Dynamics of Neo-Tropical Arachnids

Today’s post is a guest post by Andrew Mularo,  an undergraduate student in the Department of Evolution, Ecology and Organismal Biology. He is currently doing his Tropical Behavior Evolution and Ecology research project under Dr. Rachelle M. M. Adams and Dr. Jonathan Shik.

You may love them or you may fear them, but no one can deny the incredible ecological importance of spiders and scorpions. As an aspiring biologist, I have chosen to study the interactions between arachnids and their environment in the tropical rainforests of Panama for the 2017 Tropical Behavioral Evolution and Ecology course. The tropics are a biodiversity hotspot for the majority of the world’s organisms, so there are plenty of creatures to look at. From the smallest spiderling to the largest tarantula, I am curious to see how these cryptic and intriguing animals interact with their ecosystem.

For my project, I am doing an observational study where I am assessing the relationship between leaf litter and arachnid diversity and abundance. I am accomplishing this by creating several 50 meter transects in the Panamanian rainforest, sampling leaf litter with 1 square meter quadrants along each transect. For each quadrant, I take a measurement of leaf litter depth, and sift through the leaves to extract any organisms out of the area. Back at the lab, I sort through the organisms, first finding any arachnids in the sample, and then any other insect or invertebrate, such as ants, beetles, millipedes, snails, mites and many others. With these data, I hope to make a correlation between leaf litter abundance and arachnid diversity and abundance, as well as a correlation between the diversity of potential prey items and arachnid predators.

Naturally, the majority of the organisms that I have been assessing have been very small, from the size of a thumbnail to not even being visible to the human eye. However, there

Wandering Spider (Photo by A. Mularo)

are several occasions where I have observed some extremely imposing arachnids in the tropical forest. One of these includes the huntsman spider, an extremely large nocturnal species that does not rely on a web to capture its prey. This family of spiders is very poorly researched, and is largely unknown how dangerous the venom is for the majority of species. However, they are quite shy, and often scurry away at the sight or sound of a human.

Another fascinating group of organisms I see occasionally are scorpions. The two pictured below are from the genus Tityus, whose venom is very potent. I found the two in the picture below, which we believe to be different species, huddled in close quarters in the water well of a bromeliad. While potentially dangerous, these are a relatively uncommon sight in the rainforest. Nevertheless, it is always good to be careful where you step.

Tityus scorpions (photo by A. Mularo)

While many of them are feared, arachnids are some of the most fascinating organisms on the planet. They come in all shapes and sizes, and have a wide array of interesting characteristics that are of great interest to scientists. Being interested in biology since I was a child, I have always dreamed of coming to the tropics so I could study the vast diversity of organisms, and I could not have picked a better group of organisms to focus on!

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.

More than 17-year cicadas


To complement Norman’s post on the 17-year cicadas, I thought today we would look at some other species of cicada that are part of the holdings of the Triplehorn Insect Collection.

Some of our cicada specimens are pretty old, dating back to the 1890’s, but the majority were collected and preserved by Joe and Dorothy Knull between the early 1930s and 1960s.

Drawer with specimens recently returned to the collection

Drawer with specimens recently returned to the collection

There are over 190 different kinds of cicadas (that includes species and subspecies) in North America alone (Sanford, 2012) and more than 3,000 around the world.

In the collection we have species of around 200 of those, but that number is likely to increase thanks to a recent loan return which added another 800 cicada specimens to the collection.  That material had been borrowed for study in 1969 and only now was returned to us. The specimens in this batch date to 1950s and 1960s.

We don’t have an exact count of the number of cicadas in the Triplehorn Insect Collection yet, but we estimate between 8,000 and 10,000 specimens. Once we finish curating and databasing our cicadas, the data for all the specimens will be available online via the collection database interface.

Here are a few of my preferred. Notice that most were collected out west. That is a reflection of the collection’s history and the research interests of the people who helped build the collection over the past 80+ years.

Some species of the genus Okanagana:


More interesting and attractive specimens:


Some exotic beauties:

Finally, a few yet to be determined show stoppers:


As we curate the collection I’ll post more photos of interesting cicada specimens from our collection.


Literature reference: Sanborn, Allen F., and Maxine S. Heath. 2012. The Cicadas (Hemiptera, Cicadoidea, Cicadidae) of North America North of Mexico. Entomological Society of America.

About the Author: Dr. Luciana Musetti is an Entomologist and Curator of the C. A. Triplehorn Insect Collection. All photos by the author.

Toothy Customers


A frequent subject of our writings, the Bowfin

Only vertebrates have true teeth, and the type of teeth they have is indicative of the feeding niche they occupy.  Fishes portray an amazing picture of diversity in teeth and correspondent feeding niches.  Some fish species have no teeth at all and thus rely on their mouths to either crush their prey as in the sturgeon, or simply suck in their prey as in the seahorse and pipefish.  Some have very few teeth, such as the non-parasitic lampreys in adult form, and some have an absolutely terrifying array of teeth such as the pikes and the sharks.


