P. parvimensis Pentacula

Phylum: Holothuroideaia

Order: Aspidochirotida

Family: Stichopodidae

Genus: Parastichopus

Species: P. parvimensis

Hi all,

I discovered a parvimensis pentacula the other day! 

Here it is in all of its larval glory:

Isabel C.

Urechis Spawning

Today we spawned Urechis, marine worms that make "J" shaped burrows in the sand and feed on sediment and small particles. Some species of the worms can be quite large. You spawn them by inserting small glass probes into their gonopores to stimulate them.

Cephea cephea pt. 2

Some updates from May 3, 2013.

The Cephea cephea started budding! The bud on the calyx of the right polyp below will form another polyp with the stoma on the distal end of the bud. I first noticed on April 29. Yasuo Sugiura, in a paper on Cephea cephea development, observes that when this scyphistoma stage is completed each polyp has 16 tentacles with nematocysts and the mouth  projects out longer (1966). Nematocysts are the stinging cells that Cnidarians have.

They look less healthy then they did when we received them from the aquarium but with a little TLC hopefully they will continue to develop. They were in an incubator at 28 degrees celsius from April 29th to May 2. They are now in a warming bath at 28 degrees. Sugiura observes that abundant brine shrimp and a temperature of 30 degrees will increase the budding rate. Strobilation can occur when a culture of polyps at 20 degrees is raised to 25-30 degrees however, the highest rate of strobilation occurs at 29-30 degrees and it takes 3-5 days.  Still keeping an eye out for strobilation; some signs will be a color change to a more yellowish brown color, constriction of the calyx.

Our single ephyra is doing great. Here is a video of it eating a brine shrimp.

1. SUGIURA, YASUO. "ON THE LIFE‐HISTORY OF RHIZOSTOME MEDUSAE IV. CEPHEA CEPHEA." Embryologia 9.2 (1966): 105-122.

-Monica Erviti

Market Squid, Part II.

Development continues. The chorion was removed from some of the eggs to better observe embryo. The siphon is now nearly formed, and soon the edges will fuse medially to form a hollow tube. Two rows of suckers are visible on the lengthening tentacles. The optic ganglions are visible in the eye stalks behind the eyes themselves. The newly formed brachial hearts and developed gills can be seen within the mantle.

The squid has three hearts—two brachial hearts which pump blood through the gills and a systemic heart which moves blood through the rest of the body. Notice the rhythmic pumping of the two brachial hearts in the videos.

[video 1] [video 2]

The squid has developed chromataphores, which are the red-orange pigment spots on the mantle and head of the embryo. The embryo is more active now and frequently shifts within the egg. It has also started to contract its membrane.

[video]

Comparison of early and later stage embryos. Notice the expansion of the chorion in the older embryo. It is possible that the chorion expands because of osmosis due to the buildup of metabolic waste within the egg.

Fields, William Gordon. The structure, development, food relations, reproduction and life history of the squid Loligo opalescens Berry. Diss. Department of Biological Sciences, Stanford University., 1962.

-Jacqueline Brockhurst

Purple urchin

Species: Strongylocentrotus purpuratus

Phylum: Echinodermata

Class: Echinoidea

Order: Echinoida

A large part of this class involves learning how to use different techniques in microscopy to highlight particular larval features that we want to see more clearly. Below are two pictures of the same S. purpuratus larvae under different filter settings. The central pluteus is developing normally, with eight arms, clear epaulettes, and a well-defined rudiment to the left (in the image) of the gut. you can even make out the suckers of the juvenile tube feet on the rudiment! The larva in the upper right corner, on the other hand, is developing abnormally (hence the extra wide body and deformed/absent features).

The vignetting in the images is a result of the photography style--because these filter sets are only found on several of our compound scopes, I had to take these pictures down one of the eye pieces with my phone. 

- Andrew Miller

Trematodes!

