Dr Craig Young
Dr. Craig Young is a marine invertebrate biologist. He has been studying and writing about the echinoderms, mollusks, and worms of the deep-sea since the late 1970s. He and his colleagues and students study the life-history patterns and developmental processes of deep-sea animals. Currently, he is the Director of the Oregon Institute of Marine Biology, and a professor of biology at the University of Oregon.
What is a life history pattern?
In ecology, "life-history" refers to the particular set of characteristics an organism has, and things it does, that allow it to survive and reproduce. The success of an individual or species is usually measured in terms of the number of surviving offspring. Many, many different factors can affect that success, for example:
- the timing of reproduction (e.g., birds lay eggs in the spring/summer when insects and worms are available to feed the hatchlings)
- the number of offspring produced and the amount of protection provided by the parents. Some species, including many fish and invertebrates, produce hundreds, thousands or millions of gametes that are released into the water with no protection, whereas other species produce and care for only a small number of babies (think of a mother lion teaching her small family of cubs to hunt).
Over time, one approach is favored over another and becomes part of that organism's life-history pattern. Below is a life-history diagram illustrating the major stages of development for many marine invertebrates. The illustrations are of mussels but the stages apply to many different kinds of marine animals.
Research questions about life-history patterns
Dr. Young and his graduate students focus their research on the early life-history stages of marine invertebrates, starting with gametogenesis, the production of eggs and sperm (gametes). Researchers studying this life-history stage try to understand how often and how fast gametes are produced and how this is synchronized between the sexes.
In mussels, eggs and sperm are released from the parents (spawned; see picture in the right hand column of this page) and fertilization takes place outside the mussel shell, in the surrounding water. Questions about this stage of development include:
- How many eggs are successfully fertilized?
- How do sperm find eggs?
- How long do the gametes live?
- What environmental factors tell animals when to spawn?
Following spawning or mating, an embryo develops from the fertilized egg. In this stage, scientists investigate how the cells divide to form organs and how quickly this happens. After many, many cell divisions, the embryo develops into a swimming larva, an immature stage that often does not resemble the adult. The larva may or may not feed as it swims and drifts (i.e. disperses) to another area where it will find a place to spend its adult life. Studies of the larval stage tell us a great deal about how populations spread and how animals find new habitats.
Eventually, after days to months of dispersal, the larva undergoes a dramatic transformation (metamorphosis) to the juvenile stage, while moving from the water column to the sea floor. The juvenile stage is something like the teenager in our species. Invertebrate juveniles are small and delicate and often eaten by predators. Scientists studying this stage are especially interested in how many survive to adulthood.
Dr. Young's Lab at the Oregon Institute of Marine Biology
Dr. Young and his students study how deep-sea animals reproduce, how their babies develop (embryology), how the larvae develop and feed, whether they move to other locations to settle (dispersal), and how they choose a suitable place to settle (recruitment).
For example, Shawn Arellano, a graduate student in Dr. Young's lab, studies the larval ecology of a deep-sea mussel, Bathymodiolus childressi. She is trying to understand what larvae of this species eat, how far they travel, and how they develop into juvenile mussels.
Currently, Dr. Young and his colleagues are investigating a very interesting question about reproduction in deep-sea mussels: how do they know when (in the year) to reproduce? Unlike land-living animals (like birds and insects) that reproduce in the spring and summer when food for their babies is plentiful, deep-sea animals at hydrothermal vents and cold seeps have a constant source of energy from the ocean floor (sulfide or methane for chemosynthesis) and therefore can reproduce throughout the year.
In the Gulf of Mexico, cold seep communities are found at depths of 600 to 1000 meters. Here, some animals (including mussels) are mixotrophic, meaning that they get nutrition from both a seasonal "rain" of food particles from the overlying ocean, and from a constant supply of chemicals seeping out of the seafloor (their symbiotic bacteria use these chemicals to make sugars chemosynthetically).
With colleagues from Virginia and the UK, Dr. Young uses a variety of methods to to find out if reproduction in the mussels coincides with the seasonal availibility of food particles or continues year-round — for instance some work is investigating whether food from surface waters end up in mussel gonads and other body tissues.
These studies will help answer the overall question that Dr. Young has been investigating for more than 15 years: how do deep-sea animals know when to reproduce?
