By:By:Christian Jay Rayon NobChristian Jay Rayon Nob

BS-Marine BiologyBS-Marine BiologyMindanao Sate University-Naawan CampusMindanao Sate University-Naawan Campus

COPEPOD

History of Systematic of Copepod

Copepods are a group of small crustaceans found in the sea and nearly every freshwater habitat. Cope is Greek meaning an “oar” or “paddle;” pod is Greek for “foot.”  Some species are planktonic (drifting in sea waters), some are benthic (living on the ocean floor), and some continental species may live in limno-terrestrial habitats and other wet terrestrial places.

  Copepods have antennae and appendages that are

used like paddles for movement. Some species swim in a jerky fashion, while others move more smoothly.

Interestingly, several planktonic species live at different

depth in the water column as they progress through their life cycle.

Copepods have two swimming speeds.  The first is slow, steady, and accomplished using their mouthparts.  The second looks like a succession of jumps separated by stillness. This jumpy form of swimming in accomplished by the appendages on the thorax.  Planktonic copepods have been shown to collect and handle particles in a most interesting way necessary because of their small size and interaction with the water they live in. Tiny copepods (the smallest look like specks of dust) live most everywhere in the ocean in numbers too vast to count. They're a key link in ocean food webs. They eat diatoms and other phytoplankton and are eaten in turn by larger drifters, larval fishes and filter feeders. Copepods may be the most abundant single species of animal on Earth.

Physiology

Copepods have a variety of sensory capabilities. The most noteworthy are bristle-like setae that act as mechanoreceptors responding to flow that causes bending. An array of such sensors allows detection of patterns of water flow around the body caused by approaching prey or predator, and the copepod can distinguish between the two. The sensors are highly specialized for sensitivity and the nerves are even myelinated for fast conduction.

LIFE CYCLE

During mating, the male copepod grips the female with his first pair of antennae, which is sometimes modified for this purpose. The male then produces an adhesive package of sperm and transfers it to the female's genital opening with his thoracic limbs. Eggs are sometimes laid directly into the water, but many species enclose them within a sac attached to the female's body until they hatch. In some pond-dwelling species, the eggs have a tough shell and can lie dormant for extended periods if the pond dries up.

Eggs hatch into nauplius larvae, which consist of a head with a small tail, but no thorax or true abdomen. The nauplius moults five or six times, before emerging as a "copepodid larva". This stage resembles the adult, but has a simple, unsegmented abdomen and only three pairs of thoracic limbs. After a further five moults, the copepod takes on the adult form. The entire process from hatching to adulthood can take anything from a week to a year, depending on the species

Scientific classification :

Kingdom:Animalia  Phylum:Arthropoda  Subphylum:Crustacea  Class:Maxillopoda  Subclass:Copepoda

H. Milne-Edwards, 1840

Orders  Calanoida Cyclopoida Gelyelloida Harpacticoida Misophrioida Monstrilloida Mormonilloida Platycopioida Poecilostomatoida Siphonostomatoida 

Biodiversity of Copepod

Copepods are probably the most common and abundant holoplanktonic organisms worldwide, occurring in all oceans, seas, estuaries, rivers and lakes. Some 13,000 species of copepods are known, and 2,800 of them live in freshwaters. Copepods have colonized virtually every habitat from 10,000 meters down in the deep sea to lakes 5,000 meters up in the Himalayas, and every temperature regime from subzero polar waters to hot springs.

These minute arthropods inhabit all types of marine sediments - from sand to fine mud and ooze - and can even be found on land in damp moss and in subterranean habitats, such as caves and groundwater.

Marine Habitats

Although copepods can be found almost everywhere where water is available most of the more than 12.000 known species live in the sea. As they are the biggest biomass in the oceans some call them the insects of the sea. They roam the free water, burrow through the sediment at the bottom of the seas, are found on tidal flats and in the deep sea trenches. At least one third of all species live as associates, commensals or parasites on invertebrates and fishes. One of the hotspots of species diversity are the tropical coral reefs in the Indopacific. Some coral species are hosts to up to 8 copepod species. Like the tidal flats the mangroves teem with copepod life.

Freshwater Habitats

Species of the Calanoida, Cyclopoida and Harpacticoida have successfully colonised all kinds of freshwater habitats from little creeks to glacier lakes high up in the Himalaya. Although the species diversity in freshwater is not as high as in the sea copepod abundance may sometimes be great enough to stain the water. Even in the groundwater a specialised copepod fauna has evolved. Some copepod species can be found in the leaf fall of wet forests or in a wet compost heap, sometimes in rather high densities. Others live in peat moss or even in the phytothelmata (little pools formed in the leave axils of plants) of bromeliads and other plants.

