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Filopodia of mesenchymal cells in gastrulating echinoderms
These pictures show gastrulating echinoderm embryos. I was fascinated by the role filopodial processes (small-thread-like-extensions) of mesenchymal cells play during echinoderm gastrulation. The...
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Egg capsule and larva of the intertidal snail Littorina scutulata
Pictured here is the adult, egg case, and veliger larva of Littorina scutulata. L. scutulata is a small (up to 1.5 cm shell height) gastropod, common in the mid- to high-intertidal of the west coast...
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Development of the nudibranch Janolus fuscus
Nudibranchs are arguably some of the most flamboyant animals of the Pacific coast. Janolus fuscus (shown here), a sub-tidal species that is commonly found on the floating docks in Oregon, is no...
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Early cleavage in echinoderms
Early development in echinoderm embryos follows a regular and predictable pattern. The first and second cleavages are equal and meridional (cut along the animal-vegetal axis of the egg). The third...
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Planktotrophy versus lecithotrophy
Many marine invertebrates undergo indirect development, a kind of life history that includes a larval stage distinct from the adult. Two types of larval development are distinguished based on the...
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Bowling for Calliostoma
Calliostoma ligatum is a gastropod found on the rocky intertidal of the Pacific coast. Calliostoma are dioecous (i.e. have separate sexes) and, like most other archaeogastropods, free-spawn their...
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Unidentified wild-caught Müller’s larva
On April 17, 2013 I took a plankton tow off a dock in Charleston, OR. While sorting plankton I found a Müller’s larva (pictured here). The Müller’s larva is found in free-living marine flatworms from...
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Development of Trimusculus, a limpet-like marine snail
Trimusculus reticulatus, or the button-snail, is an unusual marine gastropod that looks like a limpet (i.e. a member of the Patellogastropoda) but is not. It is, in fact, a pulmonate gastropod (it has...
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Early development and spermatophore of the phoronid Phoronopsis harmeri
Phoronopsis harmeri is a member of Phoronida, a relatively small phylum of sessile, tube-building marine worms. Phoronids release sperm in packets called spermatophores, which probably drift in water...
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Reproduction in monogonont rotifers
This is a marine rotifer from the genus Synchaeta (according to a key in Wallace & Snell 2010). Rotifers are a phylum of small, mostly fresh-water invertebrates. This adult individual is 0.7 mm...
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Two types of Aeolidia papillosa larvae
This is a picture of an adult nudibranch Aeolidia papillosa, found on the Charleston docks near OIMB. As with many other nudibranchs, A. papillosa package their eggs a few per egg capsule, the capsules...
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Brooding copepods
Copepoda, with approximately 12,000 described species, is one of largest taxa of crustaceans and a large contributor in most plankton samples. This is particularly true of calanoid copepods, as most...
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Mass spawning of beached hoplonemertean Nipponnemertes bimaculata
The tide was low at 6 am on May 8th as our Embryology class descended into South cove at Cape Arago, OR. As we made our way to the tide pools we noticed a few live Nipponnemertes bimaculata, bright...
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Planktonic larvae of the polychaetes Nephtys and Capitella
I collected the two polychaete larvae pictured here from a plankton sample taken off a dock in Charleston, OR on May 8, 2013. The thing that caught my eye was the deep blue color in the lining of the...
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Brachiolaria larva of the seastar Mediaster aequalis
Mediaster aequalis is a bright red asteroid, three to seven inches in diameter, found subtidally off the coast of Oregon. M. aequalis has a breeding season from late March through May and spawns large...
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Development of the ctenophore Beroe
Below are pictures of early embryos of the ctenophore Beroe sp. Three adults were collected around Charleston docks near OIMB in mid-May and shed strings of ~ 220 µm eggs in the lab. Ctenophore...
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Procuring gametes from echinoderms
Echinoderms, sea urchins and sea stars in particular, are classical objects of embryological studies because it is relatively easy to obtain their gametes. Here I will describe two standard techniques...
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Gastrulation and early actinotroch of Phoronopsis harmeri
This is a side view of a blastula of the phoronid, a.k.a. horseshoe worm, Phoronopsis harmeri. It is about 22 hours after egg release (developing at ambient sea temperature). Eggs in this species are...
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Development of the hydrozoan Clytia gregaria
This is Clytia gregaria, formerly known as Phialidium gregarium. The instructor of our Embryology class collected many adult individuals of this hydromedusa from the plankton off F-dock in the...
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Ascidian tadpole larvae: settlement and metamorphosis
Ascidians (class Ascidiacea), commonly known as sea-squirts, are a class of sessile, filter-feeding chordates who live solitarily or colonially inside an extracellular “tunic.” Although the adults have...
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