Practical Invertebrate Zoology Prepared by Nada Hassan Lubbad

Practical Invertebrate Zoology Prepared by: Nada Hassan Lubbad 2016

The course description and objectives : • The main objective is to provide an in-depth study of invertebrate biology with an emphasis on both aquatic vertebrate and terrestrial vertebrates. • Labs will focus on the morphology and anatomy of invertebrate ( in a practical way )

The labs schedule : Labs No. Topic covered 1 Features and Classification of invertebrate 2 The Protozoan Protists (1): Sarcomastigophora 3 The Protozoan Protists (2): Ciliophora and Apicomplexa Quiz (1) 4 Phylum Porifera (Sponges) 5 Phylum Cnidaria (Coelentrata) Quiz (2) 6 Phylum Platyhelminthes ( Flatworms) 7 Phylum Nematoda ( Roundworms) 8 Phylum Annelida ( Segmented worms) Quiz (3) 9 Phylum Mollusca 10 Phylum Arthropods 11 Phylum Echinoderm

The Course Evaluation : • Attendance 10% • Activities 10% • Quizzes 30% • Final exam (practical) 50% The course textbook : - Practical invertebrate zoology , a laboratory manual. - Power. Point Slides.

Introduction to Zoology Essential Concepts

Branches of Biology Ø Zoology definition : The branch of biology that deals with animals an animal life , including the study of the structure , physiology , development , and classification of animals.

Ø Binomial nomenclature : • In order to create one system that could be used universally, Carolus Linnaeus developed binomial nomenclature. • This is a system that uses two names to identify an organism. Specifically, it uses the genus and species name. Genus Species Homo sapiens OR Homo sapiens • Species = groups of interbreeding natural populations. • Genus (genera) = all similar species grouped together based on characters that define the genus.

Ø Taxonomy : • the study of naming and classifying organisms. • Two primary reasons for taxonomy : - For simple convenience - organizational purposes. - It tries to show phylogeny or evolutionary history. • Taxonomic methods depend on : - Morphology. - Genetics. - Behaviors.

Ø Hierarchical Classification: • Linnaeus developed a system that went from broadest to most specific. The levels of classification he used are: Kingdom Phylum Class Order Kings Play Chess On Fat Guys' Stomachs. Family Genus Species

The Five Kingdoms

Zoology Animal Kingdom Metazoa Cnidaria Platyhelminthes Nematoda Annelida Mollusca Arthropoda Echinodermata parazoa Choradata invertebrate Vertebrata Protista Kingdom Porifera Protochordata protozoa Ciliophora Apicomplexa Sarcomastigophora

About 95% of species , lack backbones and are collectively called Invertebrate

Ø Essential Concepts : 1. Body Symmetry There are four types of body plan symmetry: • Asymmetry : there are no planes of regular symmetry. e. g. , In protozoans such as rhizopods

• Spherical symmetry : the body is divisible into symmetrical halves in all directions & planes. e. g. Radiolarians (Protista)

• Radial symmetry: body arranged in circle around a central axis Found in sessile or floating animals. Lines of symmetry exist but in vertical plane only e. g. , Cnidaria & Echinodermata

Bilateral symmetry: body divides equally along one plane , which splits an animal into mirror-image sides. • Animal have dorsal and ventral surfaces , anterior and posterior ends. • Found in freely mobile animals e. g. the majority of invertebrates & vertebrates.

2. Body Development v Cephalization : - It associated with bilateral symmetry. - It means the concentration of sense organs & feeding apparatus on the anterior end. - Vertebrates possess a highly specialized brain to process sensory inputs than invertebrate.

Ø Examples of animals with cephalization : Insect , crabs , birds , fish , mammals, hydra , flatworms Hydra : Mouth , photoreceptors and nerve cells are located at one end “head”. Flatworms: Sense organs and a brain located at one end.

v Metamerism: • The arrangement of the organs of the body in series of similar units along the longitudinal axis of the body. • It is most clearly in annelids , the body divided both externally and internally into number of segments( metameres ). • In vertebrate, segmentation appears in muscles, nerves, and vertebrae. • Gonads in vertebrates are reduced to one pair only, while in invertebrates, there are several pairs of gonads.

v Animal Characterization Based on Features of Embryological Development: • Fertilization: The sperm and egg nuclei fuse and the oocyte (n) becomes a zygote (2 n). The zygote is a single, typically diploid, cell. Once the zygote divides into two cells it is called an "embryo in cleavage. " • Cleavage: The zygote undergoes cleavage, converting its large yolk-filled cytoplasmic mass into small cells. No cell growth occurs, only subdivision into increasingly smaller cells, until cells reach regular somatic cell size. Patterns of Cleavage - The pattern of cleavage (where and how the zygote divides) is coded in the DNA and is affected by the quantity and distribution of yolk, as the yolk appears to get in the way of the cleavage process. .

Ø Egg Classifications: - Isolecithal eggs - small amount of yolk – mammals - Mesolecithal eggs -moderate amount of yolk - typical of amphibian eggs (frog) - Telolecithal eggs - large amount of yolk – typical of birds and reptiles - Centrolecithal eggs – Nuclei copied without cytokinesis (cytoplasm division). Yolk in center of egg. Nuclei move to surface before forming cell membranes- most insects

Types of cleavage :

• Gastrulation: It means the movement of cells. The process of gastrulation and the parts of a gastrula.

v Gastrulation in details: • During early animal development, most embryos develop into a blastula or hollow ball of cells. • Then they form a gastrula by a process called gastrulation. • During gastrulation, some of the outer embryonic cells get pushed inward in a process called invagination. • This creates many structures, including layers called germ layers. • The inner hollow part of a blastula called a blastocoel. • Invagination during gastrulation produces a pocket or space called the archenteron. • The opening of the archenteron is called the blastopore. • Depending on the type of animal, a blastopore will become either the mouth or the anus.

