User Tools

Site Tools


lecture_notes:04-23-2010

Differences

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]
svasili
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://​compbio.soe.ucsc.edu/​slugGenome/​|http://​compbio.soe.ucsc.edu/​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 
 +them. 
 + 
 +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 
 +species. 
 + 
 +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 
 +columbianus.//​ 
 + 
 + 
 +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 
 +session. 
 + 
 +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