GRAY WHALES: ESCHRICHTIUS ROBUSTUS

Young Gray Whale, Eschrichtius robustus

The lovely fellow you see here is a young Gray Whale, Eschrichtius robustus, with a wee dusting of barnacles and his mouth ajar just enough to show his baleen.

Two Pacific Ocean populations are known to exist: one of about 200 individuals whose migratory route is presumed to be between the Sea of Okhotsk off Russia's south coast and southern Korea, and a larger one with a population of about 27,000 individuals in the eastern Pacific.

This second group are the ones we see off the shores of British Columbia as they travel the waters from northernmost Alaska down to Baja California. Gray whale mothers make this journey accompanied by their calves, hugging the shore in shallow kelp beds and providing rare but welcome glimpses of this beauty.

The gray whale is traditionally placed as the only living species in its genus and family, Eschrichtius and Eschrichtiidae, but an extinct species was discovered and placed in the genus in 2017 — the Akishima whale, E. akishimaensis. Some recent DNA analyses suggest that certain rorquals of the family Balaenopteridae, such as the humpback whale, Megaptera novaeangliae, and fin whale, Balaenoptera physalus, are more closely related to the gray whale than they are to some other rorquals, such as minke. Still, others place gray whales as outside the rorqual clade, a kissing cousin if you will.

John Edward Gray placed it in its own genus in 1865, naming it in honour of physician and zoologist Daniel Frederik Eschricht. The common name of the whale comes from its colouration. The subfossil remains of now-extinct gray whales from the Atlantic coasts of England and Sweden were used by Gray to make the first scientific description of a species then surviving only in Pacific waters. The living Pacific species was described by American palaeontologist, Edward Drinker Cope as Rhachianectes glaucus in 1869.

Fin Whale, Balaenoptera physalus

Skeletal comparisons showed the Pacific species to be identical to the Atlantic remains in the 1930s, and Gray's naming has been generally accepted since. Although identity between the Atlantic and Pacific populations cannot be proven by anatomical data, its skeleton is distinctive and easy to distinguish from that of all other living whales.

In 1993, a twenty-seven million-year-old specimen was discovered in deposits in Washington state that represents a new species of early baleen whale. It is especially interesting as it is from a stage in the group’s evolutionary history when baleen whales transitioned from having teeth to filtering food with baleen bristles.

Visiting researcher Carlos Mauricio Peredo studied the fossil whale remains, publishing his research to solidify Sitsqwayk cornishorum (pronounced sits-quake) in the annals of history. The earliest baleen whales clearly had teeth, and clearly still used them. Modern baleen whales have no teeth and have instead evolved baleen plates for filter feeding. Look to the rather good close-up of this young Gray Whale here to see his baleen where once there was a toothy grin.

The baleen is the comb-like strainer that sits on the upper jaw of baleen whales and is used to filter food. We have to ponder when this evolutionary change —moving from teeth to baleen — occurred and what factors might have caused it. Traditionally, we have sought answers about the evolution of baleen whales by turning to two extinct groups: the aetiocetids and the eomysticetids.

The aetiocetids are small baleen whales that still have teeth, but they are very small, and it remains uncertain whether or not they used their teeth. In contrast, the eomysticetids are about the size of an adult Minke Whale and seem to have been much more akin to modern baleen whales; though it’s not certain if they had baleen. Baleen typically does not preserve in the fossil record being soft tissue; generally, only hard tissue, bones and teeth are fossilized.

USING BARNACLES TO TRACK ANCIENT WHALES

We can trace the lineage of barnacles back to the Middle Cambrian. That's half a billion years of data to sift through. But if you divide that timeline in half yet again, we begin to understand barnacles and their relationship to other sea-dwelling creatures and their migration patterns.

It is through the study of fossil barnacles that are roughly 270,000 million years old that help track ancient whale migrations. University of California Berkeley doctoral student Larry Taylor, the lead author of the study, published March 25, 2019, in the peer-reviewed journal Proceedings of the National Academy of Sciences published on some clever findings. 

Taylor's research showed used fossil barnacles that hitched a ride on the backs of humpback and gray whales to reconstruct the migrations of whale populations millions of years ago.

The barnacles not only record details about the whales’ yearly travels but also retain this information after they become fossilized. By following this barnacle trail, Taylor et al. were able to reconstruct migration routes of whales from millions of years in the past.

