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Wednesday, May 9, 2012
Friday, May 4, 2012
Thursday, May 3, 2012
Friday, April 27, 2012
Lecture
Phylum Mollusca (Scaphopoda and Aplacophora)
Phylum Annelida
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| Mollusca: Scaphopoda and Aplacophora Top: Scaphopodan shell and foot Bottom: Chaetodermomorph (photo) and neomeniomorph (photo) aplacophorans |
Today we briefly covered the lesser known molluscan groups Scaphopoda ("boat-like foot" molluscs) and Aplacophora (molluscs "without a shell"). We discussed their bauplan and some of their most important aspects of their ecology.
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| Annelida Left column: An errant and a sedentary polychaetes Right column: Clitellates - Oligochaeta (photo) and Hirudinea (photo) |
Then we began discussing the phylum Annelida, the segmented worms. We began with their bauplan, and then started with one of the groups: Polychaeta, the most diverse of the annelids. We covered their general characteristics and focused on the errant polychaetes. Next week, the sedentary polychaetes, and the clitellates.
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Wednesday, April 25, 2012
Lecture - Phylum Mollusca
Cephalopoda
Today we discussed some of the key features of each one of the extant groups of cephalopods. Then we proceeded to discuss some of the most important features of cephalopods as a whole and their variation across different groups. We discussed:
- Shell evolution - Presence/absence, location, material, function
- Feeding - Beak and radula
- Locomotion - Crawling and swimming. Using fins and using siphons for jetting
- Nervous system and complex behavior
- Reproduction and development
Monday, April 23, 2012
Lecture - Phylum Mollusca
Bivalvia (Lamellibranchs)
Cephalopoda
FRIDAY, APRIL 20, 2012
(entry in progress)
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| Some lamellibranch bivalves (all unionids) from the Mussels of Illlinois website |
(entry in progress)
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Field trip - Hog Creek in Hardin Co.
THURSDAY, APRIL 19, 2012
Information and pictures from the field trip coming soon
(entry in progress)
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Information and pictures from the field trip coming soon
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| Location of the sampling site, about 7miles east of ONU |
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| Google Maps image of the sampling site Hog Creek (Allen Co., OH), on Ada Rd/HWY 81, 0.5 mi (0.8 Km) west of the junction with N Phillips Rd. |
(entry in progress)
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Wednesday, April 18, 2012
Lecture - Phylum Mollusca
Gastropoda (Opistobranchs and Pulmonates)
Bivalvia (Protobranchia)
Today we finished our discussion on gastropods, by describing the diversity and defining anatomical characters of the opistobranchs (mainly the presence of rhinophores, cerata or gill plumes, complete detorsion, and reduction or loss of shell, ctenidia, and mantle cavity).
We then turned our attention to pulmonates, gastropods that have colonized terrestrial and freshwater environments, mainly through the loss of ctenidia and gills, and the development of a highly vascularized mantle cavity which acts as if it were a lung (hence the name 'pulmonates'). Some have also lost the shell.
We started the discussion of the class Bivalvia, the group comprising oysters, scallops, clams, and mussels. We discussed their general body plan and did overview of their life cycle, including a special mention of the modified veliger state of Unionoidea: The parasitic glochidium larva.
We mentioned that we will divide the Bivalvia into the traditional groupings of Protobranchia and Lamellibranchia (with no current taxonomic validity), and explained how the lamellibranchs can use their gills to filter food.
(entry in progress)
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We then turned our attention to pulmonates, gastropods that have colonized terrestrial and freshwater environments, mainly through the loss of ctenidia and gills, and the development of a highly vascularized mantle cavity which acts as if it were a lung (hence the name 'pulmonates'). Some have also lost the shell.
We started the discussion of the class Bivalvia, the group comprising oysters, scallops, clams, and mussels. We discussed their general body plan and did overview of their life cycle, including a special mention of the modified veliger state of Unionoidea: The parasitic glochidium larva.
We mentioned that we will divide the Bivalvia into the traditional groupings of Protobranchia and Lamellibranchia (with no current taxonomic validity), and explained how the lamellibranchs can use their gills to filter food.
(entry in progress)
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Friday, April 13, 2012
Thursday, April 12, 2012
Wild and Bizarre Inverts Seminar
The Wild and Bizarre Inverts project is an exercise that highlights adaptations that some invertebrates have that defy our conventional view on animal biology.
