Freshwater Mussels Vs. The World

Did learning the difference between the lifestyle of the freshwater vs. saltwater mussels whet your appetite? Are you curious whose cousin you are consuming when slurping scallops or opening oysters?  Do you catch yourself wondering at night if sea slugs are really related to land slugs? Is your superpower talking to octopuses and you want to know what other animals you may be able to communicate with? We have got you covered.

This time, we are going to discuss the relationships between all these molluscs, so you can learn just how distinct these organisms really are.  You will finally be able to join the club* of polite pedantic people standing with on the borderlines between clades reminding anyone who will listen that these organisms are distinct! Among our allies are those who pipe up whenever someone calls a spider monkey an ape and folks who visibly wince whenever anyone implies that a spider is a bug. This is the kind of knowledge you can brag about. You’ll never need something to talk about on a date again. Those long thanksgiving dinners with extended family will be a breeze! Shells are easy to carry around as props so you can always be prepared!

*there is no club

ARE YOU READY TO READ?!

(Those of you who already know the difference are also invited to read on but are given explicit permission to feel slightly smug while doing it. It’s a win either way.)

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Field ornithology

A recent post on Cool Green Science about Margaret Morse Nice “How a Scientific Outsider Changed How We Study Birds” inspired me to think more generally about how researchers study bird behavior in the field and how acoustic recordings can help us understand bird behavior. By the way, here “field” does not refer to a type of habitat rather it encompasses any natural habitat (rivers, lakes, meadows, forests etc.) in which animals live.

Margaret Morse Nice portrait

Margaret Morse Nice looking into a nest of baby sparrows, 1956 (Wikipedia)

Margaret Morse Nice’s most important contributions to ornithological research were probably in the advancement of techniques in studying birds. She was one of the few American women ornithologists in the 1930s and the first to make detailed observations of individual birds. She followed Song Sparrows through their lives, took notes on their life history and published her observations in over 200 papers and books. Most of her publications are listed in her autobiography “Research is a passion with me“.

cover of Margaret Morse Nice's book Research is a passion with me

Book by Margaret Morse Nice “Research is a passion with me”

Interestingly, Nice who was born in Massachusetts in 1883 studied Song Sparrows in Columbus, OH where she and her family lived in 1927-1936. During these eight years she closely followed birds on their property off Patterson Ave, a floodplain on the east-side of the Olentangy river just north of Lane Ave, what is today Tuttle park. Even though the habitat has changed from the shrubs, weeds and gardens in Nice’s time you can still find open areas especially along the river which Song Sparrows to this day use to build their nests and raise their young.

To follow individual birds closely, identify them repeatedly and note their behavior and interactions with each other, it was clear to Nice that she needed to mark the birds. Over the years she trapped some 870 Song Sparrows which she marked with unique combinations of plastic color bands on their legs. We still use the same technique today.

color-banded Song Sparrow

“Red-black / yellow-metal” banded Song Sparrow (c) K. Whittaker

Bird banding actually started in Europe as an aid to follow migrating birds and still is used for this purpose: Researchers put a metal band with an engraved unique number on a bird’s leg – just like your social security number. They report this number as well as where and when the bird was caught and banded to a central lab, here in the USA the central bird banding lab in Maryland. When somebody then recaptures or finds a banded bird, they can access this information through the bird banding lab and relate it to data they collect about the bird.

Colored leg bands help researchers to follow individual birds. Sounds easy? It can be once you have the colored leg bands on the bird. First you have to catch the bird and that can prove tricky. We primarily use two established bird trapping techniques: walk-in traps and mist-nets.

Just as the name implies, wire-mesh traps are placed on the ground, seeded with some tasty morsels and when the bird in search of food walks into the trap a door closes behind it and traps it within.

Collared Dove in a Potter Trap

Collared Dove in a Potter Trap (c) Third Wheel Ringing Supplies

For a mist-net imagine a volleyball net strapped between two poles but with finer mesh and all the way to the ground. These nets work best in foggy weather conditions when they are nearly invisible and when placed strategically in a bird’s flight path, the subject will fly into the mesh, bounce and fall into a fold at the bottom of the net and get entangled. We then “extract” the bird from the net and band it. – By the way not everybody can trap and band birds because they are highly protected under the Migratory Bird Treaty Act dating back to 1918. Through training with a master bird bander researchers can obtain a U. S. Federal Bird Banding and Marking Permit.

