Lifestyle of a Bobtail Squid
The Hawaiian bobtail squid averages 2.5 centimeters in mantle length as an adult. This sepiolid lives at the bottom of shallow water off the coasts of the Hawaiian archipelago, hunting crustaceans, annelids, and fish at night. During the day, they bury themselves in the sand.
This particular species lacks an internal shell and possesses a pair of paddle shaped fins and a luminescent light organ, which is used for hunting prey and avoiding predators. Typical predators are bottom-dwelling fishes like the barracuda or the lizardfish.
The males transfer spermatophores into the female mantle cavity during mating, using his sex-specific arm, and after breaking open spermatophore to fertilize the eggs, the females lay clutches, covering the eggs with sand for protection. That is the extent of parental care. After a temperature dependent embryonic period of 18 to 26 days, the juveniles hatch nocturnally and develop independently.
This YouTube video shows embryonic development of another squid species:
Behaviour of bobtail squid– YouTube Video
Hox gene Innovations: Hox gene expression in E. scolopes
Squid are model organisms used to study the nervous system. In particular, bobtail squid (E. scolopes) is a group of squid studied intensely because of the unique innovations that have evolved from other mollusks. These innovations include: well-developed eyes, extra-ocular photoreceptors, a vestibular system similar to vertebrates, different light organs, and a complex central and peripheral nervous systems. Their Hox genes are studied to find out exactly how these new features develop. Hox genes are much conserved throughout evolution of different species and should show how the bobtail squid’s features formed. In addition to Hox genes, researchers believe other type of regulatory genes in E. scolopes are involved but with lower restrictions.
Working with Light: Euprymna scolopes and Vibrio fischeri
The Hawaiian bobtail squid is known for its symbiotic relationship with the luminescent bacteria Vibrio fischeri. The squid has an adaptive light organ that houses the bacteria and directs the light produced by Vibrio fischeri in a counter-illumination technique to assist in catching prey and avoiding predators. Infection of the light organ quickly after hatching induces post-embryonic development in the squid into a mature light organ which promotes high bacterial cell density. The high cell density prompts high concentrations of quorum sensing, which regulates the luminescence within the Vibrio fischeri.
The Hawaiian Bobtail Squid’s relationship with the Vibrio fischeri forms in the light organ, which is specifically developed to host these bacteria. The light organ shares many structures with the squid’s eyes, and a recent paper has shown that the same genes that regulate eye development also assist in the light organ development.
Researching Squid Light Organ Development: Eye-specification genes in the bacterial light organ of the bobtail squid Euprymna scolopes, and their expression in response to symbiont cues.
Researching Neurological disease: Squid (Loligo pealei) as a Model for Studying Neurodegeneration and Dementia in Mammals
Scientists are currently investigating the causes of various neurodegenerative disorders using the nervous systems of squids. It is hypothesized that these disorders are a result of irregular and or hyperphosphorylation of various proteins. The axons of the squids are being studied for both the convenience of their large size in comparison to other species as well as their similarity to mammalian axons.
In general, cephalopods have also been studied extensively for neural development. With one of the most complex nervous systems of the invertebrates, several species and distant relatives of the bobtail squid such as sepiolids and loligo squids have been used as models to study the embyronic neural development of cephalopods. Because of its direct development, cephalopods are ideal for the continuous observations of certain areas without changes due to metamorphosis. Studies conducted with cephalopods can be used to explore neurocytology, electrophysiology and biophysics, and can also be used to shed light on the molecular basis of some degenerative diseases and neuromuscular disorders.
Many different cephalopods are commonly used as model organisms in efforts to better understand the development and mechanisms underlying the human eye. The coleoid eye (found in octopus, squid, and cuttlefish) is ideal for comparison because of its similar structure and its ability to produce a sharp and focused image on the retina. Better understanding coleoid eye development in embryos and hatchlings is important because it has the potential to help solve human genetic sight disorders that are present at birth.
Own your own Bobtail
If you would like to be the owner of one of these cute model organisms, contact Wet Pets Hawaii. They are a great addition to any saltwater aquarium, but they usually spend most of their time buried in the sand.
For more information on cephalopod development:
See Effects of Temperature on Early Stage Development of L. vulgaris, a synopsis of a study done on the deleterious effects of future global warming scenarios on embryonic growth and survival.
1. “43 Of The Extremely Creative Wonders Of Macro Photography.” Free and Useful Online Resources for Designers and Developers. Web. 01 May 2011. http://www.smashingapps.com/2008/12/16/43-of-the-extremely-creative-wonders-of-macro-photography.html.
2. Lee, P., McFall-Ngai, M., Callaerts, P., & de Couet, H. G. (2009). 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 of Cephalopods. Emerging Model Organisms, 45, n/a.
3. Wet Pets Hawaii. Web. 01 May 2011. http://www.wetpetshawaii.com/.
4. “YouTube – Behaviour of Bobtail Squid.” YouTube – Broadcast Yourself. Web. 01 May 2011. http://www.youtube.com/watch?v=M7CibTksgK8.