Mary R. Carman

PRESERVATION AND COLOR DIFFERENCES IN NUTTALLIDES UMBONIFERA

Abundant Nuttallides umbonifera (Cushman) in Holocene deep sea sediments of the western North Atlantic make them of great value for reconstructing deep sea paleo-environments. This species is particularly abundant in the high-deposition-rate sediments of the Laurentian Fan between Nova Scotia and Newfoundland, where variations in test color came to our attention. Specimens ranged from a white, chalky appearance to a golden, translucent brown. Because we have conducted stable isotope studies using this species, we reasoned it is important to know the basis for the different colors. Living N. umbonifera are brown due to an internal, pigmented, chitinous layer of the test. In the natural environment, tests could be etched by corrosive bottom waters, or by corrosive pore waters on the millimeter to centimeter scale. By lightly subjecting brown specimens to dilute acid, we are able to etch and frost them until their tests appeared to lose their brown color and turn white. By measuring δ 13 C and δ 18 O on large individuals from the same sample, we show that, on average, there is no significant isotopic difference between the brown and white specimens. Thus, we rule out changing bottom water properties as the source of dissolution. Instead, it is likely that bioturbation creates local pockets of reducing conditions which cause etching of some (but not all) specimens in a contemporaneous population.

Possible cryptic invasion of the Western Pacific toxic population of the hydromedusa Gonionemus vertens (Cnidaria: Hydrozoa) in the Northwestern Atlantic Ocean

We describe a possible cryptic invasion of the toxic Western Pacific hydromedusa Gonionemus vertens (Cnidaria, Hydrozoa, Limnomedusae) in the Northwest Atlantic Ocean. G. vertens was first noticed in Eel Pond in Woods Hole (Cape Cod), Massachusetts in 1894, but nearly disappeared in the 1930s, coincident with a large scale die-off of its preferred eelgrass habitat. During the 1894–1930 period, G. vertens was the object of numerous studies by local scientists, and was not reported as stinging. In contrast, Western Pacific G. vertens are known for their toxic sting symptoms, which include severe pain, respiratory distress, and paralysis. Here, we report new sightings in the northwest Atlantic from the late twentieth century onwards. Sightings are most frequent in Waquoit Bay on the southern-facing shore of Cape Cod, Massachusetts, and on the island of Martha’s Vineyard, Massachusetts, but medusae have also been found in locations ranging from Long Island (New York) to Wellfleet Harbor on the north side of Cape Cod. We also describe reports of stings with symptoms similar to those produced by the toxic Western Pacific strain. The first sting report that we are aware of occurred in 1990 in Waquoit Bay, and stings have since occurred in most of G. vertens’ known Northwest Atlantic locations. It appears likely that the recent sightings associated with toxic stings represent a new, cryptic invasion of the Western Pacific form. These new observations are cause for public health concern, particularly as warmer temperatures associated with climate change may promote G. vertens blooms and thus the likelihood of dangerous human-jellyfish interactions in a populated, tourism-dependent region.

Mitochondrial diversity in Gonionemus (Trachylina:Hydrozoa) and its implications for understanding the origins of clinging jellyfish in the Northwest Atlantic Ocean

Determining whether a population is introduced or native to a region can be challenging due to inadequate taxonomy, the presence of cryptic lineages, and poor historical documentation. For taxa with resting stages that bloom episodically, determining origin can be especially challenging as an environmentally-triggered abrupt appearance of the taxa may be confused with an anthropogenic introduction. Here, we assess diversity in mitochondrial cytochrome oxidase I sequences obtained from multiple Atlantic and Pacific locations, and discuss the implications of our findings for understanding the origin of clinging jellyfish Gonionemus in the Northwest Atlantic. Clinging jellyfish are known for clinging to seagrasses and seaweeds, and have complex life cycles that include resting stages. They are especially notorious as some, although not all, populations are associated with severe sting reactions. The worldwide distribution of Gonionemus has been aptly called a “zoogeographic puzzle” and our results refine rather than resolve the puzzle. We find a relatively deep divergence that may indicate cryptic speciation between Gonionemus from the Northeast Pacific and Northwest Pacific/Northwest Atlantic. Within the Northwest Pacific/Northwest Atlantic clade, we find haplotypes unique to each region. We also find one haplotype that is shared between highly toxic Vladivostok-area populations and some Northwest Atlantic populations. Our results are consistent with multiple scenarios that involve both native and anthropogenic processes. We evaluate each scenario and discuss critical directions for future research, including improving the resolution of population genetic structure, identifying possible lineage admixture, and better characterizing and quantifying the toxicity phenotype.

Species–specific crab predation on the hydrozoan clinging jellyfish Gonionemus sp. (Cnidaria, Hydrozoa), subsequent crab mortality, and possible ecological consequences

Here we report a unique trophic interaction between the cryptogenic and sometimes highly toxic hydrozoan clinging jellyfish Gonionemus sp. and the spider crab Libinia dubia. We assessed species–specific predation on the Gonionemus medusae by crabs found in eelgrass meadows in Massachusetts, USA. The native spider crab species L. dubia consumed Gonionemus medusae, often enthusiastically, but the invasive green crab Carcinus maenus avoided consumption in all trials. One out of two blue crabs (Callinectes sapidus) also consumed Gonionemus, but this species was too rare in our study system to evaluate further. Libinia crabs could consume up to 30 jellyfish, which was the maximum jellyfish density treatment in our experiments, over a 24-hour period. Gonionemus consumption was associated with Libinia mortality. Spider crab mortality increased with Gonionemus consumption, and 100% of spider crabs tested died within 24 h of consuming jellyfish in our maximum jellyfish density containers. As the numbers of Gonionemus medusae used in our experiments likely underestimate the number of medusae that could be encountered by spider crabs over a 24-hour period in the field, we expect that Gonionemus may be having a negative effect on natural Libinia populations. Furthermore, given that Libinia overlaps in habitat and resource use with Carcinus, which avoids Gonionemus consumption, Carcinus populations could be indirectly benefiting from this unusual crab–jellyfish trophic relationship.

Predation on the clinging jellyfish Gonionemus sp. by the spider crab Libinia dubia

Video documentation of a spider crab ( Libinia dubia ) consuming the clinging jellyfish Gonionemus sp. Published in: Carman, M.R., Grunden, D.W, Govindarajan, A.F. In Press. Species–specific crab predation on the hydrozoan clinging jellyfish Gonionemus sp. (Cnidaria, Hydrozoa), subsequent crab mortality, and possible ecological consequences. PeerJ https://peerj.com/articles/3966/