User Tools

Site Tools



This shows you the differences between two versions of the page.

Link to this comparison view

Both sides previous revision Previous revision
Next revision
Previous revision
lecture_notes:04-23-2010 [2010/04/26 11:18]
lecture_notes:04-23-2010 [2010/05/01 09:00] (current)
jlong Link to Slides of John and Jan
Line 17: Line 17:
 ====== Slides ====== ====== Slides ======
-Jeffrey Long has slides from Janet Leonard ​and he will be uploading them.\\+The slides from the presentation of John and Janet can be dowloaded here,​[[http://​​slugGenome/​|http://​​slugGenome/​]] ​.\\
-  ​+====== Additional notes ====== 
 +//​Additional notes from Jonathan follow.// 
 +===== John Pearse talk ===== 
 +John originally worked with sea urchins and sea stars primarily. 
 +Janet joined the lab about twelve years ago to study marine slugs. 
 +She was interested in hermaphrodite mating behavior. ​ Banana slugs'​ 
 +rare behavior of apophallation became a research focus. ​ No one had 
 +really studied banana slugs [academically] since the forties. ​ Alice 
 +Bryant Harper (Aptos naturalist, works with Santa Cruz Museum of 
 +Natural History) wrote __The Banana Slug__ (1988), the best book on 
 +Despite Chancellor Sinsheimer'​s desire to keep the sea lion as the 
 +UCSC mascot, students voted 95% for the banana slug. 
 +There are just two complete mollusc genomes, [California sea hare and 
 +giant owl limpet], and neither are very complete. 
 +Banana slugs habitat is very diverse. ​ Though often found in conifer 
 +forests and considered an animal of the Northwest (first found in 
 +Washington or Oregon), they'​ve been found in drier habitats: San 
 +Diego, Napa's McLaughlin Reserve (by small springs), abandoned rice 
 +patties in the Sacramento River Delta, oceanside iceplants in Pacific 
 +Grove. ​ High variation in the numbers you'll see on any day/site: none 
 +or dozens. 
 +They eat feces, hemlock, poison oak, mushrooms (reported but 
 +John has not seen), sorrel, ferns, ice plants, humus soil.  In the lab 
 +they eat hamburger, cat food, apples, beans, zucchini, mushrooms,​ 
 +yams, lettuce and milk. 
 +Colors may camouflage them, //e.g.// dead leaves often turn bright 
 +yellow, the color of species in Santa Cruz and the SF Bay area.  In 
 +other areas you'll find spotted slugs -- but they may be a different 
 +There predators may include [seemed uncertain] garter snakes, 
 +salamanders and newts, birds and some small mammals. ​ It is possible 
 +that some specific carnivorous snails and slugs eat banana slugs. 
 +//​Aphallarion buttoni// originally thought to be a different species 
 +because no penes were found when dissected (late 19th century). 
 +However, a Stanford professor later found some with penes and so sent 
 +students into the field to study. ​ They observed apophallation. ​ That 
 +was the end of //buttoni// as a separate taxon. ​ It became //​Ariolimax 
 +All banana slugs have an opening on the right side of the "​head"​ for 
 +defecation, breathing, and copulation. The only way to distinguish 
 +species is by dissection of the genitalia. ​ [See slide *//​Ariolimax 
 +Arilimax columbians//​ genitalia* for overview of genitalia.] ​ The 
 +gonad has a mix of testes and ovaries, and they can play both roles at 
 +same time curing copulation. ​ How is sperm kept separate during 
 +copulation? ​ It is not necessarily. ​ They can fertilize themselves. 
 +And aphalon are born without a penis [sometimes?​]. 
 +//Ariolimax Meadarion californicus//​ is found in San Mateo county. 
 +Santa Cruz has //​dolichophallus//​. ​ [See slide comparing their 
 +genitalia.] ​ Mead thoought //​dolichophallus//​ and //​californicus//​ 
 +were sufficiently different to be a separate species. 
 +A collaborator in Belgium has been sequencing banana slug 
 +mitochrondrial DNA.  They see at least five clades but cannot yet 
 +connect them.  ~"​Morphologically distinct and molecularly distinct are 
 +not the same thing." ​ [See slide.] 
