Arthropod diversity.Objectives:

New activities. 1. Examine living representatives of smaller clades. Pages 1-3. 2. Observe living crustaceans and examine how they use their various appendages and antennae in different ways. Pages 3-7.3. Begin to appreciate Hexapod diversity. Pages 8-11.4. Examine arachnids. Pages 11-15. 1. Examination of smaller clades.a. Limulus: Count the number of legs and see if you can identify the gnathobase or grinding organ. Food often encased in a hard shell or exoskeleton is guided by the chiliarium through the legs and to the gnathobase. After being ground here, the chelicerae are used to place it in the mouth.Can you locate the book gills, which serve as respiratory organs?

1

b, Sea spiders, if available: Describe the overall anatomy of the spider. Estimate the length of the body to that of the long legs. Note that the "body" is not that much thicker than the legs, although

2

terming the central cylinder a body is somewhat misleading as part of the GI tract + extend into the legs.

Dorsal surface showing proboscis, eyes and chelifores (appendages used to tear bits of food).

Ventral surface showing oviger (used by males to carry eggs) and gonopores or opening to reproductive organs.

Describe locomotion in these animals. Obtain a photograph if possible showing the oviger.

_____________________________________________________________________________

2. CrustaceansCrustaceans are noted for using their many appendages in various way. Please examine tagmata and locomotion in two different crustaceans besides skeletal shrimp.

You will be asked to further examine internal morphology or compare the locomotion of a particular aquatic species to a terrestrial form.

You should obtain a picture of each and be able to describe the types, number of appendages and how they and other structures are used in locomotion in each species. Are they using the whole appendages as the “effective” leg or just part of it to move? Your pictures should label antennae and “legs”. Your descriptions should include any tagmata you can see.

3

All containers should be rinsed with spring water before organisms are placed in them. Most of the crustaceans you will need to view are freshwater. The skeletal shrimp are the exception; they are marine.

a. Caprellids. These are truly spectacular creatures to watch feed and move. Please obtain a film of their feeding behavior and if possible their locomotion. You should also be able to obtain photographs of overall structure to label. Label antennae and peropods at least in photographs. .

Make a list of other animals you have found. Include 1-2 photographs of other animals that are living among the hydroids and the hydroid colony that is home to the skeleton shrimp.

Half of the class should look at isopods and half of the class should look at amphipods.

b. Freshwater isopod. Obtain a photograph, label regions, and describe how appendages are used in locomotion. If you choose these species, you should also compare how these fresh water isopods locomote to the terrestrial isopods or pill bugs. As in most crustaceans, the isopod body is divided into three distinct regions: head (= cephalon), thorax (=pereon), and abdomen (= pleon). Please use the more general terms, head, thorax and abdomen for labels on your photograph.

4

Pillbugs Examine the pill bugs or land isopods available. There are several species of varying size and color

that are living happily together in an aquarium. All are US natives.

Compare its morphology to the caprellid that you observed. Compare how it uses its legs to walk with how the caprellid used its limbs to swim?

c. Freshwater amphipods. Obtain a photograph and label regions, head, thorax and abdomen. Describe how appendages are

used in locomotion.

5

Pillbug comparisonsExamine the pill bugs or land isopods available. There are several species of varying size and color

that are living happily together in an aquarium. All are US natives.

Compare its morphology to the caprillid and sowbugy that you observed. Compare how it uses its legs to walk with how the other specimens used its limbs to swim?

If time permits please observe the copepods available. They are a study in minaturation. Do they use their appendages in the same way as the larger aquatic isopods or amphipods? d. Freshwater or saltwater Copepod. Cope is greek meaning an “oar” or “paddle;” pod is Greek

for “foot.” This should serve as a hint for how these individuals move. You will probably find copepods on most of the marine specimens you will view in the future and so you need to be able to recognize these small animals.

6

Obtain a good image of a copepod for your journal. You may have to place a copepod on a slide under the light microscope to obtain a good image. Describe how these animals locomote. Can you see egg sac on any of the specimens?

We do have marine copepods, which are bigger than freshwater forms, that you can examine. However, do not mix salt water with fresh. Rinse your dishes with several washes of spring water after viewing marine copepods. Marine specimens can tolerate some fluctuations in salinity. Your freshwater specimens however cannot be put in salt water

. In your journal, compare the structure and locomotion to the Daphnia or brine shrimp you viewed

last week.

e. Unique use of appendages. Compare how barnacles used their appendages to that of the isopods and amphipods viewed. We

have new barnacles if you wish to re-examine their feeding behavior.

Observe how mole crabs use their antennae to feed. Those of you who viewed Daphnia the first lab might want to share how they use their antennae in locomotion.

Emerita talpoida: Mole Crabs really do not look a lot like the typical crab because Mole Crabs have very short legs, and some species of Mole Crabs do not even have pincers. The shape of the back end and the short legs are adapted for digging downward and backwards into the sand. Mole crabs are filter feeders. As waves pass over antenna , the antennae filter out food particles. In intertidal areas, filter feeding is one of the primary ways of obtaining nutrients.

https://www.youtube.com/watch?v=z-nEbRj3hIMI’d appreciate any iphone videos you can get of their feeding behavior. This is the first time we have

been able to obtain this species.

