Blog

A new study provides a rare glimpse into the natural history of some extraordinary Chrysomelinae beetle species in Central and South America

Hidden in the thick foliage of tropical forests a subfamily of colorful beetles hides the secrets of the earliest stages of social behavior, showing explicit signs of maternal instincts and care. An international team of scientists from the Smithsonian Tropical Research Institute, Centro Universitário de Lavras, Staatliches Museum für Naturkunde Karlsruhe, and Université libre de Bruxelles looked into the complex subsocial behaviors present in the extraordinary Chrysomelinae subfamily to discover and describe in detail the different degrees of maternal instincts present within 8 species. The exciting insight into the biology of these species was published in the 4th “Research on Chrysomelidae” special issue of the open access journal Zookeys, alongside 6 other research articles on the family.

Within the leaf beetles, maternal care of offspring is found in just two of 15 subfamilies, the broad-shouldered leaf beetles (Chrysomelinae) and the tortoise beetles (Cassidinae), groups possibly more vulnerable to predators and parasitoids due to slow-moving and exposed immature stages. The study of subsocial behavior, additional to its intrinsic appeal, may offer a perspective on selective forces at work during the earliest stages of insect social evolution.

Complex subsocial behavior was observed in pairs of one of the species studied, D. paykulli, interacting aggressively on newly expanded leaves. Whether these were contests over resources or precopulatory courtship is unclear, however, analysis of video taken of one of these interactions shows the use of the mesosternal horn in dislodging a competitor. Adult females were discovered during mid-May in close proximity to eggs attached to the cupped apical leaves.

Observations of additional species associated with a different family of plants, the Solananceae, suggest that mothers modify leaf resources in advance of bearing live offspring, and later block and herd movement of larvae among leaves on the same food plant. An adult was also recorded following a tightly arranged group of larvae moving between leaves on their food plant. Mothers at times tightly straddled their aggregated first and second instar larvae on the natal leaf, preventing their advance down the leaf petiole.

While guarding, mothers reacted aggressively by charging to the edge of the leaf when a thin stick was introduced to the area by an observer. Charges, stamping and shaking continued for a short period of time after the stimulus was removed. The strongest reaction was given to a camera held approximately 10 cm under and to the side of the natal leaf.

Observations and field studies find evidence that mothers actively defend offspring in at least eight species and three genera of Neotropical Chrysomelinae tightly associated with two host plant families. Reports on the three Doryphora species that feed on vines in the dogbane family, Apocyanaceae, reveal that mothers defend eggs and larvae by straddling, blocking access at the petiole and greeting potential predators with leaf-shaking and jerky advances. A less aggressive form of maternal care is found in two Platyphora and four Proseicela species associated with shrubs and small trees in the nightshade family Solanaceae.

“Large voids remain in our understanding of the natural history of both groups, including the identity and importance of predators and parasitoids and the diverse ways in which mothers may be influencing the survival of offspring.”, comments Dr. Windsor, one of the authors of the study. “We urge continued study of these magnificent insects, their enemies and their defenses, both behavioral and chemical, especially in forests along the eastern versant of the Central and South American cordillera.”

Original Source:

Windsor DM, Dury GJ, Frieiro-Costa FA, Lanckowsky S, Pasteels JM (2013) Subsocial Neotropical Doryphorini (Chrysomelidae, Chrysomelinae): new observations on behavior, host plants and systematics. In: Jolivet P, Santiago-Blay J, Schmitt M (Eds) Research on Chrysomelidae 4. ZooKeys 332: 71-93. doi: 10.3897/zookeys.332.5199

A recent paper published in the open access journal Zookeys provides a first-time glimpse in the natural history of the enigmatic spider species Progradungula otwayensis. Lurking in the hollows of old myrtle beech trees and thus hard to collect, this extraordinary spider is an endemic species confined strictly to the beautiful Great Otway National Park (Victoria, Australia).

