Showing 3601 - 3610 of 5708 Items
Molecules and fossils reveal punctuated diversification in Caribbean "faviid" corals
Date: 2012-08-27
Creator: Sonja A. Schwartz, Ann F. Budd, David B. Carlon
Access: Open access
- Background: Even with well-known sampling biases, the fossil record is key to understanding macro-evolutionary patterns. During the Miocene to Pleistocene in the Caribbean Sea, the fossil record of scleractinian corals shows a remarkable period of rapid diversification followed by massive extinction. Here we combine a time-calibrated molecular phylogeny based on three nuclear introns with an updated fossil stratigraphy to examine patterns of radiation and extinction in Caribbean corals within the traditional family Faviidae. Results: Concatenated phylogenetic analysis showed most species of Caribbean faviids were monophyletic, with the exception of two Manicina species. The time-calibrated tree revealed the stem group originated around the closure of the Tethys Sea (17.0 Ma), while the genus Manicina diversified during the Late Miocene (8.20 Ma), when increased sedimentation and productivity may have favored free-living, heterotrophic species. Reef and shallow water specialists, represented by Diploria and Favia, originate at the beginning of the Pliocene (5 - 6 Ma) as the Isthmus of Panama shoaled and regional productivity declined. Conclusions: Later origination of the stem group than predicted from the fossil record corroborates the hypothesis of morphological convergence in Diploria and Favia genera. Our data support the rapid evolution of morphological and life-history traits among faviid corals that can be linked to Mio-Pliocene environmental changes. © 2012 Schwartz et al.; licensee BioMed Central Ltd.
Inter-animal variability in the effects of C-type allatostatin on the cardiac neuromuscular system in the lobster Homarus americanus
Date: 2012-07-01
Creator: Teerawat Wiwatpanit, Brian Powers, Patsy S. Dickinson
Access: Open access
- Although the global effects of many modulators on pattern generators are relatively consistent among preparations, modulators can induce different alterations in different preparations. We examined the mechanisms that underlie such variability in the modulatory effects of the peptide C-type allatostatin (C-AST; pQIRYHQCYFNPISCF) on the cardiac neuromuscular system of the lobster Homarus americanus. Perfusion of C-AST through the semi-intact heart consistently decreased the frequency of ongoing contractions. However, the effect of C-AST on contraction amplitude varied between preparations, decreasing in some preparations and increasing in others. To investigate this variable effect, we examined the effects of C-AST both peripherally and centrally. When contractions of the myocardium were elicited by controlled stimuli, C-AST did not alter heart contraction at the periphery (myocardium or neuromuscular junction) in any hearts. However, when applied either to the semi-intact heart or to the cardiac ganglion (CG) isolated from hearts that responded to C-AST with increased contraction force, C-AST increased both motor neuron burst duration and the number of spikes per burst by about 25%. In contrast, CG output was increased only marginally in hearts that responded to C-AST with a decrease in contraction amplitude, suggesting that the decrease in amplitude in those preparations resulted from decreased peripheral facilitation. Our data suggest that the differential effects of a single peptide on the cardiac neuromuscular system are due solely to differential effects of the peptide on the pattern generator; the extent to which the peptide induces increased burst duration is crucial in determining its overall effect on the system. © 2012. Published by The Company of Biologists Ltd.
Developmental Gene Discovery in a Hemimetabolous Insect: De Novo Assembly and Annotation of a Transcriptome for the Cricket Gryllus bimaculatus
Date: 2013-05-06
Creator: Victor Zeng, Ben Ewen-Campen, Hadley W. Horch, Siegfried Roth, Taro, Mito, Cassandra G. Extavour
Access: Open access
- Most genomic resources available for insects represent the Holometabola, which are insects that undergo complete metamorphosis like beetles and flies. In contrast, the Hemimetabola (direct developing insects), representing the basal branches of the insect tree, have very few genomic resources. We have therefore created a large and publicly available transcriptome for the hemimetabolous insect Gryllus bimaculatus (cricket), a well-developed laboratory model organism whose potential for functional genetic experiments is currently limited by the absence of genomic resources. cDNA was prepared using mRNA obtained from adult ovaries containing all stages of oogenesis, and from embryo samples on each day of embryogenesis. Using 454 Titanium pyrosequencing, we sequenced over four million raw reads, and assembled them into 21,512 isotigs (predicted transcripts) and 120,805 singletons with an average coverage per base pair of 51.3. We annotated the transcriptome manually for over 400 conserved genes involved in embryonic patterning, gametogenesis, and signaling pathways. BLAST comparison of the transcriptome against the NCBI non-redundant protein database (nr) identified significant similarity to nr sequences for 55.5% of transcriptome sequences, and suggested that the transcriptome may contain 19,874 unique transcripts. For predicted transcripts without significant similarity to known sequences, we assessed their similarity to other orthopteran sequences, and determined that these transcripts contain recognizable protein domains, largely of unknown function. We created a searchable, web-based database to allow public access to all raw, assembled and annotated data. This database is to our knowledge the largest de novo assembled and annotated transcriptome resource available for any hemimetabolous insect. We therefore anticipate that these data will contribute significantly to more effective and higher-throughput deployment of molecular analysis tools in Gryllus. © 2013 Zeng et al.
