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Explaining Science – taxonomy of parasitoid wasps

Professor Norm Johnson, Director of our C.A. Triplehorn Insect Collection, studies systematics of parasitoid wasps and so do his students. Graduate student Elijah Talamas collected many insect specimens during his PhD work at Ohio State and revised several taxa. Recently he published a photographic catalog of some primary types of parasitoid wasps in the large insect order Hymenoptera.

samurai wasp, Trissolcus japonicus
Trissolcus euschisti, an egg‐parasitoid of stink bugs

I contacted Elijah in his current position at the The Florida Department of Agriculture and Consumer Service and asked him to give us some insights into his life as a researcher. He recently published results from work he did as a a postdoctoral fellow for the U.S. Department of Agriculture at the National Museum of Natural History in Washington DC:

Elijah TalamasElijah: “I am the curator of Hymenoptera (bees, ants and wasps) at the Florida State Collection of Arthropods, which is part of the Florida Department of Agriculture and Consumer Services. I have broad interests in the taxonomy, morphology, and evolution of platygastroid wasps, especially groups with potential for biological control. I was trained by Dr. Norman Johnson at The Ohio State University, and maintain active collaboration with him and members of his lab.”

Angelika: “What species did you study?”

Elijah: “As a taxonomist, I study many species and genera in the superfamily Platygastroidea. These are parasitoid wasps that require development in a host to complete their life cycle, i.e. their larvae live as parasites that eventually kill their hosts. The past few years have focused on the genus Trissolcus which are parasitoids of stink bug eggs.”

(Angelika’s note: You may recall that the brown marmorated stink bug is an invasive species from Asia, now found in the eastern half of the U.S., as well as California, Oregon, Washington, Arizona, New Mexico and Texas. You may have seen one in your home, especially in late fall when they are looking for a sheltered place to overwinter)

Angelika: “What was your research questions in this particular study?”

Elijah: “A typical taxonomic project will “revise” a genus and involves many questions: What are the characters that define the genus? How many species does it contain and how do we identify them? The separation of organisms into species is the foundation of organismal biology and this is one of the jobs of a taxonomist.”

brown marmorated stink bugAngelika: “What do we know already, and why is it important to know this?”

Elijah: “We know that many parasitoid wasps attack the eggs of agricultural pests. This is important because they are often the best, and sometimes only solution to control numbers. The invasive brown marmorated stink bug is an invasive pest that can be found in Ohio, and it is not controlled by natural enemies in the United States. However, there are parasitoid wasps in its native distribution in Asia that kill the stink bugs’ eggs very efficiently. Biological control research about these wasps requires thorough study of their morphology to ensure that
species are properly identified.”

Angelika: “How did you study this question?”

Elijah: “I study parasitoid wasps by examining them under a microscope, documenting their anatomical structures, and the variability that can occur within a species. This often requires examination of specimens from all over the  world, and sometimes international travel is required to access specimens in foreign institutions and to collect fresh material. I rely heavily on photography to document and share information about these wasps, but I also use other techniques, including scanning electron microscopy and analysis of DNA.”

When looking at detailed features one may notice that some of them are different from how they were originally described and the specimen may be more closely related to to another group of specimens. This means that sometimes the classification of the species needs to be revised and renamed to reflect these new relationships. For example, in the figures below you can see the holotype, the specimen that was used to describe the species Psilanteris nigriclavata. This species was originally described with the name Opisthacantha nigiclavatus in 1905. The specimen was embedded in glue, which obscured some of its diagnostic characters and hampered a clear assessment of its identity. As part of this project, Elijah dissolved some of the glue and determined that it shared characteristics with other species in the genus Psilanteris. Thus this species was moved to this genus and now operates under the name Psilanteris nigriclavata.

62 head, mesosoma, metasoma, lateral view; 63 head and mesosoma, anterodorsal view (sk=skaphion); 64 head and mesosoma, lateral view. Scale bars in millimeters.

Angelika:  “Why is this research important?”

Elijah: “Taxonomy informs us about many aspects of the biological world. It is the science that reveals the planet’s biological diversity and discovers the evolutionary relationships between organisms. It enables other disciplines to identify organisms for the studies of behavior and ecology, and applications with large scale societal impact, such as biological control of invasive pests.”

Angelika: “What do you hope to have achieved with this study?”