Many animals have morphological or behavioral adaptations that are very different from what most people are used to see in animals (vertebrates or invertebrates). For such reason they tend to awe those who do not study the lesser known phyla or lesser known species in well known phyla.
Students in this course picked an example that appealed to them and prepared a paper and a presentation highlighting unusual anatomical, physiological, or behavioral adaptations in invertebrates.
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Many animals have morphological or behavioral adaptations that are very different from what most people are used to see in animals (vertebrates or invertebrates). For such reason they tend to awe those who do not study the lesser known phyla or lesser known species in well known phyla.
Students in this course picked an example that appealed to them and prepared a paper and a presentation highlighting unusual anatomical, physiological, or behavioral adaptations in invertebrates.
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| Wild and bizarre cnidarian and lophotrochozoans Clockwise from top: Siphonophore (Marrus orthocanna), Christmas Tree worm (Spirobranchus giganteus), Mimic octopus (Thaumoctopus mimicus), and Vampire squid (Vampiroteuthis infernalis) |
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| Wild and bizarre ecdysozoans (all panarthropods) Left to right from top: Water Bear (Tardigrada), Velvet worm (Onychophora), a Pistol Shrimp (Alpheus sp.), Goliath Bird-Eater tarantula (Theraposa blondi), Japanese Spider crab (Macrocheira kaempferi), and the Orchid mantis (Hymenopus coronatus) |
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Wednesday, April 11, 2012
Wednesday, April 4, 2012
Lecture - Phylum mollusca
Monoplacophora and Polyplacophora
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| Mollusc larvae A chiton's trochophore, a snail's veliger, and a freshwater clam's glochidium |
We talked about the general mode of reproduction in molluscs and discussed the larval stages that characterize the phylum: trochophora, veliger, and, in some cases (Unioniodea), glochidium.
We even mentioned one of the masterpieces of scientific poetry: The Ballad of the Veliger, by Walter Garstang (worth the read, for mollusc larval development and for understanding torsion in gastropods)
We then discussed the result of adaptive radiation in molluscs, which gave rise to the diversity we observe today, from an ancestral mollusc. We talked a little about mollusc phylogeny too.
After discussing such intraphylum diversity we started talking about the first classes: Monoplacophora and Polyplacophora (chitons). For both groups we discussed how their characteristics differ from those covered when discussing the generalized mollusc. We payed special attention to the shell, the foot, the mantle cavity and the visceral mass.
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| Monoplacophorans and a polyplacophoran |
Thursday, March 29, 2012
Wednesday, March 28, 2012
Lecture - Phylum Mollusca
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| Generalized mollusc from Biodidac |
Today we continued our discussion of molluscs by explaining general features using the generalized mollusc as a base line to later on explain the adaptive radiation of the various molluscan groups.
We had a brief discussion of the head-foot portion, with emphasis on the head portion and a structure that is present in most mollusc groups, the radula. Then we focused our attention on the foot, its roles, and some of its variants in different groups.
We also talked about the mantle and its role in secreting the three-layered shell (periostracum, prismatic layer, nacreous layer), and the importance of it lining the mantle cavity, where the gills, in the form of ctenidia, are found.
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Friday, March 23, 2012
Lecture - Phyla Nematoda and Mollusca
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| Parasitic nematodes Top: A hookworm and SEM of the anterior end of one Middle: A pinworm and a Guinea worm Bottom: A large human roundworm and a an intestine infested with them |
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Today we finished the chapter on nematodes, by discussing aspects of their reproduction, nervous system, and details about their lifestyles (parasitic and free living).
Among the parasitic nematodes we looked into the anatomy and life cycles of hookworms, pinworms, large human roundworm, filarial nematodes, and Guinea worms.
We closed the lecture with a brief discussion of Nematoda en its (still debated) placement in the Ecdysozoa clade within the greater metazoan phylogeny.
We then started our discussion on the phylum Mollusca, by briefly discussing which groups comprise the phylum, how ancient this lineage is, and the great diversity found within it. We reviewed some of the more general characteristics (eucoelomate, unsegmented, protostomes) and introduced the concept of the Hypothetical Ancestral Mollusc (HAM), also known as the generalized mollusc or the archetype mollusc
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Thursday, March 22, 2012
Lecture - Phyla Rotifera and Nematoda
WEDNESDAY, MARCH 21, 2012
Today we started covering a couple of examples of pseudocoelomate phyla, Rotifera and Nematoda.