Bowdoin College Catalogue (1976-1977)
Date: 1977-01-01
Access: Open access
- Bowdoin College Bulletin no. 402
Interview with JoAnn Chrisman (Class of 1973) by Ben Bousquet
Date: 2018-06-01
Creator: JoAnn Chrisman
Access: Open access
- In this interview, JoAnn Chrisman (Class of 1973) discusses her experience as one of the first women to attend Bowdoin College. She explores her decision to transfer from Scripps College in California, the reactions of students to women enrollment, and her time as a social member of the Delta Kappa Epsilon fraternity. Chrisman also describes her favorite activities, on-campus job in the Rare Books Room of the library, and how the skills she gained as a history major aided her in her corporate career.
Interview with Abdullah Muhammad (Class of 1973) by Ben Bousquet
Date: 2018-06-01
Creator: Abdullah Muhammad
Access: Open access
- Abdullah Muhammad (Class of 1973) discusses his decision to attend Bowdoin, his on-campus activism, and his involvement with the John Brown Russwurm African American Center. He describes his role as the creator of the Center’s library, as well as his broader position as the Center’s house manager. Muhammad also recounts a specific instance of protest, which occurred in response to the College’s administration reneging on their promise to ensure that at least 10% of an admitted class was African American. He tells of how his passion for activism inspired his studies in government and English, and finishes with several pieces of advice for current and future Bowdoin students.
Interview with David Anderson (Class of 1955) and Phoebe Girard by Ben Bousquet
Date: 2018-06-01
Creator: David Anderson, Phoebe Girard
Access: Open access
- In this interview, David Anderson (Class of 1955) talks about his decision to attend Bowdoin, favorite campus traditions, and how Bowdoin helped him post-graduation. He reminisces about his days as a Psi Upsilon pledge and member, and describes his involvement with The Bowdoin Orient. Anderson emphasizes how Bowdoin and the connections he made during his years as a student opened the doors to opportunities after graduation, including working for Congressmen Lud Ashley of Ohio and Henry Reuss of Wisconsin.
Interview with Jon Fuller (Class of 1968) and Beverly Fuller by Ben Bousquet
Date: 2018-06-02
Creator: Jon Fuller, Beverly Fuller
Access: Open access
- Jon Fuller (Class of 1968) speaks of himself and his great-grandfather, Arthur Taylor Parker, class of 1876. He describes two items that he donated to the Bowdoin Special collections and Archives: Parker’s diploma, bearing then-president Joshua Chamberlain’s signature, and a Class of 1876 ivory-handled cane. He also discusses his own experience transitioning from a small, rural town to Bowdoin, meeting people of different backgrounds, and mentions his involvement with the Psi Upsilon fraternity.
Interview with Nancy Prince (Class of 1974) by Meagan Doyle
Date: 2019-05-31
Creator: Nancy Prince
Access: Open access
- Nancy Prince (Class of 1974) shares her long-held desire to follow in her family’s footsteps and attend Bowdoin. Her goal was realized when she came to Bowdoin as part of an exchange program and then transferred. She reflects on the pressure and difficulties of being one of only a handful of women on campus. She discusses her study of English and Studio Art and the important spaces and places on campus where she pursued these passions. Describing her extracurricular activities, Prince speaks about photography, the Orient, leisure time with her close friends, and editing the yearbook.