Guestblog: Environmental DNA allows for the detection of cryptic seahorse species

I’m very proud to publish this guestblog by Georgia Nester. Georgia is a PhD-candidate at Curtin University, where she focuses on the use of environmental DNA on species that are otherwise hard to study. She has just published her first paper, which could be a game changer on how we detect and study seahorses and their relatives in the future.


Seahorses (members of the Syngnathidae family) have never been detected using environmental DNA (eDNA), despite the fact that globally there are 14 species classified as “Threatened” by the IUCN. We compared the ability to detect a wide range of fish including Syngnathidae of two existing fish metabarcoding assays (= methods to detect eDNA and two new fish metabarcoding assays which we developed. With our new assays, we detected three Syngnathidae species in eDNA survey of the Perth metropolitan area (Western Australia), while the existing assays did not detect any Syngnathidae. These detections include the seahorse species Hippocampus subelongatus and Hippocampus breviceps, which represents the first time a seahorse has been detected using eDNA.

 

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The West Australian Seahorse (Hippocampus subelongatus). Photo credit: Maarten De Brauwer

With increasing human pressures and climate change resulting in a continuous decline of global biodiversity, there is a growing demand for rapid and sensitive conservation and monitoring programs. Using traditional methods, accurate data on species presence/absence and distribution is often difficult to obtain in aquatic environments. Environmental DNA metabarcoding is an increasingly popular solution. eDNA metabarcoding is capable of revealing what species are present in an environment by detecting traces of DNA they leave behind in the environment (e.g. shed skin cells, scales, blood, faeces etc). While eDNA metabarcoding surveys have been applied to a wide range of aquatic environments, no one has reported the detection of a seahorse to the best of our knowledge.

Many Syngnathidae species are considered threatened, however many more species (over 30%) lack the data necessary to assess their extinction risk. With the risk of a ‘silent extinction’ for many Syngnathidae species, the design of a non-invasive method for monitoring and managing these cryptic species may be critical to their survival. False negatives (failure to detect a species when they are in fact present) are significant in conservation management. For this reason, we aimed to determine if the Syngnathidae family (seahorses, seadragons and pipefish) were being inadvertently missed in current eDNA surveys.

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Camouflaged species such as the shorthead seahorse (Hippocampus breviceps) can be hard to detect with the naked eye. Photo credit: Maarten De Brauwer

Australia is home to 128 species of Syngnathidae in 40 genera, 65 of which are found in Western Australian waters. The Perth metropolitan area in Western Australia was chosen as our study site as it encompasses several habitat types, including brackish and salt water. We sampled from five locations across the Perth metropolitan area and processed the samples back at the TrEnD Laboratory in Curtin University. The results of this study have recently been published in the scientific journal environmental DNA.

In total, we detected four species of Syngnathidae using our newly developed metabarcoding assays “16S_FishSyn_Short” and “16S_FishSyn_Long”. The Syngnathidae species we detected were the Western Australian seahorse (Hippocampus subelongatus), the shorthead seahorse (Hippocampus breviceps), the spotted pipefish (Stigmatopora argus) and the tiger pipefish (Filicampus tigris). With Syngnathidae populations declining due to exploitation for the aquarium trade and habitat degradation, we have shown that eDNA methodologies are capable of detecting Syngnathidae taxa in the environment. This will help inform conservation and management strategies by providing a much-needed non-invasive method for monitoring these populations. Importantly, our study represents the first time a seahorse species has been detected using eDNA methodologies.

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The Western Australia seahorse (Hippocampus subelongatus, one of the first seahorse species to be detected with eDNA. Photo credit: David Harasti

Does climate change create damsels in distress? – Guestblog by Tanika Shalders

TanikaThe latest guestblog on Critter Research is by Tanika Shalders. Tanika is a Technical Officer for the Marine Science Program at the Department of Biodiversity, Conservation, and Attractions in Australia. Her current work entails diving on some of the most amazing reefs in Australia and video analyses of surveys in Australian marine parks. In this guestblog she describes her recently published research on the effects of climate change on damselfishes.


It is currently spring in Australia, a lovely time to be outdoors. Nice temperatures (average maximum of 22), plants in full bloom, perfect picnic weather… just find a nice patch of grass, a cold beverage and some snacks.

Heatwave dogSummer is just around the corner and here in Perth it can get very warm, with an average maximum of 31 degrees (although temperatures up to 40 degrees are not unheard of). Unfortunately, picnics are not as pleasant this time of year. It’s hard to find shade, you’ll likely get sunburnt and your drinks will get warm.

