Biology

Although locating distinct scientific research regarding the internal organs and systems of the Atlantic Sturgeon is difficult, I will be taking examples from related species in the Acipenser family and other bony fishes to give a general glimpse into the different functions that takes place within animal bodies.

Anatomy

In the Atlantic Sturgeon (Acipenser oxyrhynchus) and other related strugeons, they have multiple features that aid them in their life, keeps them protected from predators.

The dorsal and anal fins help stabilize the sturgeon, while pectoral and pelvic fins help the fish maneuver, turn, back up, etc.

Scutes are bony plates along the spine and serve as protection from other factors in the water, and variation/distinction between species.

Their mouths lack teeth like sharks or beaks like sea turtles, but the position of their mouths on the very bottom make it easier to swim along the sea floor and gobble up prey. Their mouths are protrusible, meaning it can extend to swallow up prey, and spit out the sand and pebbles that get mixed up in the process. Food is swallowed whole, being crushed in their muscular system and broken down for further digestion.

Barbels

Barbels are used to detect motion and potential food.

Scutes

Scutes are bony plates along the spine and serve as protection from other factors in the water, and variation/distinction between species.

Physiology

Although not the same species, many sturgeon I feature share the same taxonomic tree, and share similar features in their overall structure. I will be citing research found in various sturgeon species as well, as research on the Atlantic Sturgeon's physiology (Acipenser oxyrhynchus) is still being conducted and collected, and definitive data for my animal was difficult to find across various scholarly databases.

Sturgeons are sensitive to low oxygen, temperature, salinity, and other factors in the water conditions that pose threats to their survival and physiology.

Digestive System

As food is ingested, it must pass through the esophagus, a tube that connects the stomach to the mouth. Like humans, fish also have a pharynx that allows the travel of fluids and air, giving both significant respiratory and digestive functions. Sand and other particles not beneficial to the sturgeon are expelled through its gills.

Within the stomach, food is partially digested with the help of acid and enzymes; In humans, protein digestion is done by pepsin, and as the stomach acids break down the food, pepsin is able to catalyze the protein. The mixture of gastric juices and partially digested food is chyme, moving to the small intestine at low intervals over a number of hours.

As carbohydrates, fats and proteins are digested in the small intestine, the large intestine processes the waste material to be excreted.

Other important functions of the body of the fish include the gizzard: Grinding up coarse food to be digested efficiently in smaller pieces.

The pneumatic duct connects the esophagus to the swim bladder, which allows air to travel and either release to the water, or be pushed to the swim bladder. Fish that have this feature are called physotomes, allowing the bladder to be expanded without bursting.

Endocrine System

"One of the most intriguing anomalies of sturgeon physiology is their apparently muted stress response when compared to most modern teleosts. The surprisingly low plasma cortisol levels of sturgeons compared to most modern teleosts has been known for decades (Potts and Rudy, 1972) and has been documented in many different sturgeon species and for a number of different stressors, including: salinity exposure, hypoxia, handling stress, and forced exercise". (Penny, Bugg, Kieffer, Jeffries, Pavey, 2023)

Cortisol, a hormone produced in the adrenal glands, helps the body regulate glucose, protein and fats. Scientists in 2020 conducted research to test the levels of cortisol and ion regulation in seawater in the Atlantic Sturgeon, and found that certan chemicals such as plasma chloride, cortisol glucose levels, and gill Na+/K+/2Cl− cotransporter increased in freshwater-reared Atlantic Sturgeon, as opposed to the sturgeon in saltwater.

They concluded that cortisol has a significant role in regulating mechanisms in ion secretion, and supports the hypothesis that control of osmoregulation glucose by corticosteroids is a basal trait in jawed vertebrates.

Cardiovascular System

Mechanisms of communication between cells occurs through the release of chemical hormones. They are released through body fluids such as blood, traveling to target cells to gain a response. The cells that release hormones are located in the endocrine glands. The tissues, organs and cells that also secrete hormones make up the endocrine system. Organs in this system include the pancreas, adrenal glands, and thyroid glands.

Hormones and the endocrine system are a very important process for the sturgeon, as it affects the newborn fry in their digestive system, and continues to change as they grow.

"In the Adriatic Sturgeon, (Acipenser naccarii), research found adult sturgeons the intrapericardial, nonmyocardial segment is interposed between the conus arteriosus of the heart and the ventral aorta." (Guerrero, Icardo, Duran, Gallego, Domezain, Colvee, Sans-Coma 2004)

"Between the fourth and sixth days posthatching, the distal portion of the cardiac outflow tract undergoes a phenotypical transition, from a myocardial to a smooth muscle-like phenotype. The length of this region with regard to the whole outflow tract increases only moderately during subsequent developmental stages, becoming more and more cellularized. The cells soon organize into a pattern that resembles that of the arterial wall. Elastin appears at this site by the seventh day posthatching." (Guerrero, Icardo, Duran, Gallego, Domezain, Colvee, Sans-Coma 2004)

Reproduction and Life Cycle

Atlantic Sturgeon females can lay thousands, if not millions of eggs during one spawning season. However, the chances of all of them surviving the hatching season is low. An Atlantic Sturgeon's ovaries were weighed in 1963, and were 41.4 kg, containing about 3.7 million eggs. Only a handful of eggs will survive, and need many different factors such as running water and rocky bedding.

Females will leave the spawning grounds after laying eggs, while males will remain until the autumn season to return to sea. Juveniles will remain in the rivers they were hatched in for up to six years before migrating to the ocean.

Maturity in males is 10 years old, maturity in females is 20 years.

Biology Works Cited

Campbell, R. (n.d.). Atlantic Sturgeon - Sararegistry.gc.ca. Retrieved April 21, 2023, from https://sararegistry.gc.ca/virtual_sara/files/cosewic/sr_Atlantic%20Sturgeon_2011_e.pdf

Penny, F. M., Bugg, W. S., Kieffer, J. D., Jeffries, K. M., & Pavey, S. A. (2023, January 16). Atlantic Sturgeon and Shortnose Sturgeon exhibit highly divergent transcriptomic responses to acute heat stress. Comparative Biochemistry and Physiology Part D: Genomics and Proteomics. Retrieved April 21, 2023, from https://www.sciencedirect.com/science/article/abs/pii/S1744117X23000035

Rice University. (n.d.). 16.4 endocrine system - concepts of biology. OpenStax. Retrieved April 21, 2023, from https://openstax.org/books/concepts-biology/pages/16-4-endocrine-system

Morphological changes in digestive tract of Atlantic Sturgeon Acipenser ... (n.d.). Retrieved April 21, 2023, from https://www.researchgate.net/publication/260432610_Morphological_changes_in_digestive_tract_of_Atlantic_sturgeon_Acipenser_oxyrinchus_during_organogenesis

Chesapeake Bay Program . (n.d.). Atlantic Sturgeon. Chesapeake Bay. Retrieved April 21, 2023, from https://www.chesapeakebay.net/discover/field-guide/entry/atlantic-sturgeon

McCormick, S. D., Taylor, M. L., & Regish, A. M. (2020, November 16). Cortisol is an osmoregulatory and glucose-regulating hormone in Atlantic Sturgeon, a basal ray-finned fish. USGS science for a changing world. Retrieved April 22, 2023, from https://www.usgs.gov/publications/cortisol-osmoregulatory-and-glucose-regulating-hormone-atlantic-sturgeon-a-basal-ray

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