Zoology

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Entry Category: Zoology

Acanthocephalans

aka: Spiny-Headed Worms
aka: Thorny-Headed Worms
These cylindrical metazoan worms, superficially similar to nematodes, belong to the phylum Acanthocephala and include four classes, ten orders, twenty-six families, and about 1,300 species. Recent molecular studies suggest that Rotifera (rotifers) and Acanthocephala are phylogenetically related sister groups. Adult members are highly specialized, dioecious (having distinct male and female colonies, as opposed to hermaphroditic) parasites of the intestinal tract of a variety of vertebrates (but not generally humans). They cause serious disease fairly rarely. The life cycle involves at least two hosts, either an aquatic intermediate host (Amphipoda, Copepoda, Isopoda, and Ostracoda) or terrestrial intermediate hosts including insects, crustaceans, and myriapods. Fishes, amphibians, reptiles, birds, and mammals serve as definitive hosts. Acanthocephalans range from 0.92 to 2.4 millimeters long …

Alligator Snapping Turtle

The alligator snapping turtle (Macrochelys temminckii) is North America’s largest freshwater turtle. This turtle is found primarily in major rivers, streams, swamps, and oxbow lakes throughout much of the south-central United States—all around the states of Arkansas and Mississippi and in portions of Texas, Oklahoma, Kansas, Missouri, Illinois, Iowa, Georgia, and Florida. Alligator snapping turtles have distinct morphological features that distinguish them from their closest cousin, the snapping turtle (Chelydra serpentina). For example, the dorsal shell, or carapace, of the alligator snapping turtle has three prominent keels (ridges on the carapace), whereas the keels of the snapping turtle are low and become less conspicuous with age. The tails of both species have three rows of tubercles (warty projections), but these scales …

American Alligator

The American alligator (Alligator mississippiensis) belongs to the class Reptilia, order Crocodylia, superfamily Alligatoroidea, and family Alligatoridae. There are seven species in the family endemic to the New World tropics, with an eighth species occurring in the warmer temperate regions of China. The American alligator is endemic to the southeastern coastal plain of the United States, where it inhabits freshwater wetlands such as streams, reservoirs, ponds, lakes, coastal marshes, bayous, oxbows, and cypress swamps associated with larger rivers in parts of Alabama, Arkansas, Florida (and some Florida Keys), Georgia, Louisiana, Mississippi, North Carolina, Oklahoma, South Carolina, Texas, and Virginia; it also occurs in the lower Rio Grande Valley of Texas south of San Antonio, and farther south into the thornscrub …

American Burying Beetle

aka: Giant Carrion Beetle
The American burying beetle (Nicrophorus americanus)—which belongs to the Phylum Arthropoda, Class Insecta, Order Coleoptera, and Family Silphidae—is a carnivorous beetle that feeds on and requires carrion to breed. It is the largest North American carrion beetle. In July 1989, it was placed on to the federal Endangered Species List; the International Union for Conservation of Nature (IUCN) currently lists the species as critically endangered. However, the U.S. Fish and Wildlife Service has proposed to downlist N. americanus from endangered to threatened under the Endangered Species Act. In the few states in which it is found, including Arkansas, it is ranked S1 (critically imperiled) by NatureServe. The decline of N. americanus has been attributed to habitat loss, alteration, and degradation, …

American Eel

The American eel (Anguilla rostrata) belongs to the order Anguilliformes and family Anguillidae. Common names include Atlantic eel, common eel, freshwater eel, silver eel, yellow-bellied eel, green eel, black eel, bronze eel, elver, whip, and easgann. This family includes about eighteen facultative catadromous species of eels. The American eel ranges from Greenland and Iceland and all the drainages of eastern North America along the Atlantic and Gulf slopes west to New Mexico and south to Venezuela and islands of the Caribbean and West Indies across a latitudinal range of 5 to 62° N. In North America, A. rostrata occurs inland from eastern Canada to the Great Lakes, in the headwaters of many Atlantic and Gulf slope rivers, and in the …

Ammonites

aka: Ammonoids
Ammonites are an extinct group of marine invertebrates in the Phylum Mollusca, Class Cephalopoda, and Subclass Ammonoidea. The subclass can be divided into six orders as follows: Agoniatitida (present in the Lower Devonian–Middle Devonian), Clymeniida (Upper Devonian), Goniatitida (Middle Devonian–Upper Permian), Prolecanitida (Upper Devonian–Upper Triassic), Ceratitida (Upper Permian–Upper Triassic), and Ammonitida (Lower Jurassic–Upper Cretaceous). The name “ammonite,” from which the common name is derived, was inspired by the spiral shape of their fossilized shells, which somewhat resembles tightly coiled ram’s horns. These molluscs are more closely related to living coleoids (e.g., cuttlefish, octopuses, and squid) than they are to shelled nautiloids, such as extant chambered Nautilus species. The earliest ammonites originated from within the bactritoid nautiloids, appearing during the Devonian …

