We submerge ourselves into the murky depths of what is clearly a backyard pool and meet… yet another man in a suit. This week is all about the Gillman from 1712’s The Creature from the Black Lagoon. Dave and Adam both need more bloody caffeine.
4:29 – Movie History
14:23 – Physiology of the Gillman
37:51 – Ecology of the Gillman
1:01:56 – The Gillman vs. Richard Strickland from The Shape of Water
Film: Creature From The Black Lagoon 
Production Company: Universal Pictures
Distributed By: Universal Pictures
Monster: Creature From The Black Lagoon
Featuring: Adam, David
Rating: Mature (for some offensive language and adult themes)
In the film, the creature is shown to have 5 digits with sharp claws, webbing in between the fingers, thick skin that resists damage, a 3rd eyelid, and a limited range of motion. Although many of these features can be attributed to a thick suit with a human inside, for the purpose of this discussion we will need to take this qualities into consideration. In order to take on a bipedal posture, long arms, and apparent shoulder sockets the creatures will very likely be a descendant of an early primate species. As a result they should have a metabolic rate similar to ours. The film describes the species as a reptile descendant but this would likely not be the case.
Within the film, the creature is repeatedly shown to have a very tough hide. A shot at close range with a spear gun does not seem to get that far into the skin, and no active bleeding is really seen from the wound (suggesting lack of penetration). This thick skin would suggest that creatures face fierce predation.
In nature, there are multiple semi aquatic species with similar protections. The best examples are the Alligator Gar and the Alligator/Crocodile. The alligator gar is a fish species native to North America. Their skin is incredibly resistant to attacks, and is so tough that a regular knife cannot slice through it. This is accomplished by a series of small scales that overlap in sheets like medieval armor (plate mail). Crocodiles and builds their skin like any other reptile in keratinized sheets. However, they reinforce it with alterations in the structure of the collagen and changes in the thickness to give protection against predators and extreme durability.
Final Thoughts- Integument
The creature appears to be fairly tough. It displays a resistance to spears used within the water and potentially some resistance to small arms fire on land. The skin appears to be some form of hybrid between scales and a keratinized epidermis. I am more suspicious of a skin type closer to an alligator as it would fit better with the visual appearance of the creature and would be an easier transition for a mammal descendant.
The creature seems to be breathe air like a fish, taking gulping breaths. Gills, in fish that are actively moving, work as the fish open their mouth to take in oxygenated water. When their mouth closes, the water moves out through the gills, moving across the gill arches and oxygenating the blood within the capillary beds. Although this mechanism works well for aquatic life, it is not something that can be done in terrestrial species, with a few exceptions.
The Australian lungfish, is capable of respiring through either gills or lungs/modified gills. They have a physiological adaptation, called the spiral valve of the conus arteriosus that allow them to switch been respiratory systems based on whether they are on the land or in their water. They are almost unique in the animal kingdom for this ability. They use this ability to effectively move between aquatic environments and survive in periods of drought.
Final Thoughts- Respiratory
Like the Australian lungfish, the creature would most likely have two seperate systems that it could swap between (gills and lungs/modified gills). They are too big to use O2 diffusion through the skin, and their skin is too thick. They might be able to use a system similar to a whale (holding their breaths) but as they appear to be actively gulping/breathing on land it is unlikely. Interestingly, the creature is also capable of vocalizing when on land, suggesting it is capable of using the inhaled air to make noises in a terrestrial environment.
The creature appears to have lips like a fish, and possibly some teeth further back in the oral cavity. This would suggest that the creatures might feed on the same type of life that normal bony fish subsist on.
CLAWS & WEBBING
The creature has very tough sharp claws. This would suggest fierce predation or competition within the water. The claws are mostly like a keratin composite. The problem in the film with the clws is that soft tissue does not calcify well. However, when the scientists discover a fossilized creature appendage, the webbing appears to be be intact. This would not happen in the real world.
The creature appears to have a transparent 3rd eyelid, that drops in place when in the water. This mechanisms seems to be similar to what is seen in frogs. Frogs have a third eyelid (also called a nictitating membrane) that is semi transparent and covers the eye completely when underwater. This helps the frog see underwater, hunt, and hide from predators. We assume that the creature would be using the 3rd eyelid for a similar mechanism.
The creature appears to be very strong in the film, capable of pulling the the ship down into the water and lifting humans with ease. It is true that some primates possess muscle fibre organizations that can lead to enhancements of their strength far above that of a similarly sized human. However, there is no way that the creature would be strong enough to try and pull the ship under the water.
Although both primates and lungfish have a well developed internal skeleton, the skeleton functions in different ways The way that the creature moves in the film would require it to have a skeleton more similar to that of a primate. This would allow bipedal motion, suspension off the side of the ship with just the front limbs, and the general range of motion they display.
Wen Yang, Bernd Gludovatz, Elizabeth A. Zimmermann, Hrishikesh A. Bale, Robert O. Ritchie, Marc A. Meyers. Structure and fracture resistance of alligator gar (Atractosteus spatula) armored fish scales. Acta Biomaterialia,Volume 9, Issue 4, 2013. Pages 5876-5889,
ISSN 1742-7061, https://doi.org/10.1016/j.actbio.2012.12.026.
Irene H. Chen, Wen Yang, Marc A. Meyers. Alligator osteoderms: Mechanical behavior and hierarchical structure. Materials Science and Engineering: C, Volume 35, 2014, Pages 441-448, ISSN 0928-4931, https://doi.org/10.1016/j.msec.2013.11.024.
Kemp, A. (1986), The biology of the australian lungfish, Neoceratodus forsteri (krefft 1870). J. Morphol., 190: 181-198. doi:10.1002/jmor.1051900413
MIVART, G. The Common Frog * . Nature 9, 367–369 (1874) doi:10.1038/009367a0