Annelids Flashcards
What are annelids commonly known as
Segmented worms
Body plan of Annelids
- usually soft, flexibal bodies used in movement and cylindrical and elongated
- protostomes
- bilateral symmestry
- triploblastic
Common examples of annelids
Earthworms, polychaete, worms abd leeches
Unique characteristics of annelids
- Chitinous setae
- metamerism
Chitinous setae
All adult annelids other than sipunculans possess at least one lair of chitonous bristles caled setae which is used for movement
Hairlike structures (bristles) composed of chitonous siliceous, extending from parapodia.
Metamerism
Refers to the serial repetition of segments and organ systems (skin, musculature, nervous system, circulatory system, reproductive system and excretory system)
Annelid Habitat
-moist environments to keep epidermis moist
Annelid epidermis secretes…
Epidermis secrete cuticle, whose surface is involved in respiration as it is permeable to water and gas
Annelids have 2 ______ that open at both ends per segment commonly known as ______; mainly used for excretion of waste products
Nephridia
(Also regualte amount of water in the coelomic fluid and may play a role in gamete release in some species if ducts extending from gonadal tissue connects with the nephridal tubule)
Metanephridia
Nephrostome
Opening from which coelomic fluid is drawn into the nephiriduk by ciliary action
Respiration and circulation of annelids
Parapodia and gills mainly serve for gaseous exchange
- respiratory fases diffuse through the body wall, parapodia increase the surface area for gas exchange
- closed circulatory system mostly. Oxygen is carried by respiratory pigments. Pigments are dissolved in the plasma. They are present in blood cells of animals.
- blood is colouless, green or red depending on pigment
Polychaetes respiration
No special organ for respirstion, and gas exchange takes place across the body surface
-parapodial gills further increase surface area for gas exchange
Annelid blood pigments
- Hemoglobin: majority of annelids like leeches
- chlorocruoron: greenish colour in polychaete
- hemerythrin: found within cells of some polychaetes and sipunculans
2 groups of annelids
Sedentaria and Errantia (Polychaetes)
Class Polychaeta
(Many setae)
Multi-segmented worms living in all environments in oceans of the world. Strictly aquatic (marine) worms, but are most abundant annelids
Subclass oligochaeta
Second largest group of the phylum, 30% of annelids, havitats range from freshwater, marine and terrestrial
Subclass Hirudinea
True leeches, highly specialized clitellates, separated from other annelid groups by the presence of an anterior circumoral sucker and a posterior ventral sucker
Members of class Polychaeta have what key characteristic?
Parapodia- paired outer folding of the body wall
Series of extended thin, flat outgrowth on tbe body walll
-increase surface area, gas exchange, locomtoion with support of stiffen rod called acicula
Body size, and movement of Polychaeta
Soft bodies usually only a fee centimeters long and pencil thick, move slowly aided by the retracable grup of four dense clusters of bridtles and hooks called chaetae on each segment
-body is lined with longitudinal and circular muscles for support and movement, flexibility for locomotion and burrowing
Class Polychaeta eyes
Possess a minimum of a pair of eyes and pair of sensory appendages (tentacles) on the anterior portiok of the body known as prostomium
Elytra
Presence of overlapping plates on the surface of some species
Class Polychaeata Septa
The coelom is spacious usually divided by intersegmental septa.
- septa maintain hydrostatic pressure in individual segments; allows for movement, and flexibility
- may be absent in burrowing species; ensures shape flexibility and extension of the penetrating organ which is an inverted pharynx known as proboscis for sedument penetration
Habitat of Polychaeta
- typically burrowers some live under rocks, in coral crevices, abondoned shells, mud or sand.
- divided into 2 groups: sedentary polychaetes and errant or free living polychaetes
What eats Polychaeata
-play a significant role in marine food chains because they are eaten by fish, crustaceans, hydroids and others
Sedentary polychaeta
Mainly tubicolous (tube dwellers), spending most of their time in tubes or permaent burrows.