P. otwayensis belongs to the small spider family Gradungulidae which consists of seven genera with a total of 16 described species found exclusively in eastern Australia and New Zealand. The genus Progradungula to which the species studied here belongs is among the few cribellate ones in the family. This term refers to the cribellum, a web producing organ which, unlike normal spinnerets, produces extremely fine fibers which are combed out by the calamistrum, producing silk with a wooly texture. The fibers are so small in diameter that prey insects easily become entangled in them, without any glue needed.

To add to its mystery P. otwayensis weaves highly stereotyped ladder-shaped webs, where they stand facing down after sunset, waiting for preys which will be caught by using the ladder as a trap – a behavior which was already described in detail by now retired arachnologist Mike Gray (Australian Museum) for the only known other species of this genus, P. carraensis. A single thick and shiny silk thread is then used by the spiders to provide a zip-line like connection between the external webs and the security of the enigmatic retreat in the hollows of ancient myrtle beech and mountain ash tree.

“On one occasion, we had access to a large hollow mountain ash tree and found catching ladders and supporting webs of juveniles inside of it.”, comments the lead author of the study Peter Michalik, Zoological Institute and Museum of the University of Greifswald (Germany), about the unusual bit of luck to have a glimpse into the secluded retreats of the spiders.

Martín Ramírez, from the Argentinian Museum of Natural History and co-author of the study, commented on the habitat specificity of this species, “confined to the oldest and extensively hollow myrtle beech trees in the humid forests in the western part of the Great Otway National Park, or in mountain ash trees, upon which the myrtle trees depend,” thus making an important case for the conservation of such habitats.

The unusual living habits and high degree of endemicity makes this spider a rare and remarkable species. The new study suggests that this spider is dependant on the microclimate in the hollows of old myrtle beech trees since other hollow trees were very much less inhabited and to some extent explains the confinement of the species distribution range.

Original Source:

Michalik P, Piacentini L, Lipke E, Ramírez MJ (2013) The enigmatic Otway odd-clawed spider (Progradungula otwayensis Milledge, 1997, Gradungulidae, Araneae): Natural history, first description of the female and micro-computed tomography of the male palpal organ. ZooKeys 335: 101-112. doi: 10.3897/zookeys.335.6030

Three new species of tiny frogs from Papua New Guinea are described in the latest issue of Zookeys. Dr. Fred Kraus, University of Michigan, who in 2011 in Zookeys described the world’s smallest frogs Paedophryne dekot and Paedophryne verrucosa, now adds another 3 species from the genus Oreophryne to the remarkable diversity of this region.

The three new species Oreophryne cameroni, Oreophryne parkopanorum and Oreophryne gagneorum are all rather minute, with total body lengths of around 20 mm. These tiny frogs, however are still substantially larger than the species that claimed the smallest frog prize in 2011. Paedophryne dekot and Paedophryne verrucosa are only half of the length of the three new additions to the frog diversity of Papua New Guinea, with an astonishingly small body size ranging between 8-9 mm.

The subfamily to which the new species belong is largely restricted to New Guinea and its satellite islands. Of the constituent genera, Oreophryne is presently one of the largest within the Papuan Region.

“Although the description of the new species treated herein now brings to seven the number of Oreophryne species reported from the north-coast region of New Guinea, the presence from these areas of additional specimens of uncertain identity suggests that additional species likely await description.”, explains Dr. Kraus about the diversity of the genus within the region. “I have at least a dozen more new Oreophryne species remaining to be described from this region, and large portions of this terrane system remain unsurveyed.”

Original Source:

Kraus F (2013) Three new species of Oreophryne (Anura, Microhylidae) from Papua New Guinea. ZooKeys 333: 75. doi: 10.3897/zookeys.333.5795

The Biodiversity Data Journal (BDJ) and the associated Pensoft Writing Tool (PWT), launched on 16th of September 2013, offer several innovations – some of them unique – at every stage of the publishing process. The workflow allows for authoring, peer-review and dissemination to take place within the same online, collaborative platform.

Open access to content and data is quickly becoming the prevailing model in academic publishing, resulting in part from changes to policies of governments and funding agencies and in part from scientist’s desire to get their work more widely read and used. Open access benefits scientists with greater dissemination and citation of their work, and provides society as a whole access to the latest research.

