The document discusses biology of seastars and feather stars. It provides details about their taxonomy, physical characteristics, habitat, distribution, locomotion, feeding, reproduction, threats and more. Seastars are carnivorous predators related to other echinoderms that use tube feet and a water vascular system to move. Feather stars are crinoids found in warm waters that feed by trapping particles in their feathery arms. While seastars face threats from habitat loss and temperature changes, no feather star species are currently threatened.
Assalam Alikum! here is the presentationn of PHYLUM PORIFERA. prepared to benefit you guys. material in slides is authentic 100%. Once you read the slides you will say ''OMG its soooooooo awesom dude!!''
JazakAllah!!
Why do animals need to breathe?
Breathing is important to organisms because cells require energy (oxygen) to move, reproduce and function. Breath also expels carbon dioxide, which is a by-product of cellular processes within the bodies of animals.
Respiration is the process of releasing energy from food and this takes place inside the cells of the body.
The process of respiration involves taking in oxygen (of air) into cells, using it for releasing energy by burning food, and then eliminating the waste products (carbon dioxide and water) from the body.
Respiration is essential for life because it provides energy for carrying out all the life processes which are necessary to keep the organisms alive.
The energy produced during respiration is stored in the form of ATP (Adenosine Tri- Phosphate) molecules in the cells of the body and used by the organism as when required.
KEY POINTS
Life started in an anaerobic environment in the so called ‘primodial broth’ (a mixture of organic molecules.
Subsequently, oxygen strangely enough became an crucial factor for aerobic metabolism especially in the higher life forms.
The rise of an oxygenic environment was an important event in the diversification of life.
It evoked a dramatic shift from inefficient to sophisticated oxygen dependent oxidizing ecosystems.
Anaerobic fermentation, the metabolic process that prevailed for the first about 2 billion years of the evolution of life, was a very inefficient way of extracting energy from organic molecules. Ex: A molecule of glucose, e.g., produces only two molecules of ATP (≈ 15 kCal) compared with 36 ATP molecules (≈ 263 kCal) in oxygenic respiration.
Aerobic metabolism must have developed at a critical point when the partial pressure of oxygen rose from an initial level to one adequately high to drive it passively across the cell membrane.
Respiration is a complex and highly integrated biomechanical, physiological, and behavioral processes.
The transfer of O2 occurs through a flow of tissue barriers and compartments by diffusion down a partial pressure gradient, which drops to about zero at the mitochondrial level.
Acquisition of molecular oxygen (O2) from the external fluid media (water and air) and the discharge of carbon dioxide (CO2) into the same milieu is the primary role of respiration.
The respiratory system is a biological system consisting of specific organs and structures.
Assalam Alikum! here is the presentationn of PHYLUM PORIFERA. prepared to benefit you guys. material in slides is authentic 100%. Once you read the slides you will say ''OMG its soooooooo awesom dude!!''
JazakAllah!!
Why do animals need to breathe?
Breathing is important to organisms because cells require energy (oxygen) to move, reproduce and function. Breath also expels carbon dioxide, which is a by-product of cellular processes within the bodies of animals.
Respiration is the process of releasing energy from food and this takes place inside the cells of the body.
The process of respiration involves taking in oxygen (of air) into cells, using it for releasing energy by burning food, and then eliminating the waste products (carbon dioxide and water) from the body.
Respiration is essential for life because it provides energy for carrying out all the life processes which are necessary to keep the organisms alive.
The energy produced during respiration is stored in the form of ATP (Adenosine Tri- Phosphate) molecules in the cells of the body and used by the organism as when required.
KEY POINTS
Life started in an anaerobic environment in the so called ‘primodial broth’ (a mixture of organic molecules.
Subsequently, oxygen strangely enough became an crucial factor for aerobic metabolism especially in the higher life forms.
The rise of an oxygenic environment was an important event in the diversification of life.
It evoked a dramatic shift from inefficient to sophisticated oxygen dependent oxidizing ecosystems.
Anaerobic fermentation, the metabolic process that prevailed for the first about 2 billion years of the evolution of life, was a very inefficient way of extracting energy from organic molecules. Ex: A molecule of glucose, e.g., produces only two molecules of ATP (≈ 15 kCal) compared with 36 ATP molecules (≈ 263 kCal) in oxygenic respiration.
Aerobic metabolism must have developed at a critical point when the partial pressure of oxygen rose from an initial level to one adequately high to drive it passively across the cell membrane.
Respiration is a complex and highly integrated biomechanical, physiological, and behavioral processes.
