Response to peer review / Feb. 23

Dear reviewer:


You are correct in desiring for a more elaborate reason as to why further studies are needed for understand snail body mass increases. I did mention that our tests had insufficient variation to determine a solid conclusion. Just looking a difference in close proximity locations may not be a good as a sole reason.

Chances are very likely that food and water composition are not the only factors for size alterations. Predatory attacks also are a large component to as to how a snail will or will not gain body mass. The body mass also needs to be looked at to determine whether it is the shell or the soft tissue that is gaining in mass. Shells increase for several reasons including abundance of food and lack of predations. Soft tissues increase due to abundance of food, and adaption to current flows where stronger muscle attachment is a consideration.

Should you find an studies that relate further to current flow issues, do let me know. Thank you.

Part II response / Feb. 22

The three people who reviewed my paper seemed to feel that points were clear, although the discussion needed more development. With the option of reflection of what other potential issues might be for snail total mass changes, I explored other texts that had tested variables that could affect snail mass. This helped for me to articulate the basis thoughts that I had about this.

Although it seems like there is excessive citing, all were from authors who had performed experiments that were helpful to draw upon in conclusion. Four more citing were used from prior experiments to substantiate my views.

Revised t-test caption per Price request

Table 1. Nucella lamellosa.

Differences in total body mass by the gastropod for 3 different treatments,

in a submerged water temperature of 13°C for 24 days.

All error bars represent 1 SD.

Scale measurements/ Feb. 22

Variables are characteristics of a group of objects or events that can be measured over a number of different numerical values.

In science only one variable is often changed. There is an independent and a dependent variable. If there were no change, there wouldn't be a response by the dependent variable.

Continuous - is quantitative / Categorical - is not quantitative

Discuss how to discuss in a paper / Feb 15th

To define what belongs in the results vs. what belongs in the discussion. The results is the report in miniature. This is the data. Examples phrases: …the analysis revealed…does not rule out…the test indicates…seems likely…in contrast…it is highly probable…

Results have:

· Pure numbers—raw data/facts (1,2,5,3,7) and statistical conclusions (mean=4, std error, p-value, etc.). This info goes into the tables (requires column and row headings, title (above the table). Example, “No difference was found between the 2 means (p-0.48, t-test).”

· Graphs illustrate raw data and statistical results (use captions below the figure).

· Text (report comparisons) describes but doesn’t explain data and stats.

Results don’t have:

· Comparisons to other studies—their results aren’t influenced by other researcher’s data in their field

· Context – move any context to the discussion area.

· Background info—mostly the background is inferred from the graphs

A key part in the final paper grade is making sure that information in each section is appropriate (don’t worry about the transitions between sections).

Discussion has:

· Context and no data – it’s all words explaining and interpreting

· Is subjective (as opposed to objective results)

· Conclusion: what your rejection/acceptance of your hypothesis means in the real world. Extrapolate from the specific results of your experiment to a more general question.

· Lots of reference to other scientists work looking for broader implications even if those implications weren’t tested explicitly.

· Building our case for our argument.

· No direct quotes (will deduct 5 points)

· Put in controversies to your results.

· Are you satisfied with the experiment? Admit what you might have been a better approach. What other experiments do you want to do?

Revised text on report:

Summary and conclusion

The testing performed to determine the mechanism of shell thickening indicated that there was no significant difference in shell length growth between the two groups of snails. This is probably the case because the testing was done in close proximity. Other studies have shown that growth patterns in similar levels of genetic variation exist across latitudes (Trussel, 2000)⁴. Surveys of phenotypic variation in 25 Littorina obtusata populations across an approximately 400-km latitudinal gradient in the Gulf of Maine revealed pronounced differences. The shells of snails from northern habitats weighed less and were thinner and weaker in compression than those from southern habitats. In contrast, body size (as measured by soft tissue mass) followed an opposite pattern; northern snails weighed more than southern snails (11–24% for shell mass, 13–17% for shell thickness after 115 days; Trussell). These results are consistent with the expected effects of reduced water temperature on growth (Atkinson, 1994). In addition, increased developmental sensitivity to differences in water temperature may have evolved in northern populations due to the comparably shorter growing season (Conover and Present 1990).

Future experiments that address the role of total body mass induced by food varieties and predator attacks may also help to clarify the mechanisms underlying geographic variation in shell form and body mass. There is a good probability that with studies conducted in locations further apart, and with the use of these variables snail total mass growth will be further exposed.

Library and more context / lab results

How did you set up your initial search? Snails – locality - Nucella.

How many articles did you find in this initial search: Five

What criteria did you use to determine whether an article was useful?

1. The number of citations. 2. Reading the abstracts.

"Ed" Abstract by Gary Coleman, Gary Colman Gallery

Citation #1: Biggs, P.E. 1993. Phenotypic changes in the progeny of Nucella lapillus (Gastropoda) transplanted from an exposed shore to sheltered inlets. Journal of Molluscan59: 187-194. Studies

Why is the article useful? The study was looking at shell plasticity for snails transplanted.

What’s the gap? Was there genetic mutation?

What’s the main point? The snail’s progeny differed markedly from that of their parents.

What’s the relevance? Does location matter in total snail mass depends on the site conditions.

Citation #2: Marko, Peter B. 1998. Historical allopatry and the biogeography of speciation in the prosobranch snail genus Nucella. Evolution 52.n3: 757-785.

Why is the article useful? The study was looking at the colonization of dispersal events based on geographic shell sculpture.

What’s the gap? Why did the species recently migrate?

What’s the main point? Climatic vicariance likely plays important roles in determining geographic patterns.

What’s the relevance? Does location matter in total snail mass depend on gene flow, mutation, selection, and drift causing characteristic signatures.

Citation #3: Rolan, E; Guerra-Varela, J.; Colson, I.; Hughes, R.N.; Rolan-Alvarrez, E. 2004. Morphological and genetic analysis of two sympatric morphs of the dogwhelk Nucella Lapillus (Gastropoda: Muricidae) from Galicia (Northwestern Spain). The Malacological Society of London: J. Moll. Stud. 70: 179-185.

Why is the article useful? The study was looking at morphological differentiation due to different degrees of exposure from different localities.

What’s the gap? The relative contributions of classical genetic variation and phenotypic plasticity to variation in shell morphology remains unknown.

What’s the main point? Ecotypes adapted to contrasted habitats.

What’s the relevance? There was a large difference in shell mass depending on whether the snail was exposed or sheltered, and whether they ate mussels or barnacles.

_____________________________________________________________________________

My group members are studying shell mass in relation to crab attacks, so there was no collaboration in our data searches.

My study: Will the Dogwhelk snail grow differently depending on location?

My results: The statistical null hypothesis is that there is not a significant total mass change in Nucella Lamellosa based on location, if their shelter, forging ability, and predator attacks were similar.

Cited examples discussed differences based on genetic adaption if the a new location varied from the initial locations. If there were no variation in location, the total mass change was insignificant. In my own experiment, I would be interested in fully replicating site conditions with Materials and Methods including food type, quantity, and wave pressure.