To publish effectively in open access, it is not sufficient simply to provide PDF files online. It is crucial to put them under a reuse-friendly license and to implement technologies that allow machine-readable content and data to be harvested by computers that can collate small scattered data into a big pool. Analyses and modelling of community-owned big data are the only way to confront environmental challenges to society, such as climate change, ecosystems destruction, biodiversity loss and others.

Manuscripts are not submitted to BDJ in the usual way, as word processor files, but are written in the online, collaborative Pensoft Writing Tool (PWT), that provides a set of pre-defined, but flexible article templates. Authors may work on a manuscript and invite external contributors, such as mentors, potential reviewers, linguistic and copy editors, and colleagues, who may read and comment on the text before submission. When a manuscript is completed, it is submitted to the journal with a simple click of a button. The tool also allows automated import of manuscripts from data management platforms, such as Scratchpads.

“This is the first workflow ever to support the full life cycle of a manuscript, from initial drafting through submission, community peer-review, publication and dissemination within a single, online, collaborative platform. By publishing papers in all branches of biodiversity science, including novel article types, such as data papers and software descriptions, BDJ becomes a gateway for either large or small data into the emerging world of “big data”.”, said Prof. Lyubomir Penev, managing director and founder of Pensoft Publishers.

BDJ shortens the distance between “narrative (text)” and “data” publishing. Many data types, such as species occurrences, checklists, measurements and others, are converted into text from spreadsheets into a human-readable format. Conversely text from an article can be downloaded as structured data or harvested by computers for further use.

A novel community-based peer-review provides the opportunity for a large number of specialists in the field to review a manuscript. Authors may also opt for an entirely public peer-review process. Reviewers may opt to be anonymous or to disclose their names. Editors no longer need to check different reviewers’ and author’s versions of a manuscript because all versions can be consolidated into a single online document, again at the click of a button.

“The Biodiversity Data Journal is not just a journal, not even a data journal in the conventional sense. It is a completely novel workflow and infrastructure to mobilise, review, publish, store, disseminate, make interoperable, collate and re-use data through the act of scholarly publishing!” concluded Dr Vincent Smith from the Natural History Museum in London, the journal’s Editor-in-Chief.

The platform has been designed by Pensoft Publishers and was funded in part by the European Union’s Seventh Framework Program (FP7) project ViBRANT.

Original Source:

Smith V, Georgiev T, Stoev P, Biserkov J, Miller J, Livermore L, Baker E, Mietchen D, Couvreur T, Mueller G, Dikow T, Helgen K, Frank J, Agosti D, Roberts D, Penev L (2013) Beyond dead trees: integrating the scientific process in the Biodiversity Data Journal. Biodiversity Data Journal 1: e995. DOI: 10.3897/BDJ.1.e995

A new special issue of the NeoBiota journal focuses on advancing risk assessment models to address climate change, economics and uncertainty

A new special issue of NeoBiota journal has been published, following the 2012 meeting of the International Pest Risk Mapping Workgroup (IPRMW). The workshop was sponsored by the OECD‘s Co-operative Research Program on Biological Resource Management for Sustainable Agricultural Systems, and focused on pest risks in the foodchain. The new issue addresses the interface between pest risk science and policy in an attempt to secure adequate pest control measures against potential invasions accompanying economic globalization and the intensified movement of people and goods.

With the intensification of trade, the potential for translocation of harmful pests, weeds, and pathogens capable of impacting our crops, livestock and natural resources also grows. A special IPRMW meeting was held in Tromsø, Norway from 23–26 July, 2012 to address this issue. The meeting was attended by 30 ecologists, economists, risk analysts and policy advisors from Australia, New Zealand, Canada, the United Kingdom, Finland, Norway, the Netherlands, Hungary, France, Italy, and the United States. “The conference succeeded in stimulating new ideas about how to incorporate climate change, invasion dynamics, economics, and uncertainty into pest risk models and maps for invasive alien species, and how to communicate these improved results to biosecurity policy advisors”, notes meeting convenor Dr. Rob Venette, United States Forest Service.

