Lab 4 (Arthropods) Flashcards
1
Q
What are Arthropoda?
A
- They have segmented and metameric bodies
- Fusion of metameres into distinct functional body units called tagmata
- Specialization of appendages
- They also have jointed appendages (this greatly increases the range of mobility and possible functions of the appendages
- Very diverse
2
Q
What are the shared characteristics of the animals from the Phylum Arthropoda?
A
- Bilateral symmetry
- True coelom
- Cephalization
- All organ systems are present
- Striated muscles
- A hard, chitinous exoskeleton that must be molted (shed)
- Greater specialization of appendages, which are jointed
- Open circulatory system involving hemolymph (blood)
3
Q
What are the Subphylum’s to the Phylum Arthropoda?
A
Chelicerata
Crustacea
Myriapoda
Hexapoda
4
Q
Explain the basics to the Subphylum Chelicerata
A
- Spiders, scorpions, ticks, horseshoe crabs
- They do not have a jaw (mandible) for chewing food
- Instead, the first pair of appendages is modified into structures that seize and tear their food
- These appendages are called chelicerae
- Most chelicerates have two tagmata
1) Cephalothorax
2) Abdomen - They do not have antennae
5
Q
What are the two examples we looked at for the Subphylum Chelicerata?
A
Horseshoe crab
Garden spider
6
Q
Explain the basics of the horseshoe crab?
A
- Aren’t actual crabs
- Ancient chelicerates
- Live on the soft muddy bottoms of shallow water, where they feed on molluscs, worms and dead fish
- They do come ashore to lay and fertilize eggs
7
Q
What is the external (general) of the horseshoe crab?
A
- On the dorsal surface the body has two distinct tagmata
1) the anterior cephalothorax
2) the posterior abdomen - They have median simple eyes and lateral compound eyes
- The long telson (“tail spine”) is used for anchoring in sand, ploughing through the sand and righting the animal when it flips over
8
Q
What is the structure/protection of the horseshoe crab?
A
- It’s body is covered with a tough, leathery exoskeleton made of chitin
- As the animal grows, it must molt (shed) its exoskeleton periodically
- The cephalothorax is protected by a horseshoe shaped section of exoskeleton called the carapace
9
Q
What are the appendages of cephalothorax of the horseshoe crab?
A
- There are 6 pairs of appendages on the cephalothorax
- The first, small pair is the chelicerae; these are used to detect and manipulate food
- Next come the pedipalps; these are modified to perform different functions, depending on the animals sex and the species
- On males, the pedipalps are enlarged into claspers, used to hold onto the female as she carries him out of the water and onto the shore to reproduce
- The remaining pairs of appendages are walking legs
- The mouth is the opening found where the appendages attach to the body
10
Q
What are the appendages of abdomen of the horseshoe crab?
A
- The abdomen bears a series of flat, plate like appendages
- The first pair conceals the genital pores
- The others are modified into gills
- Under the flaps are many layers, called lamellae, of the gills
- The gills are the surfaces on which gas exchange occurs
- The anus is located where the telson meets the abdomen
11
Q
Explain the basics of the garden spider
A
- Mostly prey on other Arthropods, but are known to consume birds, fish, amphibians and small mammals
- They build orb webs in sunny places with tall grass
- Webs are handy structures for passively trapping passing prey
12
Q
What is the external (general) of the garden spider?
A
- They have 2 tagmata, and a thin and flexible exoskeleton
- Sensory hairs (setae) project from all parts of the body, including appendages
- On the dorsal surface of the cephalothorax are a number of simple eyes at the anterior end
- Different types of spiders have different numbers and arrangements of eyes
13
Q
What are the appendages of cephalothorax of the garden spider?
A
- The first set of appendages are the chelicerae
- They are found at the front of the face, often obscured by the second pair of appendages (pedipalps)
- The terminal segment of each chelicera is a fang
- Poison is ejected through the fangs via a poison gland, to kill and digest the prey prior to eating
- The next set of appendages is the pedipalps
- These are used to grip and manipulate prey (they are covered in long, sensitive setae)
- Spiders are generally sexually dimorphic
- Males are much smaller than females and their pedipalps are modified to transfer sperm into the female epigyne
- The remaining appendages are walking legs
14
Q
What are the abdominal structures of the garden spider?