What do you do when the temperatures become unbearable? Head to the coast to cool off in the ocean? Hide in the air-conditioning? Increase your ice-cream consumption? We try to make ourselves as comfortable as possible, moving to a cooler environment where we have everything we need – food, water and shelter.

With this in mind, it is no surprise to learn that other animals are doing exactly the same thing when ocean temperatures rise. Over the past 5 decades ocean temperatures have been increasing due to climate change. There has also been an increase in heat waves.

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Heat waves are becoming increasingly common across the world

Many people connect these events to coral reefs, so it may come to some surprise that the ocean in temperate (southern/cool-water) Australia is warming at least twice as fast than the global average.

In 2011, the south-west of Australia experienced a heat wave. The heat wave lasted more than 10 weeks and temperatures increased up to 5 degrees above normal. This event caused massive changes to the marine environment of south-west Australia. One of the most significant documented impacts was the loss of kelp along the south-west coast. In the warmest area (north) kelp disappeared completely. Changes have also been seen in other organisms such as fish and crustaceans.

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Ecklonia radiata, the kelp species which was greatly affected by the 2011 heatwave. Source: foragersyear.wordpress.com

After the heat wave, we decided to investigate if fish had also been impacted by the extreme temperatures. We chose to look at territorial damselfish since they are ‘site attached’. Much like the Hobbits of Middle Earth, they don’t like to leave home. These damselfish farm and protect algae which they use for food and reproduction. This trait makes them a good species to indicate of change as it is unlikely individual fish will move from their home to a new location. However, juvenile fish (recruits) may set up camp in new locations.

Using diver operated stereo-video (DOV), we investigated where these damselfish lived before and after the 2011 heat wave, and how many there were.

Damselfishes

The damselfishes in this study. A) Parma occidentalis; B) Pomacentrus milleri; C) Parma mccullochi; D) Parma victoriae. Sources: Fishbase and Reef Life Survey

The main result was that the two (northern) warm-water damselfish became more common in the (southern) cooler waters. The two cooler-water damselfish showed less change.

We also saw a change in algae habitat. The kelp that dominated in 2006 had often been replaced by smaller forms of algae by 2015. This included the turfing algae such as those farmed by the damselfish.

So what does this mean?

These results show that both fish and their habitat are changing due to climate change. When warm water fish move to cooler water, they might push out the local cool water fish on their way south.

This process of warm water fish moving into cooler environments is known to the science world as tropicalisation – previously explained in a guest blog by the wonderful Dr Joseph DiBattista so I won’t go into detail here. Instead I will delve into one of the flow-on effects of tropicalisation: increased competition.

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Tanika collecting Diver Operated stereo-Video (DOV) footage. Photo: Will Robbins, DBCA

Competition happens everywhere in the natural world. Plants compete for sunlight, lions compete for antelopes, and high school boys compete for the same girl. Usually competition occurs over food, water, shelter, or booty. Any additional players entering such a highly competitive environment can have devastating effects.

The movement of warm water fish into cooler waters could increase competition for the local fish populations. Since these damsels eat the same food and are very territorial, this means they not only have to compete with each other, but also with new damsel species. It’s hard enough to compete with your siblings for the last helping of dinner – imagine having to compete with your whole street!

Often this means that the local species will have retreat from an area once the invading species starts competing with them for food. Fortunately in this case, it looks like the change in habitat meant there was more food for the damselfish. It is likely that this helped to support a larger number of damselfish by reducing competition.

Most people are starting to become aware that climate change is an issue, sadly it’s a much bigger problem than most believe. Scientists are just being to scratch the surface of understanding the full reach of its impacts. If you would like to learn more about climate change and what you can do to help, please visit this site to find out more.

 

Tanika Shalders

Technical Officer, Marine Science Program

Department of Biodiversity, Conservation and Attractions

Twitter: @TanikaCShalders

Instagram: tanikacs

Research Gate: Tanika Shalders

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Climate change might increase competition in the oceans. Photo Will Robbins, DBCA

Guestblog: Frogfish history

IMG_0737This is the second guestblog by Daniel Geary, resident marine biologist  and frogfish-enthusiast at Atmosphere Resort in Dauin, Philippines. You can read his first blog here. In this new guestblog Daniel explores the history of frogfish research and provides an introduction to a few common and not-so-common frogfish species.