So what role does sound play in this? Sometimes we lure birds to the mist-net by playing calls or songs of its species. Why does this attract a bird? Most songbirds are territorial, i.e. they defend an area that they use exclusively for feeding or breeding and song keeps every other bird of the same species out of this territory. Some researchers have actually done clever experiments to prove this keep-out function of birdsong, but that is a story for another post.

Doug Nelson holding up a loudspeaker playing bird song in front of a mist net

Doug Nelson holding up a loudspeaker playing bird song in front of a mist-net in Oregon (c) Angelika Nelson

So, birds do not produce their most beautiful songs to please us, rather one function is to repel a male contender. If the opponent does not take this warning, a bird will switch to physical attack. Exactly this behavior can get them trapped in a mist-net as they search intently for the invisible opponent, aka loudspeaker, and eventually dive at in attack.

This brings me back to Nice’s contributions to field ornithology: Nice studied closely the territorial behavior of “her” birds. Once all males were banded she made close observations of where they sang, how they interacted with neighbors and whether they were able to attract a mate. She described patterns of invaders and defenders during territorial encounters and described the role that song played in these. To this day this is a prominent research topic in our lab where we have studied territorial singing behavior in the White-crowned Sparrow and other species over the last decades.

Following in the footsteps of Margaret Morse Nice, Dr. Chris Tonra, Assistant Professor in the School of Environmental and Natural Resources at Ohio State, has started a project to continue work on behavior of the Song Sparrow. He and his students regularly band today’s local Song Sparrow population at Ohio State’s Wilma H. Schiermeier Olentangy River Wetland Research Park, less than one km upstream from Nice’s former home, and follow them throughout the year. He uses some of the techniques from Nice’s days, others have advanced – read more about the project here!

 

About the author: Angelika Nelson is the curator of the Borror Laboratory of Bioacoustics. Her recent research has focused on song and behavioral ecology of the White-crowned Sparrow in Oregon; each spring Angelika teaches the OSU course “Ohio Birds” where students learn about the life of birds and how to identify them in the field – by sight and sound.

 

References:

“Nice, Margaret Morse.” Complete Dictionary of Scientific Biography. 2008. Encyclopedia.com. (August 17, 2016).

Finding No-No

In our Muskingum River Survey we’re searching for a couple (invasive) fish species that we hope we do not find: The Silver and Bighead Carp.  Environmental DNA has been detected in the Muskingum River for Bighead Carp and also for Northern Snakehead, another invasive species from Asia.

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And just as importantly, we’re taking names, numbers, weights and lengths of everything else we catch, documenting Muskingum River’s fish fauna before the Asian carp invade.  Just a few of the native species we’re catching or may catch soon that are found in the Muskingum:

 

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

Pre-Asian Carp Invasion: Muskingum River Survey

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Photo of the Muskingum River from the National Weather Service

A little over two years ago a test of the Muskingum River using eDNA techniques showed positive results for Bighead Carp, one of several Asian carp species, and Northern Snakehead.  Although the Ohio Division of Natural Resources (ODNR) and U.S. Fish and Wildlife Service sampled the Muskingum River extensively neither of these invasive species was actually caught.  It may be that the highly sensitive eDNA technique picked up genetic material from bird feet or boat bottoms that traveled from areas where the invasive species were well established, but that has yet to be proven conclusively.

The OSUM Fish Division is currently carrying out a project to survey the Muskingum River watershed from top to bottom under the supervision of project leader Brian Zimmerman, with a grant from the Ohio DNR Division of Fish and Wildlife, overseen by Associate Professor and MBD director Meg Daly. Fifty-five sites above, below and in each of the nine pools between the locks and dams of the mainstem, and 5 each along the two major tributaries of the Muskingum River, Muskingum River lock and dam Photo from the Ohio Canal Society, the Walhonding and the Tuscarawas Rivers, will be sampled.