Rotifera, the "wheel bearers", are an interesting phylum of microscopic or nearly microscopic, mostly freshwater organisms, typically with a cephalic structure called crown, bearing a series of cilia that beat metachronally, giving the impression that a wheel is spinning. Such behavior is used by most members of this phylum to feed and swim.
We studied their main external anatomical features, feeding and swimming/"walking" behavior, their mode of osmoregulation, and their nervous system.
Then we had an overview of the main groups, Digonatans (Seisonids and Bdelloids) and Monongonontans.
When discussing the bdelloids we emphasized the fact that they reproduce parthenogenetically and no males of this group have ever been observed.
They can also undergo cryptobiosis when environmental conditions change drastically. They go into a desiccate dormant state, in some groups a cyst, that can be rehydrated months to years later, depending on the group. Cysts can be exposed to extreme conditions and still be able to rehydrate. Examples are exposure to -200º C for a few days, or exposure to nearly absolute zero temperatures (0.008º K) for a few seconds.
Monogonontan rotifer populations are composed exclusively by females, but males have been observed. When environmental conditions become stressful eggs are produced by meiosis (instead of the normal mitotic process), allowing for the birth of haploid males and females. These reproduce producing diploid eggs that are very resistant to adverse conditions, and will hatch when the stress has receded.
Nematodes, unsegmented "roundworms" are the most ubiquitous and abundant animals on earth. Insects may be the most diverse (so far), but in terms of number, nematodes take the prize. They are so abundant (free living and parasitic) that it is said that "if everything on Earth were to disappear except the nematodes, the outlines of everything would still be visible: the mountains, lakes and oceans, the plants and the animals would all be outlined by the nematodes living in every habitat." (I do not know the original source of such statement.
We discussed a cross section of their internal anatomy, their digestive and nervous systems.
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Today we started covering a couple of examples of pseudocoelomate phyla, Rotifera and Nematoda.
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| Left: Philodina gregaria (Rotifera: Bdelloidea - Micrographia) Right: Stephanoceros fimbriatus (Rotifera: Monogononta - Water Bear web base) |
Rotifera, the "wheel bearers", are an interesting phylum of microscopic or nearly microscopic, mostly freshwater organisms, typically with a cephalic structure called crown, bearing a series of cilia that beat metachronally, giving the impression that a wheel is spinning. Such behavior is used by most members of this phylum to feed and swim.
We studied their main external anatomical features, feeding and swimming/"walking" behavior, their mode of osmoregulation, and their nervous system.
Then we had an overview of the main groups, Digonatans (Seisonids and Bdelloids) and Monongonontans.
When discussing the bdelloids we emphasized the fact that they reproduce parthenogenetically and no males of this group have ever been observed.
They can also undergo cryptobiosis when environmental conditions change drastically. They go into a desiccate dormant state, in some groups a cyst, that can be rehydrated months to years later, depending on the group. Cysts can be exposed to extreme conditions and still be able to rehydrate. Examples are exposure to -200º C for a few days, or exposure to nearly absolute zero temperatures (0.008º K) for a few seconds.
Monogonontan rotifer populations are composed exclusively by females, but males have been observed. When environmental conditions become stressful eggs are produced by meiosis (instead of the normal mitotic process), allowing for the birth of haploid males and females. These reproduce producing diploid eggs that are very resistant to adverse conditions, and will hatch when the stress has receded.
A bdelloid rotifer feeding
A monogonont rotifer feeding
Nematodes, unsegmented "roundworms" are the most ubiquitous and abundant animals on earth. Insects may be the most diverse (so far), but in terms of number, nematodes take the prize. They are so abundant (free living and parasitic) that it is said that "if everything on Earth were to disappear except the nematodes, the outlines of everything would still be visible: the mountains, lakes and oceans, the plants and the animals would all be outlined by the nematodes living in every habitat." (I do not know the original source of such statement.
We discussed a cross section of their internal anatomy, their digestive and nervous systems.