The transfer of O2 occurs through a flow of tissue barriers and compartments by diffusion down a partial pressure gradient, which drops to about zero at the mitochondrial level.
Acquisition of molecular oxygen (O2) from the external fluid media (water and air) and the discharge of carbon dioxide (CO2) into the same milieu is the primary role of respiration.
The respiratory system is a biological system consisting of specific organs and structures.
this slide will help undergraduate student to study the difference between Poisonous and non poisonous snakes with examples, Poison apparatus, venom and its uses.
Fishes, amphibians, reptiles, and birds have paired pharyngeal ultimobranchial glands that secrete the hypocalcemic hormone calcitonin. The corpuscles of Stannius, unique glandular islets found only in the kidneys of bony fishes, secrete a peptide called hypocalcin.
Origin of the Lateral Line System
Lateral line is a canal along the side of a fish containing pores that open into tubes supplied with sense organs sensitive to low vibrations.
Robert H. Denison explained the origin of the lateral line system. He explained that early vertebrates had a pore-canal system in the dermis which functioned as a primitive sensory system in detecting water movement.
Through the evidences from fossils, embryology and comparative anatomy, Denison (1966) established that the inner ear is closely related to the lateral line system. He found a distinct relationship between the pore canal system and the lateral line in Osteotraci.
The inner ear and the lateral line are developed from ectodermal thickenings, called dorso-lateral placodes. These have a number of similarities, including receptors with sensory hairs, and are both innervated by fibers in the acoustico-lateral area of the brain.
The pore canal system is present and developed in Osteostraci (ostracoderm).
It is also present in Heterostraci which is another group of ostracoderms and includes early vertebrates such as lungfishes and crossopterygians.
As its presence is extensive, it is reasonable to suggest that the pore canal system was a primitive character in early vertebrates .
In transverse sections also , it is very difficult to differentiate the pore canal system from a lateral line canal.
Structure of the Lateral Line System
Epidermal structures called neuromasts form the peripheral area of the lateral line.
Neuromasts consist of two types of cells, hair cells and supporting cells.
Hair cells have an epidermal origin and each hair cell has one high kynocyle (5-10 μm) and 30 to 150 short stereocilia (2-3 μm).
The number of hair cells in each neuromast depends on its size, and they can range from dozens to thousands.
Hair cells can be oriented in two opposite directions with each hair cell surrounded by supporting cells.
At the basal part of each hair cell, there are synaptic contacts with afferent and efferent nerve fibers. Afferent fibers, transmit signals to the neural centres of the lateral line and expand at the neuromast base. The regulation of hair cells is achieved by the action of efferent fibers.
Stereocilia and kinocilium of hair cells are immersed into a cupula and are located above the surface of the sensory epithelium.
The cupula is created by a gel-like media, which is secreted by non-receptor cells of the neuromast.
Threat of sea turtle Rajeev raghavan Kufos kerala Ashish sahu
Sea turtles, sometimes called marine turtles, are reptiles of the order Testudines and of the suborder Cryptodira. The seven existing species of sea turtles are the green sea turtle, loggerhead sea turtle, Kemp's ridley sea turtle, olive ridley sea turtle, hawksbill sea turtle, flatback sea turtle, and leatherback sea turtle.
Sea turtle, any of seven species of marine turtles belonging to the families Dermochelyidae (leatherback sea turtles) and Cheloniidae (green turtles, flatback sea turtles, loggerhead sea turtles, hawksbills, and ridleys).
Seven different species of sea (or marine) turtles grace our ocean waters, from the shallow seagrass beds of the Indian Ocean, to the colorful reefs of the Coral Triangle, and even the sandy beaches of the Eastern Pacific. WWFs work on sea turtles focuses on five of those species: green, hawksbill, loggerhead, leatherback and olive ridley.
See more on worldwildlife.org
this slide will help undergraduate student to study the difference between Poisonous and non poisonous snakes with examples, Poison apparatus, venom and its uses.
Fishes, amphibians, reptiles, and birds have paired pharyngeal ultimobranchial glands that secrete the hypocalcemic hormone calcitonin. The corpuscles of Stannius, unique glandular islets found only in the kidneys of bony fishes, secrete a peptide called hypocalcin.
Origin of the Lateral Line System
Lateral line is a canal along the side of a fish containing pores that open into tubes supplied with sense organs sensitive to low vibrations.
Robert H. Denison explained the origin of the lateral line system. He explained that early vertebrates had a pore-canal system in the dermis which functioned as a primitive sensory system in detecting water movement.
Through the evidences from fossils, embryology and comparative anatomy, Denison (1966) established that the inner ear is closely related to the lateral line system. He found a distinct relationship between the pore canal system and the lateral line in Osteotraci.