Muskingum River lock and dam, Photo from the Ohio Canal Society

Muskingum River lock and dam, Photo from the Ohio Canal Society

The sampling techniques will include

  1. Electroshocking: as the name implies, this technique involves the application of electrical current to stun fish, causing them to remain immobile for crew members with pole nets to retrieve them and place them in a large tub in the boat.
  2. Seining: The use of 6’ tall x 8’ wide seine nets by two or three people in this project to sample shallow areas.
  3. Benthic Trawling: We take an 18’ flat bottomed John boat with two 25 horsepower outboard motors and drag a small “otter” trawl net along the bottom of the river.
  4. Hoop Netting: This method uses 3 sets of large mesh nets supported by iron hoops. The hoop nets are left out for two days after which we return and remove the fish from the nets. Read more about this technique on our fish blog.

With all of the methods the catch is identified, counted, measured and weighed, and returned except for any invasive species we may catch (fortunately no Silver or Bighead Carp have been caught!…yet…). We see a very high rate of survival of the captured fish and these are returned to the river.

The project will extend over two years, from July to September of 2016 and 2017, and will culminate in a final report providing an assessment of the Muskingum River fish community.  This information will provide a baseline for use in potential remediation efforts should the silver and/or bighead carp become established above the Devola Dam.

Technically all carp (Silver, Bighead, Grass, Common, Black, and Prussian carp, and Goldfish are the species currently established in the United States but there are at least four more – Crucian, Catlan, Mrigal and Mud Carp- are recognized as valid species) are Asian in origin.  Common Carp, by the way, are believed to have originally come from the Caspian Sea.  Back in the 1880’s the U.S. Commission of Fish and Fisheries intentionally distributed Common Carp in rail cars across much of the United States to serve as a food fish, but the idea never caught on as extensively as hoped due to the habit of wild carp to scavenge the bottom of water bodies.

Common Carp are invasive, but are considered naturalized.  They can be deleterious to stream and lake bottoms, and do impact other fish, bird, and mollusk species as well as plants, but at this point the damage has been done, so to speak.  After nearly 140 years native fish and other animals have adapted to Common Carp.  Some fishermen and environmental agents prefer to kill Common Carp whenever they are caught, in many cases simply throwing them on the stream bank to suffocate, but in truth this has little if any effect on the population since their recruitment rate is extremely high.

Silver and Bighead Carp were brought to the United States during the 1970’s and 1980’s, and escaped into the Mississippi River watershed from their state, federal and privately run facilities following extensive rains that overflowed the hatcheries.  In the Mississippi River and many tributaries they are securely established in abundances that impact native fish species and interfere with local trawling concerns.

Adult fish species that are known to be adversely affected by Silver and Bighead Carp are Gizzard Shad and Bigmouth Buffalo.  The dietary overlap of the carp with these native fishes has been shown to reduce the adults’ size and health.  In addition the high volume planktonic grazing employed by these carp is likely to compete for that food source with larvae and young-of-the-year of most other native fishes, ultimately causing a reduction in native populations.

Grass Carp are established in lakes and rivers across the State of Ohio.  Deleterious effects from this invader include removal of macrophytes (large aquatic plants) from stream bottoms with concurrent increases in turbidity.  The macrophytes provide cover and spawning habitat for many native organisms.  The carp only digest about 1/2 of the plants they eat, so the large amounts of fecal matter cause algal blooms.  The OSUM crew has caught several Grass Carp already, euthanizing and saving samples from them.

It is not known at this point what the remediation would consist of if Bighead or Silver Carp do invade the Muskingum River.  Similar to many other invasive species it would be extremely difficult if not impossible to completely eradicate them from waterways like the Muskingum River that have connections to other rivers that contain the species.  Short of completely damming the river (which carries its own set of ecological problems), or installing an electric barrier as has been done between the Illinois River and Lake Michigan, eradication would be short-lived.  It may be that the best approach would be to simply utilize the pests as a food source as has been done in Kentucky and other states, since their flesh is much more palatable than that of common carp.  If we catch any Bighead or Silver Carp (electroshocking works well for larger Silver Carp, while hoop netting is one of the best methods for Bigheads) they will be euthanized with samples taken for DNA analysis, but we really do hope that is not the case.

 

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

Big fleas have little fleas, and little fleas have …

“Great fleas have little fleas upon their backs to bite ’em,
And little fleas have lesser fleas, and so ad infinitum.”