A
- At the anterior end is two thin slits (these openings mark the location of the book lungs)
- These look and function very much like the book gills of the horseshoe crab
- Between the openings to the book lungs is the epigyne, which conceals the female genital pore
- There are several pairs of spinnerets on a raised area at the posterior end of the abdomen
- These structures produce silk, used for making webs, wrapping prey and encasing eggs
- Anterior to the spinnerets is another small opening
- This is the spiracle; it is an opening to the internal respiratory system
- Some spiders have both book lungs and a tracheal system, while others have only one of the two systems
15
Q
Explain the basics to the Subphylum Myriapoda
A
- Legs are the give-away
- They have segmented bodies and jointed appendages
- They have two tagmata
1) Head
2) Trunk - They have 1 pair of antennae
16
Q
What are the 2 examples we looked at for the Subphylum Myriapoda?
A
Centipede
Millipede
17
Q
What are centipedes?
A
- They are swift, active, predatory animals
- They are found under logs and stones or other moist habitats
- Some species have simple ocelli, while others have large, faceted eyes composed of many small ommatidia (simple eyes)
- The large fangs at the end of the maxillipeds are connected to poison glands and are used to subdue prey
- The toothed mandibles, which chew food, are positioned between the maxillipeds
- The mouthparts are directed anteriorly (towards the front of the face), this is because they are used to capture and subdue prey
- The single pair of antennae is located on the head
- Each trunk segment bears one pair of long legs; the leg length is an indication of speedy locomotion
18
Q
What is a millipede?
A
- They share the same types of habitats as their centipede cousins (damp, dark places) but they occupy a different dietary niche, feeding on decaying plant material
- Their most unique characteristic is that each trunk segment is a “double segment” and bears two pairs of legs
- The legs of this animal are shorter than those of the centipede; speed is not as essential for animals consuming plant material
- They have noticeable antennae, ommatidia and mandibles
- The mouthparts in this animal are pointed ventrally (downwards); this reflects the scavenging niche of this animal (food is simply lying on the ground)
- Their hard, rounded bodies can curl into a protective coil when harassed; many also excrete noxious chemical to deter predators
19
Q
Explain the basics to the Subphylum Crustacea
A
- Crayfish, lobsters, crabs, barnacles and microscopic animals (fairy shrimp)
- Most are aquatic animals that use gills to breathe, though some are terrestrial
- They have 2 pairs of antennae
- They have 2 tagmata
1) Cephalothorax
2) Abdomen
20
Q
Explain the basics to the crayfish
A
- Also known as crawdads, crawfish and mudbugs
- They live in freshwater streams and ponds
- Omnivores
- They feed on vegetation and small animals like worms, snails and small vertebrates
- Lobsters have a nearly identical body plan
21
Q
What is the external anatomy of the crayfish?
A
- They have a hard exoskeleton that must be molted periodically as the animal grows
- Cephalothorax
- Abdomen
22
Q
Explain the external cephalothorax of the crayfish?
A
- The dorsal surface of the cephalothorax is covered with a hard carapace
- The broad lateral extensions of the carapace cover the gills
- The pointed anterior part of the head is called the rostrum; emerging from beneath the rostrum are the stalked eyes and two pairs of antennae
- There are four pairs of walking legs and one pair of chelipeds originating from the ventral side of the cephalothorax
23
Q
Explain the external abdomen of the crayfish
A
- The broad tail fan at the distal end of the abdomen is made up of telson and uropods; strong, rapid flips of tail propel the animal backwards
- The anus is located above the telson
- The abdomen bears 5 pairs of swimmerets, which look different in males and females
- In a male, the pair closest to the cephalothorax will be hardened and paddle shaped while the rest are soft and feathery; in the female all pairs are soft
- The male’s highly modified copulatory swimmerets (pleopods) are used to transfer sperm from their genital opening to the female
- The female has an oval seminal receptacle between the last pair of walking legs; this is where sperm is transferred from the male
- She also has a pair of openings to her oviducts at the base of the third pair of walking legs
- Fertilization is external, and the female protects her eggs and young in a brood pouch formed by her swimmerets
- Females also use their tail fan to protect eggs and young by curling it up over her abdomen
24
Q
What are the appendages of the crayfish?
