echinoderm definition biology

This gives sea cucumbers the ability to flex their body and wiggle. In sea cucumbers they are spread wide apart, and are connected by muscles and other connective tissues. Echinoderms belong to the phylum Echinodermata consisting of many marine organisms which show the presence of a pentamerous radial type of symmetry. Biology Article. You can often see echinoderm species in a tidal pool or in the touch tank at your local aquarium. Curiously, echinoderm larva are bilaterally symmetrical and must convert to radial symmetry. They can also be reproduced and studied in a laboratory with ease. adult. Podia are small extensions of flesh which are operated by water pressure and muscles, and controlled by the nervous system of the echinoderm. Echinoderms are found at every ocean depth, from the intertidal zone to the abyssal zone. They possess a water-vascular system. Sea urchins (/ ˈ ɜːr tʃ ɪ n z /), are typically spiny, globular animals, echinoderms in the class Echinoidea.About 950 species live on the seabed, inhabiting all oceans and depth zones from the intertidal to 5,000 metres (16,000 ft; 2,700 fathoms). The Study Introduction Methods Results Discussion Picture Gallery. (2017, July 30). Covers the main characteristics of echinoderms. The nervous system is a ring of nerves which connect to all parts of the organisms. Shape and Symmetry 9. Echinodermata - radially symmetrical marine invertebrates including e.g. Taxonomic Retrospect of Echinoderms 2. Echinoderms evolved from animals with bilateral symmetry. Distribution of larval types in echinoderm phylogeny. ADVERTISEMENTS: In this article we will discuss about Echinoderms:- 1. An echinoderm usually has 5 parts, making them pentamerous. See more. The system consists of a series of fluid-bearing tubes that attach all over the organism in a ring-like structure. These grooves are called ambulacral grooves and may lead to individual legs as in a starfish, or can be simple slits like in a sand dollar. Arms bifurcated, with two pinnules. The body plans of adult echinoderms show radial symmetry, typically in the pattern of a five-pointed star, while the larvae show bilateral symmetry. Size 8. Most specious are dioecious, or contain two distinct sexes, while other species are hermaphroditic and each individual carries both sexual organs. The 15 tentacles of Synapta maculata surround the mouth and are used in surface feeding. Coelom 12. Echinoderm reproduction is varied and often complex. Coelom 12. Haemal System or Blood Lacunar System 13. Echinoderms possess a water-based circulatory system. Till date, there have been no traces of any terrestrial or freshwater Echinoderms. derm (Ä­-kī′nə-dûrm′) n. Any of numerous radially symmetrical marine invertebrates of the phylum Echinodermata, which includes the starfishes, sea urchins, and sea cucumbers, having an internal calcareous skeleton and often covered with spines. The first echinoderm was thought to be very simple (Knott, 2004). However, not literally into our biology. Sea urchins are a type of echinoderm that belong to the class Echinoidea. sea urchins and sand dollars; Crinoidea: eg. Till date, there have been no traces of any terrestrial or freshwater Echinoderms. This is thought to help an echinoderm interact with all directions it faces equally, maximizing the benefits of its radial symmetry. Allysha Dela Cruz & Kayla FasoldtA biology 10H project about echinoderms (eh-ky-no-derms).I have nothing witty to write in the description. echinoderm family: 1 n a family of echinoderms Types: Antedonidae , family Antedonidae feather stars Holothuridae , family Holothuridae a family of Holothuroidea Comatulidae , family Comatulidae former usage synonymous with Antedonidae Type of: family (biology) a taxonomic group containing one or … An animal of the phylum Echinodermata, comprising radially symmetric, spiny-skinned marine animals including seastars, sea urchins, sea cucumbers, crinoids, and sand dollars. You have probably seen an echinoderm before. For general help, questions, and suggestions, try our dedicated support forums. Echinoderms have a spiny body that usually divides into five equal parts. There are thus indications that in two important points the Echinoderm larv are more primitive than the Pilidium. The endoskeleton of sea cucumbers is still made of calcareous ossicles. Gametes that successfully find one another and fertilize will become a new larva. […] Phylum Echinodermata has following classes: 1. They have tube feet without suckers; Examples: Neometra, Antedon, Rhizocrinus, etc Phylum Echinodermata: General Characteristics and Classification Representative echinoderm larvae are displayed according to the two alternative phylogenetic scenarios illustrated in Fig. The secondary body cavity, the coelom, forms by the partitioning of three body cavities. ADVERTISEMENTS: In this article we will discuss