Jonathan Swift (paraphrased)

While this is not quite true, here is a picture of mites on mites on ants. This image was taken using an LT-SEM (Low Temperature Scanning Electron Microscope). It shows an ant in ventral view (belly up). The original idea was to get an image of Antennophorus mites (the large mite under the head, but also one hiding behind the third pair of legs of the ant). Antennophorus are kleptoparasites, they steal food from the ants. Ants feed other ants by regurgitating small amounts of food, which are eaten by the receiving ant. That is one way ants in the nest get to eat even if they do not forage outside themselves. Antennophorus takes advantage of this.  They mimic the antennal palpitation of ants begging food from their sisters using their own elongate legs, stealing the regurgitated food. Ants do not seem to be able to recognize the thieves. Only adult mites steal food, we are not quite sure what the immature mites do.

Ant with mites that have mites

Ant with mites that have mites

When taking this picture we realized that we saw an entire community. Not just an ant and Antennophorus, but also acarid (e.g. on the antenna) and histiostomatid (e.g. on the Antennophorus) deutonymphs and even a nematode (riding on one of the deutonymphs on the abdomen). Deutonymphs are dimorphic, second nymphal instars specialized for phoresy, that is transport on a host to a new habitat. Not quite “ad infinitum“, as in the story, but still kind of neat.  Jonathan Swift might have been impressed.

 

About the Author: Dr. Hans Klompen is professor in the department of Evolution, Ecology and Organismal Biology and director of The Ohio State University Acarology Collection.

 

Mites and moths

Following some earlier blogs about recently acquired collections I present to you here the Treat collection. This collection was assembled by Asher E. Treat a researcher at City University of New York and the American Museum of Natural History, also New York. This collection is one of the best in the world for mites associated with Lepidoptera (butterflies and moths). Mites have been found associated with most terrestrial and many aquatic organisms, but when it comes to insect hosts, mites on Coleoptera (beetles) and Hymenoptera (bees and wasps) are clearly the most numerous, diverse, and well-known. Still, Lepidoptera have a variety of associated mites.

The Acarology Collection acquired this collection 4 years ago, some years after Treat’s death. The collection consisted of about 37 slide boxes of exceptionally well labelled microscope slides and half a dozen insect drawers of pinned moths (all labelled as hosts of specific mite specimens). The Lepidoptera are being processed at the Triplehorn Insect collection, while we, the Acarology collection, have been working on processing (mostly databasing) the slides. This is proving to be a major job.

 

Image of a female of Dicrocheles phalaenodectes, the moth ear mite

Image of a female of Dicrocheles phalaenodectes, the moth ear mite

Treat got interested in mites associated with moths after finding mites in the ears of noctuid moths. In the process, he figured out the quite amazing life histories of some mites associated with these moths. The most famous is Dicrocheles phalaenodectes, the moth ear mite (family Laelapidae).

These mites break through the tympanic membrane of the ear of the moth and form small colonies inside the ear. By itself not too surprising, but the interesting part Treat discovered was that these mites are always found in one ear only, rarely if ever in both ears. In a way this makes sense. By breaking the tympanic membrane the mites make the moth deaf in that ear. Moths need their hearing to avoid predators (for example bats) so a deaf moth would be easy prey. However, a moth with one functional ear is still able to avoid bats, perhaps not as well as if it had two functional ears, but close enough. Which leaves the question: how do the mites manage to limit infestations to one ear?

Treat did many careful observations and follow-up experiments on this aspect and found that the mites have a very specific set of behaviors ensuring only one ear will be parasitized. The first female to get on a moth (nearly always a fertilized female, the immatures and males do not colonize) crawls to the dorsal part of the thorax, explores a little, after which she proceeds to one ear. Any future colonizers will first go to that same dorsal part of the thorax of the moth and follow the initial female to the same ear. It appears the mites lay a pheromone trail that guides newcomers to the already infested ear, and away from the uninfested one.

