Invert Bio Final

Libbie Henrietta Hyman

Wrote six volume treatise “The Invertebrates” that was \n the most exhaustive accounting of invertebrate taxonomy in English

What percent of animals are invertebrates?

\~95%

Model Organisms

Answers “How?”: helpful for taking a dive into how a system works; facilitate the precise dissection of processes

Model Clade

Answers “Why?”: used to look broadly across diversity of organisms to see how the function and difference in phenotypes due to evolution

Model Life Histories

Answers “How does organism X in Environment 1 differ from organism X in environment 3?”: Provides context to the life cycle

Important characteristics in defining invertebrates

Habitat, Growth, Skeletal Support, Feeding Strategies, Reproduction

Distinct types of pelagic organisms

Plankton and Nekton

Subdivisions of plankton

Holoplankton and Meroplankton

Holoplankton

live entire lives in the pelagos

Meroplankton

Only live part of their lives in the water column, adult stage is benthic

\n Subdivision of benthic organisms

Epifauna, Infauna, Meiofauna

Epifauna

Live on the surface of the ocean substrate

Infauna

Live in the sediments of the ocean substrate

Meiofauna

tiny microscopic organisms that live between the grains of sediment of the ocean substrate

Growth types of marine invertebrates

Unitary and Modular

Types of Skeletal Support

Endoskeleton, Exoskeleton, Hydrostatic

Types of feeding strategies

Deposit feeding and Suspension feeding

Important characteristics in construction of a phylogeny

Number of cells, tissue layers, body cavity (coelom), suite of developmental characters

Protostome

The blastopore of the gastrula forms mouth first

Deuterostomes

The blastopore of the gastrula forms mouth second and anus first

Main distinctions between protostomes and deuterostomes

1. Blastospore invaginaiton
2. Spiral or Radial early cell cleavage
3. Origin of Mesoderm
4. Cilia per cell

Spiral cleavage

At the 4 to 8 cell stage, the blastomere layers are rotated and sit in the cavity, demonstrated in protostomes

Radial cleavage

At the 4 to 8 cell stage, the blastomere layers sit atop of each other

Types of origin of the mesoderm

Schizocoely and Enterocoely

Schizocoely

Mesoderm splits and lines to form coelom (4d cell), demonstrated in protostomes

Enterocoely

Out pocketing off of endoderm to fill and create coelom, demonstrated in deuterostomes

Cilia per cell distinction in protostomes and deuterostomes

protostomes are multiciliate and deuterostomes are one cilia per cell

Cladistics

method for deducing the pattern of evolutionary relationship

Source of evidence for evolutionary relationships

1. Phenotypic characteristics of extant species
2. Developmental characters
3. Molecular characters
4. Fossil chronologies

Eumetazoa

“true animals”, encompassese all of the groups expect for Porifera

Outgroup of the metazoan phylogeny

Choanoflagellate protists

Ostia

pores on sponges in which water enters

Atrium

Large chamber water enters into

Choanocytes

cell unique to sponges that line the atrium with a collar, flagellum, and sticky collars to collect food

Microvilli

cellular membrane protrusion that increase surface area for diffusion to decrease issues as sponge grow

Microfibrils

connect the 30-40 collar fibril of choanocytes

Pinacocyte

cell that forms the “dermis” (exterior covering)

Porocyte

cell the lines the ostia

Sclerocytes

cells responsible for secreting the spicules (calcium or silica)

Oocyte

The egg cell of the sponge

Spongin fibers

polymerized collagen consisting of reinforced spicules made of calcium carbonate or silica

How do sponges exploit the volume to surface area ratio

Sponges have increased grades of construction with increased grades of complexity

Asconoid

simple and tiny sponges with side ostia that lead directly to the atrium; choanocytes line the spongocoel. the body wall is not folded to form chamber.

Syconoid

larger sponges that loop before entering the atrium; choanocytes line channels water travels before spongocoel. body wall folding allows for a greater number of choanocytes

Lyconoid

massive sponges with multiple channels, choanocyte chambers, and multiple oscula where water exits. extensive folding of the interior body wall with multiple ostia and oscula

Spicular content in different environments

High energy sites have many spicules to be stiff and strong and smaller channels, and low energy sites have less spicules to be softer and more diverse sized channel

Classes of Phylum Porifera

Class Calcarea, Class Demospongiae, Class Hexactinellida, Class Homoscleromorpha

Class Calcarea

shallow water, marine sponges, all three body plans are represented in this class. calcium carbonate spicules that may be needle-like, 3-rayed, or 4-rayed

Class Demospongiae

both freshwater and marine sponges comprise over 95% of all known sponge species. have a network of siliceous spicules held together by spongin. All exhibit leuconoid construction

Class Hexactinellida

marine sponges occur in deep water and are normally quite large. body plans are similar to the syconoid grade of construction, though much of the body consists of a syncytium. spicules are six-sided and made of silicon

Class Homoscleromorpha

exclusively marine sponges, most of which inhabit shallow hard bottoms of the continental shelf, with \\n some known from more than 1000m depth; newest class of sponges and sister group to Class Calcarea.