The inner ear and the lateral line are developed from ectodermal thickenings, called dorso-lateral placodes. These have a number of similarities, including receptors with sensory hairs, and are both innervated by fibers in the acoustico-lateral area of the brain.
The pore canal system is present and developed in Osteostraci (ostracoderm).
It is also present in Heterostraci which is another group of ostracoderms and includes early vertebrates such as lungfishes and crossopterygians.
As its presence is extensive, it is reasonable to suggest that the pore canal system was a primitive character in early vertebrates .
In transverse sections also , it is very difficult to differentiate the pore canal system from a lateral line canal.
Structure of the Lateral Line System
Epidermal structures called neuromasts form the peripheral area of the lateral line.
Neuromasts consist of two types of cells, hair cells and supporting cells.
Hair cells have an epidermal origin and each hair cell has one high kynocyle (5-10 μm) and 30 to 150 short stereocilia (2-3 μm).
The number of hair cells in each neuromast depends on its size, and they can range from dozens to thousands.
Hair cells can be oriented in two opposite directions with each hair cell surrounded by supporting cells.
At the basal part of each hair cell, there are synaptic contacts with afferent and efferent nerve fibers. Afferent fibers, transmit signals to the neural centres of the lateral line and expand at the neuromast base. The regulation of hair cells is achieved by the action of efferent fibers.
Stereocilia and kinocilium of hair cells are immersed into a cupula and are located above the surface of the sensory epithelium.
The cupula is created by a gel-like media, which is secreted by non-receptor cells of the neuromast.
Threat of sea turtle Rajeev raghavan Kufos kerala Ashish sahu
Sea turtles, sometimes called marine turtles, are reptiles of the order Testudines and of the suborder Cryptodira. The seven existing species of sea turtles are the green sea turtle, loggerhead sea turtle, Kemp's ridley sea turtle, olive ridley sea turtle, hawksbill sea turtle, flatback sea turtle, and leatherback sea turtle.
Sea turtle, any of seven species of marine turtles belonging to the families Dermochelyidae (leatherback sea turtles) and Cheloniidae (green turtles, flatback sea turtles, loggerhead sea turtles, hawksbills, and ridleys).
Seven different species of sea (or marine) turtles grace our ocean waters, from the shallow seagrass beds of the Indian Ocean, to the colorful reefs of the Coral Triangle, and even the sandy beaches of the Eastern Pacific. WWFs work on sea turtles focuses on five of those species: green, hawksbill, loggerhead, leatherback and olive ridley.
See more on worldwildlife.org
Mollusca of India and need for conservationAshish sahu
Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda. The members are known as molluscs or mollusks. Around 85,000 extant species of molluscs are recognized. The number of fossil species is estimated between 60,000 and 100,000 additional species
Phylum Mollusca, Class Polyplacophora, Class Monoplacophora, Phylogenetic con...Dr. Muhammad Moosa
In this presentation, Phylum Mollusca Is described. After watching this you will learn Evolutionary Perspective of Mollusca and Relationships to Other Animals, Molluscan Characteristics, Class Gastropoda, Torsion, Shell Coiling, Locomotion, Feeding and Digestion, Other Maintenance Functions, Reproduction and Development, Gastropod Diversity, Class Bivalvia, Shell and Associated Structures Gas Exchange, Filter Feeding, and Digestion, Other Maintenance Functions Reproduction and Development, Bivalve Diversity, Class Cephalopoda, Shell, Locomotion, Feeding and Digestion, Other Maintenance Functions, Learning, Reproduction and Development, Class Polyplacophora, Class Scaphopoda, Class Monoplacophora, Class Solenogastres, Class Caudofoveata, Further Phylogenetic Considerations. It is part of BS Zoology Course, Animal diversity.
Introduction The whale shark ,Rhincodon typus are large slow moving filter – feeders that are the largest known living fish in the ocean .
The whale shark has a very widespread distribution and occurs throughout the worlds tropical and warm temperate seas.
The largest confirmed Individual had a length of 18.8 m.
The excretory products of the sponges- ammonia and other nitrogen containing substances.
Excretion occurs through both the oscula and the surface of the sponge.
Sea turtles are reptiles that live in the ocean.
Sea turtles (superfamily Chelonioidea), sometimes called marine turtles, are reptiles of the order Testudines and of the suborder Cryptodira.
They are cold blooded animals
Sessile.
Inhibit in rocky intertidal zone.
Benthic organism.
Laterally compressed body enclosed in shell with 2 valves.
