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Cephalocaridan
The Cephalocarida, from Ancient Greek κεφαλή (''kephalḗ''), meaning "head", and καρίς (''karís''), meaning "shrimp", are a class (biology), class in the subphylum Crustacean, Crustacea comprising only 12 species. Both the Crustacean larva#Nauplius, nauplii and the adults are Benthic zone, benthic. They were discovered in 1955 by Howard L. Sanders, and are commonly referred to as horseshoe shrimp. They have been grouped together with the Remipedia in the Xenocarida. Although a second Family (biology), family, Lightiellidae, is sometimes used, all cephalocaridans are generally considered to belong in just one family: Hutchinsoniellidae. Fossil records of cephalocaridans have been found in the Ordovician Castle Bank site. Taxonomy * Class Cephalocarida Sanders 1955 ** Order Brachypoda Birshteyn 1960 *** Family Hutchinsoniellidae Sanders 1955 **** Genus ''Chiltoniella'' Knox & Fenwick 1977 ***** ''Chiltoniella elongata'' Knox & Fenwick 1977 **** Genus ''Hampsonellus'' H ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hutchinsoniella Macracantha
''Hutchinsoniella macracantha'' is a species of crustacean known as a horseshoe shrimp. It is the only species in the genus ''Hutchinsoniella'' and was first described in 1955 by Howard L. Sanders, having been discovered in Long Island Sound; they were the first example of a new class of crustacean that was given the name Cephalocarida. Description Adult cephalocaridans are between in length. The body is divided into a Cephalon (arthropod head), cephalon, a segmented thorax and a segmented abdomen, with a cephalic shield covering the cephalon. There are no eyes and the body is flexible and translucent. The thorax has a pair of limbs on each segment while the abdomen is limbless, apart from the telson with its slender caudal filaments. The body and limbs are ornamented with various setae and spines. Ecology ''Hutchinsoniella macracantha'' feeds on flocculent detritus, organic particles which have settled on the seabed in hollows and other places with little water movement. These ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hutchinsoniella
''Hutchinsoniella macracantha'' is a species of crustacean known as a horseshoe shrimp. It is the only species in the genus ''Hutchinsoniella'' and was first described in 1955 by Howard L. Sanders, having been discovered in Long Island Sound; they were the first example of a new class of crustacean that was given the name Cephalocarida. Description Adult cephalocaridans are between in length. The body is divided into a cephalon, a segmented thorax and a segmented abdomen, with a cephalic shield covering the cephalon. There are no eyes and the body is flexible and translucent. The thorax has a pair of limbs on each segment while the abdomen is limbless, apart from the telson with its slender caudal filaments. The body and limbs are ornamented with various setae and spines. Ecology ''Hutchinsoniella macracantha'' feeds on flocculent detritus, organic particles which have settled on the seabed in hollows and other places with little water movement. These particles are wafted by me ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Family (biology)
Family (, : ) is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between order and genus. A family may be divided into subfamilies, which are intermediate ranks between the ranks of family and genus. The official family names are Latin in origin; however, popular names are often used: for example, walnut trees and hickory trees belong to the family Juglandaceae, but that family is commonly referred to as the "walnut family". The delineation of what constitutes a family—or whether a described family should be acknowledged—is established and decided upon by active taxonomists. There are not strict regulations for outlining or acknowledging a family, yet in the realm of plants, these classifications often rely on both the vegetative and reproductive characteristics of plant species. Taxonomists frequently hold varying perspectives on these descriptions, leading to a lack of widespread consensus within the scientific community ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sediment
Sediment is a solid material that is transported to a new location where it is deposited. It occurs naturally and, through the processes of weathering and erosion, is broken down and subsequently sediment transport, transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand and silt can be carried in suspension (chemistry), suspension in river water and on reaching the sea bed deposited by sedimentation; if buried, they may eventually become sandstone and siltstone (sedimentary rocks) through lithification. Sediments are most often transported by water (fluvial, fluvial processes), but also wind (aeolian processes) and glaciers. Beach sands and stream channel, river channel deposits are examples of fluvial transport and deposition (geology), deposition, though sediment also often settles out of slow-moving or standing water in lakes and oceans. Desert sand dunes and loess are examples of aeolian transport and deposition. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Intertidal Zone
The intertidal zone or foreshore is the area above water level at low tide and underwater at high tide; in other words, it is the part of the littoral zone within the tidal range. This area can include several types of habitats with various species of life, such as sea stars, sea urchins, and many species of coral with regional differences in biodiversity. Sometimes it is referred to as the ''littoral zone'' or '' seashore'', although those can be defined as a wider region. The intertidal zone also includes steep rocky cliffs, sandy beaches, bogs or wetlands (e.g., vast mudflats). This area can be a narrow strip, such as in Pacific islands that have only a narrow tidal range, or can include many meters of shoreline where shallow beach slopes interact with high tidal excursion. The peritidal zone is similar but somewhat wider, extending from above the highest tide level to below the lowest. Organisms in the intertidal zone are well-adapted to their environment, facing high ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Maxilla (arthropod)