Elijah: “For parasitoid wasps in the superfamily Platygastroidea, this study provides photographs of all holotype specimens in the National Musuem of Natural History and makes them freely available online. Taxonomists all over the world now have immediate access to these specimens through the internet, enabling them to make better informed decisions for classification, and more refined hypotheses about evolution.”

Let us know if you have any questions, we would like to hear form you!

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Some explanations you may find helpful:

Anterodorsal means in front and toward the back.

A holotype is a single type specimen upon which the description and name of a new species is based.

Lateral means from the side.

The body of arthropods is composed of three parts, from front to back, the prosoma, mesosoma, metasoma.

A parasitoid is an insect whose larvae live as parasites that eventually kill their hosts.

Superfamily is an intermediate classification rank directly above family and might contain one or more related families. For example, Muroidea, a superfamily of rodents, contains six families of rats, mice, hamsters and gerbils. Taxonomists use several levels to classify living things. They follow the International Code of Zoological Nomenclature which specifically mentions superfamily, family, subfamily, tribe, subtribe, genus, subgenus, species, subspecies.

Reference: Talamas, E. J., Thompson, J., Cutler, A., Schoenberger, S. F., Cuminale, A., Jung, T., … & Alvarez, E. (2017). An online photographic catalog of primary types of Platygastroidea (Hymenoptera) in the National Museum of Natural History, Smithsonian Institution. Journal of Hymenoptera Research, 56, 187.

About the Author: Angelika Nelson is the curator of the Borror Laboratory of Bioacoustics and the Outreach and social media manager for the museum. Here she interviewed Elijah Talamas, currently Postdoctoral researcher with the U.S. Department of Agriculture at the National Museum of Natural History, Smithsonian Institution in Washington DC.

Squirreling in the Pacific Northwest

You may have heard that researchers discovered a new species of flying squirrel. These squirrels had lived in plain sight for decades but only recently did Brian Arbogast and colleagues investigate the DNA of some of these animals. Their findings were revealing: The Pacific squirrels cluster separately from the northern and southern flying squirrel. The researchers analyzed mitochondrial DNA as well as microsatellite data to reveal this new evolutionary relationship.

Note: Mitochondrial DNA and microsatellites are parts of a species’ genome that are regularly used to construct evolutionary trees. In addition to the DNA in every cell’s nucleus in our body, mitochondria, the energy powerhouses in our cells, have their own genome. This mitochondrial genome is relatively small, is inherited from the mother only and has relatively high mutation rates. It is like a small clonal lineage within an organism which makes it ideal for evolutionary studies.   Microsatellites are short sequence repeats in the nuclear genome that do not produce proteins. Thus they are free to mutate at a higher rate than coding sequences – mutations will not mess up protein production- and they frequently vary in length and thus reveal relationships among organisms. 

Flying squirrel specimens from the Burke Museum’s collection were used to help identify the new species, Humboldt’s flying squirrel. Credit: Burke Museum of Natural History & Culture
The Humboldt’s flying squirrel found in the Pacific Northwest; Photograph by Nick Kerhoulas

A few weeks ago, before this study was published, 2 species of flying squirrels were considered to exist in North America, the northern and the southern flying squirrel. Here in Ohio the northern flying squirrels is resident – it is nocturnal though, that’s why you probably have not seen one yet.

Map showing distribution of now 3 species of flying squirrels

Map showing distribution of now 3 species of flying squirrels

DNA analysis showed that the coastal squirrels in Washington and Oregon are distinct from their northerly relatives and that they actually only co-occur with them at 3 sites in the Pacific Northwest. Northern and the newly described Humboldt’s flying squirrel do not interbreed at these sites. By the way, the researchers named the new species Glaucomys oregonensis because the specimen that was used to describe the species was collected in Oregon.

You may recall from a previous post, that Dr. Andreas Chavez in our department of EEOB studies relationships among squirrels in a different genus, Tamiasciurus, the red squirrel T. hudsonicus and the Douglas squirrel T. douglasii. These two species share habitat in the Pacific Northwest and they do hybridize.

Dr. Chavez was not available for an interview for his thoughts on the new species description of flying squirrels, because he is currently pursuing his own fieldwork in the Pacific Northwest. He and his field assistant Stephanie Malinich are collecting data to better understand the hybrid zone dynamics between the Douglas and red squirrel.

