Sabbatical Part II: More sea stars than you can poke a biopsy punch at…

Well, so far no hobbits and/or ring wraith viruses, but plenty of interesting sea stars! Ian has just completed his stint at the University of Auckland, where he was working with world renowned echinoderm larvae expert Prof. Mary Sewell. Mary has an extensive knowledge of New Zealand echinoderms, and after a brief discussion of intended outcomes, we made plans for several field excursions to collect sea stars and amphipods. First, however, Mary had a rather extensive amount of paperwork to complete for risk management, which then had to be approved through the university – all of which took about 3 days (Ian is super grateful for Mary’s efforts on this!). The risk management in NZ requires identification of each site to be visited, assessment of all and any risks that may occur while doing field work, plus having on hand telephone numbers for emergency services, and checking in and out with someone on campus when arriving and leaving each sampling site. Quite a bit to get organized before stepping foot off campus!

Sampling sites at Piha – not a bad place for field work!

After a brief weekend in Australia visiting family, Ian returned to Auckland and set off with Mary back to Piha (on Auckland’s West Coast, in the Waitekere Ranges) to sample the reef star, Stichaster australis. This species of sea star has a similar role in parts of NZ to Pisaster ochraceus on the North American Pacific Coast, where it eats mussels on rocky reefs. However, it may not quite be as “keystone” to the ecosystem, since wave action may play a heavier role in maintaining the distribution of mussels than being eaten by S. australis. Upon arriving at Piha, Mary and Ian found two adjacent sampling sites – one inside a ‘blowhole’ cave (Ian’s first time in a cave sampling sea stars… managed to get absolutely soaked!), and another nearby on a protected rocky shore. We collected a total of 20 S. australis, which were separated and bagged before being put into buckets for the hike out. At the same site, Ian also collected some turf algae for amphipods. After about a 200m hike over volcanic boulders with 20 starfish (and millions of amphipods) and about 20L of seawater, we drove back to the university, where Ian subsectioned animals into various tissues (coelomic fluid, body wall, pyloric caeca, gonad, tube feet, etc).

 

Cave sea star microbiology: A new field or a new Frontiers Journal?

Click here for a video of sampling at Piha

The following day, Mary and Ian performed a plankton tow in Auckland Harbor, with the intention of finding sea star larvae (bipinarria). Auckland’s huge tidal range (=12 feet) makes plankton tows easy – there are several causeways which have bridges, so it’s simple to deploy a net and let the flood tide roar through (c.f. dragging a net behind the boat). After 2 x 5 minute tows, we had enough material to work with for the rest of the day. We then spent about 4 hours sorting through the tow looking for interesting zooplankton. The net result? 1 gastrula sea star larva, a pluteus (urchin larva) and a not-yet-settled 8-section brittle star. It’s just not the right time of year for lots of sea star larvae, but what we did find will be valuable in the future. In addition, Ian also pulled out a lot of large copepods, several amphipods, and a few other interesting microscopic crustaceans. All valuable for future work (stay tuned!).

Plankton tows in Auckland Harbor…

Attack of the amphipods…

Friday of the second week Mary and Ian did a day trip up to the Leigh Marine Lab, which is about an hour north of the city and adjacent to the stunning Goat Island Marine Reserve. After a quick tour of the lab and adjacent marine habitats, we were joined by Prof Richard Taylor, an invertebrate zoologist with extensive knowledge of amphipods and certified diver. In the afternoon, Richard kindly offered to dive on his time off work to collect another of our target sea star species, Coscinasterias muricata, a multi-armed and soft-fleshed taxon which is similar in size and function to Pycnopodia helianthoides on the North American West Coast. After an hour or so, Richard emerged with 18 C. muricata, ranging in size from a couple of inches to about 12 inches across. Rather than sacrifice such large animals, we decided to sub-sample these in the field (and draw their coelomic fluid)- and after transporting subsamples and whole animals (small individuals), divided the animals into tissue types.

The not-so-graceful Coscinasterias muricata… spiny!

The following weekend was a long one as it was Auckland Day, which gave Ian time for a bit of tourism around the Gulf of Hauraki. Stunning!

Tuesday the following week, Mary and Ian went out in search of the bat star-like species Patiriella regularis, which is similar to Patiria on the North American West Coast, although much, much smaller. We traveled to a site just south of Leigh and collected 40 individuals; 20 for immediate dissection and subsampling, and 20 for spawning experiments to determine transmission of potential densoviruses. The following day, we attempted to induce spawning of these animals by injecting them with 1-methyl-adenosine (1-MA) which normally causes animals to immediate release gametes. After 3 unsuccessful attempts with different concentrations of material, we gave up and instead sacrificed the animals for additional tissue samples.

Collecting Patiriella regularis… Mary in bottom photo! Mid-photo is a star which had 6 arms, but not the normal arrangement…

During his time in Auckland, Ian collected over 300 tissue samples and prepared metavirome fractions from each of the three target species.  Samples are now on their way back to the lab at Cornell where Ian will work on identifying densoviruses related to SSaDV and determining their prevalence in the populations. Ian also had an oppotunity to share the team’s most recent results during a departmental seminar, for which he received excellent feedback. This also provided an opportunity to put in place a reporting network for SSWD in New Zealand should it occur – this year has seen anomalously high water temperatures and wild swings in meteorology.

See here for a video of sampling near Leigh

All in all, a very productive stint at the University of Auckland that will lead to greater knowledge of sea star microbiology in the country, more collaborative opportunities with scientists in New Zealand, and opportunities for students at Cornell. Ian would especially like to thank Mary Sewell for so much work in making this possible – Ian would have walked away with next to nothing without her help!

Now it’s off to Victoria University of Wellington, where Ian will again be targeting the few sea stars that exist in that part of the North Island. But perhaps the focus will be on amphipods, which are highly abundant in the region! Stay tuned…

IMG_8081

Stichaster on the east coast! Coromandel Peninsula

 

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