Amphibians

Arkansas has within its borders a modest assemblage of salamanders, frogs, and toads, which are taxonomically grouped in the class Amphibia and, therefore, are commonly called amphibians. Amphibians were the first tetrapods (four-legged vertebrates) to walk on land, having come from an early-evolving group of lobe-finned fishes nearly 360 million years ago. Today’s amphibians possess a mostly bony skeleton with a strong “backbone” comprising a series of interlocking vertebrae. Salamanders are termed caudates because they possess a tail in both the juvenile and adult forms, whereas frogs and toads (collectively called anurans) lack tails as adults even though the larvae (tadpoles) possess them. The study of amphibians has been traditionally linked with the study of reptiles in the professional field …

Amphipods

aka: Scuds
Amphipods belong to the Phylum Arthropoda, Class Crustacea, Subclass Malacostraca, and Order Amphipoda. The Malacostraca contains seventy percent of all known crustaceans. Over 10,000 species of amphipods are currently recognized. Twenty species of amphipods are known from Arkansas, with most being found in groundwater environments. Traditionally, amphipods have been placed in four suborders: the Caprellidea, Gammaridea, Hyperiidea, and Ingolfiellidea. The Gammaridea, which contains the majority of species, includes all the freshwater and semi-terrestrial taxa. The Hyperiidea includes the pelagic amphipods, which are associated with other planktonic forms such as gelatinous zooplankton (medusae and ctenophores). Hyperiids are usually characterized by very large eyes, although some forms, like gammarideans, have normal-sized eyes. Hyperiid members are a polyphyletic group, and it is thought …

Annelids

aka: Segmented Worms
The phylum Annelida consists of over 22,000 living species of segmented worms. They include earthworms, leeches, and ragworms. Annelids are bilaterally symmetrical, triploblastic invertebrates that inhabit a wide diversity of habitats, including marine environments such as tidal zones, hydrothermal vents, lotic and lentic freshwater habitats, and moist terrestrial habitats. The term “Annelida” originated in 1802 from French naturalist, Jean-Baptiste Lamarck’s (1744‒1829), annélides. Several species of annelids can be found in Arkansas. The overall classification of the phylum is undergoing significant revisions and has not yet been stabilized completely. Phylogenomic and other molecular phylogenetic analyses have shown that taxonomic groupings previously based on morphology in many cases are invalid. The phylum was previously divided into three classes as follows: Polychaeta (marine, …

Apicomplexans

aka: Sporozoans
The protistan Phylum Apicomplexa (formerly Sporozoa) contains a tremendous variety of obligate intracellular parasites infecting many different organisms, including humans. As a group, these parasites are cosmopolitan in their range of infected hosts and geographic distribution. They include such diverse parasites as coccidians, cryptosporids, gregarines, haemosporoids, and piroplasms. All are united, not by their biology or life histories, but morphologically by the presence of a unique structure called an apical complex. The classification scheme that cites this structure has a practical purpose to sort this diversity in a functional manner that can: (1) be easily understood and, (2) serve a utilitarian purpose by non-specialists. However, the field of classifying Apicomplexa is in flux; indeed, its taxonomy has changed throughout the …

Arachnids

Arachnids belong to Chelicerata, one of four groups of living arthropods. The other three groups are Crustacea, Myriapoda (centipedes and millipedes), and Hexapoda (insects and relatives). There are eleven living arachnid orders, and Arkansas has representatives of five of these including Scorpiones (scorpions), Pseudoscorpiones (pseudoscorpions), Opiliones (harvestmen), Aranea (spiders), and Acari (mites). Overview of Arachnids Arachnid bodies are divided into two main regions called the prosoma (cephalothorax) and opisthosoma (abdomen). These regions have been subdivided in some groups (e.g., solifugids, scorpions). The prosoma holds six pairs of appendages. Unlike in all other arthropods, the first appendages in chelicerates are not sensory antennae but pincer-like mouthparts known as chelicerae (hence the subphylum name). Behind the chelicerae, there are two pedipalps that …