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| A (morphologically) typical nematode Nova Scotia nematodes |
Thursday, March 15, 2012
Lecture - Phyla Platyhelminthes and Nemertea
WEDNESDAY, MARCH 14, 2012
PLATYHELMINTHES
We briefly covered some of the main features of Monogenea, prominent fish ectoparasites, focusing on their external anatomy, which includes the presence of a complex structure at the posterior end, an opisthaptor, and an anterior adhesion organ, a prohaptor.
We then moved on to discuss the flukes, Trematoda. Some of their main characteristics are:
The stages that can enter a host are "equipped" with glands that produce enzymes that disrupt the host's tissues. One of the most interesting characteristics of trematodes is their capability to detect the correct host, and ignore individuals that cannot host them.
NEMERTEA - Ribbon worms
The nemerteans, or "ribbon worms", are a phylum of unsegmented, dorsoventrally flat, mostly marine, organisms, that have a muscular, evertible proboscis independent from the digestive system. In some cases there is only one opening shared by the mouth and the proboscis, but still the cavity containing the proboscis, the rhynchocoel, is separate from the digestive tract.
We discussed locomotion, and the nervous, excretory, digestive and circulatory systems.
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PLATYHELMINTHES
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| An SEM and a diagram of a monogenean platyhelminth |
We briefly covered some of the main features of Monogenea, prominent fish ectoparasites, focusing on their external anatomy, which includes the presence of a complex structure at the posterior end, an opisthaptor, and an anterior adhesion organ, a prohaptor.
We then moved on to discuss the flukes, Trematoda. Some of their main characteristics are:
- They are all parasitic
- They use at least two hosts in their life cycle
- The intermediate host is usually a snail
- Final hosts are vertebrates
- Most of them are hermaphrodites
The stages that can enter a host are "equipped" with glands that produce enzymes that disrupt the host's tissues. One of the most interesting characteristics of trematodes is their capability to detect the correct host, and ignore individuals that cannot host them.
NEMERTEA - Ribbon worms
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| Nemerteans in natural habitat and with the proboscis everted |
The nemerteans, or "ribbon worms", are a phylum of unsegmented, dorsoventrally flat, mostly marine, organisms, that have a muscular, evertible proboscis independent from the digestive system. In some cases there is only one opening shared by the mouth and the proboscis, but still the cavity containing the proboscis, the rhynchocoel, is separate from the digestive tract.
We discussed locomotion, and the nervous, excretory, digestive and circulatory systems.
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Saturday, March 3, 2012
Lecture - Phylum Platyhelminthes
FRIDAY, MARCH 2, 2012
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(entry on progress)
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Thursday, March 1, 2012
Wednesday, February 29, 2012
Friday, February 24, 2012
Wednesday, February 22, 2012
Friday, February 17, 2012
Exam 1
Today students took their first exam of the semester. Stats :
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| Click image for a larger view |
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Thursday, February 16, 2012
Labs 05 and 06 - Mollusca
In these labs students examined live and preserved specimens of the main molluscan groups. The goal of the labs was to do a comparison of the adaptive modifications that different molluscan groups have gone trough relative to the hypothetical ancestral mollusc (HAM). The main features to observe were visceral mass, mantle, foot and shell. In live snail specimens the radula was observed in action. There were also prepared mounts to observe the radula at the microscope.
Among cephalopods, the only representative observed was a preserved specimen of a squid.
The groups considered were:
POLYPLACOPHORA (Chitons)
GASTROPODA (Snails, limpets, slugs)
Live specimens
BIVALVIA (Scallops, oysters, mussles, clams)
Live specimens
CEPHALOPODA (Octopuses, squids, cuttlefishes, nautili)
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Among cephalopods, the only representative observed was a preserved specimen of a squid.