Based on UPMC Sorbonne University,EMBRC (European Marine Biological Resource Centre), CNRS.

GEOGRAPHICAL DISTRIBUTION

2546 species of pelagic Copepods have been inventoried to date (2011/2012) in all the world's oceans and seas, with Calanoida predominating (80.6 %), the other orders with 471 species (19.4 %). Among the 25 arbitrarily defined geographic zones, the number of forms inventoried is maximal for the Indian Ocean and minimal for the Arctic Ocean.

3- (271 named forms + 5 cited as sp.) in the Zone Sub-Antarctic (276 sp.) 4- (290 named forms + 6 cited as sp.) in the Zone Antarctic .(296 sp.) 5-  (447 named forms + 6 cited as sp.) in the Zone South Africa (E & W), Namibia (453 sp.); 6- (339 named forms + 1 cited as sp.) in the Zone Gulf of Guinea (sensu lato): Angola-Liberia (340 sp.); 7- (701 named forms + 10 cited as sp.) in the Zone Venezuela, Caribbean Sea, Gulf of Mexico, Caribbean, Florida, Sargasso Sea (711 sp.); 8- (725 named forms + 14 cited as sp.) in the Zone Cape Verde Is., Canary Is., Madeira Is., Azores, Bay of Biscay, Ibero-Moroccan Bay ( 739 sp.); 9-  (374 named forms + 3 cited as sp.) in the Zone Ireland, English Channel, Faroe, Norway, North Sea, Baltic Sea .(377 sp.); 10-  Southern Iceland, southern Greenland (E & W), Strait of Davis, Labrador Sea (205); 11- (255 named forms + 2 cited as sp.) in the Zone Cape Cod, Nova Scotia, Island of Newfoundland (257 sp.); 12- (328 named forms + 1 cited as sp.) in the Zone Central South-Atlantic (Tristan da Cunha-Trinidad-St Helena-N Ascension) (329 sp.); 13- (377 named forms + 2 cited as sp.) in the Zone Brazil-Argentina (379 sp.); 14-  (552 named forms + 1 cited as sp.) in the Zone Mediterranean Sea, Black Sea (553 sp.); 15-  Red Sea (259 sp.); 16-  (936 named forms + 28 cited as sp.) in the Zone Indian Ocean (964 sp.) 17-  (624 named forms + 4 cited as sp.) in the Zone Gulf of Thailand, Malaysia-Indonesia-Philippines (628 sp.); 18- (504 named forms + 14 cited as sp.) in the Zone Australia (E), Great Barrier Reef, Tasman Sea, New Zealand, New Caledonia (518 sp.); 19- (525 named forms + 8 cited as sp.) in the Zone Central Tropical Pacific (533 sp.); 20- (477 named forms + 3 cited as sp.) in the Zone Eastern Tropical Pacific (Central America, Galapagos, Northern Peru) (480 sp.); 21-  (602 named forms + 4 cited as sp.) in the Zone China Seas, Vietnam (606 sp.); 22- (669 named forms + 8 cited as sp.) in the Zone Japan Sea, Japan) (677 sp.); 23- (351 named forms + 2 cited as sp.) in the Zone North West Pacific (Sea of Okhotsk-Kuril Islands-Kamtchatka-Sea of Bering) (353 sp.); 24- (290 named forms + 1 cited as sp.) in the Zone North East Pacific (Gulf of Alaska, "P" station, British Columbia) (291 sp.); 25-  (439 named forms + 1 cited as sp.) in the Zone California-Gulf of California (440 sp.); 26- (433 named forms + 1 cited as sp.) in the Zone Chile (sensu lato)(434 sp.) ; 27- (157 named forms + 7 cited as sp.) in the Zone Arctic Ocean (164 sp.)

•(624 named forms + 4 cited as sp.) in the Zone Gulf of Thailand, Malaysia-Indonesia-Philippines (628 sp.)

•The geographical distribution of species is linked in some cases to the historical evolution of the continents, and in many others to general surface currents. Deep-water currents, which are poorly documented, may perhaps explain the erratic presence of some forms.

Terms in the Systematics of Copepod

Body Length - The length from the anterior margin of the head region to the posterior margin of the caudal rami excluding the caudal setae.