Ventral, exterior view of a Northern Pike jaw

The placement (marginal, medial and pharyngeal) of teeth within a fishes’ mouth is one of the many characters that are used to differentiate fish species.  But a Northern Pike seems to have almost all the surfaces covered:

Esox masquinongy teeth

Disarticulated Northern Pike jaw.  As you might imagine, once the prey fish is caught with the canine teeth and moved into the mouth there is little chance for escape.

Piscivorous fish typically have long, sharp teeth, but some piscivores rely on strategies alternative to their dentition to capture their prey.  The billfishes (marlins, sailfishes and swordfishes) stab and stun their prey with their elongated rostrums, sawfishes slash with a many-toothed rostrum to “collect” their prey.  Electric eels stun prey fishes, while toadfishes, anglerfishes and batfishes use a lure on their snouts or at the end of an extension to attract small fishes and may include a pheromonal attractant.  Such species typically have numerous smaller rows of teeth to grasp and hold their victims.

Fishes also exhibit diversity in the attachment of the teeth in their jaws:  The “Type I” arrangement has a strong mineralized connection between the tooth and and the jaw in bichirs, gars, bowfin, lower teleosts and some higher fishes (or the tooth and the pharyngeal bone in paddlefishes).  The “Type II” arrangement is seen in many teleosts with mineralization incomplete and the tooth connected to the jaw by collagen.  Stomiiformes (the order in which such bizarre, deep sea creatures as dragonfish, marine hatchetfish and viperfish are placed) have the Type III attachment with teeth hinged and depressible for moving prey to the esophagus and then erectible to prevent prey from escaping.  The Type IV attachment has collagen at the posterior part of the tooth base and acts as the hinge with the anterior edge lifting off the base (exposing the pulp cavity) to trap prey, this arrangement is found in pikes, some stomiiforms and higher teleosts.

Some fish groups such as sharks, wrasses, filefishes and triggerfishes exhibit polyphyodontia, the lifelong replacement of teeth.  A new tooth develops in the dental lamina under or behind the existing teeth.  In the sharks, for example, only the front 1 or 2 rows are used for feeding, while teeth develop posteriorly and move anteriorly to replace teeth individually as needed and on a regular basis.  In some shark species this occurs as frequently as every 9-12 days in the sandbar sharks or as infrequently as two to four times a year in the blue shark; with the old teeth drop to the ocean floor.  Exceptions include some like the cookie cutter sharks where the entire upper and lower sets are replaced as units and swallowed.  Piranhas replace one entire side of the teeth on their jaws at one time.  Polyphyodontia is a character that is not unique to fish however; a few mammals (kangaroos, elephants and manatees) and several reptiles replace their teeth too.  Many bony fish are monophydontic and develop only one set of teeth, while most mammals are diphydontic, replacing their teeth only once.

Below are several examples of fish groups or individual species that exemplify the variety in fish dentition and coincident feeding niches.  Forthcoming at the end of the week I’ll post images of these species and their teeth.

Lampreys – start out their life cycle with a toothless mouth suited to filter feeding, and in the parasitic forms develop several circular rows of sharp teeth used for latching onto and rasping a hole in their prey.

Sharks– teeth are triangular and razor sharp, those on the lower jaw have small serrated lateral cusps at the bases for enhanced cutting and tearing that is facilitated with strong jaw musculature and shaking motion of the head or chewing.  Sharks, unlike the higher fishes, do not have pharyngeal jaws associated with their gill baskets.

Lungfish – have a tooth structure unique among the vertebrates: sturdy tooth plates called “Odontodes” that are used for grasping and crushing prey

Gar – rows of small villiform teeth for capturing and holding fishes in their elongated jaws while they manipulate the fish to a headfirst position for swallowing

Bowfin – many sharp caniform, inward pointing teeth on the premaxilla, dentary and maxilla jaw bones for grasping and holding the prey (an extreme example of canine teeth is shown in the African Tigerfish)

Pike – the long, sharply curved caniform teeth on the dentary are a prelude to a villainous array of cardiform teeth  on the premaxillary, basibranchials, last two pharygobranchials, vomer, palatines, and glossohyal bones.

Grass Carp – the heavy pharyngeal teeth of these herbivores are used for shredding algae

Piranha  – teeth are triangular, razor sharp, with small lateral cusps at the bases like sharks

River Redhorse – feed on sand-dwelling mollusks with sturdy teeth on lower pharyngeal jaws (characteristic of all ostariophysans whereas higher teleosts have pharyngeal teeth on lower and upper arches like the redear sunfish) used for crushing molluscs found in the bottom substrates

Flathead Catfish – gulp prey with large, non-protrusible mouth and hold with cardiform teeth, the largest patches of which are on the premaxillary and anteior dentary bones

Largemouth Bass – have limited cardiform teeth on the medial jaw bones, but these are complimented by a large, protrusible mouth for engulfing prey

Ocean Pout – like many molluscivores have strong conical dentition on the anterior portion of their jaws for plucking mollusks from surfaces, and flattened, molariform teeth in marginal or pharyngeal jaws

Triggerfish (incisor-like dentition), Pufferfishes (teeth fused into parrotlike beak) – have powerful oral jaws to remove invertebrate prey (sponges, ascidians, coelenterates and chitons) from surfaces


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