Soft body of mussel is enveloped in a thin semi transparent covering – MANTLE.
Characteristics - Ariidae Medium to large sized fish.
Two pairs of nostrils closely on each side.
Paired maxillary and mental barbels present totally 4-6.
Dorsal fin short, with long more or less serrated spine preceded by a very short one.
Caudal fin deeply forked.
Adipose fin present.
Pectoral fin low set, with serrated spine.
Colour – Usually greyish blue, dark grey, yellow or brown sometimes with black patches or in some with silvery lateral stripe; pale to white below.
Marine Birds Marine birds are those living in and making their living from the marine environment, which includes coastal areas, islands, estuaries, wetlands, and oceanic islands.
Consists of 328 species.
Sphenisciformes -Penguins
Procellariiformes -Albatrosses, petrels, storm-petrels, fulmars, shearwaters
Ciconiiformes - Herons, egrets, storks, ibis, spoonbills
Pelecaniformes - Pelicans, frigatebirds, gannets, boobies, cormorants, anhingas
Charadrii formes - Shorebirds, skuas, j
Characters Flat body which is covered with large ,silvery, reflective scales
They have set of specialized scales called which are jagged and pointed backward.
Having very small teeth or no teeth at all.
Caudal fin well forked and lobes are pointed.
Body fusiform, elongate and subcylindrical.
Midlateral line.
Indian mackerel
The Indian mackerel belongs to the family scombridae and order perciformes .
It is commonly found in the Indian and west pacific oceans, and their surrounding seas.
Marine, pelagic –neritic, oceanodromous.
Depth range 20-90m.
It is an important food fish .
INTRODUCTION Gorgonians are marine coelenterates (referring to the hollow body cavity) of the class Anthozoa, which include sea fans, sea whips, corals, sea anemones, and other related species.
Gorgonids are soft corals commonly known as sea fans or sea whips, coming under the subclass Octocorallia and have eightfold radial symmetry.
It composed of numerous polyps—cylindrical sessile (attached) forms—that grow together in a flat fanlike pattern.
They are colonial animals that have a beautiful, branching structure that is covered by soft tissue and are generally found in warm waters and around reefs.
Introduction The Gastropods - Phylum Mollusca - Second largest class.
Includes - sea snails and slugs, as well as freshwater snails, freshwater limpets, and land snails and slugs.
The most highly diversified class in the phylum, with 65,000 to 80,000 living snail and slug species.
Older classification of the gastropods
Opisthobranchia (gills to the right and behind the heart).
Gymnomorpha (no shell).
Prosobranchia (gills in front of the heart).
Pulmonata (with a lung instead of gills).
BIOLOGY OF DUGONG Dugong dugon, also known as sea cows is a marine mammal.
It is one of four living species of the order Sirenia, which also includes three species of manatees.
It is the only living representative of the once diverse family Dugongidae; its closest modern relative, Steller’s sea cow (Hydrodamalis gigas), was hunted to extinction in the 18th century.
Corals are marine invertebrates in class Anthozoa of phylum Cnidaria typically living in compact colonies of many identical individual "polyps".
Corals are gastrovascular marine organisms. Each one of these animals is known as a coral
"polyp". Coral Polyps are tiny, primitive marine organisms.
A single polyp has a tube-shaped body with a mouth which is surrounded by tentacles.
The polyp of hard corals produces a stony skeleton of calcium carbonate which form the base. Often the skeleton forms a cup-like structure in which the polyp lives. Coral polyps in colonies make up the cora reefs.
Dolphins are appealing intelligent sea creatures well known for their love of play and friendliness to humans
Despite their appearance , dolphins are not fish but mammals ; air breathing, warm blooded animals whose young feed on their mother’s milk
The majority of adult sea snakes species grow to between 120 and 150 cm (4 and 5 ft) in length, with the largest, Hydrophis spiralis.
Most sea snakes are venomous, except the genus Emydocephalus, which feeds almost exclusively on fish eggs.
Sea snakes are extensively adapted to a fully aquatic life and are unable to move on land, except for the sea kraits, which have limited land movement
All sea snakes have paddle-like tails and many have laterally compressed bodies that give them an eel-like appearance.
They are cold blooded animals
Identification of eggs and larvae of commercially important crustaceans.pptxVinod kumar
Crustaceans/Crustacea, form a very large and diversified group of arthropods, which includes 52,000 described species.
Like other arthropods, crustaceans have an exoskeleton, which they moult to grow.
Distinguished from other groups of arthropods, such as insects, myriapods and chelicerates, by the possession of biramous limbs, and by the nauplius form of the larvae.