Errant polychaetes
Include free moving pelagic forms, active burrowers, crawlers and tube works that leave their tubes for feeding and breeding
Secual reproduction in class Polychaeta involves _____ sexes in most species
Seperate (gonochoristic)
Polychaetes
Gametes are produced by_______rather than in distinct gonads and then are released ______
Peritoneal tissue and then relessed into the associated coelomic compartments where theh matures
Approximately _____ adjacent segments of a given polychaeata are involved in gamete production and some do it in nearly all segments
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Epitoky
A form of morphological transformation undergone by mainly sedentary species in readiness for reproduction, resulting in an epitoke
Epitoke
Sexually matured worms (male or female) and are mobile by swimming
Polychaeata
Polychaetes fertiize their eggs ______. Typically the ______ embryo soon develops a _______ system and _____ of cilia
Externally in the surrounding water
Free-living
Digestive
Two rings
Prototroch
Two rings of cilia in polycheate embryo
This makes the largae on trochohore stage
Mainly a locomotive structure
Two other ciliated rings are present in the larva of polychaetes:
Middle ring: metatroch
Posterior ciliated ring: telotroch(near anys) which gives rise to the pygidium
Polyplaetes direct development
Embryo develops directly within a gelatinous mass in sediment or withon the females tube at the surface
Polychaetes brooding chamber
In some species, parent possess brooding chamber where the embryo can develop into larvae and later adult, under the protection and care of the parent
Polychaetes asexual reproduction
By fragmentation and regeneration of missing parts. New offspring sre geneticaly identical and are not regarded as true individuals, so commonly reffered to as a ramet of the parent genotype
Errant polychaetes feeding
Mostly predators and scavengers
Sedentary types of polychaetes feeding
Suspended particles or they are deposit feeders, consuming particles on or in the sediment
Polychaetes general feeding and digestion
- possess a mouth leading to the peristomium and posterior anus near the pygidium
- possess a simple linear and unsegmented gut; food moved from mouth to gut via ciliary or muscular action
- some species possess evaginated guy with digestive glands or caeca which increases the surface area of the gut for digestion and absorbtion
Two families of Annelids
Siboglinidae
Echiurans
Unique characteristics of Siboglinidae
-bacteria organ?
- Gut tissue (inner germ layer/endoderm) forms an orgab known as trophosome which becomes filled with chemosynthetic bacteria
- body segmentation is restricted to posterior portion of the organism forming an opistosoma
Cosmopolitan
Members are a small but especially intriquing group of polychaetes distribute theoughout the worlds oceans
(SOBOGLINIDS)
Lifestyle of Siboglinids
Tube-dwelling polychaetes that live in chitonous tubes; move freely within their tubes, they have tentacles which is serviced by blood vessels
The anteriormost region of Siboglinids body has a
Cephalic lobe that consists of one to many thousands of ciliated tentacles and a grandular area that secretes a chitonous tube where the animal lives
Vascularised tentacles are ysed for what in Siboglinids
Exchange gases
Habitat of Siboglinids
Marine dwellers:
- bottom of the ocean
- none pellagic
The body of Siboglinids is divided how?
Anterior region, trunk and opistosoma
Anterior region contians what
Cephalic lobe and tentacles
Trunk contains what
- longest part containing uninterrupted coelomic cavities
- unsegmented and not septa in cavity
- contains papillae (small bump), cilia and setae
- trophosome: in coelomic cavity and house numerous bacteria which play roles in nutrition as they lack digestive system
Opistosoma conatins what
Posterior aegmented portion of siboglinids, resembing that of the true annelids
Siboglinids lack which shstem
Digestive system
3 feeding habits of Siboglinids
- Particulate feeders
- Uptake of dissolved orgnajc matter
- Chemosynthesis
Particulate feeding in siboglinids
Tentacles at anterior wnd which contain surface microvilli and secretory cells
-tentacles trap food and digest them externally
(Not a substancial part of theur nutrition)
Uptake of dissolved organic matter from water in Siboglinids
Some species, especially the frenulate group (sediment dwellers), take up amino acid carbohydrates and other organic material to meet metabolic requirements
Chemisynthesis
Presence of trophosome (bacteria dwelling organ) in siblglinids houses symbiotic bacteria. Especially in the bottom sea dwellers which inhabt dark and hypoxic environment.
- bacteria get methane and sulfides through tentacular plume
- siboglinids either digest some bacteria to derive its nutrients or trap organic carbon compounds produced by the bacteria during energy generation
Characteristics of Echiurans
- worms that live in sandy or muddy burrows or rock crevices
- anterior cephalic projection has a proboscis that is muscular and mobile for food collection
- never segmented body
- setae on body surface
Feeding of Echiurans
- mostly deposit feeder, but genus Urechis are suspension feeders
- edge of proboscis curls to form a gutter
- mud and detritus that is trapped by mucous secretion of the proboscis are moved by the cilia posteriorly towards the mouth.
- digestive tract contained within the trunk is very long and convoluted with the anus opening posteriorly
What organs do Echiurans not have?
