Zoology

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Entries - Entry Category: Zoology - Starting with A

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 …

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 …

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 …