Body Regions – Useful to refer to three regions of the body of the copepod visibility distinguishable from one-another.

Cephalosome – The anterior unsegmented region of the body that includes not only the head but also, at the least, the segment of the maxillipeds.

Metasome – the segmented region of the body immediately posterior to the cephalosome and anterior to the urosome.

Urosome – the posteriormost region of the body of the copepod, usually narrower than the rest of the body and marked off from the metasome by a distinct articulation in virtue of which the urosome can be freely moved about like a tail.

Caudal Rami – A pair of laminar structures at the posterior end of the anal segment, movably articulated with the latter and each provided typically with six setae.

Geniculation – Modification of the first antennae for prehension or grasping, through the formation of an elbow or hinge.

Endopods – the inner or medial branch of a two-branced crustacean leg or appendage

Pereiopods – walking legs (swimming legs of copepods); located under the cephalothorax or metasome of crustaceans

Uniramous – in arthropods, an unbranched appendage. In crustaceans the exopodite is often lacking in walking legs.

Biramous – in crustacea it describes the condition in which appendages are divided into two segmented branches: exopodite (external branch of the appendages of Crustacea) and endopodite ( the inner or medial branch of a two-branched crustacean leg or appendage), these branches arise from a basal segment called the basipodite (basal joint of the legs of crustaceans).

Appendages – a limb or other process extending from the body, usually articulated (having a joint or joints)

Abdomen – posterior section of the body, behind the thorax or cephalothorax

Thorax – the portion of the body between the head and the abdomen

The consensus cladogram based on morphology and small subunit ribosomal DNA sequence data is superimposed on the geological column and shows the known body fossil record of copepods (red lines), as well as the predicted origin of the group (blue lines).

Cladogram

Evaluation: The phylogenetic relationships of copepods have been debated in

the last decades. Some authors proposed evolutionary schemes on account of the ecological radiation of copepods (Boxshall, 1986; Ho, 1994) , other authors pointed out cladistic approaches. Particularly Huys & Boxshall (1991). Calanoids, cyclopoids and harpacticoids show a remarkable ecological interest, since most species of these orders generally form the first link of the aquatic food chains, from the microscopic phytoplanktonic algae up to the fishes and mammalians. Recent researches, including those carried out by the Dipartimento di Scienze Ambientali of the University of L'Aquila (Italy), are pointing out an analogous importance for cyclopoid and harpacticoid species inhabiting both surface and underground fresh waters, and particularly the sediments between the superficial hyporheic zone and the rivers bottom, an interesting transitional system or ecotone between epigean and stygal waters. As a matter of fact, the contiguity with surface waters and the regular occurence of epigean elements in the hyporheic habitats let now the hydrobiologists to consider that a good estimation of rivers meiobenthic conditions must pass through a careful knowledge of the relative groundwater communities. In this last regard, an increasing number of harpacticoid and cyclopoid species are actually revealing their noteworthy importance as "pollution markers" in the environmental control of hyporheic systems and other aquatic habitats, such as lakes, springs, rivers and superficial ground (phreatic) waters.

Anatomy:

Copepods are usually very small and measure 0.019 to 0.78 inches

(0.5 to 20 millimeters) in length. A few free-living species, those that are not parasites, reach 0.7 inches (18 millimeters). The copepod body consists of a head, a middle section called a thorax, and the terminal section called the abdomen. The abdomen consists of four or five discrete segments, depending on the species. The thorax contains six segments. The unsegmented head is integrally united with the first segment of the thorax.The copepod head has a pair of segmented antennules (little antennae). The segments at the end of each antennule have bristle-like structures called setae and thin-walled hairs called aesthetascs. The aethetascs of the male copepod have receptors that can sense chemical substances emitted by female copepods. The male has longer antennules which develop a joint that enables it to grasp the female during copulation. Some copepods have only one eye. The copepod’s mouthparts are complex and vary from species to species. Sometimes the mouthparts of the male and the female differ. They possess three pairs of mouth parts. Two pairs are called maxillae and the other is a pair of mandibles. The setae of the antennae assist in directing food to the mouth, and a pair of maxillipeds on the first thoracic segment also assist in feeding. Each segments of the copepod thorax has a pair of appendages, but the abdomen has none. The last segment of the abdomen terminates in a sort of tail called a “caudal rami.