A
- Good example to study serial homology and specialization in appendages
- Chelipeds
- Maxillae
- Antennae
- Copulatory swimmerets (males)
25
What is the chelipeds of the crayfish?
These formidable appendages have greatly enlarged chelae (pincers) used in protection and food handling
26
What is the maxillae of the crayfish?
In addition to moving food towards the mouth, the second maxilla also bears a long blade called a gill bailer, which is used to draw water (and thus oxygen) through the gill chambers
27
What is the antennae of the crayfish?
- These are tipped with long and many jointed filaments
- They are sensitive to touch, vibrations and chemicals in the water
- The antennules are additionally concerned with equilibrium
28
What are the copulatory swimmerets (males) of the crayfish?
These are paddle shaped and used to collect sperm from the genital openings and transfer it to the female seminal receptacle
29
What are the muscles of the crayfish?
- The carapace is stuck to certain muscles in the head; these were the anterior and posterior gastric muscles
- In addition to suspending the stomach from the carapace, these all move the stomach walls during feeding
- On each side of the posterior gastric muscles are mandibular muscles, which move the mandibles
- To each side of the animals midline, a narrow "tube" of muscles runs along the body to the abdomen; the job of these extensor muscles is to straighten the abdomen
- Nearly filling the abdomen are the large flexor muscles
- They flex (or bend ventrally) the abdomen
30
What is the digestion/excretion of the crayfish?
- The stomach is two chambered
- The cardiac stomach is the large anterior chamber; the smaller pyloric stomach lies posterior to it
- Within the stomach is a pair of chitinous teeth
- The pale lobes of the digestive gland (lying posterior to the stomach, and wrapping around the sides of the body) release digestive enzymes into the stomach
- The intestine is a tube that runs from the stomach and under other organs in the cephalothorax and continues down the abdomen where it is more visible
- Waste exits via the anus
- In the head region is a pair of roundish, beige antennal glands lying ventrally on either side of the head cavity
- Each gland is connected to a bladder; the bladder in turn empties urine through openings at the base of each antennae
- This is the renal system (kidneys) and is analogous to the Malpighian tubules in the grasshopper
31
What is the respiration/circulation of the crayfish?
- When the appendages move, it helps circulate water over the gills
- The rest of the gills lie in the gill chambers on either side of the body
- Water enters the gill chambers via the open ventral ledge of the carapace and is drawn over the many rows, folds and extensions that maximize the surface area for gas exchange
- The small, pinkish and somewhat angular heart is nestled in behind the posterior gastric muscle
- They have an open circulatory system
- The hemolymph leaves the heart and via arteries (which direct the oxygenated hemolymph to other organs) but it returns to the heart (after being re-oxygenated by the gills) via sinuses and re-enters through small holes in the wall of the heart called Ostia
32
What is the reproduction (internal) of the crayfish?
- The pair of gonads of either sex lie just under the heart
- They are dioecious
- Females gonads are slender and pinkish, though they may be large and distended with eggs depending on when the animal was preserved
- Males testes are whitish and more delicate
- Eggs and sperm are released by pores on the ventral surface
- Fertilization is external
33
Explain the basics to the Subphylum Hexapoda
- Most diverse group
- They are found in almost every type of habitat, although few inhabit the oceans (their relatives, the crustaceans, rule the seas)
- They have 3 pairs of walking legs, one pair of antennae, and three tagmata (head, thorax, abdomen)
- Many adult insects also have one or two pairs of wings
- Wings are a fairly remarkable development; only 3 other types of animals have accomplished this evolutionary feat
- Highly specialized in terms of their diets and habitats and also in the form of their bodies and appendages
- This specialization has allowed them to diversify extensively by exploiting unique ecological niches
34
What is the general external of the grasshopper?
- The body is covered with a hard, chitinous exoskeleton
| - The three tagmata present in all insects are evident on the grasshopper
35
Explain the head of the grasshopper?