There are many places across the globe where divers can see frogfish, but the Philippines (especially the Dauin area) is one of the best frogfish destinations of them all. I have personally seen thirteen species in this country, including 11 species here in Dauin. Sometimes we will see over 30 individuals on a single dive! It is not uncommon for some of the frogfish to stay on the same site for over a year, especially Giant Frogfish. Another great destination for frogfish is Indonesia, especially Lembeh, Ambon, and also some places in Komodo. Generally, if there is good muck diving, there is good potential for frogfish action. Australia also has some unique frogfish species, as well as the Caribbean, where there are a few places with reliable frogfish sightings.

Although frogfish are relatively well known critters to divers in the Indo-Pacific, this has not always been the case. Stories of frogfish and their accompanying drawings and sketches have existed for hundreds of years, with encounters spanning the globe. The first ever documented frogfish comes from Brazil. At some point before 1630, a drawing was given to the director of the Dutch West India Company. A woodcut was made from this drawing, and that woodcut was published in 1633. The first color drawing appeared in 1719, published by Louis Renard, an agent to King George I of England. He published a collection of color drawings of Indo-Pacific fish and other organisms and some of these represent the earliest published figures of Indo-Pacific frogfish. One was called Sambia or Loop-visch which translates directly to “walking fish.”

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First colour drawing of a frogfish – Louis Renard 1719

Albertus Seba and Philibert Commerson were two important scientists in the 1700s when it comes to frogfish. Seba believed frogfish were amphibians and tried very hard -incorrectly of course – to prove that they were the link between tadpoles and frogs, although anyone who has seen a baby frogfish knows this to be false. Even though he incorrectly identified a few nudibranchs as juvenile frogfish, he was still able to identify two species, the Hairy Frogfish (Antennarius striatus) and the Sargassumfish (Histrio histrio) during his studies. Commerson was the first scientist to focus solely on frogfish. He was a botanist and naturalist employed by the King of France and he described three species from Mauritius (Painted Frogfish – Antennarius pictus, Giant frogfish – Antennarius commerson, Hairy Frogfish – Antennarius striatus).

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Commerson’s drawing of the hairy frogfish – Antennarius striatus

There have been plenty of identification problems when it comes to frogfish, even today.  Frogfish colorations and patterns are highly variable, so it is nice to know people have been struggling with frogfish identification for hundreds of years. Albert Gunther, a scientist who attempted describe the different species of frogfish, said in 1861 that “[their] variability is so great, that scarcely two specimens will be found which are exactly alike…although I have not the slightest doubt that more than one-half of [the species] will prove to be individual varieties”. He listed over 30 species, but only 9 of those species are still accepted today. Since 1758 there have been over 165 species described and over 350 combinations of names. Currently there are around 50 accepted species, roughly one third of the total species described.

FROGFISH SPECIES PROFILES

Painted Frogfish – Antennarius pictus

This is the most abundant frogfish species in the Indo-Pacific. They can be identified by having 3 distinctive spots on their tail. They prefer to live near sponges, rocks, ropes, mooring blocks, and car tires. They can grow to a maximum size of around 15 cm.

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Painted frogfish (Antennarius pictus) with its typical three tail spots

Sargassumfish – Histrio histrio

This is the species with the largest distribution. They can be found in floating seaweed or debris as well as anchored seaweed and other marine plants. They can reach a maximum size of around 15 cm and are often sold in the marine aquarium trade.

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Sargassumfish (Histrio histrio), a surprisingly good swimmer that lives on floating seaweed

Psychedelic Frogfish – Histiophryne psychedelica

This is one of the rarest frogfish species. They are only found in Ambon, Indonesia at a handful of dive sites, usually at around 2-3m hidden in rock crevices or in coral rubble.

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“Snooted” picture of a psychedelic frogfish (Histiophryne psychedelica)

Giant Frogfish – Antennarius commerson

This is the biggest frogfish species, reaching lengths of more than 40 cm. They prefer to live on sponges and have two large spots on their tail, as well as lines coming from the eye and enlarged dorsal spines.

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Giant frogfish (Antennarius commerson) resting on a sponge. Note the two tail spots

Ocellated Frogfish – Nudiantennarius subteres

This frogfish species is the “newest” frogfish species. Originally thought to be a new species, it turns out this species is the previously described, relatively unknown “Deepwater Frogfish”, although the lure is incorrect in the original drawing. It was thought that the adults lived deep and only the juveniles were found in the shallows, but  adult mating pairs of this species have been seen at less than 10m depth. They grow to around 5 cm.

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Typical coloration of the Ocellated frogfish (Nudiantennarius subteres)

Guestblog: Frogblogging – insights in the world of frogfishes

IMG_0737This month’s guestblog is written by Daniel Geary, the resident marine biologist at Atmosphere Resort in Dauin, Philippines. It’s safe to say that Daniel is very passionate AND knowledgeable about frogfishes. He’s been studying them for years in Dauin and even wrote (and teaches) a PADI speciality course on these awesome critters! In this blog he gives a taste of some of the many ways frogfish are fantastic and deserve a closer look.