Crustaceans exhibit a number of larval forms, of which the earliest and most characteristic is the nauplius.
Several larval forms are met within Crustaceans and specified terms are applied to each one of them.
Instructions for Submissions thorugh G- Classroom.pptxJheel Barad
This presentation provides a briefing on how to upload submissions and documents in Google Classroom. It was prepared as part of an orientation for new Sainik School in-service teacher trainees. As a training officer, my goal is to ensure that you are comfortable and proficient with this essential tool for managing assignments and fostering student engagement.
The French Revolution, which began in 1789, was a period of radical social and political upheaval in France. It marked the decline of absolute monarchies, the rise of secular and democratic republics, and the eventual rise of Napoleon Bonaparte. This revolutionary period is crucial in understanding the transition from feudalism to modernity in Europe.
For more information, visit-www.vavaclasses.com
Synthetic Fiber Construction in lab .pptxPavel ( NSTU)
Synthetic fiber production is a fascinating and complex field that blends chemistry, engineering, and environmental science. By understanding these aspects, students can gain a comprehensive view of synthetic fiber production, its impact on society and the environment, and the potential for future innovations. Synthetic fibers play a crucial role in modern society, impacting various aspects of daily life, industry, and the environment. ynthetic fibers are integral to modern life, offering a range of benefits from cost-effectiveness and versatility to innovative applications and performance characteristics. While they pose environmental challenges, ongoing research and development aim to create more sustainable and eco-friendly alternatives. Understanding the importance of synthetic fibers helps in appreciating their role in the economy, industry, and daily life, while also emphasizing the need for sustainable practices and innovation.
How to Make a Field invisible in Odoo 17Celine George
It is possible to hide or invisible some fields in odoo. Commonly using “invisible” attribute in the field definition to invisible the fields. This slide will show how to make a field invisible in odoo 17.
Biological screening of herbal drugs: Introduction and Need for
Phyto-Pharmacological Screening, New Strategies for evaluating
Natural Products, In vitro evaluation techniques for Antioxidants, Antimicrobial and Anticancer drugs. In vivo evaluation techniques
for Anti-inflammatory, Antiulcer, Anticancer, Wound healing, Antidiabetic, Hepatoprotective, Cardio protective, Diuretics and
Antifertility, Toxicity studies as per OECD guidelines
The Roman Empire A Historical Colossus.pdfkaushalkr1407
The Roman Empire, a vast and enduring power, stands as one of history's most remarkable civilizations, leaving an indelible imprint on the world. It emerged from the Roman Republic, transitioning into an imperial powerhouse under the leadership of Augustus Caesar in 27 BCE. This transformation marked the beginning of an era defined by unprecedented territorial expansion, architectural marvels, and profound cultural influence.
The empire's roots lie in the city of Rome, founded, according to legend, by Romulus in 753 BCE. Over centuries, Rome evolved from a small settlement to a formidable republic, characterized by a complex political system with elected officials and checks on power. However, internal strife, class conflicts, and military ambitions paved the way for the end of the Republic. Julius Caesar’s dictatorship and subsequent assassination in 44 BCE created a power vacuum, leading to a civil war. Octavian, later Augustus, emerged victorious, heralding the Roman Empire’s birth.
Under Augustus, the empire experienced the Pax Romana, a 200-year period of relative peace and stability. Augustus reformed the military, established efficient administrative systems, and initiated grand construction projects. The empire's borders expanded, encompassing territories from Britain to Egypt and from Spain to the Euphrates. Roman legions, renowned for their discipline and engineering prowess, secured and maintained these vast territories, building roads, fortifications, and cities that facilitated control and integration.
The Roman Empire’s society was hierarchical, with a rigid class system. At the top were the patricians, wealthy elites who held significant political power. Below them were the plebeians, free citizens with limited political influence, and the vast numbers of slaves who formed the backbone of the economy. The family unit was central, governed by the paterfamilias, the male head who held absolute authority.
Culturally, the Romans were eclectic, absorbing and adapting elements from the civilizations they encountered, particularly the Greeks. Roman art, literature, and philosophy reflected this synthesis, creating a rich cultural tapestry. Latin, the Roman language, became the lingua franca of the Western world, influencing numerous modern languages.
Roman architecture and engineering achievements were monumental. They perfected the arch, vault, and dome, constructing enduring structures like the Colosseum, Pantheon, and aqueducts. These engineering marvels not only showcased Roman ingenuity but also served practical purposes, from public entertainment to water supply.
Francesca Gottschalk - How can education support child empowerment.pptxEduSkills OECD
Francesca Gottschalk from the OECD’s Centre for Educational Research and Innovation presents at the Ask an Expert Webinar: How can education support child empowerment?