The groups considered were:
POLYPLACOPHORA (Chitons)
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| Representatives of Polyplacophora (from Chilebosque forum) |
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| Micrograph and diagram of a chiton's radula (http://hyperaccu.com/e_06.htm - www.asnailsodyssey.com/LEARNABOUT/CHITON/chitFeed.php) |
GASTROPODA (Snails, limpets, slugs)
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| Miscellaneous representatives of Gastropoda Upper row: Cone, marine slug, banana slug Lower row: Cowrie and three land snails |
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| Micrographs of snail radulae left; right (for details of the anatomy of the gastropod radula click HERE) |
Live specimens
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| Live gastropod specimens observed in the lab Left: right after the lab session. Right: 24 hours later |
BIVALVIA (Scallops, oysters, mussles, clams)
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| Representatives of bivalvia Top row: A scallop, a live scallop, a giant clam Bottom row: A mussel, oysters, a razor clam |
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| Some freshwater clams ("mussels") from Eastern North America Top row: Rock Pocketbook, Plain Pocketbook, Wartyback, and Paper Pondshell Bottom row: Elktoe, Pistolgrip, Rainbow, and Mucket (Photos from the Illinois State Museum) |
Live specimens
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| Freshwater clams available in the lab, most likely Spikes (Elliptio dilatata) Top: Detail of an individual Bottom: left, individuals "planted" in gravel; right, after allowed to wander for 24 hours |
CEPHALOPODA (Octopuses, squids, cuttlefishes, nautili)
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| Representatives of Cephalopoda Top: Octopus and squid Bottom: Cuttlefish and nautilus |
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Wednesday, February 15, 2012
Lecture - Phylum Cnidaria
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| Nerve nets in different cnidarian body plans from Brusca, RC and GJ Brusca. 2003. Invertebrates (2nd edition). Sinauer. |
Today we discussed the kinds of cells found in cnidarians, mainly the epitheliomuscular/nutritivemuscular and nerve cells, and their functions.
We then discussed the means of support: Hydrostatic skeleton (mainly in Scyphozoa) and hard skeletons (mainly in Anthozoa). We also discussed the main shapes in the cnidarian bauplan, the polyp and the medusa, and their role in the diversity of cnidarian life cycles.
We started discussing the biology of the cnidarian groups, with the anatomy and a little of the physiology of Scyphozoa.
Next: Hydrozoa and Cubozoa.
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Paper discussion 1 - Feeding behavior and physiology of a carnivorous sponge
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| The cladorhizid sponge Asbestopluma hypogea capturing small crustaceans (from Les Bulles du Recife) _____________________________________________________________________________ |
Today in class we held a discussion on the feeding behavior and physiology of the carnivorous sponge Asbestopluma hypogea. Our discussion was specifically based on the paper
Vacelet, J. and E. Duport. 2004. Prey capture and digestion in the carnivorous sponge Asbestopluma hypogea (Porifera: Demospongiae). Zoomorphology, 123:179–190.
The discussion was largely based on aspects that the students found interesting, which for the most part were:
- Passive mechanism of hunting
- Cell changes to engulf prey
- Mode of digestion (partially extracellular)
- Speed of digestion (2-8 days depending on size of prey)
- Features in prey and sponge that allow the sponge to capture its meal
- Overall morphological changes during the digestion process
Students seemed to show a special interest for the video associated to the paper and the various SEM micrographs published by the authors.
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Thursday, February 9, 2012
Lab 04 - Phyla Platyhelminthes, Rotifera, and Nematoda
Phylum Platyhelminthes (Flatworms, tapeworms, flukes)
Students observed live and preserved representatives of this phylum, as well as slides of whole individuals and cross sections of some of them. The specimens available in this lab are
Phylum Rotifera ("wheel animals")
Students made observations on live specimens of the genus Philodina. They focused on locomotion and external anatomy.
Phylum Nematoda (roundworms, hokworms, pinworms, etc.)
Some of the most abundant metazoans on the planet. Students observed slides of the following representatives
There were also displayed pictures of some nematodes of importance for humans, such as pinworms, hookworms and heartworms.
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| Dugesia, a free-living platyhelminth (from Great Lakes Water Life Photo Gallery) |
Students observed live and preserved representatives of this phylum, as well as slides of whole individuals and cross sections of some of them. The specimens available in this lab are
- Turbellaria
- Dugesia (planaria; live, whole mounts and cross section)
- Trematoda (flukes)
- Clonorchis (human liver fluke)
- Fasciola (sheep liver fluke)
- Schistosoma (blood fluke)
- Clonorchis (human liver fluke)
- Cestoda (human tapeworms)
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Phylum Rotifera ("wheel animals")
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| Philodina, a rotifer (from La soledad del excéntrico) |
Students made observations on live specimens of the genus Philodina. They focused on locomotion and external anatomy.
- Eurotatoria
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Phylum Nematoda (roundworms, hokworms, pinworms, etc.)