__________________________________________________________________________________

3. Hexapodaa. Springtails or Collembola compared to termites. Although considered hexapods (having six legs), springtails are not considered true insects.

It is because their mouthparts are not free as in most insects. Go ahead and examine

7

the head on high power and compare the head of a springtail to that of a termite or true insect of about the same size.

Obtain a photograph of the springtail and termite. Label antennae, head and abdomen in both species. Describe which body structure contains the legs. The springtails are in petri dishes and so will not “jump” or use their furcula. To see this structure, please view one of the slides we have available of Collembola.

The name Collembola, derived from the Greek "coll" meaning glue and "embol" meaning a wedge, refers to a peg-shaped structure, the collophore, on the underside of the first abdominal segment.  The collophore was once thought to function as an adhesive organ, now is thought to play a role in osmoregulation. These were once considered insects, now placed in a separate group under the Hexapoda, a group that also contains the insects. They are also known as springtails because of their forked jumping organ (the furcula) found on the fourth abdominal segment. 

.

Termites are true insects. They are social and many species have castes, or individuals that differ in morphology and their role in termite society. You should have some workers and perhaps a soldier (larger, larger head and jaws) in your petri dish. Do note the exposed mouthparts. Take a photograph of your termite and label as many body parts as you can. I could not find a labeled diagram of a termite for you, so the grasshopper diagram will have to suffice for common structures found in most insects..

8

b. Choose one of the following species to examine. Compare locomotion and tagmatization in one of these species to that of the termite.

Darkling Beetles.. Please compare adults to larvae if they are available. Newly hatched larvae are almost microscopic and may molt 50 times or more before reaching pupation size. If larvae of these are not available, I have ordered a few larvae of larger species. Note the head region and fully

9

functional mouth parts. One way to tell most beetle larvae from dipteran larvae is by the moth parts. If it has jaws, it a beetle larva.

Domino roaches

Adults are beetle mimics, possibly of Anthia sp. tiger beetles. Nymphs tend to be more roach like and to burrow during the day, These roaches feed primarily on dried leaves, but love small bits of protein-based pet foods and fruit.

Desert beetles.Flightless beetles often seen trudging across trails and over sandy terrain. If bothered, the beetle

does a headstand, signaling that it's ready to squirt a noxious substance onto an assailant. The spray is foul to the nose, and isn't dangerous to people.

Activity c. Parasitic insects:If time permits, look at the slides of lice. My daughter came home with these a few times from school. Lice are insects but modified structurally for their ectoparasitic lifestyle. There are three species that infect humans, identified by structure and habitat, hair, body or pubic area. You will be asked to compare the structure of one of these species to those of the eyebrow mite. Make sure in your journal you note the species that you examined.

10

3. Arachnids : Please examine a slide of a pseudoscorpion and hair follicle mite. a. Pseudo scorpions. Compare the tagmata of Pseudo scorpions to that found in insects and crustaceans. Verify your examination by obtaining a labeled photograph for your journal. Pseudo scorpions are predators feeding on ants, mites and small flies among other small arthropods. Many species spin silk from a gland in their jaws to make cocoons for mating, etc. They do have venom glands located within their palps.

11

.

b. Note the adaptations for a parasitic life cycle on mites found on humans primarily in the hair follicles of eyelashes and eyebrows. Two species have been identified and we have slides of Demodex folliculorum. The adult mites are only about .4 millimetres long with an very elongated body. The mites can leave the follicles and walk around on the skin at night. Almost all adults over the age of 17 carry them. It is only in rare cases that the mites result in any skin eruptions.

The species that infects dogs however can result in serious disease (mange).

12

Obtain a photograph and compare the overall structure of the mite to that of the pseudoscorpion or to that of a typical spider diagrammed below. .

c. Examine the living arachnids we have. Please observe these carefully. You may want to ask Abby to show these specimens to the class. They often lose appendages easily when handled and best just viewed in their plastic habitat cages.

13

VinegaroonsAlthough ferocious looking, most vinegaroons are shy delicate creatures. The vinegaroons have no venom and rely as millipedes on a vinegar, in this case spray, to ward off potential predators. Note their whip. It is this tail, or “whip”, combined with their general scorpion-like body shape, which is key to the origin of one of their common names; the “whipscorpion.” Note the front pair of appendages that have evolved into long, thin, highly-sensitive feelers that scan the ground in front of the vinegaroon. They can “pinch” with their pedipalps, at least things small enough to fit within them, such as those crickets they prey upon.

Watch a vinegaroon spray https://www.youtube.com/watch?v=nNnKzoQwdAc

HarvestmenAlthough superficially similar to spiders, the Opiliones are a distinct order that is not closely related to spiders. They can be easily distinguished from long-legged spiders by their fused body regions and single pair of eyes in the middle of the cephalothorax. Harvestmen can swallow chunks of solid food. They too secrete a noxious fluid when disturbed, but the contents of this liquid various among species. They also boost a penis and mating then is direct unlike in spiders where sperm is transferred to the pedipalps, which deposit it in the female’s genital openings.

14

Again compare the morphology of the vinegaroons and harvestmen to that of the anatomy of the typical spider. Obviously Arachnids are a highly diverse group.

15