Embracing GenAI - A Strategic ImperativePeter Windle
Artificial Intelligence (AI) technologies such as Generative AI, Image Generators and Large Language Models have had a dramatic impact on teaching, learning and assessment over the past 18 months. The most immediate threat AI posed was to Academic Integrity with Higher Education Institutes (HEIs) focusing their efforts on combating the use of GenAI in assessment. Guidelines were developed for staff and students, policies put in place too. Innovative educators have forged paths in the use of Generative AI for teaching, learning and assessments leading to pockets of transformation springing up across HEIs, often with little or no top-down guidance, support or direction.
This Gasta posits a strategic approach to integrating AI into HEIs to prepare staff, students and the curriculum for an evolving world and workplace. We will highlight the advantages of working with these technologies beyond the realm of teaching, learning and assessment by considering prompt engineering skills, industry impact, curriculum changes, and the need for staff upskilling. In contrast, not engaging strategically with Generative AI poses risks, including falling behind peers, missed opportunities and failing to ensure our graduates remain employable. The rapid evolution of AI technologies necessitates a proactive and strategic approach if we are to remain relevant.
2. SEA STAR
Starfish are also referred to as sea stars because of their star-shaped
appearance.
They are a part of the phylum Echinodermata and are related to sand dollars,
sea urchins, and sea cucumbers.
Starfish belong to the class Asteroidea, derived from the Greek words “aster”
(a star) and “eidos“ (form, likeness, appearance).
There are more than 1600 species of starfish alive today, and they have an
important role in the community structure of the ocean floor.
All echinoderms share similar pentamerous radial symmetry and spiny skin
characteristics, although sea stars differ slightly because they have five or
more arms large enough to contain space for digestive and reproductive
glands.
3. EVOLUTION AND SYSTEMATICS
The class Asteroidea is a highly diverse group comprised of seven orders, 35
families, and an estimated 1,600 known living species, although their precise
phylogenetic relationship and hence classification still proves challenging to
taxonomists.
Kingdom - Animalia
Phylum - Echinodermata
Class - Asteroidea
Order - Brisingida, Forcipulatida, Notomyotida, Paxillosida, Spinulosida,
Valvatida and Velatida and two extinct ones, Calliasterellidae and
Trichasteropsida.
5. PHYSICAL CHARACTERISTICS
Sea stars vary considerably in size, shape, and color, even within the same
populations.
Their diverse forms reflect evolutionary adaptation to the cosmopolitan
habitats they occupy.
Despite this diversity they all share similar physical characteristics. All are
star-shaped (stellate) with a central body or disc that has symmetrically
projecting arms with rows of tube feet running along the lower surface of a V-
shaped furrow called the ambulacral groove.
6. Typically, the number of arms is
five, but some species such as the
coral-eating crown-of-thorns
Acanthaster planci can have up to
30.
Patiriella parvivipara, which gives
the appearance of a nearly
spherical body,
7. In most species, the arm tips carry an optic cushion of red-pigmented and
light-sensitive cells that sense changes in the prevailing environment.
The skeleton of a sea star consists of small calcium carbonate plates called
ossicles. These are often studded and spiny, and provide a firm but flexible
skeleton of connective tissue.
Flexibility enables a variety of postures to be adopted without muscular
effort, thus providing an effective means to capture and handle prey and
allow individuals to closely follow irregular substrates in search of food.
8.
9. DISTRIBUTION
The greatest diversity of sea stars occur in coastal regions, although as a
group, they are well represented globally from the Antarctic, Pacific,
Atlantic, and Indian Oceans.
They inhabit wave-exposed inter-tidal zones of coastal waters to the calm
sandy pavements of the deepest oceans.
The Benthopectinidae family of sea stars, for example, lives exclusively in the
deep-sea of the Atlantic and Pacific Oceans, whereas the species Odontaster
validus, which belongs to the family Ganeriidae, are found only in the
Antarctic Ocean.
Perhaps the most well-known and ubiquitous group of sea stars belongs to the
order Forcipulatida. This group includes the genus Asterias, a veracious
predator of mussels and oysters in many coastal waters around the world.
10. HABITAT
As a group, sea stars live in virtually every habitat found in the sea, ranging
from tidal pools, rocky shores, sea grass and kelp beds, beneath rock rubble,
on coral reefs, sand, and mud.
In some species a broad and flattened body may act as a snowshoe when
foraging on very soft mud. In the upper shore, they are periodically exposed
by the retreating tide, resulting in extended periods of desiccation.
