Zoology

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Entries - Entry Category: Zoology - Starting with N

Nematodes

aka: Roundworms
The phylum Nematoda includes three classes (Anoplea, Chromodorea, and Rhabditida), sixteen to twenty orders, and about 27,000 described species (and possibly up to one million) of mostly dioecious, elongate, bilaterally symmetrical pseudocoelomate worms. They can be found in abundance in nearly every habitat on Earth, with a diverse array of species existing in both marine and terrestrial habitats. Most are free-living, with less than half considered to be parasitic. Nevertheless, many species threaten the health of plants and animals (including humans) on a global scale. Nematodes are variable in size from less than one millimeter to more than one meter in length. They have been in existence for an estimated one billion years, having evolved from simple animals some 400 …

Nematomorpha

aka: Horsehair Worms
aka: Hairworms
Horsehair worms belong to the phylum Nematomorpha and are typically obligate parasites of terrestrial arthropods (e.g., beetles, crickets, cockroaches, locusts, grasshoppers, and mantids). As adults, however, they are free-living in aquatic environments. These worms are sometimes found in coiled clusters termed “Gordian knots” from the intricate legendary knot of Greek mythology. Another myth is related to the common name given these worms, “hairworms” or “horsehair worms,” originating from the idea that horse hairs that fell into water became worms. This belief was not disproved scientifically until American anatomist and paleontologist Joseph Leidy (1823–1891) noted in 1870 that horse hairs placed in water for many months did not come to life. The first published report of a horsehair worm from Arkansas …

Nemertea

aka: Ribbon Worms
The phylum Nemertea is an invertebrate phylum that contains over 1,000 species within 250 genera of mostly marine organisms known variously as ribbon, proboscis, or nemertean worms. Only a few taxa inhabit freshwater, and there are several terrestrial species. Most are free living; however, a few are known to be parasitic. The name means one of “Nereis” (unerring one), which refers to the unerring aim of the proboscis. Ribbon worms are unique in having an eversible muscular proboscis that is used for grasping prey. It lies free inside of a cavity above the alimentary canal known as the rhynchocoel. This muscular tube can be swiftly thrust out to catch prey items. This phylum is also occasionally called the Rhynchocoela, which …

Northern Snakehead

aka: Channa argus
aka: Snakehead
The northern snakehead (Channa argus) is a modern bony fish belonging to the family Channidae. It is native to China, eastern Russia, and parts of the Korean peninsula. The fish was discovered in Arkansas in 2008, leading to attempts to eradicate it. The northern snakehead has an elongate body, with long dorsal and anal fins, and a truncated tail. Coloration is dark tan to brown with darker spots laterally, extending above and below the midline. The jaws have sharp, pointed teeth. The fish can reach a size of one meter and weigh as much as eight kilograms. The northern snakehead breathes with gills but also possesses a suprabranchial organ, which consists of chambers filled with folded tissue that allow atmospheric …