 +Interestingly the distribution of the salamander genus //Ensatia// is 
 +similar to that of banana slug [//​dolichophallus//?​ -- see slide]. ​ Is 
 +this a remnant of five million years ago when there were islands in 
 +the Monterey Bay?  Morphologically distinct but molecularly 
 +[mito. DNA] indistict suggests recent change. 
 +===== Janet Leonard talk ===== 
 +Janet'​s interest is in sex selection. ​ Eberhard'​s hypothesis: [That we 
 +can ] classif[y] based on genitalia (as done with insects, spiders, 
 +//etc.//) suggests the importance of sex selection. ​ Genitalia 
 +differences in nearby counties are not explicable by natural 
 +selection, //e.g.// how would NS explain [improved fitness by a 
 +different vaginal muscle in the same geographical area.] 
 +The talk focused on courtship behavior: ​ much effort/​expense in banana slug mating. 
 +//Ariolimax stramineus//​ courtship: antiparallel alignment of slugs is 
 +standard. ​ They line up right sides of their heads until the alignment 
 +allows copulation. ​ The first copulation takes place in about twenty 
 +minutes with subsequent occuring over about two hours. ​ No apophallation in the 
 +one shown on film. 
 +Mating film for //​brachyphallus//:​ This is one of the three under 
 +//Ariolimax Meadarian//​. ​ Note the initial biting and head swinging 
 +which seem to cause no damage. ​ The biting helps line up the head 
 +regions. ​ Banana slugs cannot reverse so the cirlcing helps get them 
 +get into position for mating. 
 +Mating film for //​californicus//:​ Unilateral copulation (after two hours 
 +biting, head swinging). ​ It is hard to tell which plays the role of 
 +male and female but Janet thinks they alternate over a copulation 
 +Mating film for //​dolicophallus//:​ Example of apophallation (by the 
 +first to withdraw). ​ How costly is this for a hermaphrodite? ​ It is 
 +pretty rare: 5 out of 100 copulations end in apophallation. 
 +Why does apophallation occur and when?  They have observed it only nine 
 +times and never by virgins. ​ Is it done as retaliation if one partner does not give 
 +any sperm? ​ Do they run out, and perhaps later in life focus on egg laying? 
 +Note in the table comparing copulations that //​dolicophallus//​ and 
 +//​californicus//​ are indistinguishable by mitochondrial DNA. 
 +The rapid morphological changes are among the evidence for sex 
 +selection, as well as the high cost of courtship/​mating. ​ There is 
 +some evidence for sperm competition. 
 +Soon we should have based on microsatellite data (nuclear DNA) ... 
 +It is unknown how many chromosomes they have, though chromosome 
 +variation is usually not seen till "quite high" taxonomic levels. 
 +Their egg laying habits in the field are uncertain. ​ Perhaps under 
 +leaflitter. ​ They do not dig holes in moist soil like garden 
 +snails. In the lab at 19^C, they take seven weeks to hatch, 
 +sometimes two to three weeks longer. ​ The record for a clutch is 
 +seventy-five eggs (but this could have been multiple clutches since 
 +they don't check every day).  Egg size varies. ​ //​Dollicophallus//​ 
 +eggs are almost the size of jellybelly and weigh up to half a gram. 
 +For //​californicus//​ they'​re usually under 0.3g. 
 +Egg laying starts in fall and copulation is associated with foggy 
 +nights (late summer, Santa Cruz). ​ Eggs are laid October through 
 +December when the rains come and usually finished by February. 
 +Hypothesis: Low pressure systems trigger egg laying. ​ (This is based 
 +on lab observations,​ and makes sense since dehydration is the highest 
 +mortality source. ​ You want to lay eggs at the start of the rainy season 
 +in a moist place.) 
 +They have observed copulation for slugs as young as six months and egg 
 +laying as young as ten. 
 +How long do they live?  No one knows but perhaps two to three years. 
 +Some have lived thirty months in the lab (when sacrificed).
lecture_notes/04-23-2010.1272305918.txt.gz · Last modified: 2010/04/26 11:18 by svasili