Arkansas Darter

aka: Etheostoma cragini
Arkansas darter (Etheostoma cragini) populations are scattered among some small, spring-fed tributaries of the Arkansas River basin in Colorado, Kansas, Oklahoma, Missouri, and Arkansas. This fish species is rare in Arkansas, being found only in a few spring runs in the Illinois River basin of Benton and Washington counties. The small streams occupied by Arkansas darters are characterized by slow current and silt substrates. The darters shelter in watercress and other aquatic plants, overhanging or flooded terrestrial vegetation, and even in the loose silt of the stream bottom. In some places, they have been observed to move down into larger streams, but this has not been so in Arkansas. They grow to a maximum size of around two inches and …

Arkansas Entomological Society

The Arkansas Entomological Society (AES) was founded in May 1991 by entomology educators, researchers, and industry professionals under the guidance of Dr. William Yearian, former chair of the Entomology Department at the University of Arkansas (UA) in Fayetteville (Washington County). The first president of the society, Dr. Timothy Kring, drafted the society’s constitution with the purpose of fostering entomological accomplishment among its members as well as bringing about closer coordination and understanding among research, regulatory, educational, and commercial entomologists. Entomology is the study of insects and related organisms. Meetings of the society have been held annually since its founding, with locations and dates varying, but most often held on the first Friday and Saturday in October. Every other year, the …

Arkansas Fatmucket

aka: Lampsilis powellii
The Arkansas fatmucket is a bivalve mollusk belonging to the family Unionidae, commonly referred to as freshwater mussels, naiads, or clams. Each freshwater mussel is composed to two halves (valves) of a hard outer shell, with the living animal (soft tissues) residing securely inside. The Arkansas fatmucket (Lampsilis powellii) was described as a species new to science in 1852 by Isaac Lea, a naturalist and publisher by trade residing in Philadelphia, Pennsylvania. Lea based his description on specimens provided to him by Dr. Josiah Hale and Professor W. Byrd Powell from the Saline River at Benton (Saline County). Adults rarely reach a length of four inches (100 millimeters), and males and females are sexually dimorphic—that is, they have slightly different …

Asian Longhorned Tick

aka: Bush Tick
The Asian longhorned tick (Haemaphysalis longicornis) is an ectoparasite belonging to the Phylum Arthropoda, Class Arachnida, Order Acari, and Family Ixodidae. The Asian longhorned tick is native to temperate areas of eastern and central Asia, including China, Japan, and Korea, as well as various Pacific islands, including Australia, New Zealand, Fiji, New Caledonia, western Samoa, Vanuatu, and Tonga. In August 2017, a tick from an Icelandic sheep (Ovis aries) brought to the Hunterdon County Health Department in New Jersey was identified as H. longicornis. In November 2017, a large number of H. longicornis were discovered on a sheep farm, again in Hunterdon County. This tick had also been intercepted at U.S. port cities on imported animals and materials several times …

Aspidogastreans

aka: Aspidobothrians
aka: Aspidobothreans
An interesting group within the Class Trematodes (flukes) includes the Subclass Aspidogastrea. The Aspidogastrea is a very small taxon with around eighty species within thirteen genera, and their hosts include molluscs (sometimes spelled “mollusks”) and various vertebrates. They are of particular curiosity among parasitologists because of their unique structure, their simple life cycles (which may well be the most “primitive” ones among the trematodes), and the extraordinarily complex sensory/nervous systems found in some species.  There has been some debate among taxonomists about the relationships of the various genera of aspidogastreans; however, according to the prevalent view, there are four families as follows:  (1) Rugogastridae: with two caeca and single row of transverse rugae comprising a single genus Rugogaster; there are two species from the rectal glands of holocephalan ratfishes;  (2) Stichocotylidae: with one caecum and a single row of well separated suckerlets; includes a monotypic species (Stichocotyle nephropis) from …

Atherinopsids

aka: Neotropical Silversides
Atherinopsids, or neotropical silversides, belong to the order Atheriniformes and family Atherinopidae. There are about 104 species within thirteen genera found in euryhaline, marine, and freshwater habitats distributed throughout the tropical and temperate waters of the Western Hemisphere. Three well-known atherinopsid fishes are the Atlantic silverside (Menidia menidia), California grunion (Leuresthes tenuis), and Gulf grunion (L. sardina). There are three species in Arkansas: the brook silverside (Labidesthes sicculus), golden silverside (L. vanhyningi), and Mississippi silverside (Menidia audens). Prior to the Neogene Period of the late Tertiary Period (66 to 2.5 million years ago), there is no fossil record of atherinopsids in North America. However, on San Francisco Bay, important prehistoric intertidal fisheries were especially well documented for atherinopsids. Silversides are …