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| Trichinella, a nematode (from Science Photo Library) |
Some of the most abundant metazoans on the planet. Students observed slides of the following representatives
There were also displayed pictures of some nematodes of importance for humans, such as pinworms, hookworms and heartworms.
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Wednesday, February 8, 2012
Lecture - Phyla Porifera, Placozoa, and Cnidaria
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| Top: A nematocyst, before and after being discharged Bottom: Generalized cnidarian body plan |
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Today we finished our discussion of porifera by talking about their reproduction, asexual (cellular regeneration, budding, through gemmules) and sexual (internal fertilization, with zygote developing into an amphiblastula or parenchymula larva).
We closed the chapter with a brief mention of the most accepted poriferan phylogeny.
We briefly discussed the phylum Placozoa, a phylum with one species as a representative, although there is some molecular evidence suggesting there could be several species.
Finally, we started our discussion on Cnidaria. We started with some of the general features of the phylum, in terms if diversity, habitat, and development. It is the first phylum we consider showing symmetry, in this case radial, and true tissues, derived from two embryological layers (diploblasts)
We discussed the general body plan, with an epidermis, a gastrodermis, and a mesoglea between the two, with the gastrodermis lining a gastrovascular cavity. We also discussed one of the defining characters of the phylum: the presence of cnidae, specialized organelles in cells called cnidocytes, with a variety of functions, but most prominently used for feeding and defense, in which case the specific cnida is called nematocyst.
Learn a little about sponge reproduction
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Friday, February 3, 2012
Lecture - Phylum Porifera
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| Types of canal systems in sponges: Asconoid, syconoid, and leuconoid |
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- Asconoid - the spongocoel is lined with choanocytes
- Syconoid - choanocytes are organized in radial canals and not exposed to the spongocoel
- Leuconoid - choanocytes are organized in interconnected chambers and the individual sponge may have multiple oscula
We also discussed what skeletal elements observed (spicules, collagen fibers, including spongin) and how they are used to classify sponges in three different groups:
- Calcarea - Sponges with calcareous spicules and no spongin (but they do have collagen fibers)
- Hexactinellida - Sponges with six-rayed siliceous spicules and no spongin (they do have collagen fibers)
- Demospongiae - Sponges with spongin and/or siliceous spicules. Most common of all; they include the carnivorous deep sea sponges (Cladorhizidae, which lack spongin, ostia, and oscula, but have distinctive hooked siliceous spicules)
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| Representatives of Porifera from left to right: Sycon quadrangulatum (Calcarea), Xestopongia sp. (Demospongiae), and Euplectella aspergillum (Hexactinellida) |
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Thursday, February 2, 2012
Lab 03 - Cnidaria & Ctenophora
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| Miscellaneous cnidarians | Pleurobrachia, a ctenophore |
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Cnidarian and Ctenophora are a phyla of animals with radial symmetry and two tissue layers, exclusively aquatic, mostly marine. Cnidarians include anemones, corals, sea jellies ("jellyfish"), and other less known groups, whereas ctenophores are the comb jellies.
Today students became familiar with the typical morphology of most of the cnidarian groups, and a little of the behavior of one of them. Only one representative of the Ctenophora was observed.
The following groups were studied
Cnidaria
Ctenophora
We had live individuals of the genus Hydra, which students observed under a dissecting scope. Movement was analyzed as a response to disturbance and as response to having food available (the branchiopod crustacean, Daphnia, the water flea [incidentally the animal with the record number of genes!])
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| Hydra feeding on Daphnia |
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Wednesday, February 1, 2012
Lecture
Metazoan life cycles
Phylum Porifera
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| A crustacean embryo (http://www.flickr.com/photos/artour_a/4174414482/) |
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Today we briefly mentioned the two types of life cycle that we will find in invertebrate phyla: Direct and indirect. Being indirect the most common case in the phyla that we'll cover in this course.
We discussed how developmental characters can be used to help inferring phylogenies and showed how, if looking early enough in the development of an organism, similarities across widely different metazoan phyla can be found. For instance, we talked about how the pattern of cell division after fertilization can determine two major groups of bilaterians: Protostomia and Deuterostomia.
We also started our discussion on the phylum porifera.
We talked about the basic body plan, how the choanocytes promote water movement so an entire individual can filter feed, and how non-specialized ameoboid cells, the archaeocytes can differentiate into the other cell types characteristic of this phylum (porocytes, pinacocytes, sclerocytes, choanocytes).