The new issue of NeoBiota contains 12 research articles and an editorial reflecting the major outcomes and findings following the IPRMW meeting. The articles focus on issues of interactions between pest risk and climate change, policy and economics. Also featured is research about pest control and surveillance as well as the issue of pest risk and uncertainty, which is a key to the correct implementation of scientific research by policymakers.

“Since its first meeting in 2007, the IPRMW has made significant advances in pest risk modelling and mapping methods.” explains Dr. Darren Kriticos, CSIRO, Australia. “The meeting in Tromsø continued this tradition, with significant advances in economic model integration, a new understanding of the irreducible uncertainties in climate change forecasts, and the desirability of an adaptive management framework for dealing with these uncertainties, as well as new methods for dealing with other forms of uncertainty. Clearly, more work needs to be done in the area of risk communication and the improvement of niche modelling methods to produce timely and reliable models.”, he adds.

Original Source:

Kriticos DJ, Venette RC, Baker RHA, Brunel S, Koch FH, Rafoss T, van der Werf W, Worner SP (2013) Invasive alien species in the food chain: Advancing risk assessment models to address climate change, economics and uncertainty. In: Kriticos DJ, Venette RC (Eds) Advancing risk assessment models to address climate change, economics and uncertainty. NeoBiota 18: 1–7. doi: 10.3897/neobiota.18.6108

Scientists discovered a new species of a peculiar cave-dwelling snail in one of the 20 deepest cave systems in the world, Lukina Jama–Trojama in Croatia. The newly discovered species belongs to a genus of minute air-breathing land snails that have lost visual orientation and are considered to be true eutroglobionts, or exclusive cave-dwellers. The study describing the new species was published in the open access journal Subterranean Biology.

The new species Zospeum tholussum is a miniature and fragile snail, with a beautifully shaped dome-like translucent shell. Only one living specimen was found during the expedition around the galleries of the Lukina Jama–Trojama cave system. The animal was found at the remarkable depth of 980 m, in an unnamed chamber full of rocks and sand and a small stream running through it.

All known species from the cave-dwelling genus Zospeum possess a limited ability to move. Their preference of a muddy habitat and the fact that they are usually located near the drainage system of the cave, in a close proximity to running water, however suggest that these animals are not exactly immobile. Scientists hypothesize that dispersal is achieved through passive transportation via water or larger mammals.

The Lukina Jama–Trojama is the deepest cave system in Croatia, extraordinary for its vertical shape, long pits and great depth of -1392 m. From an ecological point of view this cave system is extremely interesting for having three microclimatic layers: firstly entrance icy part with the temperature of about 1 °C, secondly, middle part with the temperature up to 2 °C and bottom part with temperature till 4 °C. These unusual living conditions make the cave extremely interesting for scientist from a biodiversity point of view.

Original Source:

Citation: Weigand AM (2013) New Zospeum species (Gastropoda, Ellobioidea, Carychiidae) from 980 m depth in the Lukina Jama–Trojama cave system (Velebit Mts., Croatia). Subterranean Biology 11: 45–53. doi: 10.3897/ subtbiol.11.5966

Metro Manila – the world’s 10th largest megacity and 6th largest conurbation, based on official statistics – is not a place one would normally expect to discover new species, even in a country that is known as a biodiversity hotspot.

In a 83-hectare green island amidst the unnatural ocean of countless man-made edifices, researchers of the Ateneo de Manila University have discovered a tiny new species of aquatic beetle, aptly named Hydraena ateneo. It was named after the University, a 154-year-old Jesuit-run institution that is recognized as one of the premier universities in the Philippines and in the region. The international open access scientific journal Zookeys has published the paper about the unusual discovery in its latest issue [329: 9 (2013)]. The publication of the fact is just timely, given that the university’s Department of Biology is celebrating its 50th anniversary this year.

During field training in November 2012, Biology students and a faculty member of the Department of Biology sampled small creeks, ponds, and pools in wooded areas within their sprawling university campus. The group found seven species of water beetles, of which one was a new record for the entire island of Luzon and another was Hydraena ateneo.