We will give you an update on Dr. Chavez’ research once he returns.

About the Author: Angelika Nelson is the curator of the Borror Laboratory of Bioacoustics and writing this post for Stephanie Malinich, collection manager of the tetrapods collection. Stephanie is currently doing fieldwork on the red and the Douglas squirrel in the Pacific Northwest.

Songs on both sides of the Atlantic

Like every year I will leave for Hog Island, Maine tomorrow morning. I will teach at two of the Audubon summer camps that have been held on the island almost every summer since 1936. You may recall this from my previous post.

This year I am particularly excited to watch birds along the Atlantic coast as I just returned from a trip to Ireland, on the other side of the Atlantic ocean. There I spotted birds of several species that also occur along the US coast. I doubt that the birds themselves make the crossing, but members of their species reside and breed on both sides of the Atlantic.

Rathlin Island

So which birds are we talking about? In Europe we visited Rathlin island, a small island off the coast of Northern Ireland, where we watched Atlantic Puffins Fratercula arctica, Razorbills Alca torda and Common Murres Uria aalge – or Common Guillemot as they are referred to in the UK. The Royal Society for the Protection of Birds (RSPB) runs a seabird center along the cliffs of the island where volunteers and staff regularly survey the breeding colonies and answer visitors’ questions. The resident naturalist shared with us the latest numbers: they estimate 100,000 Common Murres to breed on the cliffs, with them 20,000 Razorbills and some 700 pairs of Atlantic Puffins, everyone’s favorite due to their colorful breeding plumage.

Two Atlantic Puffins on Eastern Egg Rock

Atlantic Puffin on Eastern Egg Rock

On the US side of the Atlantic, in Maine, some 550 breeding pairs of these colorful seabirds have been reported in the largest colony on Seal island, ME.

Enjoy some photos of the Irish coastal scenery – I wish my photos conveyed the noise and smell that comes with large seabird colonies like these … David Attenborough in his Life of Birds series refers to these breeding conditions as the” slums in the bird world”.

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Most of these seabirds are not known for their vocalizations (although Black Guillemots may be exceptional with their distinct whistle; you can hear some in the background of the puffin recording below). Here are some recordings that I found in our collection:

Doug Nelson recorded this Atlantic Puffin on Matinicus Rock, Knox county, Maine, USA on 3 June 1981 (BLB23883):

Lang Elliott recorded a Common Murre on water near the Gaspesie Provincial Park, Bonaventure Island, Quebec, Canada on 1 July 1989 (BLB17181):

Common Eider is another bird that breeds on both sides of the Atlantic. Hear some nestling calls recorded by Don Borror on Eastern Egg Rock, Muscongus Bay, Knox county, Maine, USA on 23 June 1958 (BLB3508):

As you can see, most of these recordings were made a long time ago; time to go back and get some more recent recordings!

About the Author: Angelika Nelson is the curator of the Borror Laboratory of Bioacoustics and team-teaches at the Audubon summer camp on Hog Island, ME.

An 1892 Framed Plant Mount on display at the Thompson Library

The first director of The Ohio State University Herbarium and his wife, Dr. and Mrs. William Ashbrook Kellerman, prepared quite a large number of framed mounts of Ohio plants in 1892. According to the previous curator of the herbarium, Dr. Ronald L. Stuckey, these were “part of an exhibit of the Ohio flora displayed in the Ohio State Building … at the Columbian World’s Fair in Chicago in 1893. The total collection consisted of a display of mounted specimens of leaves, twigs, flowers, fruits, section of wood and bark of Ohio’s forest trees, and flowering plants, mosses, lichens, and algae.”

One of these framed mounts, twigs and wood section of the white oak tree, Quercus alba L., is currently on display at the Thompson Library until May 14, 2017. Dr. Florian Diekmann, head of the Food, Agricultural, and Environmental Sciences Library and Student Success Center, was in contact with the staff of the OSU herbarium early June last year seeking help in displaying specimens of white oak as many of the wooden structures of the main library were obtained from that plant.

Since the original twigs and leaves were not in good condition and the glass was chipped in a corner, Dr. Diekmann agreed to have it restored and refurbished. This is just one of the many framed, mounted but not displayed items in the Herbarium hitherto. The idea behind the gallery is to show the “unique connections and history shared between The Ohio State University and Ohio’s forests.” The Ohio State University Herbarium was glad to share its resources with the general public and has also made other items available for display at the gallery.