Dichotomous Key

Second antennae and mouth parts present; developmentalstages usually free swimming; adults free swimming orEctoparasitic (Parasites that live on the surface of the host )

only…………………………………………………………………… Second antennae and mouth parts absent in the adult

which is free swimming; developmental stages parasitic ………………………………………………………………………….MONSTRILLOIDA

Urossome includes not only the genital and abdominalsegments but one further segment bearing the 5th pair oflegs; first antennae of the male, if geniculate, geniculate onboth sides…………………………………………………………………….

Urosome includes the genital and abdominal segments only; first antennae of the male, if geniculate, geniculate on one side only, commonly on right side………………………………………………….. CALANOIDA

Body usually cylindrical, the metasome passing into the urosome without abrupt change in width; basal segment of the fifth legs usually showing an inner expansion; males distinguished from the females in all cases by the geniculation of the first antennae ; egg sacs usually unpaired, carried underneath………………HARPACTICOIDA

Body usually depressed with the metasome much wider urosome; basal segment of the fifth legs without an inner expansion; geniculation of the first antennae of the male is usual but not invariable; eggsacs paired, carried laterally of subdorsally……………………………………CYCLOPOIDA

Urosome 4-segmented ; 5th legs symmetrical, fully setose (covered with setae or bristles )

…………………………………………………………FEMALES Urosome 5-segmented ; 5th legs unlike on the two sides;

the left leg being usually longer through the greater elongation of the two proximal exopodite segments, the terminal segment being rather short…………………….MALES

Characters:

Copepods are placed into ten orders:

Order Calanoida

include around 40 families with about 1800 species of both marine and freshwater copepods. Calanoid copepods are dominant in the plankton in many parts of the world's oceans, making up 55%–95% of plankton samples. They are therefore important in many food webs, taking in energy from phytoplankton and algae and 'repackaging' it for consumption by higher trophic level predators. Many commercial fishes are dependent on calanoid copepods for diet in either their larval or adult forms. Baleen whales such as bowhead whales, sei whales, right whales and fin whales eat calanoid copepods.

Calanoids can be distinguished from other planktonic copepods by Calanoids can be distinguished from other planktonic copepods by having first having first antennae at least half the length of the body and  at least half the length of the body and biramous second antennae. Their key defining feature biramous second antennae. Their key defining feature anatomically, however, is the presence of a joint between the fifth anatomically, however, is the presence of a joint between the fifth and sixth body segments. The largest specimens reach 18 and sixth body segments. The largest specimens reach 18 millimetres (0.71 in) long, but most are 0.5–2.0 mm (0.02–0.08 in) millimetres (0.71 in) long, but most are 0.5–2.0 mm (0.02–0.08 in) longlong

Order Cyclopoida

Like many other copepods, members of Cyclopoida are small, planktonic animals living both in the sea and in freshwater habitats. They are capable of rapid movement. Their larval developmentis metamorphic, and the embryos are carried in paired or single sacs attached to first abdominal somite.

Cyclopoids are distinguished from other copepods by having first antennae shorter than the length of the head and thorax, and uniramous second antennae. The main joint lies between the fourth and fifth segments of the body

Order Gelyelloida Gelyella a genus of freshwater copepods  which are "surrounded by

mystery".They live in groundwater in karstic areas of southernFrance and western Switzerland. Gelyella shows some paedomorphosis, in which animals reach sexual maturity while still partly resembling juveniles. The adults are 300–400 micrometres (0.012–0.016 in) long with a nearly cylindrical body that tapers towards the rear. There are eleven body segments, the last of which is the length of the previous two segments combined.

Order Harpacticoida This order comprises 463 genera and about

3,000 species; its members are benthic copepods found throughout the world in the marine environment (most families) and in fresh water (essentially the Ameiridae, Parastenocarididae and the Canthocamptidae). A few of them are planktonic or live in association with other organisms. Harpacticoida represents the second-largest meiofaunal group in marine sediment milieu, after nematodes. In Arctic and Antarctic seas, Harpacticoida are common inhabitants of sea ice.

Harpacticoids are distinguished from other copepods by the presence of Harpacticoids are distinguished from other copepods by the presence of only a very short pair of first only a very short pair of first antennae. The second pair of antennae are . The second pair of antennae are biramous, and the major joint within the body is located between the fourth biramous, and the major joint within the body is located between the fourth and fifth body segments. They typically have a wide and fifth body segments. They typically have a wide abdomen, and often , and often have a somewhat worm-like body. Sixty-seven families are currently have a somewhat worm-like body. Sixty-seven families are currently recognised in the Harpacticoidarecognised in the Harpacticoida

Order Misophrioida

Carapace-like extension from the head covers the first segment bearing a swimming leg; heart present in some; no eyes; antennule with up to 27 segments.

