Invertebrates: Sponges and Cnidarians

Practice 2 Phylum: Sponges (Porifera), Cnidarians (Cnidaria) Species: Common hydra (Hydra vulgaris) (Cnidaria)  Invertebrates Phylum: Sponges (Porifera) Phylum: Cnidarians (Cnidaria) Phylum: Flatworms (Platyhelminthes) Phylum: Segmented worms (Annelids...

Practice 2 Phylum: Sponges (Porifera), Cnidarians (Cnidaria) Species: Common hydra (Hydra vulgaris) (Cnidaria)  Invertebrates Phylum: Sponges (Porifera) Phylum: Cnidarians (Cnidaria) Phylum: Flatworms (Platyhelminthes) Phylum: Segmented worms (Annelids) (Annelida) Phylum: Molluscs (Mollusca) Phylum: Arthropods (Arthropoda) Phylum: Sponges (Porifera)  Characteristics of the Phylum Porifera Pseudotissues (Group Parazoa): multicellular animals, two cell layers, but without tissue differentiation their cell layers do not form real tissues and not organ-forming hollow, tubular-shaped, porous body totipotent cells do not have nervous system (nerve cell or tissue) or muscle tissue two-cell layer + intermediate (gelly-like) Ephydatia fluviatilis – Freshwater sponge layer primarily sea, secondarily freshwater organisms sessils (no movement) colonial, filter-feeding  Sponges (body structure) Their body is divided into 2 cellular layers and a jelly-like intermediate layer: 1. Dermal layer (pinacoderma): outer covering, protective, strengthening layer Cell types: pinacocyte porocyte 2. Gastral layer (choanoderma): internal nutrient- absorbing layer (phagocyte-digesting function) Cell type: choanocytes (choanocyta): flagellum plasma collar  Sponges (body structure) Intermediate layer (mesoglea/mesohyl): jelly-like layer strengthening not germ-layer originated Spicules water Spongin skeleton Cell types: outflow scleroblasts (skeleton-forming cells)  sclerocytes  spicule (spiculum): (calcium carbonate or silica, or spongin protein – contains iodine) gastric Based on number of spiculum: cavity monoaxon, diaxon, triaxon, tetraaxon, poliaxon archeocytes (stem cells)  regeneration myocytes (contractile) amoebocytes (amoeboid migratory cells) mouth Choanoderm layer Mesoglea layer gastric cavity  Sponges (movement, respiration, nutrition, transport,excretion) No movement, they are sessils. They have no respiratory system, resrpiration is carried out by diffusion. They have no separate circulatory and excretory systems. Myocytes: contractile elements, located around the pores and regulate the water flow. Nutrient distribution is carried out by amoeboid migratory cells (no separate transport system). Sponge digestion is exclusively intracellular (within the cell) and mainly in the amoeboid migratory cells. Excretion takes place separately in each cell, with the metabolites being excreted either into the gastric cavity (spongocoel) or into the environment. A system of water flow, supplying nutrients, oxygen and removing metabolites  exovascular system.  Types of Sponge Structure based on the fragmentation of choanoderm layer:  Sponges (asexual reproduction) 1. budding colony formation under favourable conditions Budding 2. gemmulatio formation of gemmules gemmule = archeocytes covered with a double layered capsule. (reproductional formulation)  passive spreading, survival Gemmulatio  Sponges (sexual reproduction) Primarily hermaphrodites. Hermaphrodite: an individual capable of producing both male and female gametes. ovum Archeocytes  gametes (male, female). Proterandry: male gametes mature earlier (avoid self-fertilisation). Development and larval forms: the larva is a blastula (free-swimming ciliated larva), and gastrulation occurs when the larva settles. Phylum: Cnidarians (Cnidaria)  Characteristics of the Phylum Cnidarians Their body can be considered a double-walled cylinder. Cnydocite cell is common to the group. Tissues first appear in this group (Group Eumetazoa = real tissue animals). Without a real body cavity (acoelomata): no primary body cavity is found between epidermis and gastrodermis layers. Blastocoel (body cavity) replaced by a gelatinous interlayer (mesogloea/mesohyl) containing no cellular elements (diploblastic animals). Germ layers: ectoderm mesoglea entoderm  Characteristics of the Phylum Cnidarians Radially symmetrical. They have digestive, muscular, nervous and sensory systems. High regenerative capacity, some cells are totipotent (interstitial cells). They are mainly marine, but some are freshwater. They have extremely diverse body shapes (sessile polyp form, free-floating jellyfish form, colonial coral form). 