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Mesfin Tadesse, curator OSU herbariumAbout the Author: Mesfin Tadesse is curator of vascular plants at The Ohio State University Herbarium.

*** We would like to hear from you, please leave a comment ***

Dragonflies and Damselflies of Ohio

Dragonfly at Magee Marsh Wildlife Area.

Dragonfly at Magee Marsh Wildlife Area.

The Triplehorn Insect Collection is beginning a collaborative project to survey the dragonflies and damselflies of Ohio.

These spectacular aerial predators are surprisingly diverse: currently 164 species have been recorded in the state. Brilliant colors and striking markings make them the songbirds of the insect world. The immature stages of all species are aquatic, and these animals are found in lakes, rivers, ponds, and streams from Lake Erie to the Ohio River.  Although many dragonflies and damselflies are common, a number are listed as threatened or endangered.

This new Ohio Odonata Survey is scheduled to last 3 years. The work will be done together with the ODNR Division of Wildlife, the Ohio Odonata Society, and a network of avid volunteers and citizen scientists across the state.

MaLisa Spring, an Entomologist and recent OSU graduate, just joined us as coordinator for all of these efforts.  She will be working out of the Triplehorn Insect Collection in Columbus, and will be actively interacting with participants around the state.

Information on the project can be found in the newly created Ohio Odonata Survey website.  Project activities will also be widely advertised on social media.

Ohio naturalists are invited to contribute to the project. If you have images that can help document the distribution and seasonality of the various species of dragonflies and damselflies in our state, please check out the guidelines.

Finally, the Ohio Odonata Society will be holding its 2017 annual meeting, ODO-CON-17 on 23-25 June at the Grand River Conservation Campus in Rock Creek, OH.

Damselfly in Columbus, Ohio.
Dragonfly at Magee Marsh Wildlife Area.
Halloween pennant. Specimen from the Triplehorn Insect Collection.
Dragonfly on window screen in Columbus, Ohio.
Close-up of dragonfly on window screen in Columbus, Ohio.

Resources:

Photos by L. Musetti (dragonflies) & Huayan Chen (damselfly).

About the Author: Dr. Norman F. Johnson is an Entomologist, Professor at Ohio State University, and Director of the Triplehorn Insect Collection.

Flight of the Butterfly

What does re-animated life in the Triplehorn insect collection look like? What if a butterfly took flight from its drawer? Watch for yourself: Flight of the Butterfly by Tamara Sabbagh

THANK YOU Luciana Musetti, curator of the OSU Triplehorn Insect collection for facilitating the students’ visit.

About the Author: Angelika Nelson is the outreach and multi-media coordinator at the Museum of Biological Diversity and facilitates visits of school classes and students.

*** Which of the animations is your favorite? ***

Samsara – Cyclicality of life

Another video of re-animated life produced by a student in the Moving Image Art class organized by Amy Youngs, Associate Professor of Art:

Samsara – Cyclicality of life by Yuntian Zang: Inspired by the antlers on the wall, a deer goes wandering …

THANK YOU Stephanie Malinich, collection manager of Tetrapods, for facilitating the students’ visit.

About the Author: Angelika Nelson is the outreach and multi-media coordinator at the Museum of Biological Diversity and facilitates visits of school classes and students.

*** Which of these animals is your favorite? ***

re-animated Life I

We scientists look at our natural history collections as a great resource for our studies. Specimens tell us about life in the past (where species lived, what they looked like, how many individuals existed etc.) and let us hypothesize about the future. This is one way of looking at these dead “things” that we so meticulously curate. Artists may have a quite different view. This was greatly illustrated by a Moving Image Art class organized by Amy Youngs, Associate Professor of Art, last semester. Students visited our collections of dead things and were asked to find ways to re-animate these animals. We were amazed by the imagination of these young artists-to-be. Over the next days we will share some of the best pieces with you. Here is the first animation, Re-Animated Life by Alina Maddex: Birds and one turtle moving in their natural environment

THANK YOU Stephanie Malinich, collection manager of Tetrapods, Marc Kibbey, Associate Curator of the Fish Division, Caitlin Byrne, Collections Manager of the Division of Molluscs, and Luciana Musetti, curator of the OSU Triplehorn Insect collection for facilitating the students’ visit.