Audubon Arkansas

Audubon Arkansas was established in 2000 as the twenty-fifth state office of the National Audubon Society through a seed grant from the Winthrop Rockefeller Charitable Trust. Audubon Arkansas’s mission is to inspire and lead Arkansans in environmental education, resource management, habitat restoration, bird conservation, and enlightened advocacy. In 2003, Audubon Arkansas was recognized as “Conservation Organization of the Year” by the Arkansas Wildlife Federation. Robert Shults was the founding board chairman of Audubon Arkansas. Shults, an Arkansan, served on the National Audubon Society board of directors from 1980 to 1986. The chairman of the National Audubon Society at the time was Donal C. O’Brien. O’Brien and Shults both served on the board of trustees of the Winthrop Rockefeller Charitable Trust. …

Audubon, John James

John James Audubon, a frontier naturalist and artist, is famous for illustrating and writing The Birds of America. He visited Arkansas Territory in 1820 and 1822 and documented Arkansas’s birds, including the Traill’s flycatcher, also known as the willow flycatcher, which is the only bird originally discovered in Arkansas. John Audubon was born Jean Rabin on April 26, 1785, in Saint-Domingue (Haiti). He was the illegitimate child of Jean Audubon, a ship’s captain, and Jeanne Rabin, a French chambermaid. His mother died in 1785 or 1786, and Jean Audubon and his children returned to France after a slave revolt. Along with his sister, he was adopted by his father and stepmother in 1794. Audubon stayed with his father and stepmother …

Bachman’s Warbler

aka: Vermivora bachmanii
Bachman’s warbler (Vermivora bachmanii) was a small, yellow-and-black bird of the American wood-warbler family (Parulidae) that formerly nested in the southeastern United States, including Arkansas. In winter, Bachman’s warblers migrated south to spend the winter on the island of Cuba. Preferring swampy bottomland habitat, the species suffered severe population decline in the early twentieth century when that habitat began disappearing and believed by most ornithologists since the 1960s to be extinct. It was officially declared so by the U.S. Fish and Wildlife Service in 2021. Bachman’s warbler was discovered in 1832 near Charleston, South Carolina, by the Reverend John Bachman, a skilled amateur naturalist. Bachman (pronounced BACKman) was a close friend to John James Audubon, the famed naturalist and artist. …

Baerg, William J.

William J. Baerg was a naturalist, entomologist, and teacher who served as head of the Department of Entomology at the University of Arkansas (UA) in Fayetteville (Washington County) for thirty-one years. His research on black widow spiders, tarantulas, scorpions, and other arthropods led to descriptions of their behavior, biology, and natural history that had previously been largely ignored by biologists and entomologists. William Baerg was born in Hillsboro, Kansas, to Johann and Magaretha (Hildebrand) Baerg on September 24, 1885. His parents, who had left Russia in 1874, worked as field hands on a Kansas wheat farm. The family later acquired a small piece of land for their own. Baerg was the sixth of seven children. Baerg began school at age seven. At …

Banded Pygmy Sunfish

The banded pygmy sunfish (Elassoma zonatum) belongs to its own family (Elassomatidae) and the Order Perciformes. It is a diminutive sunfish that is about 25 to 40 mm (1.0 to 1.5 in.) in total length. This fish is endemic to the United States, where it ranges in the Mississippi River drainage from Indiana and Illinois south to Texas and east along the Atlantic Coast from North Carolina south to Florida. There are six additional species of Elassoma, including spring pygmy sunfish (E. alabamae), Carolina pygmy sunfish (E. boehlkei), Everglades pygmy sunfish (E. evergladei), Gulf Coast pygmy sunfish (E. gilberti), bluebarred pygmy sunfish (E. okatie), and Okefenokee pygmy sunfish (E. okefenokee). Interestingly, E. zonatum was described by the “Father of American …

Bats

Bats belong to the class Mammalia and the order Chiroptera. There are two suborders: the Yinpterochiroptera (formerly Megachiroptera), which includes the horseshoe and Old World fruit bats (megabats), and the Yangochiroptera (formerly Microchiroptera), the remainder of bats. Worldwide, there are eighteen families, 202 genera, and more than 1,100 species of bats with only about four percent (at least forty-five species) occurring in the United States. This mammalian order is second only in number of species behind the rodents (order Rodentia). Sixteen bat species occur in Arkansas. Much of the past research on bats in Arkansas was conducted by Michael J. (Mick) Harvey (1934–2015) of Tennessee Technical University in Cookeville. His research on several endangered bats in Arkansas was instrumental in …