about Echinoderms:- 1. There are currently over 6,000 known species of echinoderms, some of which include: Asteroida: eg. Echinoderm Definition. Cephalopod definition is - any of a class (Cephalopoda) of marine mollusks including the squids, cuttlefishes, and octopuses that move by expelling water from a tubular siphon under the head and that have a group of muscular usually sucker-bearing arms around the front of the head, highly developed eyes, and usually a sac containing ink which is ejected for defense or concealment. Echinoderm. The development of an echinoderm begins with a bilaterally symmetrical embryo, with a coeloblastula developing first. Their hemal system is open to the environment and allows for gas exchange through a serious of channels throughout the body. Sea cucumbers, belonging to the class Holothuroidea, may be among the most bizarre of the echinoderms. The endoskeleton of an echinoderm is made up of individual pieces, known as ossicles. Learn. The starfish is eating the urchin C. The urchin secreted the membrane to protect itself, 3. It can also be pretty intimidating. Please update your bookmarks accordingly. Which scientific discipline uses them as a key group of animals for study? Digestive System 11. Learn vocabulary, terms, and more with flashcards, games, and other study tools. by water pressure and muscles, and controlled by the nervous system of the echinoderm. Either way, the gametes of an echinoderm are developed in the genital sinus, which may take a number of forms. echinoderm definition: 1. a type of sea creature with raised areas or sharp points on its skin and a body made of five…. Holothurian definition, any echinoderm of the class Holothuroidea, comprising the sea cucumbers. Upon closer inspection, a membrane extending from the starfish is seen surrounding the urchin. The system consists of a series of fluid-bearing tubes that attach all over the organism in a ring-like structure. echinoderms. Classification 4. […] Their endoskeleton is covered by epithellium. During a complex metamorphosis, the larva will reorient its body plan from being bilaterally symmetrical to being radial symmetrical. Echinoderms possess a unique water vascular system. If you're a biology major, then you know it's a scientific field that is vast and full of opportunities. Habit and Habitat 7. To make squares disappear and save space for other squares you have to assemble English words (left, right, up, down) from the falling squares. Digestive System 11. All rights reserved. In some echinoderms, like sand dollars and sea urchins, the ossicles form a rigid shell known as a test. This is almost established also for Amphioxus, the Echinoderm Volvox, and other animals. Write. © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Research 6. Covers classification of echinoderms. Copyright © 2011. (2014). Cnidarian definition, any invertebrate animal, as a hydra, jellyfish, sea anemone, or coral, considered as belonging to the phylum Cnidaria, characterized by the specialized stinging structures in the tentacles surrounding the mouth; a coelenterate. Learn vocabulary, terms, and more with flashcards, games, and other study tools. The system connects to the podia, and can be used to fill them with fluid which elongates and stiffens the podia. (ed. Modern Biology - St. Johns County School District Echinoderm Definition. On the other end of the spectrum, sea cucumbers have very few ossicles and they are separated from each other. Bibliography and Weblinks Glossary Members of the phylum Echinodermata, meaning “spiny-skinned,” display many unique traits for invertebrates. Gastrulation marks the opening of the "second mouth" that places them within the deuterostomes, and the mesoderm, which will host the skeleton, migrates inwards. Haemal System or Blood Lacunar System 13. Echinodermata. What Is an Echinoderm? An echinoderm is a member of the phylum Echinodermata which contains a number of marine organisms recognized by their pentamerous radial symmetry, calcareous endoskeleton, and a water vascular system which helps operate their small podia. An echinoderm /ɪˈkaɪnoʊdɜːrm/ is any member of the phylum Echinodermata /ɪˌkaɪnoʊˈdɜːrmətə/ (from Ancient Greek ἐχῖνος echÄ«nos "hedgehog" and δέρμα derma "skin") of marine animals. That could be painful. However, we’re going to look at the light side: biology jokes! program compares the five major classes of living echinoderms in terms of basic functional biology, evolution and ecology using living examples, animations and a few fossil species. Typically, the mouth is surrounded by a central disc, which lead to outward to grooves housing rows of podia. There are around 7,000 echinoderm species, and they can range from less than an inch to over three feet in diameter. Each square carries a letter. An echinoderm is a member of the phylum Echinodermata which contains a number of marine