Arielle Vidal, at the time of the training enrolled in the Department’s B.S. Life Sciences program, says: “I was so amazed that there are new species even in the Ateneo Campus in the middle of Manila. Then I was sure that I wanted to write my thesis on a taxonomic topic.”, said Kimberly Go, her thesis partner, adds: “Then we pushed through and investigated a remote river catchment in Mindoro. We found several new species of the same genus there, too.”

Their thesis adviser and author of the recent paper, Associate Professor Dr. Hendrik Freitag, explains: “The Long-palped Water Beetles (genus Hydraena) are in fact one of the most overlooked and diverse genera of aquatic beetles. Only 14 species of this genus – all endemic – are known from the country by now, but many more wait to be named and described. All of them display these extremely enlarged palps of the maxilla. These are real mouthpart appendages and not the antennae. Those species that were found in the Ateneo campus must have re-colonized the area after the tree cover has re-established in the last 50 years and the small creeks began to flow again.”

Clister Pangantihon and Dr. Ronald Lagat, both facilitators of the “Philippine Aquatic Biodiversity Workshop” held at the Ateneo earlier this year confirm: “We found Hydraena ateneo also in the neighboring Province of Cavite during our workshop.” A few additional exemplars of the new species formerly collected in the Laguna Province were also detected among the copious collections of the Natural History Museum in Vienna, Austria, which houses the world’s largest scientific collection of water beetles.

The study has shown that small patches of semi-natural habitats amidst the densely populated and highly urbanized capital region can accommodate an astonishing assemblage of species. This will hopefully be an inducement to protect and extend such islands of urban biodiversity in the cities.

Nevertheless, this should not lead to the illusion that the ongoing dramatic loss of biodiversity in the Philippines can be reversed. A large proportion of endemic organisms are closely associated with primary forests. Therefore, it should be an ultimate priority for nature conservation to protect the last remaining rainforests in the country.

 

Original source:

Freitag H (2013) Hydraena (Hydraenopsis) ateneo, new species (Coleoptera, Hydraenidae) and other aquatic Polyphaga from a small habitat patch in a highly urbanized landscape of Metro Manila, Philippines ZooKeys 329: 9. doi: 10.3897/zookeys.329.5955

 

Additional Information:

The Ateneo researchers are also very thankful to the Natural History Museum of Vienna, Austria from where additional specimens were made accessible for this study.

Only a fraction of the biodiversity on the planet is known to scientists and exploration of new places and habitats continue to yield exciting discoveries and new species to describe by taxonomists. This task is becoming increasingly urgent as a function of the continuous overexploitation of natural resources and destruction of habitats. In fact, it has recently been estimated that it takes on average 21 years from the discovery of a species in nature to its formal scientific description. The ‘shelf life’ can sometimes be significantly longer, as for the millipede Ommatoiulus schubarti found in Spain in 1863 and just very recently described in 2012.

Illustrations constitute one of the fundamental bases of any taxonomic work, but they could often be misleading and generate problems of synonymy, the Achilles’ heel of descriptive taxonomy. Thus, the demand for improving the quality of images and methods of visualization of taxonomic traits has significantly increased in the course of time, catalysed by the recent development of open access publishing. Interactive media illustrating important differences between species have the potential to further accelerate taxonomic works.

A paper, published in the open access journal ZooKeys, provides a modern revision of 12 millipedes of genus Ommatoiulus. The authors present an innovative illustration technique that allows the integration of scanning electron microscope images into an interactive rotatable model (rSEM) to visualize complex morphological features. This allows the structure in question to be seen from multiple angles of view. The development of rSEM is widely accessible, requiring no more than available scanning electron microscope and a software for image integration (Flash, Java Script based programs, etc.). The new illustrating technique can be viewed here. On the other hand, authors present a highly visual identification key to serve species identification. The key design prioritizes the visual delivery of taxonomic information via interactive media including line drawings, photographs and scanning electron micrographs of the most informative taxonomic characters in the studied group.