About the Author: Angelika Nelson is the outreach and multi-media coordinator at the Museum of Biological Diversity and facilitates visits of school classes and students.

*** Which of these animals is your favorite? ***

More than just a pretty (fish) face – Do you recognize some of these small fish from your aquarium?

As I mentioned in Monday’s post, species in the genus Anableps post the largest size (at just about a foot long) in an order of rather small fishes, the Cyprinodontiformes. Don’t let their small size fool you, it does not reflect their importance in several areas. Many are quite easy to raise, and some are cultivated for beautiful colors, particularly in their fins. Unfortunately, being popular fishes in aquaria frequently results in introductions to non-native areas from aquarium owners. In several instances exotic populations have become established. Here are some of the more enigmatic species that the OSUM Fish Division has vouchers for, arranged by family:

CYPRINODONTIDAE

Sheepshead Minnow, Cyprinodon variegatus, occur along the Atlantic coast from Massachusetts south to northern South America.  Abundant and easily cultured for the aquarium trade, also used as bait.  One introduced specimen was actually caught (back in the 1950’s) next to the Olentangy Indian Caverns in a small stream tributary to the Olentangy River.

Flagfish, Jordanella floridae, are common in the St. John’s and Ocklocknee Rivers to southern Florida. This species is listed in The Guinness Book of World Records as the fish with the fewest eggs, laying only 20 over several days.

FUNDULIDAE

Members of this family are distributed across North and Central America including some of the Caribbean islands, in coastal and interior low gradient, slow moving rivers, streams, and swamps.

Male Northern Studfish; note the twisted maxilla (posterior portion of the upper jaw bone) that is characteristic of the Fundulidae, photo by Uland Thomas

Northern Studfish, Fundulus catenatus. Although reputed to be difficult to keep it is popular in the aquarium trade because of the male’s vibrant breeding coloration. This species is native in disjunct populations in several states along the Ohio and Mississippi Rivers, but has recently been introduced and established in small to medium streams in Ohio and West Virginia.

OSUM 104822 Fundulus catenatus

OSUM 104822 is the voucher for the first specimen found on the eastern side of Ohio, in little Pipe Creek, across the Ohio River from Graves Creek in West Virginia, where there is a well established and thriving population that is believed to have been intentionally introduced.

Golden Topminnow, Fundulus chrysotus.  Common in Florida, but can be found in low lying swamps and backwaters from North Carolina along the Atlantic seaboard and around the Gulf of Mexico to eastern Texas.

 

Female Mummichog, photo by Dave Neely

The Mummichog, Fundulus heteroclitus, frequently spawns inside mussel shells, a life history attribute that is hypothesized to be facilitated by a very long urogenital sheath.

The Diamond Killifish, Fundulus xenicus, inhabits marine, freshwater and brackish waters of the Gulf of Mexico shoreline from Florida to Mexico.

Bluefin Killifish, photo by Julie Zimmerman

Bluefin Killifish, Lucania goodei

Male Rainwater Killifish, photo by Brian Zimmerman

Rainwater Killifish, Lucania parva

GOODEIDAE

This family contains many species that are critically endangered in Mexico and Central America, due to their endemism to restricted bodies of water that are denigrated by anthropological modifications.

Tuxpan Splitfin, Alldontichthys tamazulae, is endemic to the Rio Tuxpan in the State of Jalisco, Mexico.

Butterfly Splitfin, Ameca splendens, is endemic to the State of Jalisco, Mexico, raised and sold commercially to the aquarium trade.

Redtail Splitfin, Xenotoca eiseni, are listed as endangered and declining.  The species was split as recently as 2016 to add two new species from the original distributions, where the critically endangered X. lyonsi is found in the Tuxpan and Tamazula Rivers and the critically endangered X. doadrioi in the “endorheic region of Metzatlan in the state of Jalisco, Mexico”.

POECILIIDAE

Possibly due to the ease of breeding, this family contains many popular aquarium species like guppies and swordtails.  One species, Poeciliopsis latidens, lives in marine waters, although several others are secondary freshwater species.