Order Monstrilloida is an order of copepods with a 

cosmopolitan distribution in the world's oceans. The order contains a single family,Monstrillidae; The taxonomy of the family is undergoing a period of revision. The order is poorly known, biologically and ecologically, although the life cycle is known to differ from that of all other copepods. Thelarvae are parasites of benthic polychaetes and gastropods, while the adults are planktonic and incapable of feeding, functioning solely to reproduce. but a rudimentary or absent fifth pair. Adults have no oral appendages, and the mouth leads only to a short, blind pharynx. Females carry a long pair of spines to which the eggs are attached, while males have a "genital protuberance, which is provided with lappets"; in both sexes, the genitalia are very different from those of all other copepods.

Order Platycopioida

Members of the Platycopiidae have a primitive form, thought to be similar to the most recent common ancestor of all copepods. Few synapormorphies have been found to unite the family, but they include the presence of a second dorsal seta (hair) on particular segments of the legs. They share with calanoid copepods the possession of Von Vaupel Klein's organ, a sensory organ near the base of the first swimming leg.

Order Poecilostomatoida

The classification of these copepods has been established on the basis of the structure of the mouth. In poecilostomatoids the mouth is represented by a transverse slit, partially covered by the overhanging labrum which resembles an upper lip. Although there is variability in the form of the mandible among poecilostomatoids, it can be generalized as being falcate (sickle-shaped). The antennules are frequently reduced in size and the antennae modified to terminate in small hooks or claws that are used in attachment to host organisms.

Most poecilostomatoid copepods are ectoparasites of saltwater fish or invertebrates (including among the latter mollusks andechinoderms). They usually attach to the external surface of the host, in the throat-mouth cavity, or the gills. One family of poecilostomatoid copepods, however, have evolved an endoparasitic mode of life and live deep within their hosts' bodies rather than merely attaching themselves to exterior and semi-exterior surface tissue.

In addition to typical marine environments, poecilostomatoid copepods may be found in such very particular habitats as anchialine cavesand deep sea vents (both hydrothermal vents and cold seeps). Here, many primitive associated copepods belonging to the orders Poecilostomatoida and Siphonostomatoida and have been found. Representatives of one Poecilostomatoida family have successfully made the transition to freshwater habitats and host animals therein.

Order Siphonostomatoida

are copepods of the order of the subclass Maxillopoda, inside the subphylum Crustacea. There are 42 recognised families. They are ectoparasites on the body surface of marine fishes; not the parasitic adaptations.The body shows a fushion of the ancestral body somites: a large, flat cephalothorax followed by one to three free thoracic segments (prosome), a large genital segment, and a smaller unsegmented abdomen (urosome). The principal appendages for prehension are the second antennae and maxillipeds.

Ten Species

(From Order Calanoida and Cyclopoida)

Order Calanoida

Family Specie Distinguishing charactestics

Image

Acartiidae Small and slender; Single eye present.

Acartia tranteri

Cigar-shaped body. Rounded edges on prosome posteriorly. Naupliar eye very prominent.Colour: transparent to

dark grey when alive.

Acartia danae

Top of head is flat or slightly triangular. Long, slender cigar-shaped body. Long, spaced out setae on antennae. Fresh specimens usually transparent, with prominent eye-spot (red or black).Metasome is pointed anteriorly in dorsal view and bears a pair of sharp

points posteriorly.

Calanidae Body elongate-oval shaped.Abdomen moderately long.Long antennules.

Calanus

australis Relatively large species.Cephalosome is rounded anteriorly.Inner margin of basipodite (2nd segment) 1 of leg 5 is serrated (toothed). No recurved spine on the outer distal border of the 1st exopodite segment of leg 2.1st antenna exceeds the body

length by a few segments Nannocalanus

minor Bullet shaped.Readily recognized from other Calanus species by the small size.Cephalosome is rounded anteriorly.Head and 1st leg-bearing segment of the metasome are fused.

Centropagidae Wide, rectangular shaped bodies.Posterior corners of prosome often quite pointed and

distinct. Centropages australiensis

Cephalosome is rounded anteriorly in dorsal view and bears a pair of sharp

points posteriorly

Paracalanidae

Paracalanus

indicus Cephalosome is rounded anteriorly. Head and pedigerous segment 1 are fused.5th pereiopods redu

ced and terminate in a spine 

Delibus nudus Very small, less than 1 mm;Cephalosome, pedigerous somite 1, 4 and 5 fused; A1 extends to posterior border of prosome;Rostrum bifurcate, branches short and wide;Basis of P1 with inner edge setae;P2-4, outer edge of exopod segments 2-3 are smooth;Leg 5 is reduced only left leg present, 2 segments in female, 5 in male

Order Cyclopoida

Oithonidae Small, long and slender bodies.

