Tag Archives: sousa sahulensis

Ba-Bopsy

“Okay. All my life, I had a lump at the back of my neck, right here. Always, a lump. Then I started menopause and the lump got bigger from the “hormonees.” It started to grow. So I go to the doctor, and he did the bio… the b… the… the bios… the… b… the “ba-bopsy.” Inside the lump he found teeth and a spinal column. Yes. Inside the lump… was my twin.” – Aunt Voula, My Big Fat Greek Wedding

Andrea Martin is a genius, a straight-up acting genius. She was genius on Sesame Street and on Broadway and of course in this movie, and as a result since 2002 I’ve been:

  1. Terrified of any sort of bodily lump
  2. Sympathetic to the plight of vegetarians trying to explain themselves
  3. Aware of the concept of biopsy.

A biopsy is an investigative surgery; it doesn’t kill the subject, but provides information to the doctor or researcher performing the operation. In Aunt Voula’s case, it provided some really unexpected news, and Team Sousa hopes for revelations of the same magnitude (if not the same comedic heights).

That’s right, in addition to our observational data, we’ve started collecting genetic information via dolphin biopsies. Using a special rifle and large, red, sterile, buoyant darts, we (really just Tim, but it’s a team effort) take careful aim at a peduncle (dolphin back, below the fin) and fire, hoping to remove a neat plug of skin and blubber. This sample gets preserved on ice, shipped back to Adelaide, and analyzed to determine the sampled dolphin’s sex and potential genetic relationships.

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*This photo shows the whole red dart en route to contact with a Sousa peduncle. The actual sample taken is much smaller (5mm in diameter) and likely couldn’t be seen from this distance.

It does feel like a drastic procedure- I mean, we do actually shoot at the dolphins with a rifle. But the dolphins barely react, generally diving on hearing the noise of the dart hitting skin or water, and then returning to whatever it was they were doing before. (According to Krützen et al., 2002, dolphins react the same way whether they were hit or missed, indicating that it’s really the sound and disturbance of the dart that causes them to duck.) Additionally, the scar created by the biopsy rifle has been observed in several dolphin populations (this method is well-documented and historically proven among people who study cetaceans) to disappear within a month or two. Compared to the gouges and scrapes we see and recognize on Sousa sahulensis and Tursiops aduncus fins, the plug is hardly noticeable.

I don’t advocate shooting anything at dolphins or really bothering them at all (how would you like it?) but short of waiting around for all of our catalogued individuals to turn upside down and wave their genitals through the air, there’s no other way to determine the sex of the various members of our study’s social groups. And the other data (relatedness, genetic distance, etc.) that we will gain will be a fascinating addition to our observations of the fission-fusion groups of mixing dolphins. Do related dolphins spend more time together? How long does a subadult or young adult stay near its mother? Are allied males related to one another?

Most of the time the biopsy rifle stays in its box at the back of the boat. But we’re hoping to collect as many samples as possible to unlock the genetic gold mine that could be present and underlying our Sousa sahulensis’ behavior and environmental needs.

Krützen, M., Barré, L.M., Möller, L.M., Heithaus, M.R., Simms, C., Sherwin, W.B., 2002. A biopsy system for small cetaceans: darting success and wound healing in Tursiops spp. Marine Mammal Science 18, 863–878.

Why

So the new official species name Sousa sahulensis has supplied me with sibilant alliterative opportunities, but has also changed the nature of the research we’re doing here on the North West Cape. There has been some research done on Indo-Pacific humpback dolphins, but the humpback dolphins that live their lives around the continent of Australia (and maybe Papua New Guinea?) may have less in common with their relatives than we had previously thought.

According to Science News (shame on me for not reading the actual paper yet…), skull morphology and DNA sequencing were used to determine the separation of S. sahulensis from their northern cousins, S. chinensis. Our dolphins cannot cross Wallace’s Line, a deep ocean barrier separating Australia from the rest of the world and, incidentally, explaining in part why Australia and its waters contain so many endemic (local only) species- as the Line formed, these coastal dolphins could no longer cross between the home waters of S. chinensis and the Australian continental shelf. Those on the southern side of the barrier evolved through genetic drift and natural selection such that they are significantly different from the northern side, and have now been recognized as their own unique group. But why does that matter?