Recently we collected some Arenicola egg cases in preparation for our unit on annelid worms. These egg cases were covered in tiny snails. We assumed the snails were eating the eggs, so we pulled them off of the cases and put them in a separate tupperware. The next day when we checked the tupperware we found tiny animals swimming around in it along with the snails that were crawling around on the sides. When we put these animals under the microscope, no one recognized them, so we consulted with one of the station parasitologists, Chelsea Wood, who had this to say:

"It's a trematode cercaria!  I sometimes get them in water from the seawater system, but I've never seen one with such luxuriant setae on its tail - good find!"

Trematodes are mostly parasites on snails. They belong to the phylum of worms Platyhelminthes, and often have complex life cycles. The cercaria we found swimming in the water are larvae looking for second hosts that they can infect until they develop into sexually mature adults. The adults will produce eggs and sperm, which will develop into miracidia larvae and look for more snail hosts.

Circaria larvae have long tails with bristles on them. Chelsea sent us this description from Sukhdeo and Sukhdeo (2004):

"Swimming cercariae have tails of various lengths that may be forked, single, or bestudded with setae and other appendages (Kearns 1998). Cercaria setifera and Opectonia bacillarus have tufted tails that greatly enhance their speed; the rapid undulations of the tails sweep the tufts of setae backwards to push against the water to generate speeds of up to 13 m/h (Koie 1975; Bartoli 1984). These tufted tails often accumulate debris and these species have an interesting behaviour where they stop swimming, reach around with their body to clasp the tail, and then they draw the tail through their body to clean it."

Here are some pictures of the snails that came in on our egg cases:

And here are some videos of the ghostly and beautiful cercaria larvae:

http://youtu.be/_PmkshAyvVU

http://youtu.be/kPx2rc8XB7Q

Market squid

Phylum: Mollusca

Class: Cephalopoda

Order: Teuthoidea

Family: Loliginidae

Species: Doryteuthis opalescens

We recently received some fertilized market squid eggs! The market squid is a common cephalopod along the central coast of California. In the spring and fall, huge schools of the squid enter Monterey Bay to spawn. They lay large, communal egg masses on the sandy seafloor and then die.

[image from SeaNet]

Each egg mass consists of groups of eggs contained within a jelly capsule membrane. The eggs themselves contain a large ball of yolk surrounded by a transparent shell. The embryo begins formation through epiboly, where cells at the top of the yolk mass migrate around to the opposite pole, encapsulating the yolk with a layer of cells in the process. The market squid, like other cephalopods, exhibits direct development and will hatch out as a miniaturized adult.

[5/9/13] Several days after we received the eggs, the blastoderm began to differentiate into new structures and bilateral symmetry was developed.

The circular, raised cap on the end of the embryo will give rise to the mantle in the adult animal. The two bulges beneath the developing mantle are the rudimentary eye-stalks, and in their center the early stages of the eye can be seen.

Here, bilateral symmetry can be seen as the embryo rotates within the egg shell. The embryo appears to be ciliated and often moves. The space within the egg shell seems to be filled with a cloudy fluid of some sort.

L. opalescens

[5/10/13] The shape of the forming embryo is even more distinct at this point. The rudimentary arms of the squid can be seen as a ridge or little projections around the center of the embryo beneath the eye stalks.

[5/11/13] The mantle now overhangs the body on both sides, and the eye stalks are much larger. The project of the yolk into the mantle and eye-stalks can be seen clearly. The rudimentary arms are even more distinct at this stage. Newly visible are the inner and outer siphon-folds, which will eventually form the siphon in the adult animal. The siphon-folds are seen as paired, symmetrical ridges of tissue in the center of the embryo between the eye stalks. The presence of the siphon indicates that this will be the ventral side of the adult animal.

[5/12/13] The embryo is much more complex. The arms have elongated and the mantle and mantle cavity (where the gills are forming) are even more distinct. Rudimentary fins can be seen on the surface of the mantle.  The rectum is now present as a raised hollow rod and the free edges of the two inner siphon folds have bent towards each other to form the opening of the siphon. The eye stalks are even more complex and the yolk protuberances no longer entirely fill them. See this diagram.