Big Arkie

Big Arkie was a thirteen-foot-long alligator caught in 1952 near Hope (Hempstead County). He was the Little Rock Zoo’s main attraction for eighteen years. Weighing 500 pounds, Big Arkie was considered to be the largest alligator in captivity in the western hemisphere. Big Arkie was spied by a young boy in a flooded pasture by Yellow Creek, which is west of Hope. Ed Jackson, caretaker of a local hunting club, was alerted and, with some companions, wrapped Big Arkie in a fifty-foot-long cable attached to a tractor. The alligator spent one night in Hope’s public children’s pool, encased in chicken wire. On the following day, he was delivered to the Little Rock Zoo, doubled up in a crate. When the …

Birds

The birdlife of Arkansas (its avifauna) comprises just over 400 species, although that number includes more than forty species that have been extirpated (that is, they no longer occur) in the state, are completely extinct, or are rarities that have strayed into Arkansas fewer than a half dozen times. Around 350 species, then, can be found in Arkansas with some regularity. About 145 species nest within the state. Others nest north of Arkansas and spend the winter here or pass through the state in spring and fall as they migrate to and from nesting grounds to the north and wintering areas to the south. Arkansas’s location in the south-central United States means that its avifauna is generally typical of North …

Birdwatching

aka: Birding
Birdwatching, also commonly called birding, is the hobby of observing wild birds. Involvement in the pursuit ranges from enjoying birds on backyard feeders to traveling thousands of miles, nationally or internationally, to see new and different species. Birdwatching is usually considered to be distinct from ornithology, which is the scientific study of birds, although there is considerable overlap between the two. Birdwatchers often keep records of when and where they saw different species. Many people keep records simply for the personal satisfaction of remembering interesting and unusual sightings. Records kept by amateur birdwatchers, however, have made significant contributions to ornithology by helping with the knowledge of bird distribution and abundance. Most birdwatchers keep a life list—a record of all the …

Black Bears

aka: Ursus americanus
Black bears have a rich and varied history in Arkansas. Once giving to the state its unofficial nickname (the “Bear State”), bruins long shaped society and culture in Arkansas and continue to do so. Used for meat, fur, and fat, bears were a valuable commodity in the colonial period. By the early nineteenth century, although bears were still prized for their original uses, the bear-human relationship began to shift toward overt exploitation and bear hunting as a quest for masculine identity. By the first decades of the twentieth century, Arkansas black bears were at the brink of extirpation, but the population has since been revived. Native Americans were the first to hunt black bears in the region. Documented evidence of …

Bowfin

aka: Grinnell
Bowfin (Amia calva) belong to the primitive North American fish family Amiidae and Order Amiiformes. The family is monotypic and contains a single genus and species (A. calva). Bowfin are basal bony fishes related to gars in the infraclass Holostei. They are native to North America and are commonly found throughout much of the eastern United States, the St. Lawrence River, and Lake Champlain drainages of southern Ontario, and Quebec, Canada. Their range extends farther westward around the Great Lakes into Minnesota and south to the Colorado River in Texas. In Arkansas, A. calva is found in all major river drainages of the Gulf Coastal Plain lowlands and westward through the Arkansas River Valley; they are rarely found in the …

Branchiobdellidans

aka: Crayfish Worms
Branchiobdellidans, or crayfish worms, are leech-like, clitellate annelids belonging to the Phylum Annelida and Order Brachiobdellida (single family Brachiobdellidae) that form an obligate, ectosymbiotic association primarily with astacoidean crayfishes. They have long been known as “branchiobdellid worms” because they were considered a separate family of the oligochaetes; however, more recent treatment of these worms as a separate taxonomic order technically renders their epithet more correctly as “branchiobdellidan worms” or simply “branchiobdellidans.” Branchiobdellidans are a monophyletic clade of more than 150 ectosymbiont species within twenty-one genera found throughout North and Central America, Europe, and eastern Asia, of which about fifteen genera and 107 species have been reported from North America, including in Arkansas. However, branchiobdellid fauna in Arkansas need further study. …

Bryozoans

aka: Ectoprocta
aka: Moss Animals
Bryozoans (commonly called moss animals) are generally sessile, colonial invertebrates that belong to the phylum Bryozoa (or Ectoprocta), which is sometimes combined with two other phyla (Phoronida and Brachiopoda) to form a possible clade within the Deuterostomia. The three are sometimes referred to as the Lophophorata. Fossil bryozoans commonly found in Arkansas can be divided into two broad groups: the lacy colonies and the twig-shaped colonies. One fossil, the Archimedes, is especially abundant in northwestern Arkansas. In the southeastern United States, large gelatinous colonies of P. magnifica are a common sight, sometimes called “dinosaur snot.” These are often seen at Lake Wilhelmina in Polk County, and some have been reported in eastern Arkansas County. The primary uniting characteristic of this …