Oithona atlantica Slender, tapered body.Pointed rostrum

Oithona tenius Detailed study of the swimming legs is needed to identify this species.

Cephalosome oval in shape; cephalosome and uros

ome equal in length

Oncaea media Readily identified by reddish colour concentrated at anterior region of the head and at the cuticle edges of metasome, urosome and appendages. Colour can persist after several years in formalin. Oval

shaped prosome. Nauplius eye present

Molecular Systematics of 34 Calanoid copepod species of the Calanidae and Clausocalanidae

DNA sequences for a 639 bp region of mitochondrial cytochrome oxidase I (mtCOI) were determined for 34 species of ten genera in two familiesofcalanoidcopepods,including: Calanoides,Cosmocalanus, Meoscalanus, Nannocalanus, Neocalanus, and Undinula (familyCalanidae);andClausocalanus, Ctenocalanus, Drepanopus,and Pseudocalanus (family Clausocalanidae). MtCOI gene sequences proved to be diagnostic molecular systematic characters for accurate identification and discrimination of the species. Levels of mtCOI variation within species (range: 1–4%) were significantly less than those between species (9–25%). Higher levels of intraspecific variation (>2%) usually resulted from comparisons between ecologically distinct or geographically isolated populations. MtCOI sequence variation resolved evolutionary relationships among species of Clausocalanus, Neocalanus, and Pseudocalanus, although there was evidence of saturation at some variable sites. 

Impact on Molecular Phylogenetics

Phylogenetic relationships among 11 copepod genera were reconstructed using a 660 bp region of nuclear small-subunit 18S rRNA, a slowly evolving gene that showed no variability within a species and differed by <1–6% among the genera. The 18S rRNA molecular phylogeny was consistent with the accepted limits of the Calanidae and Clausocalanidae and clearly resolved relationships among genera within each family.

Historical Content

With the universal aquatic occurrence of copepods, it is not surprising that they were noted by the earliest naturalists. Beginning two thousand years ago, many scientists and "lovers of wisdom" with names still known and respected throughout the world, like Aristotle, Pliny, Rondelet, Redi, Leeuwenhoek, and Linnaeus, observed copepods. Their careful records became a part of our long written heritage, now numbering around 57,000 published works about copepods. The copepod world took shape against the vast background of other invertebrates. Our science saw many valuable contributions in the century after the establishment of Linnaeus's taxonomic system in 1758. Pioneer scientists revealed the surprising reproduction and developmental metamorphosis of copepods as well as their roles throughout the natural world, particularly their significance at the food-base of fisheries.

Honored names and landmark monographs from this period include those of Otto Friderich Müller (1730-1784, Denmark), Jean Baptiste Lamarck (1744-1829, France), Georges Cuvier (1769-1832, France), Louis Jurine (1751-1819, Switzerland), James Dwight Dana (1813-1895, United States), and William Baird (1803-1872, England). Since copepods did not have the immediate impact or urgency of plants, insects, or larger animals, they were studied only incidentally until the middle of the 19th century. Even so, by that time, there was a strong conceptual framework that recognized a wide variety of copepod species and habitats; even the remarkably "degenerate" parasitic copepods were no longer thought to be worms or mollusks but were revealed by their larval stages to be true crustaceans. The name "copepod" (Greek for paddle-footed) was introduced in 1830 by Henri Milne Edwards (1800-1885) in France. The early taxonomic systems echo in our classifications of today. The first prominent scientist to devote most of his life to copepods was Carl Claus (1835-1899),

Professor of Zoology at the University of Vienna. In 1863, Claus published the first book dealing only with copepods. This helpful treatise summarized the knowledge of free-living copepods of western Europe and the Mediterranean Sea. Claus's other works included classic studies of parasitic copepods, adding especially to the useful papers of Henrik Krøyer (1799-1870) from Denmark. After Darwin, in 1859, naturalists focused on completing Nature's book by describing and indicating the relationships of every species, a task that is far from finished. This quest took biologists to the far corners of the earth and to the greatest depths of the seas. Extensive oceanographic expeditions in the last quarter of the 19th century brought an unbelievable harvest of copepods for an expanding and exclusive copepod literature. The decade before and after 1900 was the Golden Age of Copepodology, with the beautiful and indispensable monographs of Wilhelm