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Longlure frogfish (Antennarius multiocellatus) from Florida

Frogfish. You have probably heard of them, and if you’re a diver you might have seen one or two before. You have definitely swam right past a few of them without knowing they were there. Although most of them have a face only a mother could love, behind this outer layer exists a well-adapted, expert fisherman with amazing camouflage capabilities. They are more than just a lazy, camouflaged blob that sometimes doesn’t change location for a year.

Frogfish are anglerfish, although they are what I call a shallow, less ugly version of anglerfish. They have a rod and a lure that they actively fish with when necessary. Their fins look like limbs that somewhat resemble those of a frog. They must inhale water though their mouth to then push it out of their gills which aids in locomotion. Frogfish are experts at changing color and can change color multiple times, usually to blend in with their surroundings. Normally a full color change takes about 2 weeks, but frogfish have been witnessed to change color in under ten seconds when disturbed by divers’ bubbles and needing to switch to a different coral.

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The same giant frogfish (Antennarius commersoni) changing colour in two weeks

There are around 50 species of frogfish, with a new species or two being described every few years. Frogfish can be found worldwide in tropical and subtropical waters (but not in the Mediterranean). Some species are only found at a handful of dive sites, others are only found in one country or continent. A handful of species are found in the majority of the warm water areas, but only the Sargassumfish is found worldwide. There have been a few occasions where Sargassumfish were found all the way up in the cold waters of Norway and Rhode Island – way out of their preferred habitat, but they live their lives floating in seaweed and/or other debris and are at the mercy of the ocean currents.

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Sargassum frogfish (Histrio histrio) often wash up on the shore of the Atmosphere housereef, when they do, they get released back into deeper water

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Painted frogfish (Antennarius pictus) using its lure to attract prey

Frogfish are ambush predators which is why they seem to be so lazy. The less they move, the better predators they can become due to algae, coral polyps, and any other organisms that use the frogfish as habitat. I call this being lazily efficient, or efficiently lazy. Frogfish will make minimal adjustments to their body positioning before they begin to lure prey, although sometimes the frogfish are so camouflaged that they don’t need to actively attract prey. Frogfish swallow their prey whole by opening their mouth and creating an instant vacuum since the volume of the mouth increases up to twelve times the original amount. This means frogfish can swallow their prey whole in six milliseconds. They feed on a variety of organisms, depending on where the frogfish lives. Generally they like small fish like cardinalfish, shrimps and crabs, and sometimes other frogfish. They can comfortably swallow prey that is their own size, and with a bit of effort they can swallow prey up to twice their size, although this can result in the death of the frogfish if the prey item is too large and gets stuck in their throat. Frogfish do not have many predators, but they are sometimes preyed on by moray eels, triggerfish, and lizardfish. Flounder will sometimes suck up juveniles from the sand and fishermen in the Philippines have been known to capture and eat Giant Frogfish.

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This giant frogfish (Antennarius commersoni) bit of more than it could chew and did not live to tell the tale. Photo taken at Apo Island

 

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Frogfish egg raft

Frogfish have been known to eat each other if they get too close, especially after failed mating attempts. A male will approach a female when she is bloated with eggs. He will do his best to show off for her, which includes expanding his fins to their maximum sizes, rapidly opening and closing his mouth, as well as violently shaking his body. At this point, the female either accepts him or tries to eat him. If accepted, he gets to stand next to the female, which is the frogfish equivalent of holding hands. Once he is ready to mate, he will start again with his flashy moves, but this time bouncing around the female. Sometimes he has to physically swim her off the substrate to mate, other times she is able to swim on her own. Once they are a meter or two above the substrate, the female releases her egg raft, causing her to spin rapidly. The male then fertilizes this egg raft, also spinning rapidly. Both the frogfish then return to the bottom as the eggs float off into the distance. The eggs will hatch a few days later and become tiny planktonic frogfish babies, which will continue to float for a month or two until they are big enough to settle in the substrate, change color, and begin their lives as adorable frogfish.

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A male (red) painted frogfish (Antennarius pictus) trying to convince the female (yellow) to mate

Stay tuned for more frogfish insights coming in December, where I’ll write about the history of frogfish research and describe a handful of frogfish species, including a potentially “new” species. Until then, keep an eye for frogfish on all your dives, especially if you’re in warm water.