- The head is freely moveable
- It contains different appendages modified into one pair of antennae and several mouthparts
- Two large compound eyes
- 3 ocelli on the top of the head
36
Explain the thorax of the grasshopper?
- Each segment of the thorax bears a pair of legs
- 2 pairs look similar, but the third pair is highly specialized
- The length and girth of these specialized hind legs indicate that they are well muscled and used for jumping
- The other legs are used for walking and grasping
- Near the proximal end of the hind legs, there are oval shaped membranes
- They are tympana and act like ear drums; they are used for hearing
- Grasshoppers and their kin communicate using sound, so a structure built to receive sound waves is critical
- The middle and last segments of the thorax each bear a pair of wings
- The forewings are thicker and more leathery than the pliable, membranous, hindwing folded up underneath
- The forewings protect the hindwing, which are used to power short bursts of rapid flight when the animal leaps
37
Explain the abdomen of the grasshopper?
- Tiny holes may be seen on the lateral areas of each of the abdominal segments, at about the midline of each side; these are spiracles, and are entrances to the respiratory tracheal system
38
What are the genitalia of the grasshopper?
- Not the same as gonads
- Located at the tip of the abdomen
- The end of the abdomen in males is rounded
- In females, the end is pointed and consists of two pairs of plates that form the ovipositor (the structure used to deposit eggs)
39
What are the appendages of the grasshopper?
- Antennae (multi-segmented and used as tactile sensory structures)
- Labrum (the 2 appendages of the upper lip are fused into a single bi-lobed structure that manipulates food and conceals the mandibles)
- Mandibles (large and toothed; the main tools used to chew food)
- Maxilla (Toothed, used in chewing and handling food. Each has a maxillary palp, used in touch/taste)
- Labium (Fused, bi-lobed lower lip used to handle food; bears two labial palps used in touch and taste)
40
What are the internal muscles of the grasshopper?
- A large amount of muscle tissue should be evident in the thoracic region; these power the wings and legs that attach to the thorax
- Other muscles are visible behind the head
41
What is the internal digestion/excretion of the grasshopper?
- Consumed food passes from the mouth to a pharynx in the head to the large, sac like crop (which stores food), and then into the gizzard (which begins physical digestion)
- Chemical digestion, aided by enzymes secreted fromm the lobes of the gastric cecae, takes place in the stomach
- Absorption of nutrients occurs in the intestine and wastes pass through a rectum and anus
- Lying in the region of the stomach and intestine, is a tangled mess of tiny filaments
- These are Malpighian tubules; they are outgrowths of the digestive tract and serve as excretory structures, emptying their waste products into the gut
42
What is the reproduction of the grasshopper?
- Rows of ovaries, containing oval ish eggs, are attached to oviducts on either side of the body
- These are released through the ovipositor at the posterior tip of the abdomen
- The male reproductive organs are located in the same vicinity but are less distinct
43
What is the insect growth and development?
- Most change the form of their bodies several times after hatching from an egg
- This is called metamorphosis
- As it grows, the insect molts (sheds) its exoskeleton, thereby becoming larger and/or changing its body form; the stages between molts are called instars
- Different types of insects undergo different patterns of development; there are 3 main patterns with different numbers of stages
44
What are the 3 types of development?
Ametabolous
Hemimetabolous
Holometabolous
45
What is ametabolous?
- The immature larvae look like miniature adults and they simply grow; these animals do not actually undergo true metamorphosis because the form of their body does not change
- There are 3 stages of growth (egg, juvenile and adult)
- This only occurs in wingless hexapods such as silverfish
46
What is hemimetabolous?
- The wings of the immature larva (nymphs) start as buds and gradually develop with each successive molt
- There are 3 stages of growth (egg, nymph and adult)
- Fully developed wings only appear after the final molt to the adult form
- This occurs in true bugs, grasshoppers and dragonflies
47
What is holometabolous?
- They undergo the most dramatic changes
- The larvae are wormlike (often called grubs, caterpillars, maggots, etc)
- Wings develop internally during the larval stages, are usually visible in the pupal stage as buds and become fully formed in the adult stage
- Larvae typically form a cocoon around themselves in which to pupate
- There are four stages (egg, larva, pupa, adult)
- Butterflies, bees, beetles and flies