Sailfin Molly, Poecilia latipinna, is native to coastal lowlands from North Carolina to Vera Cruz, Mexico, but has been introduced to many countries with “adverse ecological impacts” reported.

Variable Platy, Xiphophorus varietus, is endemic to Mexico but is another popular aquarium fish that has been carelessly introduced with resultant harmful ecological impacts (for this species the impacts are primarily competition with native fishes for resources).  These and several other species in the genus Xiphophorus are listed as exotic pests by governmental agencies.

The fact that many cyprinodontiforms (and cichlids) are tolerant to higher salinities as opposed to the primarily freshwater orders of fishes has made them the subject of biogeographical studies particularly for dispersal from one stream to another along coastal areas.  It is hypothesized that their adaptability to variable habitat conditions facilitated their invasion and predominance of the Central American fish fauna as they made their way across the narrow, open waters from South America to Central America before the rise of the Panamanian isthmus.  This hypothesis, formulated by ichthyologist George S. Meyers in the mid ’60s, has been strengthened by genetic work in the current decade.

Photo Credits:
All photos of museum specimens were taken by Marc Kibbey; other photos with permission of members of the North American Native Fishes Association (NANFA.org).

Detailed information for each specimen is available through the OSU Fish Division Database.

About the Author: Marc Kibbey is Associate Curator of the Fish Division at the Museum of Biological Diversity.

 

*** Which of these fish species do you have in your aquarium at home? ***

Hey, Four-Eyed Fish!

Sure, those of us who wore glasses when we were younger may have been called “Hey, four eyes!”.  But I wonder if anyone ever took offense to the level of “Hey, you four-eyed fish!”.  ‘Cause that would be combining two insults, the discrimination against an ocular disability and the idea that you were kind of cold…or wishy-washy…well, anyway.  I sometimes get to share the fact that I once caught a Four-eyed Fish, and recently I found out that the species belonging to the Genus Anableps that I caught is rather rare, so I feel even more special!

(Imagine me affecting a British accent here, to make my story sound more adventurous).  “There I was, standing in the river with my doughty crew, when one of the young stalwarts excitedly shouted “Quatros ojos, quatros ojos!””.  Yes, just a few feet away from me cruised the rare and dangerous (dangerous if you’re an insect, that is) Pacific Foureyed Fish Anableps dowei!

In 1999 I accompanied members of my church on a mission trip to the area of Siguatepeque, Honduras, to assist in building cement block housing for victims of Hurricane Mitch (in 1998 Mitch was responsible for the death of at least 11,000 people in Central America) that caused a flood perhaps 40 feet deep in a valley near Siguatepeque.  After the rest of the mission left I stayed behind to travel to the Pan American School of Agriculture near Tegucigalpa, where the fisheries instructor there graciously allowed me to accompany them on trips to waters near the school.

view of Universidad Zamorano

Universidad Zamorano. Photo by EAP Zamorano [CC BY-SA 4.0], via Wikimedia Commons

The streams we sampled were the mainstem and tributaries of the Rio Choluteca, the major river on the Pacific slope of Honduras that winds through mountainous terrain until it empties into the Gulf of Fonseca, an estuary shared by El Salvador, Honduras and Nicaragua.  At a site on the Choluteca, near the village of Zamorano, the school’s students and I seined up the Pacific Foureyed Fish (Anableps dowei).  This was a species I’d read about prior to making the trip, so when I heard the student’s cry I became quite excited!

Drawing of a Foureyed Fish

Drawing by Unknown [Public domain], via Wikimedia Commons

The species is named for a Captain J. M. Dow, who skippered the steamer “Guatemala” of the Panama Railway Company.  Captain Dow collaborated with two associates to send over specimens from over 1500 samples in Central America to the U.S. National and the British Museums.