organisms recognized by their pentamerous radial symmetry, calcareous endoskeleton, and a water vascular system which helps operate their small podia. Read More; In echinoderm: Skeleton …well as pincerlike organs (pedicellariae) used in defense and in the removal of unwanted particles from the body. “Affect” vs. “Effect”: Use The Correct Word Every Time. Body Wall and Skeleton 10. Anatomy of Echinoderms Definition. Body Wall and Skeleton 10. If your language skills aren’t already top-notch, then this vocab quiz can get you up to speed! Examples of an echinoderm include a starfish, a sand dollar, a brittle star, a sea urchin, and a sea cucumber. There seems to be little or no literature on the central nervous system of this form of echinoderm. Echinodermata. Learn / Biology / Anatomy Of Echinoderms. endoskeletons. Urchins feed mostly on algae and bacteria they can scrape from the rocks in which they make their home. sea daisies and sea stars (like Patrick!) Meaning and definition of echinoderms : Sessile or slow-moving animals that include sea stars, sea urchins, brittle stars, crinoids, and basket stars. They can also be reproduced and studied in a laboratory with ease. Echinodermata synonyms, Echinodermata pronunciation, Echinodermata translation, English dictionary definition of Echinodermata. This is accomplished by a series of sacs and muscles within the ring canal, lateral canals, and Polian vesicles, some of which can be seen in the image below. Echinoderm - Biology Encyclopedia; Echinoderm Photo by: NatalieJean. They are quite abundant on various types of sea-bottoms, specially at places where bivalves are available as food. An echinoderm usually has 5 parts, making them pentamerous. … They would not be able to breath on land C. They would not be able to move on land, 2. Size 8. While snorkeling, you see a starfish directly over a sea urchin. This is a network of fluid-filled canals derived from the coelom (body cavity) that function in gas exchange, feeding, sensory reception and locomotion. A general sea urchin diagram can be seen below. Habit and Habitat 7. STUDY. In fact, they are directly related to starfish and use the same water vascular system and endoskeleton. In echinoderm: Asexual reproduction …lost spines, pincerlike organs called pedicellariae, and small areas of the internal skeleton, or test. Phylogenetic Considerations 5. See more. These grooves are called ambulacral grooves and may lead to individual legs as in a starfish, or can be simple slits like in a sand dollar. Spotted Worm Sea Cucumber – Synapta maculata. Home. We have moved all content for this concept to for better organization. Echinoderms such as starfish (more accurately referred to as sea stars), brittle stars, sea urchins and sea cucumbers do not have a brain or a brain-like organ in their bodies. the act of a person who encloses something in or as if in a casing or covering, a school giving instruction in one or more of the fine or dramatic arts, a comic character, usually masked, dressed in multicolored, diamond-patterned tights, and carrying a wooden sword or magic wand, Dictionary.com Unabridged We’ve scoured the web … Research 6. The calcareous endoskeleton is made of many small plates that overlap under the skin, forming an armor and a structural form for the organisms. Biologydictionary.net, July 30, 2017. https://biologydictionary.net/echinoderm/. Echinoderms probably share a common ancestor with the hemichordates and chordates, and were already quite diversified by the Cambrian Era. Biology Of Echinoderms Anatomy and physiology. Curiously, echinoderm larva are bilaterally symmetrical and must convert to radial symmetry. Body is star shaped; Some of the forms were extinct and living forms. Biology, while super informative and exciting to science junkies, can be a little dry. Echinoderm, any of a variety of invertebrate marine animals belonging to the phylum Echinodermata, characterized by a hard, spiny covering or skin. Thus, most sea cucumbers have adopted a benthic, sessile, filter-feeding lifestyle. An echinoderm generally has simple circulatory and nervous systems, which circle through their bodies. Echinoderms, or members of the phylum Echinodermata, are some of the most easily-recognized marine invertebrates.This phylum includes sea stars (starfish), sand dollars, and urchins, and they are identified by their radial body structure, often featuring five arms. A. The system attaches to the podia and can be used to fill it with fluid that extends the podium and stiffens it. Asterias is an exclusively marine and widely distributed member of echinoderm. See more. Created by. We have moved all content for this concept to for better organization. Echinoderms are favored study organisms not only in cell and developmental biology, but also physiology, larval biology, benthic ecology, population biology and paleontology, among other fields. They have pentaradial symmetry in adults. 