Well, first of all Tim has to change all the abbreviations we’ve been using on spreadsheets (Sc to Ss) and the title of his PhD…

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Okay, the real reason why it matters is that, having proven significantly different from their relatives Up Above, S. sahulensis is now virtually unknown. We can’t assume they behave the same, use space in the same way, or require the same resources or protection as S. chinensis, nor can we rely on the larger population size of both species combined to buffer any human-caused losses or stresses. As oil, gas, and mining operations descend upon Australia’s coastal waters, coral reefs begin to feel the impacts of global climate change, and fishing and ocean recreation continue to increase, we need as much knowledge as we can get about these animals. Their impact on coral reefs and surrounding ecosystems could be a key part of healthy seas around Australia, and we don’t even have a good population estimate, nor any indication of whether the population is growing, shrinking, or neither. Tim’s working hard to break open the wealth of information that the North West Cape dolphins have to offer, but they’re elusive and research requires a lot of time and patience.

Much has been written about the importance of coral reefs for economic and environmental reasons, and much has been written about wildlife in general having inherent importance to humanity. I support all those reasons, and can give you pages and pages of arguments on why it’s important to maintain diverse and stable ecosystems of all types. However, I also think simply that we humans, as a species (yes, one global and multiplying species), ought to tread lightly on the world.

Yes, it’s important to understand and preserve the world around us because without diversity we and our world will be more easily overcome by change, because reefs and mangroves and wetlands provide storm shelter and water filtration to human habitations, because icy tundras and redwood forests and tigers and whales and tiny colorful fishes inspire us and make us wonder. But that all presupposes that it’s our right to choose to destroy or save those wonderful things. We approach the world assuming that we can manipulate it at will, but we are just students of systems much larger and more complex than the ones we have created.

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Species-ous Allegations

 

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As I’ve mentioned before, our focal animal, Sousa sahulensis or the Australian humpback dolphin, has only recently entered the official rolls of described species. In a recent report, scientists named this newly-identified species and thus spake Science- a species was born. Does that sound sort of arbitrary to you? Good, it probably ought to.

Let’s talk about species definitions for a second:

 

I love species names. I love using those distinct descriptions to identify the organism I’m looking at, and I love the way the fake-Latin words (so science! Very officialness) feel in my mouth. There’s a pleasing elegance to the system through which you can categorize groups of related species, like nested folders or bags-within-bags (kingdom, phylum, class, order, family, genus, species, subspecies). But do I trust species boundaries as absolutes? No, I do not. 

A “species” can be defined quite a few different ways, is part of the problem. For example, the biological definition states that for a species to be valid, the population that makes it up must not be able (for reasons of geography, genetic change, or physical incompatibility, among other potential reasons) to produce viable, or fertile, offspring with the group from which it is being separated. Several issues arise with this definition.

 

First, we consider many animals to be part of one species despite the fact that they’re almost certainly never going to meet and exchange genetic material without the aid of humans. For example, northern and southern hemisphere killer whales in all oceans are still listed officially as Orcinus orca, which is absurd. They can reproduce in captivity, probably, but even groups of killer whales (for example, Southern Residents and the area’s Transients) that live in the exact same bays and straits avoid each other completely in the wild, and probably haven’t exchanged genes for tens of thousands of years. I could go on and on about killer whales and species definitions but I will spare you (for now, mwa-ha-ha) and move on to the next problem.

Second, some domestic animals like farmed turkeys, certain cows, and many dogs cannot reproduce without human assistance. Are they species? They can’t reproduce at all, in reality, so they don’t pass the “fertile offspring” test unless people intervene quite a bit (artificial insemination, cesarean section, etc.).

Some people don’t hold with the biological definition. They prefer to define a species based on the percentage of functional genes that are different between two groups (which varies wildly depending on the age and genetic purity of a presumed species), or physical characteristics that show distance between populations. There isn’t really a definition that captures the flawed system we have (understandably) superimposed on the natural world, and the flawed system doesn’t even capture the nuance that the evolutionary process constantly creates and changes.

Meanwhile, what do you do with mushrooms and plants that can self-fertilize, or other less-identifiable organisms like bacteria, constantly passing genes from one individual to another. How about viruses, just tiny packets of DNA and self-replication machines? People think of things in groups that feel natural (haha, biology = natural…) but that’s not very scientific. It is, however, very convenient and intuitive. We group things to make them study-able, understandable, explainable, referable. For the most part, the species definition really does work to distinguish different types of organisms. We just can’t explain exactly why.

 

So anyways, it’s a bit tricky to explain why Sousa sahulensis has been officially designated a new group within that system. In this case, a combination of geographic separation, physical characteristics, and genetic difference added up to the split of the Australian humpback dolphins from Sousa chinensis, the Indo-Pacific humpback dolphin. Tomorrow’s post will explain exactly how our Sousa have earned their species stripes- this is likely enough of a biology-nerd’s rant for today.

Stay posted, dearest readers! I’m going to go track down some more cute photos of our resident charismatic megafauna and then turn in- today was long, but wonderful. I’ll dream of manta rays and humpback whales and leaping dolphins- I hope you do too.