\n Carnivorous sponges

“Family Cladorhizidae”

Ecological/Economic Relevance of Sponges

Aquaculture/Mariculture (which improves sustainability, provides employments, and facilitates medicinal drug discovery process)

Phylum Ctenophora

comb jellies

\n Characteristics of Ctenophora

Tissue grade organisms, Muscles, Nervous systems, Far more complex than sponges, all share bands along length of body of ciliated structures used for locomotion

Debate about Ctenophora and Placozoa

\n Which is more ancestral? Neurons and muscles could have evolved separately and independently two different times

Ctenes

Ciliated structures or combs used for locomotion

\n How do cilia used comb-rows for locomotion?

Cilia beat at same time at same rate, does "the wave" down the comb row, (metachronal wave)

Why are ctenophores transparent?

Adaptation for the open ocean to camouflage from predators

Symmetry of Ctenophores

Biradial symmetry

Statolith

A hard mineralized ball that can roll around, it is a balancing stone, bumps nerves to understand position in the water column

Colloblast

structures on ctenophores which glue on end so prey gets stuck on tentacles

Ctenophore defecation method

Transient anus, 4 anal pores exist, but only one opens at a time dependent on which section of gastrovascular cavity is full

Ecological Importance of Ctenophores

species Mnemiopsis leidyi is considered an invasive species in the Eurasian Seas; they are highly effective as an invasive species due to their cannibalization of larvae

Placozoa discovery

Discovered late 19th c. growing on aquarium glass

Placozoa characteristics

3 species, 4-6 cell types reproduce via asexual budding and sexual reproduction, chromosomes small, genome bacterial-sized and circular mtDNA

Placozoa and Cnidaria relationship

form a sister clade

Phylum Cnidaria Taxonomy

Subphylum Medusozoa (Cl. Hydrozoa, Cl. Scyphozoa, Cl. Cubozoa, Cl. Staurozoa)

Subphylum Anthozoa (Cl. Anthozoa)

\n Class Hydrozoa members

colonial hydroids, smaller jellyfish, siphonophores

Class Scyphozoa

Large jellyfish (moon jellies)

Class Cubozoa

Sea wasps

Class Staurozoa

Stalked jellyfish

Class Anthozoa

Sea anemones, corals, sea pens

\n Cnidaria characteristics

Cnidaria characteristics

\n Tissue layers of Cnidarians are comprised of

epithelial cells (an apical to basal polarity)

\n \n Dermal layers of Cnidarians

Epidermis, Mesoglea, Gastrodermis

Mesoglea

cartilaginous structure made of connective tissue composed of protein fibers, a \\n watery ground substance, and a few cells; on inside of bell that functions as a hydrostatic skeleton as the cnidarian contracts against is and releases

Difference in mesoglea between anthozoans and medusa

Amount and composition affects the mechanical properties; sea anemones and other polyps have relatively little mesoglea while most medusae have a relatively large amount

Traditional life cycle of cnidarians

Asexaul in polyp stage and sexul in medusa stage (Hydrozoan polyp → Hydrozoan medusae → Egg + sperm → Planula larva)

\n myoepithelial cells

muscular cells of cnidarians

Interstitial cells

cells waiting for instruction of what type of cells that should become in cnidarians

Cnidocytes

\n specialized neural cells launch a toxic barb or blob (nematocyst) or enable cnidarians to stun prey or deter invaders

\n Nematocyst mechanism

Mechanically trigger (bumped) harpoon like structure with adhesive material and potentially neurotoxin

Distinct features hydrozoan polyps

gastrozooids and gonozooids

Hydrotheca

cup for hydroid gastrozooids

Obelia life cycle (typical)

Budding polyp → Hydroid colony → Medusi pop out of gonozooids → Medusi sexually reproduce (gametes) → Planular larva → Budding polyp

Velum

muscular ring of tissue in hydrozoan jelly that increases jet propulsion when they contract the bell

Hydrozoans with alternative life cycle

Tubularia (medusoids and actinula larva), Hydra (polyp only), Aglaura (medusa with actinula larva)

\n Siphonore examples

Portuguese man-of-war, Porpita porpita

\n Order Siphonophora

pelagic, highly polymorphic, colonial organisms; multiple individuals that are genetically identical but are specialized

\n Dactylozooids

\n tentacular mouthless zooid in certain hydrozoans that performs tactile and protective functions for the colony

pneumatophore

float filled with mixture of gases and helping the colony to float on the surface

\n Rhopalium

sensory structures of scyphozoan jellyfish containing statocyst and ocellus responsible for balancing with statolith and detecting light with ocellus

Scyphozoan digestive systems

4 gastric pouches with channels coming off that allow for nutrients to be distributed throughout the body

Subgenital pit

in scyphozoans, allows for circulation of water in dimple next to gonads to allow for oxygen access for gametes in gonads

Asexual reproduction of class scyphozoa

budding of polyp and strobilation

\n Strobilation

scyphistoma (polyp) produces many ephyra stacked upon each other with the most developed on top and they pop off and begins swimming away into ephyra

Typical Cubozoa life cycle

Scyphozoan for a long period, undergoes strobilation, ephyrae pops off and develops into medusa → Medusa sexually reproduces into planular larvae when attaches and develops into Scyphistoma

Typical Staurozoa life cycle

Does not includes swimming medusa stage; strictly sessile polyp

Muscular system of sea anemone

Two opposing sets of muscles the contract to change body shape