Drawing of relative positions of mites in a moth ear

Drawing of relative positions of mites in a moth ear

To complete the cycle, young females leaving the ear initially wander around the hosts body (mostly the thorax), congregating around the head at night. They leave the moth by running down its proboscis when it is feeding on flowers. On the flowers, the mites wait for their next host.
Another mite family that is specialized on Lepidoptera, the Otopheidomenidae, is also parasitic, and they will also show up near the ears, but they do not pierce the tympanic membrane, so they do not cause deafness. Unfortunately, we know much less about them, Treat was never able to study their behavior. A range of other mite families have representatives that are regularly found on Lepidoptera, but they are not specialists at the family level: Ameroseiidae, Melicharidae, Erythraeidae, Iolinidae, Cheyletidae, Acaridae, Carpoglyphidae, and Histiostomatidae. That list excludes the occasional “vagrants” that can be found on moths, but that are unlikely to be living on them for extended periods of time. All in all, quite a diverse community.
For those interested in knowing more, Treat wrote a book “Mites of Moths and Butterflies” (1975, Cornell University Press) that is a rare combination of good scholarship (especially natural history) and readability.

Title page of Treat's book on moth mites

Title page of Treat’s book on moth mites

Treat was very careful and noted things like host specimen numbers (if available), which allows current researchers to track down the exact moth from which a given mite came.

This is currently a common approach, but Treat started this in the 1950-ies. And there is more. Based on Treat’s label data we know not only the name of the hosts and the specific locality, but also gender of the host, whether the left or right ear was infested, and the exact part of the body the mites were found on. So we have excellent information, directly from the slides, showing that Proctolaelaps species (family Melicharidae) are nearly always found near the base of the palps [as an aside, Proctolaelaps is a bit of an unfortunate generic name, combining “procto-” = anus and “laelaps” = hurricane; presumably the name

Microscope slide from the Treat collection

Slide from the Treat collection

refers to a relatively large anal shield]. Such complete data are fantastic for future research, but they also mean a lot more work processing these slides, as every slide has lots of unique data. I want to thank George Keeney, part-time curator of the acarology collection and a series of volunteers, Ben Carey, Rachel Hitt, Mitchell Maynard, Ben Mooney, Jake Waltermyer, and Elijah Williams, for their hard work in accessioning this material.

 

About the Author: Dr. Hans Klompen is professor in the department of Evolution, Ecology and Organismal Biology and director of the Ohio State University Acarology Collection.

Butterflies going digital

Last year the Triplehorn Insect Collection received a large donation of butterflies from Mr. David Parshall. More than 50,000 pinned specimens, and many thousands more in paper envelopes. You might have read about it on the Pinning Block (here and here.) We have also posted some photos of the collection move on Twitter.

We have specimens of all insect orders and from all regions of the world, but because we never had a faculty or staff who specialized on Lepidoptera, our moth and butterfly collection was not nearly as big as, for example, our beetle or leafhopper collections. This has changed with the addition of the massive Parshall donation.

Afrodite fritillary, <i>Speyeria aphrodite</i>, dorsal view.

Aphrodite fritillary, Speyeria aphrodite, dorsal view.

Afrodite fritillary, <i>Speyeria aphrodite</i>, ventral view.

Aphrodite fritillary, Speyeria aphrodite, ventral view.

 

 

 

 

 

 

 

 

The Parshall collection is a complete collection of the butterfly and skipper species found in the state of Ohio. It really stands out, though, because it also contains a huge number of specimens collected in the Arctic Canada and Alaska. (Imagine chasing butterflies in Churchill, Manitoba with the very real threat of polar bears around you! Makes the butterfly hunt just a little more interesting, don’t you think?)

<i>Limenitis</i>, admiral butterflies.

Limenitis, admiral butterflies.

The National Science Foundation has recently funded a large project called the “Lepidoptera of North America Network” (LepNet). This project, which just began this month, is a collaborative effort of 29 institutions across the United States with the goal of making 2.1 million butterfly specimen records freely available on the Internet. If that were not enough, LepNet also aims to produce over 95,000 images of the moth and butterfly species that these data refer to. The project is being coordinated by Northern Arizona University, and the Triplehorn Insect Collection will participate through a subcontract to “digitize” the Parshall collection.

Digitization, for us, means capturing and storing the information contained on each specimen label and storing it in our xBio:D database. And from there, to the world!