Today, Humpback whales come from both the Southern Hemisphere (July to October with over 2,000 whales) and the Northern Hemisphere (December to March about 450 whales along Central America) to Panama (and Costa Rica). They undertake annual migrations from polar summer feeding grounds to winter calving and nursery grounds in subtropical and tropical coastal waters.

One surprise find is that the coast of Panama has been a meeting ground for humpback whales going back at least 270,000 years.

To see how the barnacles have travelled through the migration routes of ancient whales, the team used oxygen isotope ratios in barnacle shells and measured how they changed over time with ocean conditions. Did the whale migrate to warmer breeding grounds or colder feeding grounds? Barnacles retain this information even after they fall off the whale, sink to the ocean bottom, and become fossils. As a result, the travels of fossilized barnacles can serve as a proxy for the journeys of whales in the distant past.

Barnacles can play an important role in estimating paleo-water depths. The degree of disarticulation of fossils suggests the distance they have been transported, and since many species have narrow ranges of water depths, it can be assumed that the animals lived in shallow water and broke up as they were washed down-slope. The completeness of fossils, and nature of the damage, can thus be used to constrain the tectonic history of regions.

In the Kwak̓wala language of the Kwakiutl or Kwakwaka'wakw, speakers of Kwak'wala, of the Pacific Northwest, barnacles are known as k̕wit̕a̱'a and broken barnacle shells are known as t̕sut̕su'ma.

MANATEES AND DUGONGS

I had always grouped the dugongs and manatees together. There are slight differences between these two groups. Both groups belong to the order Sirenia.

They shared a cousin in the Steller's sea cow, Hydrodamalis gigas, but that piece of their lineage was hunted to extinction by our species in the 18th century. Dugongs have tail flukes with pointed tips and manatees have paddle-shaped tails, similar to a Canadian Beaver.

Both of these lovelies from the order Sirenia went from terrestrial to marine, taking to the water in search of more prosperous pastures, as it were. They are the extant and extinct forms of the oddball manatees and dugongs.

We find dugongs today in waters near northern Australia and parts of the Indian and Pacific Oceans. They inhabit rivers and shallow coastal waters, making the best use of their fusiform bodies that lack dorsal fins and hind limbs. I have been thinking about them in the context of some of the primitive armoured fish we find in the Chengjiang biota of China, specifically those primitive species that were also fusiform.

They favour locations where seagrass, their food of choice, grows plentiful and they eat it roots and all. While seagrass low in fibre, high in nitrogen, and easily digestible is preferred, dugongs will also dine on lower grade seagrass, algae, and invertebrates should the opportunity arise. They've been known to eat jellyfish, sea squirts, and shellfish over the course of their long lives. Some of the oldest dugongs have been known to live 70+ years, which is another statistic I find surprising. They are large, passive, have poor eyesight, and look pretty tasty floating in the water; a defenceless floating buffet. Their population is in decline and yet they live on.

ANTHOZOA: CORALS

Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria. They typically live in compact colonies of many identical individual polyps.

Corals are important reef builders that inhabit tropical oceans and secrete calcium carbonate to form a hard skeleton.

A coral "group" is a colony of a myriad of genetically identical polyps. Each polyp is a sac-like animal typically only a few millimetres in diameter and a few centimetres in length. A set of tentacles surround a central mouth opening. Each polyp excretes an exoskeleton near the base. Over many generations, the colony thus creates a skeleton characteristic of the species which can measure up to several meters in size. Individual colonies grow by asexual reproduction of polyps. Corals also breed sexually by spawning: polyps of the same species release gametes simultaneously overnight, often around a full moon. Fertilized eggs form planulae, a mobile early form of the coral polyp which when mature settles to form a new colony.

Although some corals are able to catch plankton and small fish using stinging cells on their tentacles, most corals obtain the majority of their energy and nutrients from photosynthetic unicellular dinoflagellates of the genus Symbiodinium that live within their tissues. These are commonly known as zooxanthellae and gives the coral colour. Such corals require sunlight and grow in clear, shallow water, typically at depths less than 60 metres (200 ft). Corals are major contributors to the physical structure of the coral reefs that develop in tropical and subtropical waters, such as the Great Barrier Reef off the coast of Australia. These corals are increasingly at risk of bleaching events where polyps expel the zooxanthellae in response to stress such as high water temperature or toxins.

Other corals do not rely on zooxanthellae and can live globally in much deeper water, such as the cold-water genus Lophelia which can survive as deep as 3,300 metres (10,800 ft). Some have been found as far north as the Darwin Mounds, northwest of Cape Wrath, Scotland, and others off the coast of Washington State and the Aleutian Islands.