Giesbrecht (1854-1913, Germany and Italy), Eugène Canu (1864-1952, France), Otto Schmeil (1860-1943, Germany), and Georg Ossian Sars (1837-1927, Norway). Also, toward the end of the 19th century, the founder of ecology Karl Möbius (1825-1908) and his followers began to measure the precise impacts of copepods on their living and non-living surroundings. More consideration was given to developmental, geographical, and population characteristics of copepods. With the 20th century, women scientists became equal partners in the study of copepods. Among the first were Maria Dahl (1872-1972) and Marie Lebour (1876-1971). These years saw marvelous technical improvements in microscopes and sampling, and a movement toward physiology and the investigation of living copepods. Sheina Marshall (1896-1977), Andrew Picken Orr (1898-1962), Aubrey Nicholls (1904-1986), and Frederick Russell (1897-1984) laid the foundation of these studies, a large part of copepodology's present efforts. The lives of many of our heroes are overwhelming, and they stand in the highest ranks of biology in every nation. Many who are well known for other accomplishments made critical additions to the body of copepod knowledge.

Their teachings and research became centers of excellence, attracting students from far and wide. Their names are linked forever with the variety, distribution, and behavior of the freshwater, marine, free-living, and parasitic copepods they described. Among these immortals are P. J. Van Beneden, V. Brehm, A. Brian, K. Brodsky, C. van Douwe, C. O. Esterly, G. Grice, R. Gurney, H. J. Hansen, W. A. Herdman, A. G. Humes, Fr. Kiefer, W. Klie, H. Kunz, K. Lang, A. Markevich, C. D. Marsh, H. Marukawa, T. Mori, J. Richard, M. Rose, V. Rylov, T. & A. Scott, A. Steuer, O. Tanaka, C. B. Wilson, and many others who have become our own. The working copepodologist sees in these names essential publications kept close at hand, milestones in a unique science. Copepodology continues uninterrupted into the 21st century, looking now at copepods in ecosystems of oceans, lakes, and rivers, from deep-sea vents to groundwaters. Armed with new tools like electron microscopes, remote sensing, molecular biology, and computers, copepodologists explore genetics, medical/morphological applications, mathematical modeling, precision sampling, a wealth of new species from extreme habitats, environmental pollution and over-harvesting, introduced species, and many other consequences and opportunities undreamed of by our predecessors.

Taxonomic Techniques for Copepod

1. Initial treatment of specimens

a. Narcotizing agents Narcotizing agents can be useful to avoid flexion of the body and the antennae, and to aid

retention of egg sacs and gut contents during fixation. The agent is usually added slowly, drop by drop.

b. Fixation Fill sample bottles 3/4 full. Try to fix within 5 minutes after catch.

c. Staining for sorting Staining samples before or during fixation helps visual separation of specimens from sediment or

detritus-filled samples.

d. Storage Storage Media: Within 7-10 days transfer specimens to ethanol or other long-term storage medium; do not

leave material in formalin, even buffered, for long periods. This is because specimens become brittle and setae break off easily.

e. Recovery of dried specimens

2. Microscopic examination Copepod taxonomy is based mainly on external

morphology. Therefore one needs to see details of the integument. It may be desirable to use a clearing medium to reduce visual interference from internal structures, and to stain the integument in order to highlight spine patterns, pores, and other features. Sequence of treatment:

Pre-treatmentStainsMediums, temporary or permanentDissectionMounting on slides, temporary or permanentMaking a record of the specimen

3. Procedure for examination and mounting

a. Manipulation and Dissectionb. Mounting The choice of mounting medium

depends on the use to be made of the mounted specimens, the type of microscopy employed, and the need for long-term preservation.

