Crab Meets its own Face Hugger

facehugger, guys.

Elysia chlorotica: Meet the Photosynthetic Sea Slug

How a brilliant-green sea slug manages to live for months at a time "feeding" on sunlight, like a plant, is clarified in a recent study published in The Biological Bulletin.

The authors present the first direct evidence that the emerald green sea slug's chromosomes have some genes that come from the algae it eats.

These genes help sustain photosynthetic processes inside the slug that provide it with all the food it needs.

Importantly, this is one of the only known examples of functional gene transfer from one multicellular species to another, which is the goal of gene therapy to correct genetically based diseases in humans.

"Is a sea slug a good [biological model] for a human therapy? Probably not. But figuring out the mechanism of this naturally occurring gene transfer could be extremely instructive for future medical applications," says study co-author Sidney K. Pierce, an emeritus professor at University of South Florida and at University of Maryland, College Park.

The team used an advanced imaging technique to confirm that a gene from the alga V. litorea is present on the E. chlorotica slug's chromosome. This gene makes an enzyme that is critical to the function of photosynthetic "machines" called chloroplasts, which are typically found in plants and algae.

It has been known since the 1970s that E. chloritica "steals" chloroplasts from V. litorea (called "kleptoplasty") and embeds them into its own digestive cells. Once inside the slug cells, the chloroplasts continue to photosynthesize for up to nine months--much longer than they would perform in the algae. The photosynthesis process produces carbohydrates and lipids, which nourish the slug.

How the slug manages to maintain these photosynthesizing organelles for so long has been the topic of intensive study and a good deal of controversy. "This paper confirms that one of several algal genes needed to repair damage to chloroplasts, and keep them functioning, is present on the slug chromosome," Pierce says. "The gene is incorporated into the slug chromosome and transmitted to the next generation of slugs." While the next generation must take up chloroplasts anew from algae, the genes to maintain the chloroplasts are already present in the slug genome, Pierce says.

link.

Neogene Marine Vertebrate Paleodiversity in Temperature Pacific South America

Rise and fall in diversity of Neogene marine vertebrates on the temperate Pacific coast of South America

Authors:

Villafaña et al

Abstract:

Even though Neogene outcrops along the temperate Pacific coast of South America harbor a rich marine vertebrate fossil record, no studies have examined the diversification patterns of these taxa. Here, we analyze diversification trends based on the stratigraphic ranges of 86 genera of marine vertebrates, including sharks, rays, chimaeras, marine mammals, and seabirds. The richness of genera shows a hump-shaped trend, with maximum values around the late Miocene, driven by a large pulse of origination during mid-Miocene and higher extinction rates during the Pliocene. Trends varied markedly among taxa and departed largely from expectations based on global diversification patterns. Moreover, these trends cannot be explained solely as a sampling artifact derived from sampling intensity (i.e., number of occurrences) or sedimentary rock availably (i.e., number of geologic maps). A large fraction of genera (42%) went globally extinct by the late Pliocene–Pleistocene, and the extinction was highly selective according to different ecological and life-history traits. An analysis using “randomForest” showed that taxonomic structure and the geographic midpoint of distribution could explain up to 83% of extinction of genera. The extinction was taxonomically clumped (i.e., disproportionally high in Cetacea and very low in Carcharhiniformes) and concentrated in the northern area of the temperate Pacific coast of South America. Our results suggest that the particular paleogeographic, paleoclimatic, and paleoceanographic events that took place during the Neogene along the temperate Pacific coast of South America had a significant effect on the structure of marine biodiversity.

A Social Octopus Found

If recent octopus discoveries have taught us anything, it's that these eight-armed ocean dwellers are smart. They can use tools, change color in an instant, and commission their arms to solve problems. But they generally do all this as loners.

Now, new research into a surprisingly social octopus is shattering even the most expansive ideas of known octopus behavior.

Panamanian biologist Aradio Rodaniche first reported the Pacific striped octopus in 1991 off the coast of Nicaragua, noting its strange behavior—living in groups of possibly up to 40, laying multiple egg clutches, and mating face-to-face and sucker-to-sucker. Most other octopus species, for instance, come together only to mate.

But scientists didn't see another one of these curious octopuses for another 20 years, when Richard Ross, a biologist at the California Academy of Sciences, came across one in 2012. Through a commercial collector, he acquired several wild specimens to study in the lab.

Ross is one of the few scientists who are studying and observing some of this octopus's truly bizarre—and sometimes anxiety-provoking—behavior, which he and his team will describe in an upcoming publication.

"Regular octopus mating, where the male is behind and on top of the [female]—or far away—that's scary enough to watch," said Ross. Females of many species, for instance, will sometimes kill and eat their mate, even if they are mating from a distance.

But "watching these guys come and interact with their beaks—wrapped up in a ball of limbs—are they fighting or mating?" he recalled wondering.

link.