Ruth Turner, late of Harvard, was the first female observer to visit the ocean depths in the Alvin deep-sea submersible. She was also the first biologist to visit hydrothermal vents, initially discovered by a team of geologist, who on seeing the abundant animal life surrounding the vents called Dr. Turner. She is one of my biological heroes.
She studied mollusks, particularly shipworms, which are not worms but clams that eat and bore into wood. One early hypothesis she made was of life in the deep sea. Basically her idea was that life was far more abundant in the deep ocean than folks at the time were able to comprehend. All you needed was an energy source and life would be found. She was correct, of course, we now know of many deep sea organisms, including deep-sea coral reefs, to say nothing of the hundreds of communities of organisms living around vent ecosystems, the energy source spewing out as hot sulfur. A whole new base of a food web, processes of chemosynthesis, were discovered.
Did she envision another chemical process of energy cycles, probably not. She had previous dropped hunks of wood into the deep and shown that they were inhabited by life in short order. One of the organism she found on her hunks of wood were those shipworms mentioned previously, an organism she become the world’s expert in. She knew that energy, in some form would sink from surface waters. One of the most interesting of these are whale falls. Whales, massive marine mammals, sometimes die and sink into the ocean depths. Their bodies are large nutrient sources.
The entire body of a whale disappears into an array of deep-sea organisms. A number of fishes from deep-water sharks, to chimeras (a shark relative), to the not quite a fish, hagfish, visit whale falls and take advantage of the food source. All sorts of other deep-water life comes as well; Arthropods including crabs, large isopods, shrimp, and lobsters. The array of life includes worms of several varieties too. Worms are everywhere, and I’m not meaning the badly named shipworms. Among the wormy denizens are species of polychaetes in the genus Osedax. These worms are commonly called bone worms, this means they, yes, you guessed it, feed on bones.
There is some contention on this point, that is, they can feed on bones but do they only feed on bones? These worms are found throughout the world both at depth and in shallow waters. If they only feed on bones why are they so widespread, and diverse (there are currently 30 species recognized and considering that some are very deep-water inhabitants the number recognized will triple or quadruple in coming years).
Shipworms, okay, again (see previous essay/blog), I’m going to have to change this common name to shipclams: I’m starting this sentence over in the next paragraph:
Shipclams and bone worms have some things in common; they bore into hard substrates. This behavior is called bioerosion. The bone worms bore into bone for shelter and for food. The worms secrete (note below) enzymes and acids that start the break down of bone. It seems that they do this in conjunction with symbiotic bacteria that live within them. Maybe it’s the bacteria that do all the work.
These warms are tiny critters. Most females have a diameter less than 1 mm with some species reaching nearly 1 cm thick. They have been described as looking like flowers because they have many tendrils which are often colored, at one end, with many other root-like projections from the other end. The root-like projections house the bacteria while the flowers are gills to grab oxygen. The males of most species are much smaller.
Figure 2. (right) This quick line drawing is of Osedax mucofloris, known as the bone eating snot flower. This animal is about is a little longer than O. rubiplumus shown in figure 1.
In one species, Osedax priapus, the males are about the same size as the females. These males are able to search, with an extensible tentacle, for females in nearby areas of the bone. In order to achieve this size the males feed on bone. I would suspect that this situation was the evolutionarily older condition, the ancestral or plesiomorphic trait. The authors of the study, cited below on this, suggest it is going back to the old ways, that is these large males were first large, then tiny, and now have reverted to large again. Quite an evolutionary history, apparently they didn’t want to be part of a harem anymore.
Imagine if Dr. Ruth Turner had also used dead vertebrates or just their skeletons in her experiments. She would have been the world’s expert on not only shipclams but bone worms.
Note:
The worms have no gut but are able to absorb nutrients that have been broken down outside their bodies. This is how fungus feed.
Sources and Further Readings:
Eilertsen MH, Dahlgren TG, and Rapp HT. 2020. A New Species of Osedax (Siboglinidae: Annelida) From Colonization Experiments in the Arctic Deep Sea. Frontiers of Marine Science 7: 443. doi: 10.3389/fmars.2020.00443
Higgs, ND, Glover, AG, Dahlgren, TG et al. 2014. The morphological diversity of Osedax worm borings (Annelidia: Siboglinidae). Journal of the Marine Biological Association of the United Kingdom 94: 1429 - 1439. ISSN 1469-7769
Rouse GW, Worsaae K., Johnson S.B., Jones W.J. and Vrijenhoek R.C. 2008. Acquisition of dwarf male “harems” by recently settled females of Osedax roseus n. sp. (Siboglinidae; Annelida). Biological Bulletin. Marine Biological Laboratory, Woods Hole 214: 67–82.
Rouse GW, Wilson NG, Worsaae K, Vrijenhoek RC. 2015. A dwarf male reversal in bone-eating worms. Current Biology 25: 236–241
Turner RD. 1947. Collecting shipworms. Limnological Society of America. special publication no. 19: 1-8, text figs.
Turner RD, and Hoagland KE. 1981. Evolution and adaptive radiation of shipworms. Malacologia 21: 111-148