Case Study

MORPHOLOGICAL AND MOLECULAR PHYLOGENETIC ANALYSIS OF

EVOLUTIONARY LINEAGES WITHIN CLAUSOCALANUS (COPEPODA:

CALANOIDA)

ftp://www.cmarz.org/pub/cmarz/pdf/cmarz_refs/Bucklin_Frost_JCrustBiol_2009.pdf

ABSTRACT

Phylogenetic relationships among 13 species of Clausocalanus (Copepoda: Calanoida) were examined based on morphological, quantitative (morphometrical), and molecular characters. This study builds upon monographic analysis by Frost and Fleminger (1968) and seeks to determine whether three described species groups are monophyletic evolutionary lineages. DNA sequences were determined for portions of three genes: mitochondrial cytochrome oxidase I (mtCOI; 639 base-pairs), nuclear internal transcribed spacer region (ITS-2; 203 base-pairs), and nuclear ribosomal gene (5.8S rRNA; 73 base-pairs). Phylogenetic analysis was carried out based on morphological, molecular, and combined morphological and molecular data using maximum parsimony, maximum likelihood, and Bayesian algorithms, with evaluation of best-fit models of nucleotide evolution. Phylogenetic reconstructions based on morphological characters provided strong support for species groups I and II; group III was not well-resolved. Analysis of the concatenated sequences of the three genes resulted in a tree resolving three of five group II species, with weak support for two pairs of group I species; the remaining species were not clearly resolved into groups. Although ITS-2 was statistically incongruent with the other data sets, the combined analysis of morphological, quantitative, and molecular data by maximum parsimony resolved all four group I species and four of five group II species; group III was not well resolved. All molecular and combined analyses consistently paired C. arcuicornis(group II) with C. parapergens (group III). This study provides independent evidence that some elements of Clausocalanus species groupings reflect evolutionary lineages. Additional genes and longer sequences may help resolve remaining questions about the evolutionary relationships among species of Clausocalanus.

Discussion

Monographic revision of the calanoid copepod genus, Clausocalanus, by Frost and Fleminger (1968) resulted in the description of 13 species in three species groups, which were hypothesized to represent evolutionary lineages within the genus. In a previous molecular systematic analysis of all 13 species of Clausocalanus by Bucklin et al. (2003), patterns of DNA sequence variation for the mitochondrial cytochrome oxidase I (mtCOI) gene supported the revision of the genus by Frost and Fleminger (1968), with mtCOI differences among all species typical of that of well established calanoid copepod species (Bucklin et al., 2003).

In this study, Clausocalanus species groups were resolved most clearly by phylogenetic reconstructions using only Frost and Fleminger’s four group-defining morphological characters. Phylogenetic reconstructions using either 10 morphological characters or all 16 morphological and quantitative characters had lower bootstrap values and did not resolve group III species. These results indicate that useful taxonomic characters may have quite different evolutionary histories, and not all such characters will accurately reconstruct the evolutionary history of a species group.

Molecular phylogenetic analyses using mtCOI, ITS-2, or the concatenated gene sequences provided strong consistent support only for an evolutionary lineage comprising three of five group II species and another pairing of two sister taxa C. arcuicornis and C. parapergens from groups II and III, respectively. Neither groups I nor III were resolved using the molecular data, either treating genes separately or as concatenated sequence.

Although there was evidence of incongruence among the morphological, quantitative, and molecular data sets, phylogenetic reconstruction based on all these characters in combination yielded a tree that resolved all four group I species and four of five group II species. Thus, despite the necessary use of the maximum parsimony algorithm for the combined data set, the integrated and combined analysis of independently-evolving morphological and molecular characters resulted in better resolution and more accurate reconstruction of phylogenetic relationships within this genus of copepods.

When are combined analyses useful and when not?

One approach to answering such questions is to reconstruct the phylogenetic history of a sibling species group using separate analysis of different characters, including, e.g., morphological, quantitative, and molecular traits, and to compare and contrast the resultant evolutionary patterns. The data sets should also be evaluated for difference of their phylogenetic histories using tests of congruence (Farris et al., 1995). Such analysis can help identify appropriate characters for the accurate reconstruction of the evolutionary relationships of the group and valid combinations of data sets.

Conclusion

Copepods are identified as key species in the marine pelagial, not only in the capacity of being a link between primary producers of fish but as predators on other consumers. Moreover, copepods are the most species-rich and abundant invertebrates recorded from deep-sea hydrothermal vents and seeps. They are considered the most plentful multicellular group on the earth, outnumbering even the insects, which include more species, but fewer individuals. Particularly, the copepods are the dominant forms of the marine plankton and constitute the secondary producers in the marine environments and a fundamental step in the trophodinamics of the oceans. Only a few studies of their biology, functional morphology, and evolution have been conducted. The systematics of copepods has been subjected to numerous revisions during the last decade and before. Calanoids, cyclopoids and harpacticoids show a remarkable ecological interest, since most species of these orders generally form the first link of the aquatic food chains, from the microscopic phytoplanktonic algae up to the fishes and mammalians. 

End……..

Thank you……..