11. FEEDING ECOLOGY AND DIET
Sea stars are carnivorous, preying on sponges, shellfish, crabs, corals, worms,
and even on other echinoderms.
Most are generalists, feeding on anything that is too slow to escape, such as
mussels and clams, whilst others are specialized feeders preying exclusively
on sponges, corals, bivalves, or algae.
Prey is located by the chemical odors emanating from its waste products.Or
by small movements that betray its presence when detected by a sea star.
Several species have specialized feeding behaviors including eversion of their
stomachs..
This means the starfish extends its stomach out of its mouth and over the
digestible parts of its prey. The prey tissue is partially digested outside of the
body, then the starfish brings its stomach back inside into its 10 digestive
glands to finish feeding.
12. They have few predators as adults due to their armored spiny skeleton and
rigid nature.
In less heavily armored and juvenile sea stars, protection from predators
comes from having a cryptic coloration.
Other defensives include toxic spines or skin (e.g., Crossaster papposus and
Acanthaster planci) and predator avoidance by burrowing beneath the
sediment surface (e.g., Astropecten irregularis and Anseropoda placenta).
13. LOCOMOTION
On their ventral side, starfish contain thousands of tube-like feet that contain
cells that are specialized for adhesion.
starfish can use these tube feet to move across a surface. Each foot has two
sets of secretory cells that secrete compounds that allow the foot to first
attach then detach to a surface.
Sea stars have an unusual way of moving. Water is taken in through the
madreportite, a small, perforated plate on the upper surface of the disc, and
into the water vascular system, a canal of tubes connected to the tube feet.
Following muscular contraction water is directed under pressure to the tube
feet, which then extend under its force. Movement is achieved through a
coordinated stepping motion where, on muscle contraction, the feet adhere
to the sediment surface, pushing the individual forward.
14. REPRODUCTION
Most sea stars have separate sexes with no visible differences between them.
Internally, each arm contains a pair of gonads that become almost filled with
eggs or sperm, depending on the sex, at the time of breeding.
The majority of species are broadcast spawners where eggs and sperm are
released into the water column to be fertilized.
To increase the chances of fertilization, sea stars aggregate when they are
ready to spawn.
Asexual reproduction is another method of development that involves either
fission or regeneration of entire animal from arm parts.
Almost a dozen species divide through their disc, producing clones with
identical genetic makeup (e.g., Linckia laevigata).
15.
16. BEHAVIOUR
Sea stars have a "central nervous system," or diffuse nerve net, but lack
anything identified as a brain.
Despite this, they are sophisticated enough to adapt to change based on
previous experiences (conditioning), whereby behavior that is persistently
unsuccessful, usually a feeding one, is stopped.
They are not considered social animals, yet many species tend to aggregate or
swarm in large numbers during certain times of the year.
17. RESPIRATION
Sea stars don't use gills or lungs to breathe.
They rely on diffusion across surfaces in their body.
For example, most oxygen is taken up from water that passes over their tube
feet and papulae or skin gills.
18. EXCRETION
Starfish have no distinct excretory organs; waste ammonia is removed by
diffusion through the tube feet and papulae.
The body fluid contains phagocytic cells called coelomocytes, which are also
found within the hemal and water vascular systems.
19. WATER VASCULAR SYSTEM
The water vascular system is a hydraulic system used by echinoderms, such as
sea stars and sea urchins, for locomotion, food and waste transportation, and
respiration.
The system is composed of canals connecting numerous tube feet.
The exact structure of the system varies somewhat between the five classes
of echinoderm.
The system is part of the coelomic cavities of echinoderms, together with the
haemal coelom (or haemal system), perivisceral coelom, gonadal coelom and
perihaemal coelom.
20. Threats and conservation status
The biggest threats to starfish are a reduction of coral reef habitat, pollution,
and marked changes in water temperature.
The iconic sunflower sea star has been listed as critically endangered by the
International Union for Conservation of Nature following a groundbreaking
population study led by Oregon State University and The Nature Conservancy.
21. FEATHER STAR
feather star, any of the 550 living species of crinoid marine invertebrates
(class Crinoidea) of the phylum Echinodermata lacking a stalk. The arms,
which have feathery fringes and can be used for swimming, usually number
five.
Feather stars use their grasping “legs” (called cirri) to perch on sponges,
corals, or other substrata and feed on drifting microorganisms, trapping them
in the sticky arm grooves.
A feather star is not the same as a starfish (also known as a sea star and
sometimes misspelled as star fish).
Close relatives of feather stars include sea stars, brittle stars, sea cucumbers
and sea urchins.