If you look closely, you can see some sort of contraction in the center of the embryo.

                                      

Arnold, John M., William C Summers, Daniel L. Gilbert, Richard S. Manalis, Nigel W. Daw, and Raymond J. Lasek (1974). A Guide to Laboratory Use of the Squid Loligo Pealei. Woods Hole, MA: Marine Biology Laboratory, 74pp. [x]

Brooks, W. K. Anniversary Memoirs of the Boston Society of Natural History ; Pub. in Celebration of the Fiftieth Anniversary of the Society's Foundation. 1830-1880.Boston: Society, 1880. Web. [x]

-Jacqueline Brockhurst

Arenicola brasiliensis

Species: Arenicola brasiliensis

Phylum: Annelida

Class: Polychaeta

Order: Scolecida

Today we took a look at an Arenicola brasiliensis egg mass to see what we could find. The eggs aren't incredibly far along, but you can clearly see the blastopores on several (look for the light spots):

- Andrew Miller

Hermissenda crassicornis, round 3

Species: Hermissenda crassicornis

Phylum: Mollusca

Class: Gastropoda

Order: Opisthobranchia

Sometimes you get the bear, and sometimes the bear gets you. On Friday 4/26, Chris and I went collecting out on the cable in the HMS kelp bed. We found a fresh Hermissenda egg mass on a piece of Pugettia firma, along with another nudibranch who later laid in the sea table. I split the eggs up into two mixed cultures in order to prevent overcrowding, and then added Plumularia (a thecate hydroid) to our original culture in order to induce metamorphosis. Unfortunately, the Plumularia (or something attached to it) released a mucous film that killed the entire culture, so we're now relying on the two most recent cultures to produce juveniles before the end of the quarter. When the time comes, I will experiment with several different thecate hydroids in multiple small cultures to maximize the possibility of metamorphosis. For the time being, though, here are some pictures of our new friends:

Egg mass on Pugettia firma section

                                        

Late stage cleaving embryo:

                           

Embryos in egg capsules:

                                          

Early transformation to veligers:

Early transformation to veligers (note the cilia):

Early and more developed veligers preparing to hatch:

                                

Veligers ready to hatch:

Recently hatched veliger:

- Andrew Miller

Dendraster metamorphosis!

Dendraster excentricus (otherwise known as a sand dollar) is a flattened, burrowing echinoid. Like traditional sea urchins, its rounded body is covered in spines. D. excentricus uses its spines to move sand grains over its body to bury itself into the substrate.

The Dendraster in the lab were fertilized on the fourth of April. By the 25^th of April, we started to see the rudiment forming in the late pluteus larvae. The rudiment appeared on the left side of the larvae, taking up more than half of the space within the body. 

The fenestrated spines and early tube feet of the juvenile sand dollar are visible even within the larva. The juvenile will emerge from its larval skeleton oral-side first so that it can orient itself correctly on the substrate.

Here is a metamorphosed juvenile Dendraster. It is extremely active as it moves along on its tube feet.

         -Jacqueline and Monica

Patiria miniata metamorphosis

Species: Patiria miniata

Phylum: Echinodermata

Class: Asteroidea

Order: Valvatida

Today, we noticed that our Patiria have begun to metamorphose. Below you can see a brachiolaria (advanced Asteroid larva) crawling along the filmy substrate in preparation for metamorphosis, as well as several juveniles that have already metamorphosed.

Up close shots of the brachiolaria:

Juvenile up close:

- Andrew Miller

Lined Shore Crab eggs!

Hey team, 

Here is a short clip of the Lined Shore Crab eggs that Andrew helped me to take off the brooding female.  There is a little bit of movement in the middle of the video, don't miss it!  Otherwise, I know nothing about what is going on and will more research on this species' (Pachygrapsus crassipes) embryology.  

-Chris