“Differences between species are often subtle, and the pronouncedly “3D” nature of their anatomy makes recognition of the differences difficult. In many older papers dealing with millipedes, authors have illustrated the copulatory organs as isolated pieces which has led to not only “angle-of-view” problems, but also to difficulties of relating the various components spatially to each other. By using rSEM, we have overcome these problems.”, comments the lead author of the study Dr. Nesrine Akkari, Natural History Museum of Denmark.

The slow tempo of incorporating innovative methods in taxonomic research is very likely due to the perception that sophisticated imaging requires special software, e-infrastructure, and significant funding. The multimedia driven, interactive taxonomic paper by Akkari et al. demonstrates that much can be accomplished using accessible equipment and methodology.

Original Source:

Akkari N, Cheung DK-B, Enghoff H, Stoev P (2013) Revolving SEM images visualising 3D taxonomic characters: application to six species of the millipede genus Ommatoiulus Latzel, 1884, with description of seven new species and an interactive key to the Tunisian members of the genus (Diplopoda, Julida, Julidae). ZooKeys 328: 5. doi: 10.3897/zookeys.328.5763

 

See also:

Cheung DK-B, Brunke AJ, Akkari N, Souza CM, Pape T (2013) Rotational Scanning Electron Micrographs (rSEM): A novel and accessible tool to visualize and communicate complex morphology. ZooKeys 328: 47. doi: 10.3897/zookeys.328.5768

Stoev P, Penev L, Akkari N, Cheung DK-B, Enghoff H, Brunke A, de Souza CM, Pape T, Mietchen D, Erwin T (2013) Revolving images and multi-image keys open new horizons in descriptive taxonomy: ZooKeys working examples. ZooKeys 328: 1. doi: 10.3897/zookeys.328.6171

 

Contact:

Nesrine Akkari
Email: nakkari@snm.ku.dk ; nes.akkari@gmail.com
Tel: +45 35 32 10 01 (switchboard)

The tiny diamondback moth (scientific name: Plutella xylostella) gets its common name from the array of diamond shapes along the margin of its forewing. Despite their diminutive size, the caterpillars of the diamondback moth exert tremendous damage on many crops including cabbage, broccoli, and crucifers at large. More than $1 billion is spent globally each year in efforts to control damage by this moth, reflecting its amazing capacity to evolve resistance to both insecticides and biological control agents.

A global study of DNA barcodes by two Canadian entomologists revealed unexpected complexity: the occurrence of two distinct species among Australian diamondback moths. One of them is the well-known diamondback pest which is found nearly everywhere. The other is a new species, named Plutella australiana by Dr. Jean-François Landry of the Canadian National Collection in Ottawa and Dr. Paul Hebert of the University of Guelph, Ontario, the authors of the study. Their results have been published in the open access journal ZooKeys. The new species has so far been found only in Australia, where it occurs together with typical Plutella xylostella.

The new species was initially detected by Dr. Hebert in a general survey of Australian moths aimed at developing a library of DNA barcodes representing all the species of the fauna. Subsequent study of the anatomy revealed significant, previously unsuspected, differences in internal reproductive organs between typical diamondbacks and the new species.

DNA barcodes are short fragments of DNA used to identify organisms. They provide genetic traits that complement traditional morphology/anatomy. DNA barcoding is increasingly used in applications to identify species, especially cryptic organisms.

Although the new species of diamondback moth has now gained recognition and a name, key aspects of its biology remain uncertain. For example, what is its role as a crop pest in Australia and does it pose a threat to agriculture?

Original source:

Landry J-F, Hebert PDN (2013) Plutella australiana (Lepidoptera, Plutellidae), an overlooked diamondback moth revealed by DNA barcodes. ZooKeys 327: 43–63. doi: 10.3897/zookeys.327.5831

Much as human siblings can have vastly different personalities despite their similar resemblance and genetics, two closely related species of electric fish from the Amazon produce very different electric signals. These species, new to science, are described in the open access journal ZooKeys by Drs. John Sullivan of Cornell University in Ithaca, New York, Jansen Zuanon of the National Amazonian Research Institute in Manaus, Brazil and Cristina Cox Fernandes of the University of Massachusetts, Amherst.