Next, we'll discuss the types oc canal systems found in sponges, which allow for the diversity of shapes that is found among the 7000+ (up to 15000) species of poriferans.
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| Basic body plan in Porifera and detail of a choanocyte and an amoebocyte |
Monday, January 30, 2012
Lab - Phylogenetics, Protozoa, Porifera
Thursday, January 19, 2012
PHYLOGENETICS
In this lab students learned how to approach classifying the diversity of invertebrate animals based on evolutionary relationships rather than in overall morphological similarity. The main approach to do so was by examining the most basic concepts of phylogenetics by using cladistics as a tool.
They did a small exercise in which a character data matrix was completed, by observing a variety of specimens of several invertebrate phyla, and used to generate a cladogram. By doing so, some of the difficulties that systematists have to face became obvious, and students attempted to solve them with a variety of approaches.
Thursday, January 26, 2012
PROTOZOA AND PORIFERA
Preserved specimens from the main groups of protozoans were observed under the microscope for students to identify their main morphological features:
Ciliates: Spirostomum, Vorticella, Didinium, Stentor, Paramecium
Flagellates: Trichonympha, Euglena, Volvox, Trypanosoma, Ceratium
Ameobeoids: Amoeba, Foraminifera, Radiolaria, Actinosphaerium
Preserved specimens of the various classes of the phylum Porifera (click here for more sponges) were displayed for students to observe their general morphology. Some specimens ere available to be treated with commercial bleach to dissolve the organic matter and observe the spicules of different individuals. By using polarizing filters students were able to determine if the spicules were calcareous or siliceous.
Observed specimens belonged to the classes:
See the filtering activity of sponges
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| A radial phylogenetic tree of life (version of the tree found in Life: the Science of Biology [9th edition] by Sadava, Hillis, Heller, and Berenbaum) |
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PHYLOGENETICS
In this lab students learned how to approach classifying the diversity of invertebrate animals based on evolutionary relationships rather than in overall morphological similarity. The main approach to do so was by examining the most basic concepts of phylogenetics by using cladistics as a tool.
They did a small exercise in which a character data matrix was completed, by observing a variety of specimens of several invertebrate phyla, and used to generate a cladogram. By doing so, some of the difficulties that systematists have to face became obvious, and students attempted to solve them with a variety of approaches.
Thursday, January 26, 2012
PROTOZOA AND PORIFERA
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| Amoeba proteus, a protozoan |
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| Spicules from a sponge |
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Preserved specimens from the main groups of protozoans were observed under the microscope for students to identify their main morphological features:
Ciliates: Spirostomum, Vorticella, Didinium, Stentor, Paramecium
Flagellates: Trichonympha, Euglena, Volvox, Trypanosoma, Ceratium
Ameobeoids: Amoeba, Foraminifera, Radiolaria, Actinosphaerium
Preserved specimens of the various classes of the phylum Porifera (click here for more sponges) were displayed for students to observe their general morphology. Some specimens ere available to be treated with commercial bleach to dissolve the organic matter and observe the spicules of different individuals. By using polarizing filters students were able to determine if the spicules were calcareous or siliceous.
Observed specimens belonged to the classes:
See the filtering activity of sponges
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Lecture - Phylogeny and Protozoa
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| Choanoflagellate (left), and colony |
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| Traditional Metazoan Phylogeny |
January 11 - 27, 2012
So far we have introduced the main animal phyla that we will cover in this course, introduced the basic concepts of cladistics and overall evolutionary view of diversity ("tree thinking"), and we have studied the most basic features of the Protozoa the informal (not taxonomically valid) grouping of protists that have "animal-like" characteristics.
Among the Protozoa, we considered some of the major groups, following the traditional (more like ancient) classification. The current classification has shifted to reflect evolutionary relationships, but in the scope of this class the traditional groupings will suffice. The groups we considered were the flagellates, the ciliates, and the amoeboeoids.
The flagellates are of special interest since some of its representatives, the choanoflagellates, are considered, mostly based on molecular evidence, as the sister group of metazoa (more metazoa), and probably very similar to our last common ancestor.
We discussed the traditional metazoan phylogeny, and mentioned that the "new" metazoan phylogeny will be discussed over the course of the semester (it's not that new any more).
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