1. ECTODERM (epidermis) layer: has a skeletal role Cell types: epitheliomuscular cells:  buildt up from actin and myosin  help the movement primary sensory neurons: sensing interstitial cells: totipotent cells  help the regeneration of cells neurons: 2 dimensional neural network cnidocytes:  can be triggered  hollow thread releases in case of danger, or predation  hollow thread is spiked, sticky 2. ENDODERM (gastrodermis) layer: has a role in food transfer and digestion Cell types: epitheliomuscular cells: transfer the food digestive cells: - ciliated - glandular 3. MESOGLOEA/MESOLAMELLA (middle layer): - Not germ layer-originated. - Transport mechanisms. - Support function.  Cnidarians (body structures) Poyp/hydra form: cylindrical, handle-like trunk basal disk at the basal part on the opposite site: mouth surrounded by tentacles thin mesogloea layers sessils (no movement) Medusa form: actually an upside down polyp form free-swimming lifestyle thick mesoglea layer (high jelly content)  specific gravity nearly equal to water  floating  Cnidarians (movement and nutrition) Movement is carried out by epithelio- muscularis cells Nutrition: carnivorous (animal-eating) organisms. They feed mainly on small crustaceans, larvae. Tentacles are important in catching the food (passing it to the mouth with the help of cnidocytes).  Cnidarians (digestion and respiration) Their digestion is both intracellular and extracellular. Absorptive muscle cells: collect the food gastrovascular system Contraction of epitheliomuscular cells help the movement of digested food within the animal. Metabolites are discarded from the gastrovascular cavity through the mouth. Gastrovascular system (gastroderm + gastric cavity): the formation that performs the digestive and distributive function Excretion and osmoregulation:  The gastrointestinal tract and the gastrodermis also function as an osmoregulatory organ Respiration: by diffusion  Cnidarians (nervous system) The nervous system of the hydra consists of a nerve fibers diffuse network of nerves. It may have different nerve cells (neurons), according to their spines. e.g.  Unipolar neuron  Bipolar neuron  Pseudounipolar neuron  Multipolar neuron From the outer layer, bipolar neurons transmit stimuli to multipolar neurons in the middle layer. There are gap junctions (electrical synapses) nerve cells between the neuron spines, through which the forming nerve nest stimulus can travel in both directions.  Species: Common hydra (Hydra vulgaris) Classes: Hydrozoa Tentacles Size: 2 cm, fresh-water polyp (tentaculum) Color: can range from greyish to Mouth opening reddish (influenced by food). (os) Hypostome Tentacles arranged to a wreath. (hypostoma) Basal disk at the basal part of Body body (fixing role). coloumn (truncus) Predators (small invertebrates Buds in and crustaceans). budding zone High regenerative capacity (due Basal disk to totipotent interstitial cells). (discus)  Common hydra (reproduction) Asexual and sexual reproduction. 1. Asexual reproduction: exvagination. budding new individual emerges from the body the new individual will be separated 2. Sexual reproduction (hermaphrodites) unpleasant stimuli (e.g. cooling of water) differentiation of sexual organs (gonads) on polyp ovaries, testes: do not mature at the same time  to avoid self-fertilisation (proterandry) fusion of gametes (on the animal) embryo (separated)  hatching of young polyp.  Related videos Sponge feeding: https://www.youtube.com/watch?v=pTZ211cIjX8 Sponge reproduction: https://www.youtube.com/watch?v=Y_IqJUkhIjs Sponge dissection: https://www.youtube.com/watch?v=UG8SOpFWQ0A Hydra structure: https://www.youtube.com/watch?v=dFvJTmjUOyU Hydra feeding: https://www.youtube.com/watch?v=SS_HYY97ehw https://www.youtube.com/watch?v=618tHYueLhY Hydra cniadocytes release: https://www.youtube.com/watch?v=6zJiBc_N1Zk Hydra movement: https://www.youtube.com/watch?v=-UI531GMRTM Hydra budding 3D modell: https://www.youtube.com/watch?v=d5-hPkcQDrU Sexual reproduction of Green hydra: https://www.youtube.com/watch?v=1u9n_n7VaYk Hydra summary video: https://www.youtube.com/watch?v=jnD_YitEk5M