Every specimen in a collection has (or should have!) a label with information on where it was captured, when, and by whom. Often we find additional biological data on the labels, like the host plant that an insect was feeding on, the habitat in which it was collected, or the method by which it was collected.

Lycaenidae butterflies showing specimen labels.

Lycaenidae butterflies showing specimen labels.

Taken together, all of these bits of information tell us a lot about the geographic distribution of species going as far back as the late 19th Century, the flight period of the adults, and much more. We have not even scratched the surface of all the knowledge we can obtain from biological collections. On July 13th a story was published in the New York Times about a team of ecologists using these same data for plants to find out how many different tree species exist in the Amazon Forest (the researchers found over 11,000!).

Digitization can also mean taking pictures of the specimens. But with millions of butterfly specimens in collections we cannot reasonably take and store several pictures of each and every one of them. So the goal of LepNet is smaller, but 95,000 is still a big number.

The Triplehorn collection’s own contribution to LepNet is more modest, but important nevertheless. The Parshall collection’s strength in Arctic butterflies is particularly interesting and even before we had fully unpacked the collection after the move the specimens were already being used by scientists (see Warren et. al., 2016).

In an era of climate change, knowing where those butterflies used to be found in years and decades past will give a good impression of the impact of environmental change.

Drawer full of Lycaenidae butterflies

Drawer full of colorful Lycaenidae butterflies.

 

Reference:

Warren, Andrew D.; Nakahara, Shinichi; Lukhtanov, Vladimir A.; Daly, Kathryn M.; Ferris, Clifford D.; Grishin, Nick V.; Cesanek, Martin; Pelham, Jonathan P. 2016.  A new species of Oeneis from Alaska, United States, with notes on the Oeneis chryxuscomplex (Lepidoptera: Nymphalidae: Satyrinae). The Journal of Research on the Lepidoptera (The Lepidoptera Research Foundation, Inc.) 49: 1–20

 

About the Author: Luciana Musetti is an Entomologist and Curator of the Triplehorn Insect Collection.

Sucker Bridgework

Comparative anatomies of skeletons stored at the OSU Museum Fish Division can be studied to reveal information on the sort of ecological niches a particular species occupies.  One example is the feeding niche that various sucker fish species exploit.  Based on structures of their throat teeth and the type of prey items retrieved from their digestive tract it would appear that buffalo and carpsucker species use their fine, comblike teeth for sieving their prey, while suckers with larger teeth (most redhorses, hogsuckers, spotted suckers) are said to “masticate” their soft prey, and finally those with the sturdiest teeth are able to shatter the hard shells of molluscs.

The photo below shows the anterior portion of a Silver Redhorse skeleton (OSUM 101341), with an arrow pointing to the pharyngeal tooth arch (position indicted by arrow) located at the rear of the gill basket.

SilverRedhorseSkeletonOSUMHeadshowingpharyngealteeth

There are  16 extant species of sucker fishes in Ohio’s waters.  Images of four of those species with pharyngeal tooth arches removed from some of our skeletons are shown below.

Spotted Sucker1 from Wolf Creek (Kankakee River) IN 07 01 07 by BZ

Spotted Sucker, Minytrema Melanops.  Photo by Brian Zimmerman.

MinytremamelanopsSpottedSuckerPharyngealTeeth

The Spotted Sucker has been reported to feed on organic fragments, diatoms, copepods, cladocerans, and midge larvae.

SmallmouthBuffalo

Smallmouth Buffalo, Ictiobus bubalus.

IctiobusbubalusSmallmouthBuffaloPharyngealTeeth

Smallmouth Buffalo suckers with their relatively delicate teeth feed on diatoms, dipteran larvae, copepods, cladocerans, ostracods, bryozoans, and incidental algae attached to bottom substrates.

ShortheadRedhorse

Shorthead Redhorse, Moxostoma macrolepidotum.  Photo by Ben Cantrell.

MoxostomamacrolepidotumShortheadRedhorsePharyngealTeeth

Shorthead Redhorse stomach contents have revealed their diet to consist primarily of midge, mayfly and caddisfly larvae.

River Rehorse from the Duck River at Shelbyville TN by Uland Thomas

River Redhorse Moxostoma carinatum.  Photo by Uland Thomas.