The reason for the Four-eyed Fish’s common name is the presence of two pupils in each eye, one in the upper and one in the lower half, separated by a band of tissue. This enables them to see above and below the water while they cruise at the surface of the water body and makes the Four-eyed Fish extremely difficult to catch with a seine: they are able to see you (or an eagle, or other bird of prey) coming from a long ways away. They are known to leap right over a seine and like fish in another family, topminnows, they dive down to the bottom to avoid capture.  An effective method of capture is described as using a group of fishermen to drive a school of quatros ojos toward a concealed individual waiting with a cast net that is thrown over the school, ensnaring a “bushel full” of the prey.

photo of Largescale Foureyes (from above water)

Largescale Foureyes, Trinidad. Photo by Charlesjsharp [CC BY-SA 4.0], via Wikimedia Commons

The Anableps‘ eye is flattened on the top and rounded on the bottom half, with a thickening of the lens from the bottom to the top to adjust for the refractive differences in the two mediums.  The upper pupil casts the terrestrial image through the lens on the lower retina, while the lower pupil’s image is reflected on the upper retina.  The Four-eyed Fish’s eye recently inspired at least one contact lense company to develop lenses that work extremely well both out of and in the water.

 

Scheme of the eyes of a four-eyed fish showing the basic functions

Diagram of the eye of a four-eyed fish, [public domain] via Wikimedia Commons

1. Underwater retina 2. Lens 3. Air pupil 4. Tissue band 5. Iris 6. Underwater pupil 7. Air retina 8. Optic nerve

Swimming at the surface with the head exposed is relatively unusual for fishes in general, but species of this genus show other oddities as well.  Not only do the quatros ojos leap out of and skip along the surface of the water, but when they see terrestrial insects on the banks they will actually leap onto the shallow, inundated bank side areas to capture their prey.  These fish have been observed lying in the sun, sometimes for several minutes, before pushing their way back into the water.  Once they’re out of the water their mobility is severely limited since unlike eels they cannot locomote with a wriggling motion, nor can they push off with their tails to leap forward on land. Unlike mudskippers and the “walking” catfish their pectoral fins are unsuited to pulling themselves along.  So, although they may push themselves along with their tail and pectoral fins to chase their prey, the extent to which they are able to do so is severely limited.

Another anomaly that characterizes anablepids is that their genital organs are oriented either to the left or right, thus they can reproduce only with mates having compatible organs.  They share this character with the group of species to which they are said to be most closely related, the “One-Sided Livebearers”, or Jennysina.  The functional significance of this anomaly is not known.  Anableps species are viviparious, meaning the young are birthed live rather than from an egg deposited in the water.  The eggs are carried to term inside follicles in the female’s ovary at which point they hatch and are extruded from the genital pore.  The male of the species has a gonopodium, a modified anal fin ray that develops as the males mature and facilitates placement of the sperm into the oviduct, fertilizing the female’s eggs.

At present three species of Four-eyed Fish are recognized: Anableps anableps, the Largescale Foureyes, is found in South America from the island of Trinidad and Tobago, and Venezuela to the Amazon Basin of Brazil.  Anableps dowei, the Pacific Foureyes, has the most limited distribution of the three species, occurring in Central America from southern Mexico to Nicaragua. Anableps microlepis, the Foureyes, is the most salt tolerant species of the three. They are found in open marine areas in full seawater (also from Trinidad to the Amazon Basin in Brazil) and follow tidal rhythms, moving up into sheltered lagoons and further upstream with the high tides, and back out into open waters as the tide wanes.

Anableps congregate in schools of up to 200 or so as juveniles, with their gregariousness decreasing with age until at adulthood they are as likely to be found as individuals as in small groups.  Some of their known fish associates include characins, pimelodid catfish, poeciliids, atherinids, eleotrids, flatfishes and cichlids.

If you are looking for an unusual fish for your aquarium the species that is most commonly available from suppliers (there are several that raise their own stock), the Four-Eyed Fish, is moderately hardy, but they are comparatively large in size, growing to around a foot in length.  Since they are surface swimmers they do best in a long, relatively shallow tank in fresh to moderately brackish water (depending on the species).  They are gregarious so it is best not to keep them singly or in pairs.  They will probably do well with Sailfin Mollies, bottom-dwelling Gobies, Mudskippers, and even Orange Chromide Cichlids, Archer Fish and Monodactylus.

The Family Anablepidae is placed within the Order Cyprinodontiformes (and, the Pacific Foureyed Fish attains the largest size of any species in that order).  That order contains a bounty of fascinating forms, with a wide variety of reproductive types, a plethora of adaptations to environments, and high importance in terms of biogeography.  My next post will portray some of those very diverse species.

About the Author: Marc Kibbey is Associate Curator of the Fish Division at the Museum of Biological Diversity.

*** Have you ever seen a four-eyed fish? Let us know, leave a comment ***