Category: General Article
Wednesday, December 6, 2017
Summary: Team members Sebastian Velez and Laura Timm study baby animals to help assess the health and future of marine populations.
By Sebastian Velez
While most of my team members are interested in some of the deep-sea fishes we collect, my fishes are usually found near the surface of the ocean. In particular I’m interested in the baby snappers and groupers of the Gulf of Mexico and what sorts of currents they like to hang out in. Snappers and Groupers represent some of the most popular fish that people like to eat and sport-fish for in the southern United States, so it’s really important to know the behaviors of their babies and how they end up where they want to end up as adults.
After these fishes hatch from their eggs the larvae get pulled of offshore by the currents in the Gulf of Mexico. They eat plankton that float around in the top layer of the oceans. The larvae try to get as big as possible as quickly as possible so that they don’t become dinner for predators. Many of these juvenile fishes often look like miniature versions of adults.
Though there are some that camouflage themselves with long threadlike appendages to mimic siphonophores and jellies which makes them unappetizing to predators. It can take 20-50 days for the larvae to grow and become strong enough swimmers to escape these currents. Then they start looking for a place to call home. By that time the currents often move them hundreds of miles away from where they started. That helps move individual fish to new habitats and helps replenish established populations.
If we study these baby fishes we can try to figure out where they come from, where they end up, and how many survive into adulthood. All that information can help us make sure that we keep future populations sustainable. For example; let’s say one year it’s a little too cold for these larval fishes and many of them die. If we know that ahead of time, and we know it takes three years for these baby fish to grow into adults, then we can plan ahead. We can make sure that we don’t eat or fish for too many of these fish because their numbers will be very low. That way we can make sure that the populations are harvested sustainably.
By Laura Timm
Lots of animals (especially invertebrates) have a larval phase that is very different from the adult phase. Lots of larvae swim in the water column while the adults are sedentary and benthic. This phase is often crucial for species survival. (See images in the righthand sidebar.)
Because the adults largely stay in the same place, they keep their DNA with them in one population. However, when larvae hatch they swim away from their parent population and bring new genetic material to a new population where they settle into adulthood. This is a very important means of “gene fow.”
Now, it may seem very easy to match a larval form to the adult it eventually becomes. Unfortunately, it is rarely that easy. Because larvae swim and face different challenges than adults they can look very very different than the adult form. For instance, mantis shrimp larvae are almost completely transparent and can be very fat. Their eyes are on long stalks and they have relatively large carapaces. The mantis shrimp larvae also have lots of sharp spines. That’s right, they are almost invisible and are covered it sharp-as-glass spines!
Adult mantis shrimp are (obviously) much larger and can be very colorful. They have powerful clubs that the larvae don’t possess. The adults’ eyes sit much closer to their bodies. The adults also lack protective spines.
Without being able to watch a larva become an adult how could we possibly match a larva to an adult?
As part of DEEPEND, we are studying their DNA. We are genetically “barcoding” crustaceans we find in the Gulf, even the babies! This means we’re run the DNA of larvae, then compare that code with known crustaceans.
Regardless of life stage (larva, juvenile, adult) and appearance, the genetic barcode for a species will be the same for all individuals within the species. Genetic barcoding has already helped us match a number of larvae to adults. The better we understand the life histories and abundance of these species at all life stages, the better we understand the Gulf as a whole!
I better get back to barcoding baby crustaceans.