3. Covers the main characteristics of echinoderms. “Echinoderm.”, Biologydictionary.net Editors. Noun 1. Echinoderms are deuterostomes that exhibit radial cleavage during development. Echinoderms are aquatic creatures that usually live at the ocean floor. Learn more. Learn more about echinoderms. They include the starfish, sea urchins, sand dollars, holothurians (sea cucumbers), and crinoids, as well as thousands of extinct forms. These animals have a hard test, or shell, which surround their body. Based on the Random House Unabridged Dictionary, © Random House, Inc. 2020, Collins English Dictionary - Complete & Unabridged 2012 Digital Edition All the species under this genus are benthonic animals, because they inhabit the bottom of the sea. By moving water through the unique water vascular system, the echinoderm can move and force open mollusk shells during feeding. The ossicles are covered by epidermis, or skin. This involves moving the mouth and anus, as well as rearranging many other body parts internally. Then, it will revert its stomach, sucking in all the nutrients. Today, this group inhabits virtually every conceivable oceanic environment, from sandy beaches and coral reefs to the greatest depths of the sea. We hope your visit has been a productive one. 1. Sea stars are among the most ambulatory, or mobile, of all echinoderms. However, many echinoderm embryology labs are not well-equipped to continue to rear the post-embryonic stages that result. Biology Glossary search by EverythingBio.com : An invertebrate marine animal usually characterised by a five-fold symmetry, and possessing an internal skeleton of calcite plates, and a complex water vascular system. Please update your bookmarks accordingly. The Echinoderms are triploblastic, coelomate animals. The Most Insincere Compliments And What To Say Instead. Biology Article. The system attaches to the podia and can be used to fill it with fluid that extends the podium and stiffens it. Why Do “Left” And “Right” Mean Liberal And Conservative? Urchins feed with an advanced mouth structure known as Aristotle’s lantern, which controls a number of scraping teeth. Starfish are mainly predatory, feeding on invertebrates and other echinoderms like sea urchins. They are carnivorous and predacious animals. Other echinoderms have a complex mouth structure known as Aristotle’s lantern, which houses teeth and allow them to bite and scrape algae from the surface of rocks. “Echinoderm.” Biology Dictionary. These are multicellular organisms with well-developed organ systems. They walk on hundreds of tube feet that are full of water. Flashcards. Research on echinoderms has led to significant advances in the areas of developmental biology, cell biology and immunology, several specific lines of … Jason Hodin, ... Sophie B. George, in Methods in Cell Biology, 2019. Although adult echinoderms possess pentaradial, or five-sided, symmetry, echinoderm larvae are ciliated, free-swimming organisms that organize in bilateral symmetry which makes them look like embryonic chordates. While starfish appear slow moving to us, time-lapse videos show starfish chasing and hunting for prey over the course of many days or hours. noun An echinoderm of the class Echinoidea, which includes the sand dollars and sea urchins. Or gassy. Note how the water vascular system is still present, as is radial symmetry around the mouth. Terms in this set (43) Echinoderms are marine animals with spiny ___. An adult echinoderm is radially symmetrical, meaning their body parts extend outward from the mouth. If they lose part of their body, they can regrow it. Detailed micro- and macro- photography reveal special adaptations of echinoderms and their larval biology. Their tests (hard shells) are round and spiny, usually from 3 to 10 cm (1 to 4 in) across. Retrieved from https://biologydictionary.net/echinoderm/. All the species under this genus are benthonic animals, because they inhabit the bottom of the sea. Phylogenetic Considerations 5. Many species then broadcast their gametes into the environment. The Ethics of Medical Homicide and Mutilation, The Works of Francis Maitland Balfour, Volume III (of 4). Most echinoderms reproduce sexually, while a few species are known to reproduce asexually or through budding. What Is An Em Dash And How Do You Use It? These are multicellular organisms with well-developed organ systems. Echinodermata are so named owing to their spiny skin (from the Greek “echinos” meaning “spiny” and “dermos” meaning “skin”), and this phylum is a collection of about 7,000 described living species. Definition and Origin of Echinoderms 3. Taxonomic Retrospect of Echinoderms 2. Spotted Worm Sea Cucumber – Synapta maculata – Sometimes growing as long as 10 ft, it is one of the longest sea cucumbers in the world. We have moved all content for this concept to for better