting is the most critical and stressful time in a bird's life. It is vitally important that photographers keep an appropriate distance from nesting birds so as to ensure that they do not: - accidentally, or deliberately, cause damage to the nest or nest site; - cause nest desertion or stress to the nesting adults or nestlings; - attract predators to the nest site; and/or - remain at a distance from the nest site, which elicits a behavioural response from the nesting bird(s) - such as ‘broken wing’ response or the nesting bird not returning immediately to the nest." Further reading
The largetooth sawfish (Pristis pristis) can be found across the globe, and consists of four separate sub populations; the Western Atlantic, Eastern Atlantic, Eastern Pacific, and Indo-West Pacific (including northern Australia – spanning the Kimberley to Cape York Peninsula). The species was once considered common across many of these sub populations but has unfortunately undergone drastic population reductions. The largetooth sawfish is now thought to be locally extinct in many regions, and as such is listed as Critically Endangered under the IUCN Red List. The Kimberley region in north-Western Australia represents one of the last intact nurseries for the largetooth sawfish, however even within Australia the species is threatened and listed as Vulnerable under Australia's EPBC Act.
The species is biologically fascinating, both in appearance, due to its large rostrum (averaging between 17 and 24 teeth per side) which is used for predation and defence, and also in its ability to tolerate a wide range of salinities (euryhaline). The largetooth sawfish will spend the first three to four years of its life within freshwater systems growing to a length of approximately 3-4m, before then migrating into the estuarine and marine environments where they reach over 6m in length as an adult. Within the freshwater systems, the diet of the largetooth sawfish consists primarily of species found in the lower water column or benthic environment, such as the blue-catfish (Neoarius graeffei), and detritus. Recent research has furthered the understanding of habitat utilisation of the largetooth sawfish in the Fitzroy River (Whitty et al., 2009, 2017; Gleiss et al., 2017). Although key findings for the species were identified, such as habitat partitioning between age cohorts in the lower and tidal reaches of the river (Whitty et al., 2009), patterns of depth migration and thermal stratification of pools (Gleiss et al., 2017), recommendations for future research were made such as the collection of comprehensive fine-scale temperature data to further understand thermoregulatory behaviour and vertical migrations by largetooth sawfish. A great deal of work is still required to understand how this fascinating species and the Fitzroy system will respond to changes arising from climate change and water use in the catchment. Fun Facts!
Further reading
|
AuthorMy name is Garry and I am extremely passionate about the environment. I have completed my BSc. Conservation and Wildlife Biology with First Class Honours and have worked in the Environment sector since 2009. Archives
September 2019
Categories |
Photos used under Creative Commons from sean.kelleher1, BioDivLibrary, BioDivLibrary