Respiratory
Use diffusion instead
Reproduction of Echiurans
- Gonochoristic: male and female organs
- do not possess distinct sex gonads, gametes produced by the peritoneal lining of the coelom and released into coelomic cavity
- gametes leave body through aid of metanephridia into surrounding sea-water where fertilization occurs which results in trochophore larva
Class Clitellata unique characterisitcs
- pronouced cylindrical glandular region known as clitellium that plays a major role in reproduction
- have gonads
- no parapodia
- hermaphrodites: male and female sex cell in an individual
Some members of Clitellum release_____and _____
Cocoon which secreted mucus for sperm exchange and albumin for food for the developing embryo
85% of Clitellates are _____
Oligochaetes
-more streamlined body when compared to most polychaetes
Oligochaetes use ______ for excretiok and osmoregulation
Metanephridium
2 subclasses of Clitellata
Oligochaetes (few or no setae)
Hirudinea (leeches)
Oligochaetes possess ____
Clitellum-enlarged specialized region of the epidermis, play role in reproduction
Most oligochaetes live where
Inhabit fresh water And terrestrial environment mainly
Body of Oligochaetes is ______ and more _______ than most polychaetes
Streamlines and elongated
Characterisicts of Oligochaetes
- no parapodia
- have satae
- lack respiratory organs; use diffusion
- segmented with septa body
Lumbrius terrestris importance
Oligochaetes
Terrestrial
Good bioindicator of the environment stress and contamination and play a role in soil aeration and water percolation
Locomotion in Oligochaetes
-body limed with inner longituinal musxles and superficial circular muscles which aide in movement by contraction and relaxation of the muscles in peristaltic waves (also in polychaetes)
Reproduction in Oligochaetes
- all hermaphrodites
- gametes produced by a fee segments into distinct ovaries and testes
- mating individuals form pair and exchange sperm which are stored in a structure called spermathecae
- egg and sperm are transferred into an external cocoon secreted by the clitellum
- fertilization occurs externally within the cocoon, wmbryo develop with it, while feeding on mucus secreted by the clitellum.
- lack larval stage; emerge from cocoon and develop to adult directly
Other forms of reproduction in oligochaetes
- Transverse division of an adult into 2 or more section: common in fresh water species
- each part develop into new individual - Partehnogenesis: common in terrestrial species where egg develops difectly into adults without fertilization
Subclass Hirudineans unique characteristics
- anterior and posterior suckers
- Are leeches
- no parapodia, respiratory or head appendage
- no setae
- no body divided into segments by septa
Leech movement
Move over substrates by anchoring by means of the anterior and posterior suckers
Feeding system of Leeches
- mostly ectoparasites (blood sucking annelids)
- possess 3 tooth jaws in the mouth for attachment to host skin
- some have protrusible proboscis, for talikg blood into the gut
- mouth of the leech opens into a muscular, pumping pharynx
- salivary glands associated with the pharynx secrete hirudin, an anticoagulant
- a crop and digestive glands are found in some
Leech reproduction
- hermaphroditic
- only few segments of each individual are directly involved in gametogenesis
- fertilization is internal either by copulation or by storage of sperm in spermatophore
- embryo develop in cocoon externally secreted by clitellum
- free living larval stage is absent
- embryo directly to adults
Phlyum Tardigrada are known as
Water bears
Tardigrade habitat
Surface films of fresh water on terrestrial plants, especially mosses and lichens
Tardigrade cuticle
Posses a complex, chitonous cuticle that is periodically molted
Tardigrades possess ________ like straited muscles, and their capacious body cavity appears to be a ______ formed from spaces in the connective tissue
Arthropod
Hemocoel
Unique Tardigrade characteristics
- mouthparts: protrusinle, oral stylets for piercing plant and to a lesser exent, animal tissues
- complex chitinous cuticle
- lack mobile cilia
- arthropod like straited muscles
- organized nervous system
Class Onycophora
- Posses some characteristics that are cleary annelid and some clearly arthropod
- all free living
- protostomous coelomates
- appendages that are hihgky modified to form jaws around mouth
- specialized glands to discharge adhesive materials theough openings on the oral papillae
- all modern are terrestrial, fossils primarily marine
Unique characteristics of class Onychophoran
- second pair of appendages that are highly modified to form jaws surrounding the mouth
- possession of third pair of appendgaes to for stubby projections
- body wall musculature
- single pair of feeding appendages
- no joints
- hydrostatic skeleton for locomotion
- one pair of nephridia
Onychophoran feeding
- Some carnivorous: on various small arthropods
- attack prey from a distance by shooting a proteinaceous glue from large (and unique) “slime glands” opening at the tips of two specialized oral protuberances, the oral papillae
- onychorphoran bites theough ang protective coverings, secreting into the tisshes substances that kill the prey and partially liquify the tissues
