Banana Slug Genomics

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All About Banana Slugs April 1, 2015


**Guest Lecturers: John Pearse and Jan Leonard**


**Slug Overview**

**Habitat**

Wide range of habitats: conifer forests, open woodlands, dry-land springs, coastal ice plants


**Diet**

Lab: lettuce, yams, hamburger, milk, cat food

Field: mushrooms, plants, seem to prefer animal feces


**Color**

Different species have different colors, but colors are not species specific

Not sure why they have their color

 
**Predators**

Garter snakes, birds

No main predator in particular

Their slime serves as a protection against predation



**Distribution**

Found along Pacific Coast line

5 major clades seem to have geographical specific ranges with little overlap

Similar distribution as salamanders



**Slug Taxonomy**

mtDNA doesn’t separate our local Meadarion species, but they are known to differ based on social cues, egg size and morphology

2 subgenera based on penis morphology

1)    Meadarion with epiphallus A.(A.)

2)    Ariolomax with no epiphallus and thin-walled apical end of penis A.(M.)

5 clades in the genus: 2 within columbianus (A.(A.) columbianus and A.(A.) buttoni), A.(A.)  stramineus, a 4th clade in San Diego County that is as of yet undescribed, and 5th clade (Meadarion) comprising of at least 4 subclades (A. (M.) californicus, A. (M.) brachyphallus, A.(M.)  dolicophallus and a 4th undescribed species found in Fremont Peak)

Further molecular taxonomy only performed with three genes CO1-16S-CytB






**Slug Sex: The Basics**

Simultaneous hermaphrodites; can’t distinguish sex until dissection

Complex mating behavior with apophallation at times

Copulate: internal fertilization, either simultaneous or alternating copulation

Eggs are laid underground, take 1-2months to develop, requires humid envirnoment to protect from dessication

Hatch as small individuals

Same reproductive system as all terrestrial gastropods



**Slug Sex Behavior: Apophallation**

During copulation, penis of one and/or both slugs is bit off, this process is termed apophallation

Penis does not regenerate, but slug continue its sex life as a "female" or "male" (incomplete apophallation)

Does not occur until copulation has occurred for an extended period of time already

Unknown if has effect on mating behavior/preference thereafter

Apophallation rarely occurs (~5% observed by Jan Leonard), only seen in A. (M.) californicus and A. (M.) dolichophallus species in Meadarion subgenera

Species differ in courtship and copulation behavior: A. (M.) californicus have longest courtship, A. (M.) dolicophallus have longest intromession, and A. (M.) bracyphallus display penile loop (distinguishing feature observed initially by Mead in 1943)

Other phallus polymorphisms (developmental) are very common among gastropods and can associate with a certain environmental signal (eg. increased water temperatures)

 



**Goal of Sequencing Project**

Assemble and compare slug genomes to identify genes related to their rapid evolution of sexual phenotypes:

Genital morphology

Sexual behavior

Pally polymoprhism

Egg size

Species recognition molecules

Self-fertilization



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Banana Slug Genomics

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