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


(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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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.


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.


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


Smallmouth Buffalo, Ictiobus bubalus.


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


Shorthead Redhorse, Moxostoma macrolepidotum.  Photo by Ben Cantrell.


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.


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.

Do Domestic Breeds have a place in a Museum?

Afroduck in a box

Retrieval of Afroduck, a doemstic white duck from OSU Mirror Lake © Chelsea Hothem

The recent death of a white, domestic duck with curly feathers on its head (lovingly named “Afroduck” by many OSU students) raised an interesting issue: should this specimen be archived in the tetrapods collection at the Museum of Biological Diversity (MBD)? At the MBD, we focus our research on systematic studies of organisms worldwide. Our research includes species discovery and delimitation as well as studies of the evolutionary relationships among species. Does “Afroduck” meet these criteria?

Obviously this duck was not a wild animal even though it seemed to survive on the pond for several years (though it can be questioned whether it truly was the same duck throughout that period). It was a curiosity, and isn’t that what started many natural history collections during the Renaissance? Aristocrats in Europe were proud of their cabinets of curiosities, collections of objects that could be categorized as belonging to among others natural history, geology, or archaeology. Objects that stood out seemed most worthy of collection. Our collection is witness of this based on the number of white aberrant squirrels, American Robins, Northern Cardinals, etc., that we house. These forms clearly do not reflect their natural abundances.

“Afroduck” though is not just a white form (albino or leucistic form) of its wild relative the Mallard (Anas platyrhynchos). It is a domestic breed, an animal that has been selected for characteristics that we humans like or can benefit from.  In Afroduck’s case it would be the curly feathers on its head. The fact that it was able to survive for some time in the wild though is proof that it still shares some genes and characteristics with its wild ancestor that enable it to find food, seek shelter and who knows maybe even breed?

Domestic species play a large role in the study of evolution. Did you know that Charles Darwin used domestic pigeons to support his theory of evolution? After he wrote the Origin of Species he  wrote  a book about The Variation of Animals and Plants under Domestication. Though he wrote about all types of domestication he suggested that the pigeon was the greatest proof that all domestics of one species descended from one common ancestor. In his own words:

Domestic Pigeon

Domestic Pigeon © Stephanie Malinich

Domestic Pigeon

Domestic Pigeon © Stephanie Malinich

“I have been led to study domestic pigeons with particular care, because the evidence that all the domestic races have descended from one known source is far clearer than with any other anciently domesticated animal.” – Charles Darwin

In his book, he described detailed measurements from study skins of over 120 different domestic breeds. These skins were later donated to the Natural History Museum in London, UK. In 2009, those same study skins received again research attention. In honor of the 150th anniversary of the Origin of Species scientists compared the specimens that Darwin studied to living pigeon breeds today to examine any changes in artificial and natural selection. This study concluded that the same changes continue today due to artificial selection exactly as Darwin saw in his time.

How does this relate to our collections at The Ohio State University?

In the Tetrapod Collection we possess many domestic breeds to represent the evolutionary relationships of their ancestral species. We use these specimens to educate people about Darwin’s research and evolution in general. When you look at a domestic species next to their ancestor you can see the subtle similarities of how they feed, move, and more.

Here is an example of an ancestor and some of its domestic descendants:

Going back to our question, should the domestic white duck from Mirror Lake have a place in the collection? We think it should. During our annual Open House on April 23rd, 2016 you will be able to see it as an example of artificial selection, the Mallard and its domestic descendant “Afroduck”. Even though the White Crested Duck has a tuft of feathers which makes it look quite different, it descended from the Mallard. In fact, almost all domestic breeds of ducks descended from the Mallard with the exception of the Muscovy Duck which is of South American origin. Join us during our  Open House to see the White Crested Duck, “Afroduck,” next to its ancestor the Mallard and observe the similarities for yourself!

About the Author: Stephanie Malinich is the Collection Manager for the Tetrapod Collection.

Christmas Tree Ornament Snails


Halotudora gruneri (Pfeiffer, 1846)

Halotudora gruneri (Pfeiffer, 1846)

As the holidays are upon us, it is comforting to know that even the lowliest creatures celebrate the season.

The Caribbean land snails in the family Annulariidae do a lot of strange things, but among the strangest is their propensity to hang upside down from a thread or threads of hardened mucus like Christmas tree ornaments. Why they do this is a mystery. But as near as we can tell, many of them do it – no matter where they are from: Cuba, Jamaica, Hispaniola, Puerto Rico, Curaçao, Guatemala – their entire zoogeographic range. This suggests that this odd behavior is quite ancient. The thread-spinning trait must have evolved very early on in the history of these snails before they dispersed throughout the Caribbean and Central America.

When do they do it? Well, they seem to do it at night and they will suspend themselves from caves, trees, walls – pretty much anything, including other snails. They secrete a mucus thread or threads from which they hang. To my knowledge no one has actually seen them do it. The previous evening they are crawling around, the next morning they are suspended. From where is the thread produced? Unknown. The snails have an operculum – a trapdoor attached to their foot that seals the shell opening when the animal is withdrawn. The operculum is clamped down on the thread suggesting that the animal does not have to expend energy holding on to the thread.

Why do they do it? No one knows. But the thread is very fragile – the slightest touch will break it, causing the snail to fall to the ground. The most plausible suggestion as to why they bother is that the behavior is an antipredator device. Any would-be predator crawling down the thread would cause the thread to break, thus losing the snail and their potential lunch. The fall apparently does not harm the snail; dented and broken shells are common in some species.

The photos below show some ornamental snails from Guatemala.

Diplopoma osberti (Tristram, 1861)

Diplopoma osberti (Tristram, 1861)

Gouldipoma coltrorum Watters, 2014

Gouldipoma coltrorum Watters, 2014

Parachondria rubicundus (Morelet, 1849)

Parachondria rubicundus (Morelet, 1849)

Diplopoma rigidulum (Morelet, 1851)

Diplopoma rigidulum (Morelet, 1851)

















About the Author: Dr. G. Thomas Watters is Curator of Molluscs at the Museum of Biological Diversity.

Fish Face


Although any individual fish might be hard to pick out of its school photo,  fish faces can be  remarkably distinct.


About the Authors: This blog post is a collaboration between Dr. Meg Daly, Director of the Fish Division & Marc Kibbey, Associate Curator of the Fish Division.  All photos by Marc Kibbey.


“(S)he got legs,” a look at mite legs


Mites are notorious for not following the “rules.”  For example, we generally teach that you can separate Insects from Arachnids by the number of legs, 3 pairs in insects, 4 pairs in arachnids. Simple, right?  Mites are arachnids, and most have 4 pairs of legs, but not all


And of course legs can get highly modified for various (known or unknown) purposes


About the Author: Dr. Hans Klompen is Professor in the Department of Evolution, Ecology and Organismal Biology & Director of the Ohio State University Acarology Collection.