In arthropods, the maxillae (singular maxilla) are paired structures present on the head as mouthparts in members of the clade Mandibulata, used for tasting and manipulating food. Embryologically, the maxillae are derived from the 4th and 5th segment of the head and the maxillary palps; segmented appendages extending from the base of the maxilla represent the former leg of those respective segments. In most cases, two pairs of maxillae are present and in different arthropod groups the two pairs of maxillae have been variously modified. In crustaceans, the first pair are called maxillulae (singular maxillula). Modified coxae at the base of the pedipalps in spiders are also called "maxillae", although they are not homologous with mandibulate maxillae. Myriapoda Millipedes In millipedes, the second maxillae have been lost, reducing the mouthparts to only the first maxillae which have fused together to form a gnathochilarium, acting as a lower lip to the buccal cavity and the m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mandible (arthropod)
250px, The mandibles of a bull ant The mandible (from or mandĭbŭ-lum, a jaw) of an arthropod is a pair of mouthparts used either for biting or cutting and holding food. Mandibles are often simply called jaws. Mandibles are present in the extant subphyla Myriapoda (millipedes and others), Crustacea and Hexapoda (insects etc.). These groups make up the clade Mandibulata, which is currently believed to be the sister group to the rest of arthropods, the clade Arachnomorpha (Chelicerata and Trilobita). Unlike the chelicerae of arachnids, mandibles can often be used to chew food. Mandibulates also differ by having antennae, and also by having three distinct body regions: head, thorax and abdomen. (The cephalothorax (or prosoma) of chelicerates is a fusion of head and thorax.) Insects Insect mandibles are as diverse in form as their food. For instance, grasshoppers and many other plant-eating insects have sharp-edged mandibles that move side to side. Most butterflies ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antenna (biology)
An antenna (plural: antennae) is one of a pair of appendages used for Sensory system, sensing in arthropods. Antennae are sometimes referred to as ''feelers''. Antennae are connected to the first one or two Segmentation (biology), segments of the arthropod head. They vary widely in form but are always made of one or more jointed segments. While they are typically sensory organs, the exact nature of what they sense and how they sense it is not the same in all groups. Functions may variously include sensing tactition, touch, air motion, heat, vibration (sound), and especially insect olfaction, smell or gustation, taste. Antennae are sometimes modified for other purposes, such as mating, brooding, swimming, and even anchoring the arthropod to a substrate (biology), substrate. Larval arthropods have antennae that differ from those of the adult. Many crustaceans, for example, have free-swimming larvae that use their antennae for swimming. Antennae can also locate other group members i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Telson
The telson () is the hindmost division of the body of an arthropod. Depending on the definition, the telson is either considered to be the final segment (biology), segment of the arthropod body, or an additional division that is not a true segment on account of not arising in the embryo from teloblast areas as other segments. It never carries any appendages, but a forked "tail" called the caudal furca may be present. The shape and composition of the telson differs between arthropod groups. Crustaceans In lobsters, Caridea, shrimp and other Decapoda, decapods, the telson, along with the uropods, forms the tail fan. This is used as a paddle in the caridoid escape reaction ("lobstering"), whereby an alarmed animal rapidly flexes its tail, causing it to dart backwards. Krill can reach speeds of over 60 cm per second by this means. The Induction period, trigger time to optical stimulus (physiology), stimulus is, in spite of the low temperatures, only 55 milliseconds. In th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thorax (arthropod Anatomy)
The thorax is the midsection ( tagma) of the hexapod body (insects and entognathans). It holds the head, legs, wings and abdomen. It is also called mesosoma or cephalothorax in other arthropods. It is formed by the prothorax, mesothorax and metathorax and comprises the scutellum; the cervix, a membrane that separates the head from the thorax; and the pleuron, a lateral sclerite of the thorax. In dragonflies and damselflies, the mesothorax and metathorax are fused together to form the synthorax. In some insect pupae, like the mosquitoes', the head and thorax can be fused in a cephalothorax. Members of suborder Apocrita (wasps, ants and bees) in the order Hymenoptera Hymenoptera is a large order of insects, comprising the sawflies, wasps, bees, and ants. Over 150,000 living species of Hymenoptera have been described, in addition to over 2,000 extinct ones. Many of the species are parasitic. Females typi ... have the first segment of the abdomen fused with the thorax ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arthropod Leg
The arthropod leg is a form of jointed appendage of arthropods, usually used for walking. Many of the terms used for arthropod leg segments (called podomeres) are of Latin origin, and may be confused with terms for bones: ''coxa'' (meaning hip (anatomy), hip, : ''coxae''), ''trochanter'', ''femur'' (: ''femora''), ''tibia'' (: ''tibiae''), ''tarsus'' (: ''tarsi''), ''ischium'' (: ''ischia''), ''metatarsus'', ''carpus'', ''dactylus'' (meaning finger), ''patella'' (: ''patellae''). Homology (biology), Homologies of leg segments between groups are difficult to prove and are the source of much argument. Some authors posit up to eleven segments per leg for the most recent common ancestor of Neontology, extant arthropods but modern arthropods have eight or fewer. It has been argued that the ancestral leg need not have been so complex, and that other events, such as successive loss of function of a Homeobox, ''Hox''-gene, could result in Parallel evolution, parallel gains of leg segments ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hermaphrodite
A hermaphrodite () is a sexually reproducing organism that produces both male and female gametes. Animal species in which individuals are either male or female are gonochoric, which is the opposite of hermaphroditic. The individuals of many taxonomic groups of animals, primarily invertebrates, are hermaphrodites, capable of producing viable gametes of both sexes. In the great majority of tunicates, mollusks, and earthworms, hermaphroditism is a normal condition, enabling a form of sexual reproduction in which either partner can act as the female or male. Hermaphroditism is also found in some fish species, but is rare in other vertebrate groups. Most hermaphroditic species exhibit some degree of self-fertilization. The distribution of self-fertilization rates among animals is similar to that of plants, suggesting that similar pressures are operating to direct the evolution of selfing in animals and plants. A rough estimate of the number of hermaphroditic animal species ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