The two new species are bluntnose knifefish, genus Brachyhypopomus, that live under rafts of unrooted grasses and water hyacinth along the margins of the Amazon River called “floating meadows.” These are weakly electric relatives of South America’s famous electric “eel” (not a true eel) that can produce strong electric discharges of hundreds of volts. By contrast, these weakly fishes produce pulses of only a few hundred millivolts from an organ under the body that extends out onto a filamentous tail. Nearby objects in the water create distortions to the electric field that are sensed by receptor cells on the fishes’ skin. In this way, they are able to “electrolocate” through their complex aquatic environment at night. Their short electric pulses, too weak to be sensed by touch, are also used to communicate the sender’s species identity and gender to other electric fishes.

“The most striking differences between these two similar species have to do with their electric organs and their electric organ discharges, or EODs.”, says lead author John Sullivan, Curatorial Affiliate at the Cornell University Museum of Vertebrates. “If it weren’t for these traits, we undoubtedly would have thought they were a single species. The one we are calling Brachyhypopomus bennetti has a huge electric organ, a short, fat tail, and produces a monophasic EOD; the other one that we’re calling Brachyhypopomus walteri has a more typical electric organ, a long thin tail, and a more typical biphasic EOD.”

It turns out the monophasic EOD of the new species Brachyhypopomus bennetti is highly unusual. Most species of this kind of knifefish produce EOD waveforms with both a positive and negative phase to them, as viewed on an oscilloscope: essentially alternating current. In this way, there is no net positive or negative current generated by the signal. “All of this fish’s relatives, including its newly described sister species, have biphasic EODs.”, says Sullivan, “For that reason we know that this trait evolved in this species’ lineage. The interesting question is why.”

One widely accepted idea is that the biphasic EOD with its reduced amount of direct current (DC) is an adaptation to hide from predatory fish, like catfishes and electric eels, that are equipped with a type of electroreceptor that are sensitive to DC. So why would one species seemingly court danger by evolving a monophasic EOD?

The only other electric fish in the Amazon with a similar monophasic EOD is the fearsome electric eel. This fish has both a weak EOD used for electrolocation and communication as well as a much more powerful EOD used to stun prey and for defense. A theory proposed by Dr. Philip Stoddard of Florida International University contends that, in much the same way that the Viceroy butterfly—a species tasty to birds—evolved wing color patterns to mimic the distasteful Monarch butterfly, the harmless B. bennetti ‘s EOD waveform evolved to mimic that of the electric eel, a species electroreceptive predatory fishes may have learned to avoid.

In this paper, the authors suggest an additional possible benefit of of B. bennetti’s monophasic EOD. Unlike biphasic species, B. bennetti’s EOD waveform is largely unaffected after their tails are partially bitten off by predators, a common type of injury in this species. They suggest that this species’ preference for floating meadow habitat near river channels may put them at particularly high risk of predation and ”tail grazing” by other fishes.

The authors show that the EOD waveforms of Brachyhypopomus species with biphasic EODs are severely altered after such injuries, whereas those of B. bennetti are not. “Any change to the EOD waveform likely impairs electroreception and communication and the monophasic EOD waveform may have been favored by natural selection in a species that suffers a lot of tail injuries.”, says Sullivan, “Selection for both EOD stability and mimicry of electric eels could be going on simultaneously…both hypotheses make predictions that should be tested.”

###

The research that led to the discovery of the two new Brachyhypopomus species was funded by the National Science Foundation of the United States and CNPq of Brazil.

 

Original Source:

Sullivan JP, Zuanon J, Cox Fernandes C (2013) Two new species and a new subgenus of toothed Brachyhypopomus electric knifefishes (Gymnotiformes, Hypopomidae) from the central Amazon and considerations pertaining to the evolution of a monophasic electric organ discharge. ZooKeys 327: 1–34. doi: 10.3897/zookeys.327.5427