Hawaiian Bobtail Squid
Euprymna scolopes
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JT Beausoleil
Classification:
Kingdom: Animalia
Phylum: Mollusca
Class: Cephalopoda
Order: Sepiida
Family: Sepiolidae
Subfamily: Sepiolinae
Genus: Euprymna
Species: E. scolopes
Introduction
Euprymna Scolopes or “Hawaiian bobtail Squid” is a species of bobtail squid that fall in the family Sepiolidae. Bobtail squid are a group of cephalopods that are very closely related to cuttlefish but differ in the fact that they have rounder mantles and a lack of a cuttlebone. These squid grow up to 1.2 inches in mantle length.
Feeding
Bobtail squid are predators that hunt for primarily smaller shrimp and crustaceans. They also find themselves prey to animals like seals and lizardfish. E. Scolopes do their all hunting between dusk and dawn. When they are not busy hunting, they sink to the ocean floor and cover themselves in sand and mud to hide from predators(Shears, 1988).
Mating and Habitat
This dioecious species of squid have approximately equal numbers of males and females and mate by having the male deliver spermatophores into the female mantle cavity. Females aren't burdened with the task of tending to the eggs and in fact just bury the eggs in sand. Females can lay serial clutches and in some cases have been observed to lay a total of 15 clutches throughout the average 1 year life span that this species goes through. Embryonic period differs based on environment and ranges from 18-26 days long. This species lacks a true larval stage, like most cephalopods, and hatch into a mini adult form. The hawaiian bobtail squid’s hatching is inhibited by light so they only hatch at the onset of darkness. They also can survive solely off egg yolk reserves for the first couple of days after hatching(Lee Patricia,1970).
These organisms can be found in near shore to open ocean (~200m) environments. They are located in the pacific ocean all throughout the Hawaiian Islands.
Models of Animal-Bacteria Relationships
E. Scolopes have been looked at and used as model organisms for a couple different reasons. As mentioned earlier, they are quite small in size. Hawaiian bobtail squids also have relatively short life spans, rapid growth and are available year round. This species is also heavily studied on multiple factors. These being that they are a model of cephalopod development, they have tissues interacting with light and most importantly that they are a model of animal and bacterial symbioses(Lee Patricia,1970).
Counter-Illumination
E. Scolopes use a method of camouflage called counter illumination. Counter illumination is a method that utilizes means of bioluminescence as a way to match down welling light. What is meant by this, is that it produces light in order to match the brightness and the wavelength of its background in order to reduce the shadow it produces underneath it(Jones, 2004). This allows it to blend in with its surroundings and hide from predators below it. It has also been found that the hawaiian bobtail squid is able to adjust the amount of light it gives off underneath it if the light hitting the top of it’s mantle were to change. This was found in Jones’ study where there changed the amount of light intensity above the organisms. In this study, they increased the light slowly and saw an increase in the bioluminescence from the bobtail squid up to a certain point where it is determined it must have been too bright and not energy efficient enough to maintain.
The way these squid are able to produce this effect is through the help of some friendly bacteria. Vibrio fischeri is a species of bioluminescent bacteria that benefits by being housed in a light organ found in the Hawaiian bobtail squid(Tong D, 2009). Not only that but it is fed sugars and amino acids by the squid in return for its bioluminescence(Mcfall-ngai, 2012). E. Scolopes hatchlings are born without the presence of V. fischeri and must capture them. They do this by secreting mucus around the light organ and capturing a large variety of bacteria. Then, through an unknown method, the bioluminescent bacteria is able to outcompete all other species and is selected for.
Another interesting thing about their light organ is that it is very similar to an eye. It also has been found to express similar genes found in the development of the eye, suggesting they use the same “toolkit. What’s also cool, is that the same genes(dac, eya, six, pax6) are also found to be expressed in the development of house mice(Peyer, Suzanne M., 2014).
Accessory nidal gland is a female reproductive organ that houses more symbiotic bacteria. This bacteria is then transferred to the egg cases of the squid and functions to prevent microbe fouling and contamination from microorganisms in the environment(Li Hau-Wen, 2019).
Astronaut Squid?
On June 3, 2021, SpaceX sent about a dozen Hawaiian bobtail hatchlings (and some water bears) into space to the International Space Station. The goal of this study is to see whether or not being in space affects the ability of the squid to take up the bioluminescent bacteria. They also want to see how space alters the symbiotic relationship between the two organisms, if at all. The purpose for this study is to apply it to human astronauts. What they’ve found is that on long space missions, astronauts have issues with immune systems and other aspects of the body that rely heavily on the symbiosis of humans and the bacteria in their microbiomes. They want to apply the symbiosis in the squid and try to understand what’s happening in humans. They say this is necessary to keep humans safe if we ever want to spend time on mars or the moon(Associated Press, 2021).
References
Associated Press. “Dozens of Hawaiian Baby Squid Aboard Space Station for Study.” The Guardian, Guardian News and Media, 22 June 2021
Cephalopods of the World: An Annotated and Illustrated
Catalogue of Cephalopod Species Known to Date, by P. Jereb and Roper Clyde F E., Food and Agriculture Organization of the United Nations, 2005, pp. 153–203.
Jones, B. W., and M. K. Nishiguchi. “Counterillumination in the Hawaiian Bobtail Squid, Euprymna Scolopes Berry (Mollusca: Cephalopoda).” Marine Biology, vol. 144, no. 6, June 2004, pp. 1151–1155. EBSCOhost, doi:10.1007/s00227-003-1285-3.
Lee, Patricia., et al. “The Hawaiian Bobtail Squid (Euprymna Scolopes): A Model to Study the Molecular Basis of Eukaryote-Prokaryote Mutualism and the Development and Evolution of Morphological Novelties in Cephalopods.” Cold Spring Harbor Protocols, 1 Jan. 1970, cshprotocols.cshlp.org/content/2009/11/pdb.emo135.
Li, Hau-Wen, et al. “The Characteristics and Expression Profile of Transferrin in the Accessory Nidamental Gland of the Bigfin Reef Squid during Bacteria Transmission.” Scientific Reports, vol. 9, no. 1, 2019, doi:10.1038/s41598-019-56584-8.
McFall-Ngai, Margaret, et al. “The Secret Languages of Coevolved Symbioses: Insights from the Euprymna Scolopes–Vibrio Fischeri Symbiosis.” Seminars in Immunology, vol. 24, no. 1, 2012, pp. 3–8., doi:10.1016/j.smim.2011.11.006.
Peyer, Suzanne M., et al. “Eye-Specification Genes in the Bacterial Light Organ of the Bobtail Squid Euprymna Scolopes, and Their Expression in Response to Symbiont Cues.” Mechanisms of Development, vol. 131, 2014, pp. 111–126., doi:10.1016/j.mod.2013.09.004.
Shears, James C.. “The use of a sand-coat in relation to feeding and diel activity in the sepiolid squid Euprymna scolopes.” Malacologia 29 (1988): 121-133.
Thorbecke, Catherine. “SpaceX Launches Glow-in-the-Dark Baby Squid to the International Space Station.” ABC News, ABC News Network, 3 June 2021, abcnews.go.com/Technology/spacex-launch-glow-dark-baby-squid-international-space/story?id=78062966.
Tong, D., et al. “Evidence for Light Perception in a Bioluminescent Organ.” Proceedings of the National Academy of Sciences, vol. 106, no. 24, 2009, pp. 9836–9841., doi:10.1073/pnas.0904571106.
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