22. HABITAT
A feather star habitat is slightly different from a starfish habitat.
Feather stars, also called crinoids, reside in the ocean, typically in shallow,
warm waters. Some species do, however, exist in colder waters and deeper
areas.
A sea star or starfish habitat needs the right surface for the creature's feet to
move across. Sea stars with tube feet reside among rocks, and sea stars with
pointed tube feet tend to live on the seabed in sand or mud.
Feather stars, however, live in areas with strong currents. They do not tend to
live around silt, which can clog their feet. Living in areas with these currents
ensures their survival, as they yield more opportunities to capture food.
They may also swim through the water column if disturbed.
23. DISTRIBUTION
They are most abundant from the Indian Ocean to Japan.
where Tropiometra is the commonest genus. Antedon is the best known genus
in the Atlantic.
24. SYSTEMATICS
KINGDOM - ANIMALIA
PHYLUM - ECHINODERMATA
CLASS - CRINOIDEA
ORDER - COMATULIDA
Feather star species distributed among 150 genera and 17 families in one
order.
26. LOCOMOTION
These amazing creatures swim, float and “walk” through the sea.
Feather stars swim by beating their arms up and down, or at times
parachuting with their cirri out to grasp new substrate.
When needed, however, feather stars can attach to rocks or other materials
via their cirri.
Feather stars previously were not considered fast movers.
27. FEEDING BIOLOGY
They feed on small food particles, which they pick up by moving their
feather-like arms. After they grab some food, they push it toward their
mouth, which is in the center of their body.
They usually inhabit shallow waters, and they prefer a reef with a bit of
current so the food comes directly to them.
Feather stars are usually nocturnal, but you can also observe them swimming
or moving their tentacles during the day when they’re feeding or moving from
one coral to another.
28. REPRODUCTIVE BIOLOGY
Male or female feather stars reproduce via water fertilization. Eggs,
produced in spring, hatch as larvae. The swimming larvae eventually
attach to the sea bottom via stalks
The fertilised eggs hatch to release free-swimming vitellaria larvae.
The bilaterally symmetrical larva is barrel-shaped with rings of cilia
running round the body, and a tuft of sensory hairs at the upper pole.
Crinoids are not capable of clonal reproduction as are some starfish
and brittle stars, but are capable of regenerating lost body parts.
29. WATER VASCULAR SYSTEM
Like other echinoderms, crinoids possess a water vascular system that
maintains hydraulic pressure in the tube feet.
This is not connected to external sea water via a madreporite, as in other
echinoderms, but only connected through a large number of pores to the
coelom (body cavity).
The main fluid reservoir is the muscular-walled ring canal which is connected
to the coelom by stone canals lined with calcareous material.
30. NERVOUS SYSTEM
The crinoid nervous system is divided into three parts, with numerous
connections between them.
The oral or uppermost portion is the only one homologous with the nervous
systems of other echinoderms. It consists of a central nerve ring surrounding
the mouth, and radial nerves branching into the arms and is sensory in
function.
Below this lies an intermediate nerve ring, giving off radial nerves supplying
the arms and pinnules. These nerves are motor in nature, and control the
musculature of the tube feet.
31. Threats and conservation status
The main threats are recreational fishing, commercial fishing with gillnets,
and habitat degradation.
No species are listed by the IUCN.
32. CONCLUSION
Sea stars are related to sand dollars, sea urchins, and sea cucumbers, all of
which are echinoderms, meaning that they have five-point radial symmetry.
However, this does not mean that all sea stars have five arms and species
with 10, 20, or even 40 arms exist.
Pycnopodia helianthoides, commonly nown as the sunflower sea star, is a
large sea star found in the northeast Pacific.In 2020, the IUCN first assessed
that the sunflower sea star was critically endangered.
Feather stars are a type of marine invertebrate with featherlike arms that
radiate from a central body.
Feather stars are not considered threatened or endangered.
33. REFERENCES
Lawrence, J. M. (Ed.). (2013). Starfish: biology and ecology of the Asteroidea.
JHU Press.
Garm, A. (2017). Sensory biology of starfish—with emphasis on recent
discoveries in their visual ecology. Integrative and Comparative Biology, 57(5),
1082-1092.
Vogler, C., Benzie, J., Lessios, H., Barber, P., & Wörheide, G. (2008). A threat
to coral reefs multiplied? Four species of crown-of-thorns starfish. Biology
letters, 4(6), 696-699.
Holland, N. D. (2020). Cell cycle in regenerating feather star arms. In
Echinoderms through time (pp. 217-220). CRC Press..