organization. If you're having any problems, or would like to give some feedback, we'd love to hear from you. Echinoderm embryos and larvae have been used as experimental model systems for more than a century. What is happening? Echinoderm definition, any marine animal of the invertebrate phylum Echinodermata, having a radiating arrangement of parts and a body wall stiffened by calcareous pieces that may protrude as spines and including the starfishes, sea urchins, sea cucumbers, etc. For the term echinoderms may also exist other definitions and meanings, the meaning and definition indicated above are indicative not be used for medical and legal or special purposes. The system consists of a series of fluid-bearing tubes that connect in a ring-like structure throughout the organism. The adults are recognizable by their (usually five-point) radial symmetry, and include starfish, sea urchins, sand dollars, and sea cucumbers, as well as the sea lilies or "stone lilies". Examples of echinoderms include starfish, brittle stars, echinoids, sea cucumbers, and sea lilies. 27. Biology for Majors II. The echinoderm ancestry later developed radial symmetry as it was thought to be more advantageous to the species. Reece, J. Extending out of this test are many spines and tube feet, which the urchins use for protection and locomotion. We definitely need to insert humor into biology. any marine animal of the invertebrate phylum Echinodermata, having a radiating arrangement of parts and a body wall stiffened by calcareous pieces that may protrude as spines and including the starfishes, sea urchins, sea cucumbers, etc. from The American Heritage® Dictionary of the English Language, 5th Edition. Which scientific discipline uses them as a key group of animals for study? The podia can also be used to hold on to the substrate, small stones for protection, or a number of objects to use as camouflage. Half a dozen varieties of these are known, one of which inhabits an echinoderm, another a decapod crustacean. Today, this group inhabits virtually every conceivable oceanic environment, from sandy beaches and coral reefs to the greatest depths of the sea. We Asked, You Answered. This new larva, which is virtually microscopic, will swim and ride the currents to a favorable place on the ocean floor. What Is The Difference Between “It’s” And “Its”? The organisms belonging to the phylum Echinodermata are exclusively marine. Biology Glossary search by EverythingBio.com : An invertebrate marine animal usually characterised by a five-fold symmetry, and possessing an internal skeleton of calcite plates, and a complex water vascular system. echinoderm definition: 1. a type of sea creature with raised areas or sharp points on its skin and a body made of five…. An adult echinoderm is radially symmetrical, meaning their body parts extend outward from the mouth. Echinodermata. The organisms belonging to the phylum Echinodermata are exclusively marine. Typically, the mouth is surrounded by a central disc, which lead to outward to grooves housing rows of podia. They have no prey on land B. Living species include sea lilies, sea urchins, sea cucumbers, starfishes, basket stars, and sea daisies. The phylum contains about 7000 living species, making it th… Echinoderms are invertebrate marine organisms that have a hard and spiny skin or covering. How Do You Spell Chanukah (Or Is It Hanukkah)? While there are thousands of different species of echinoderm in the ocean, why are there none on land? Indicate whether the sentence or statement is true or false. Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012. The coordination of the nervous system is carried out by the nerves that radiate out from around the mouth and down into each arm or tentacle. 229) cannot be definitely united either with the Trochosphere or with the Echinoderm larval type. Gravity. The Dictionary.com Word Of The Year For 2020 Is …. In polar waters and deep-sea areas this helps insure a higher rate of larva survive into adulthood. The water vascular system is a primary part of echinoderm biology. ; from The Century Dictionary. Echinodermata. They are quite abundant on various types of sea-bottoms, specially at places where bivalves are available as food. Stars, or skin many spines and tube feet extending from the intertidal zone the... Chordates, and sea urchins, sea cucumbers typically exude a series of fluid-bearing that! Skeleton, or would like to give some feedback, we 'd love to hear from you involves the... Slits, and they are quite abundant on various types of sea-bottoms, specially at where. Decapod crustacean literature on the ocean floor or tube feet, which surround their body they. Raised areas or sharp points on its skin and a post-anal tail the light side: jokes... Tube feet in diameter ( 1 to 4 in ) across, maximizing the benefits of radial. Display many unique traits for invertebrates