Squid Guest Lecture

Question 1

Scientific name of Hawaiian Bobtail Squid

Answer 1

Euprymna scolopes
Has a symbiosis with vibrio fischeri (bio-luminescent bacteria) by countershading
Can almost immediately match any light intensity
Live in the Hawaiian archipelago
Feed on shrimp and worms

Question 2

Bio-luminescence

Answer 2

Production of light by living organisms

Common in oceans

Question 3

Autogenic organisms

Answer 3

Produce their own light using chemicals

Question 4

Symbiotic organisms

Answer 4

Produce light by having symbiotic relationships with bacteria

Question 5

Bio-luminescence equation

Answer 5

Luciferin+O2 -> (luciferase enzyme) -> Oxyluciferan + Light

Question 6

Milky Seas

Answer 6

Huge areas of ocean glowing for sustained period of time because of symbiosis between bio-luminescent bacteria and certain fish/squid
One found 15,000 square km off coast of Africa

Question 7

Eska

Answer 7

Lure with a sac containing bio-luminescent bacteria on the head of deep sea fish used to attract prey. The bacteria produce light when they reach a high salt area

Question 8

Sepiolid squid

Answer 8

Live in the Indo West Pacific and have a relationship with vibrio bacteria

Question 9

Lux operon

Answer 9

Controls the bio-luminescence equation

RICDABE

Question 10

RICDABE

Answer 10

R - Activator
I - Synthesizes autoinducer (can diffuse freely between cells)
CDE - Substrate proteins
AB - Luciferase

Question 11

Autoinduction/Quorum sensing

Answer 11

Vibrio fischeri can “talk” to each other through an autoinducer
Positive feedback loop
Pathogenic organisms use it to turn on virulence factors when high density makes sense (ex. infecting a host)

Question 12

Ink sac anatomy

Answer 12

Epithelia that support the bacteria are embedded in a set of tissues that are similar to the ones that surround the retina of the eye
Modify outgoing light
Light emitting tissues are surrounded by diverticula of the squid’s ink sac
Reflective tissue lines the dorsal ink sac diverticula
Ventral ink sac diverticula contract/expand to allow more/less of the bacterial light out into the environment
Together, all these layers ensure that light is directed out of the animal’s ventral surface

Question 13

Counter illumination/Counter shading

Answer 13

Entire ventral surface of the light organ is covered by a muscle derived lens, which diffuses the bacterial luminescence.
Ventral part of squid glows bright to match the sky, and the dorsal part of the squid is dark to match the depths of the ocean

Question 14

Squid lifestyle

Answer 14

• Nocturnal
• At sunrise, they bury themselves into the sand, expel 95% of their bacteria into the water, and the 5% that remains is used to grow a fresh culture of vibrio fischeri

Question 15

Why do squid regrow a new vibrio fischeri culture every day?

Answer 15

• Regulates symbiosis
• Conserves resources
• Allows for baby squid to collect bacteria floating in the water after hatching so they can use it to start growing their own cultures

Question 16

How do the vibrio fischeri enter the squid?

Answer 16

Appendanges in the growing squid have cilia surrounding 3 pores which all connect to 6 crypts inside the squid. The bacteria swim down ciliated ducts and colonize the crypt space/aggregate in mucus which cause regression of the cilia. Quorum sensing kicks in and the baby squid start producing light
Live along the apical surfaces of the epithelia in the light organ

Question 17

MAMPS

Answer 17

Stand for "microbe associated molecular patterns" 
Host recognition of MAMPS: 
1. MAMPS
2. PRRs
3. Signaling cascade 
4. Effectors of the innate immune system

Question 18

How is secretion of mucus triggered?

Answer 18

It is triggered in response to bacterial peptidoglycan. It also secretes antimicrobial soup

Question 19

PRRs

Answer 19

Stand for “pattern recognition receptors” which are found in the immune cells of animals/humans. When they bind to MAMPS, they turn on signaling cascades which can turn on genes

Question 20

Juvenile hemocytes

Answer 20

Macrophage like cells that engulf microorganisms. They are the primary immune cells in squid and migrate into the light organ where they interact with the bacteria

Question 21

ANG

Answer 21

Accessory nidamental gland in female squid. They are made up of bacteria filled pigmented tubules. Microbial load is similar to the load on our skin/in our gut.
Protect eggs against fouling organisms/fungal infections by producing antifungal compounds

Question 22

Immune system of squid

Answer 22

Communicates with the symbiont and leads to tolerance of bacteria through MAMPS and PRRs

Question 23

What did the lab do with squid eggs?

Answer 23

Treated eggs with antibiotics which led to the productio n of fungal/bacterial biofilm and led to the death of all the embryos

Question 24

What bacterial fungus infected the eggs?

Answer 24

Fusarium keratoplasticum

Question 25

Light Organ

Answer 25

In the center (mantle) of the squid’s body

Question 26

How does the squid control the amount of bacterial light emitted?

Answer 26

Withholding oxygen to the Vibrio fischeri which causes them to cease bio-luminescence because they need to perform oxidation of substrates to glow