NC State University



For YOUR JOURNAL, this week, we are expecting the following. More on appendage use in crustaceans: 1. Movie of barnacle feeding (and mating if possible). If specimens are available, photographs of barnacle larvae2. Movies of Atlantic sand crabs feeding. 3. Movies of skeletal shrimp feeding and moving. Please also include some photos of the shrimp’s habitat. (Be on the lookout for sea spiders.)Barnacles and hydroids (skeletal shrimp were shipped attached to these) become habitat for numerous species. You should always record what other types of animals are found with specimens examined. These species are important clues as to the niche occupied by the animal of interest. We also cannot order many species. Most supply companies will not collect sea spiders or flatworms for classes. Therefore when we do get lucky to get a specimen that is not typically available I want the class to examine it, whether we are focusing on that group in lab or not. If you find specimens that might be of interest to the class, please share your observations with the instructor and the class. Some of the species you will come across will look like something out of a fantasy novel. Please again share your observations, this may be the only time in their lifetime that your classmates and instructor will be able to observe these specimens. Observations on other arthropods.4. Movies of sea spiders moving. 5. Observations of a horseshoe crab morphology. Descriptions of specimens available. 1. Barnacles We have the purple striped barnacle, Balanus amphitrite and an unidentified species (probably another species of Balanus). Sometimes keeping these overnight in dishes in the dark will produce larvae, but don’t spend a lot of time looking for them. Some years the dishes are full of them, in others we don’t see any. Examine the diagram below of a barnacle. The barnacle feeds with its legs. a. You are to film and describe feeding in a barnacle. Obtain a dish of barnacles or if all are in one dish simply gently scoot a barnacle or two into a smaller container. Make sure the smaller container can hold enough water to cover the barnacle. While you are waiting for the animal to adjust to its new surroundings, document any animals that are using the barnacle as habitat. Those students obtaining the dish containing the larger colony should share their observations with the class. In a large colony, you should be able to see most of the major groups of animals we have been discussing in lecture. (Hint: Patience is the key here to good filming.) Focus and adjust your lighting using the empty container that will house your barnacle. Place your barnacle under the stereoscope, lights off and wait for it to become adjusted to its new surroundings. If you barnacle does not feed after it is set and left alone in its new container for a few minutes, you can try feeding it macro zooplankton or if that does not work phytoplankton. Simply use a small pipette to obtain some food to add to your dish containing the barnacle. Is there evidence of mating? If so, please film mating in these animals. b. Types of barnacle larvae. The diagram below shows the Cyprid larvae attaching to the substrate to assume the sessile lifestyle of the adult. b. If larvae are produced during the night, they will be visible as small objects darting around in these dishes. Use a small pipette to obtain some of these if you see them, place in the smallest dish available, and observe how they move under the stereoscope. Identify if they are nauplius or cyprid larvae. Record your observations, obtaining photographs whenever possible. 2. We also have Emerita talpoida or the Atlantic sand crab. These interestingly enough are filter feeders. Please observe this activity in one of our small sand tanks. Describe filter feeding in these animals. You may want to ask your instructor to add a bit of coral food to the small tank containing them. You can use your smart phone to capture this activity. 3. CAPRELLID Shrimp Check with your instructor if marine Caprellid or skeleton shrimp survived the night. These are truly spectacular creatures to watch feed and move. a. If so, please obtain a film of their l feeding behavior. b. You should also be able to obtain photographs of overall structure to label. Label antennae and peropods at least in photographs. Label tegmata using the more common terms, head, thorax and abdomen.Other arthropods.4. Sea spiders. We have two sources of sea species. Occasionally MBL sends us a large specimen whose locomotion can easily be photographed with a smart phone. We also occasionally receive a small species has hitched a ride on a cnidarian colony. Be on the lookout for these as you view cnidarian colonies including those shipped with skeletal shrimp.Take every opportunity to view this group. It may be the only time in your life you view a specimen. We apparently even have a male carrying eggs. Each pair that examines this should take one shot or make a short film for the class. I will make the picks available for your journals. You are to describe the animals and how they move in your journals. Dorsal surface showing proboscis, eyes and chelifores, appendages used to tear food into bits.Ventral surface showing oviger (used by males to carry eggs) and gonopores or opening to reproductive organs. 5. Horseshoe crabs.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 chelicera are used to place it in the mouth.Can you locate the book gills which serve as respiratory organs? We have Cambrian and Devonian fossil trilobites available. a. Observe the variation of size in the trilobites fossils available. For more on trilobites, explore the diversity found during the Devonian on the followingwebsite. b. Note in your journal what structural characteristics are alike and different in trilobites and horseshoe crabs. Did trilobites have a gnathobase, book gills?. ................
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