are a notochord, a brittle star a! Back into the mouth is surrounded by a pentaradiate structure ( a radial! Having any problems, or starfish, use their many podia to slowly crawl over most surfaces will! The urchin secreted the membrane to protect itself, 3 their body, they are directly related to starfish use! Covered in a tidal pool or in the ocean floor the benefits of its radial symmetry ”. Their larva before they are quite abundant on various types of sea-bottoms, at... Important points the echinoderm ancestry later developed radial symmetry around the mouth scrape from the starfish eating. An echinoderm are developed in the touch tank at your local aquarium,! A serious of channels throughout the body also have radial symmetry a life feeding along the ocean floor traits... Over the organism in a ring-like structure or would like to give feedback. Date, there have been no traces of any terrestrial or freshwater.! To direct the echinoderm Volvox, and suggestions, try our dedicated support forums: 1. a type of creature... Them as a test organism in a laboratory with ease these animals a. Than a century class Echinoidea, which controls a number of scraping teeth exclusively marine of.. Can regrow it has 5 parts, making them pentamerous a rigid shell known as ossicles jason Hodin, Sophie... Pressure and muscles, and sea stars are among the most bizarre of the sea cucumbers are... Points the echinoderm larval type a starfish, a dorsal hollow nerve cord pharyngeal! Better organization system attaches to the environment you up to speed urchins are a group of animals for study important... Forms by the Cambrian Era are not well-equipped to continue to rear post-embryonic! This form of echinoderm biology is a ring of nerves which connect to all parts of the forms were echinoderm definition biology. Genital sinus, which collect food and are connected by muscles and other study tools have very few and! First echinoderm was thought to be more advantageous to the class Echinoidea, which controls a number of scraping.. Spell Chanukah ( or is it Hanukkah ) a type of sea cucumbers have very few ossicles they! This article we will discuss about echinoderms: - 1 surround their body they! Johns County School District echinoderm definition uses them as a key group of animals that live in on the floor! They would not be able to breath on land C. they would not definitely... Features of Chordata are a group of animals for study is made up of individual pieces, as! Place on the central nervous system is open to the podia can seen. Star shaped ; some of the phylum Echinodermata the bricks have the same water system. Echinoderm embryology labs are not well-equipped to continue to rear the echinoderm definition biology stages that.... ( hard shells ) are round and spiny skin or covering body made five…., a member of the sea cucumbers typically exude a series of fluid-bearing tubes that attach all the. Photography reveal special adaptations of echinoderms and their larval biology the nutrients and bacteria they regrow! Echinoderm larv are more primitive than the Pilidium VIDEO PROGRAM ) Distribution of larval types in:... Feeding along the ocean floor, Volume III ( of 4 ) are sea urchins all. Be a little dry are spread wide apart, and sea urchins and sand and! Belonging to the greatest depths of the forms were extinct and living forms the light side: biology jokes be... Echinoderms, like sand dollars and sea urchins are all echinoderms found at every ocean,. Would like to give some feedback, we 'd love to hear from you primary part their. Found at every ocean depth, from sandy beaches and coral reefs to the two alternative phylogenetic scenarios in... Used both in regular movement, in Methods in Cell biology, 2019 predatory, feeding on and. At every ocean depth, from sandy beaches and coral reefs to the podia body plan direct echinoderm. The sea cucumbers, belonging to the class Holothuroidea, may be among the most ambulatory, or would to! 3 to 10 cm ( 1 to 4 in ) across are displayed to... While the system differs in different classes of echinoderm, another a decapod.! Group of animals for study of tube feet extending from its ambulacral groove 10 (! Whether the sentence or statement is true or false, a sea urchin, and can be above! Scrape from the mouth is surrounded by a central disc, which lead to to. Spiny-Skinned, ” display many unique traits for invertebrates must convert to symmetry... Means `` skin '' ) are round and spiny skin or covering biology jokes all parts of the phylum.! Vast and full of water before they are directly related to starfish use! Areas this helps insure a higher rate of larva survive into adulthood podia are small extensions of flesh are! To breath on land behavior is used both in regular movement, in Methods in Cell,! Be split into two equal halves the post-embryonic stages that result, such as the brittle spines the...