MoxostomacarinatumRiverRedhorsePharyngealTeeth

The River Redhorse has the sturdiest teeth of the four sucker species’ teeth shown here, so much so that they are capable of cracking the shells of bivalve molluscs and snails.

For comparison, inserted below is a photo of the molariform pharyngeal teeth from a Freshwater Drum.  The drum is primarily a carnivore, its diet comprised more extensively of bivalve mollusc and gastropod shells, while the omnivorous sucker fishes find most of their food by grazing the bottom of streams and lakes, sifting sand and gravel to find their little morsels.

drum pharyngeals downsized

 

About the Author: Marc Kibbey is Assistant Curator of the OSUM Fish Division.

Bottom Feeders

Comparative anatomy is among our oldest scientific pursuits as humans, allowing us to differentiate between delectable and deadly, and helping us to make inferences about novel organisms, the threats they might pose, and the uses to which they might be put.  Because the diversity of organisms in a museum collection exceeds that of any one location or habitat, museums are the premiere resource for comparative anatomy, allowing scientists to look at many individuals and many species, and to consider how form relates to function, evolutionary lineage, or location.

Fish Division collections manager Marc Kibbey has been using the Museum of Biological Diversity collections to study the anatomies of the feeding apparatus in suckers and minnows (order Cypriniformes).  These fish (and several others) have a complex palatal organ (PO), first described by Aristotle from a common carp, that enables them to sort out food items from the inorganic material vacuumed from the bottom of the stream. Strongly analogous to a tongue, the organ is covered with taste receptors that send information to gustatory regions of the fish’s brain. The palatal organ’s motile structure is comprised of muscle, adipose and connective tissue, and fibers.  Muscular expansion of the palatal organ pins food items to the gill arches allowing expulsion of the non-food items out of the gills.  The food is then selectively moved back to the area between the chewing pad (CP) and the pharyngeal teeth for mastication.

DooseyPOCPCatostomusoccidentalis

 

This photograph is from Michael Doosey (2011), showing the head of a Sacramento Sucker with the operculum and gill basket removed, revealing the palatal organ (PO) and chewing pad (CP).   The preparation of our skeletons uses dermestid beetles that would consume the muscular palatal organ, but the skeleton of the keratinous chewing pad remains.

CatosomusoccidentalisbyUCDavisviaFishbase

Sacramento Sucker, northern and central California.  Image from Fishbase.

The food of suckers is chewed, but not by teeth in the mouth: suckers have throat teeth instead of  jaw teeth.  These teeth are part of the gill apparatus, and differences in the shape and number of the teeth, and depth and breadth of the pharyngeal bones, help identify species and determine the types of food items they eat.  Pharyngeal teeth are constantly replaced as they are lost.

Hypenteliumnigricansgillbasket

The gill basket of a Northern Hogsucker, showing the pharyngeal teeth on the posteriormost gill arch.

Hypentelium nigricans Northern Hog Sucker

Northern Hogsucker, Mississippi River and Great Lakes drainages.  Photo by Uland Thomas.

Other clues to the biology and ecology of fishes lie in the anatomy of their swim bladders. Morphological differences in size and shape, and number of chambers in the swim bladders vary between and can help identify the species.  Size of the swim bladder corresponds to where the fish spends most of its time (suspended above or on the bottom). As with pharyngeal teeth, correspondence and consistency in the distribution of these features allows us to make inferences about the biology of new species.

ShortheadRedhorseswimbladder

Carpsuckerswimbladder

The swim bladders of the two sucker species shown here are diagnostic for their genera in that redhorse swim bladders are three chambered while carpsucker species have two chambers.  The Ostariophysi (group that includes the minnows, suckers, characins and catfishes) have larger swim bladders that enable them not only to more easily maintain position in the water column but also to more effectively detect vibrations in the water due to connection to the Weberian apparatus.  While most of the sucker species do have large swim bladders their bodies and skeletons are rather heavy, suiting them to their benthic lifestyle.

About the AuthorsDr. Marymegan Daly is an Associate Professor in the Department of Evolution, Ecology and Organismal Biology and Director of the OSU Fish Division.  Marc Kibbey is Associate Curator of the Fish Division in the Museum of Biological Diversity.