Ø Germ layers : • Gastrulation, the process that produces different germ layers. • Germ layers are the initial tissue layers of an embryo, and animals can have up to three. 1. Ectoderm is the outermost layer of cells. 2. Mesoderm is the middle tissue layer. 3. Endoderm is the innermost germ layer.

Animals develop either two or three embryonic germs layers: 1. Radially-symmetrical animals are diploblasts, developing two germ layers: • an inner layer (endoderm) and an outer layer (ectoderm). • Diploblasts have a non-living layer between the endoderm and ectoderm. 2. Bilaterally-symmetrical animals are called triploblasts, developing three tissue layers: • an inner layer (endoderm), an outer layer (ectoderm), and a middle layer (mesoderm).

During embryogenesis, diploblasts develop two embryonic germ layers: an ectoderm and an endoderm. Triploblasts develop a third layer, the mesoderm, between the endoderm and ectoderm.

Presence or Absence of a Coelom • Triploblasts can be differentiated into three categories: 1. Those that do not develop an internal body cavity called a coelom (Acoelomates). 2. Those with a true coelom (Eucoelomates), 3. Those with "false" coeloms (Pseudocoelomates).

Ø Functions of coelom : The coelomic cavity represents a fluid-filled space that lies between the visceral organs and the body wall. 1. It houses the digestive system, kidneys, reproductive organs, and heart, and it contains the circulatory system. 2. The epithelial membrane also lines the organs within the coelom, connecting and holding them in position while allowing them some free motion. 3. The coelom also provides space for the diffusion of gases and nutrients, as well as body flexibility and improved animal motility. 4. The coelom also provides cushioning and shock absorption for the major organ systems, while allowing organs to move freely for optimal development and placement.

v Embryonic Development of the Mouth Bilaterally symmetrical , triploblastic eucoelomates Deuterostomes Protostomes Annelids Arthropods Mollusks - Complex animal : chordates - Simple animals : Echinoderms The word Protostome comes from the Greek word meaning "mouth first. " The word Deuterostomes comes from the Greek word meaning "mouth second. "

v. Development of the Coelom There are two processes : o Schizocoely, when a solid mass of the mesoderm splits apart and forms the hollow opening of the coelom. E. g. Protostomes. o Enterocoely, when the mesoderm develops as pouches that are pinched off from the endoderm tissue. These pouches eventually fuse to form the mesoderm, which then gives rise to the coelom. E. g. Deuterostomes

Eucoelomates can be divided into two groups based on their early embryonic development. In protostomes, part of the mesoderm separates to form the coelom in a process called schizocoely. In deuterostomes, the mesoderm pinches off to form the coelom in a process called enterocoely.

Glossary : • Zoology: The branch of biology that deals with animals an animal life, including the study of the structure, physiology, development, and classification of animals. • Taxonomy: The study of naming and classifying organisms. • Asymmetry: there are no planes of regular symmetry. e. g. , In protozoans such as rhizopods. • Spherical symmetry: the body is divisible into symmetrical halves in all directions & planes , e. g. Radiolarians (Protista). • Radial symmetry: body arranged in circle around a central axis, it found in sessile or floating animals. Lines of symmetry exist but in vertical plane only e. g. , Cnidaria & Echinodermata.

• Bilateral symmetry: body divides equally along one plane , which splits an animal into mirror-image sides. Animal have dorsal and ventral surfaces , anterior and posterior ends. Found in freely mobile animals e. g. the majority of invertebrates & vertebrates. • Cephalization: It means the concentration of sense organs & feeding apparatus on the anterior end. • Metamerism: The arrangement of the organs of the body in series of similar units along the longitudinal axis of the body. • Isolecithal eggs - small amount of yolk – mammals • Mesolecithal eggs -moderate amount of yolk - typical of amphibian eggs (frog) • Telolecithal eggs - large amount of yolk – typical of birds and reptiles • Centrolecithal eggs – Nuclei copied without cytokinesis (cytoplasm division). Yolk in center of egg. Nuclei move to surface before forming cell membranes- most insects. • Holoblastic : complete cleavage. • Meroblastic : incomplete cleavage.

• Gastrulation: the process that produces different germ layers. • blastula : hollow ball of cells forms after cleavage. • Triploblast: a blastula in which there are three primary germ layers: the ectoderm, mesoderm, and endoderm; formed during gastrulation of the blastula • Diploblast: a blastula in which there are two primary germ layers: the ectoderm and endoderm • Deuterostome: Any animal in which the initial pore formed during gastrulation becomes the anus, and the second pore becomes the mouth • Protostome: any animal in which the mouth is derived first from the embryonic blastopore ("mouth first")

• Enterocoely: the process by which deuterostome animal embryos develop; the coelom forms from pouches "pinched" off of the digestive tract • Schizocoely: the process by which protostome animal embryos develop; it occurs when a coelom (body cavity) is formed by splitting the mesodermal embryonic tissue • Acoelomate: any animal without a coelom, or body cavity • Coelomate: any animal possessing a fluid-filled cavity within which the digestive system is suspended. • Pseudocoelomate: It has a coelom derived partly from mesoderm and partly from endoderm. Although still functional, these are considered false coeloms. The phylum Nematoda (roundworms) is an example. • archenteron Invagination during gastrulation produces a pocket or space.