Biological Sciences
Presenter(s): Luke Arnold
Advisor(s): Dr. Douglas Fudge
Hagfishes are elongate, eel-shaped marine organisms notorious for their ability to produce large volumes of slime as a defense mechanism against predators. They are commonly found in the depths of the ocean, where they act as scavengers. Hagfishes have been known to squeeze through tight spaces and burrow in a variety of substrates, including sand, mud, and large animal carcasses, but the mechanisms of hagfish burrowing have not been widely researched. In this project, we studied the behaviors of the Atlantic hagfish (Myxine glutinosa) burrowing in sand. This was accomplished by studying an Atlantic hagfish in a tank partially filled with sand and artificial sea water (ASW), filming with a mounted camera. Videos were used for kinematic analysis of tailbeat frequency and behavioral patterns. It was found that Atlantic hagfish sand burrowing occurs in two sequential phases: the first phase began with the hagfish entering the substrate head-first, followed by lateral tail beating that decreased in frequency along with rotational movements of the body. This persisted until the hagfish was partially submerged in the sand; the second phase began with a gradual lurching where the body would enter the substrate in a saltatory pattern over a longer period of time. These findings are significant within the context of vertebrate evolution as well as bettering our understanding of the diversity of Atlantic hagfish locomotor behaviors. A biphasic burrowing strategy has also been noted in burrowing and sand diving Osteichthyes indicating that the lack of a vertebral column and the presence of an elongate body form of hagfishes does not impede, and may even functionally enhance, the burrowing lifestyle of myxinids.
Intra and Interspecific Skein Scaling in Hagfish
Presenter(s): Skylar Petrichko, Kristen Nieders
Advisor(s): Dr. Douglas Fudge, Yu Zeng
Hagfishes are bottom-dwelling creatures that are known for their defensive slime. Slime is composed of thread cells that coil into an organized structure, or “skein”, and reside within specialized cells known as gland thread cells. In most organisms, cell size is independent of body size. This means that the cell size of an organism remains fixed as body size and body proportions change. However, skeins function outside of the hagfish, which raises the question of whether the evolutionary and biophysical constraints that keep cell size constant also apply to thread skeins. One study found that the average skein is smaller in glands that were in the process of refilling than in full glands. Here, we analyzed skein size over a range of body sizes in nine different hagfish species to understand whether larger hagfishes possess larger thread skeins. Specifically, we recorded the length, mass, and girth of individual hagfish. We also collected slime exudate from full glands on the right side, posterior to the gill and measured the skein length and width. Our preliminary results suggest that skein size is conserved within and across a species, i.e. it is independent of body size. However, the variation of skein size relative to other cells across species hint that these evolutionary and biophysical constraints may be more relaxed.
How Does Hagfish Slime Clog so Efficiently?
Presenter(s): Luke Taylor
Advisor(s): Dr. Douglas Fudge, Gaurav Jain
Hagfish slime consists primarily of mucus vesicles and protein-based threads, which come packaged in coiled structures known as skeins. Much is understood about the structure and function of the thread skeins, but little is known about the nature of the mucus component. The purpose of this research is to better understand the structure of hagfish mucus and the mechanism behind its capacity to retain remarkable quantities of water. Hagfish slime has also been shown to act as a defense mechanism by clogging the gills of gill-breathing predators and hindering the flow of water. Our current field of research focuses on the entrapment of water molecules between mucin threads within the hagfish mucus. Mucins are large glycoproteins that potentially trap water molecules through hydrophobic interactions and disulfide bonding. A previous study has shown that mixing is necessary for expansion of the whole slime, but also leads to its collapse. It is unclear whether the results from this study are caused by the mucus component, skein component, or both. To better understand the contribution of mucus, we conducted mixing trials that modeled the previous study using pure mucus only. We used quantitative drain rate measurements and varied mucus mixing times to better understand the role mucus plays in the expansion and collapse of the whole slime.
Scaling of Skeins in Hagfish
Presenter(s): Kristen Nieders, Skylar Petrichko
Advisor(s): Dr. Douglas Fudge, Yu Zeng
Hagfish are benthic scavengers that produce slime as a defense mechanism against predators by clogging their gills. The unique properties of this slime are mainly attributed to the silk-like threads produced by cells in the slime gland. These threads are coiled and stored in ellipsoid shaped “skeins” that reside in gland thread cells. Since the function of a skein is to be ejected from the hagfish, it has been hypothesized that size of skeins is not conserved across organisms as evolutionary and biophysical constraints may not apply to cells ejected from the body. Preliminary investigations have revealed skein size may still be conserved within hagfish however, there is still much variation in skein size. Additional studies have found that the average skein is smaller in glands that are in the process of refilling with less mature skeins than in full glands with mature skeins. To better understand this evident variation of skein sizes in hagfish we investigated how thread diameter varies with skein size by measuring the thread diameter and skein length. Initial findings have shown that as skein size increased, the thread diameter increased as well in a positive linear fashion.
Apple Transcriptome Responses to Irradiation Treatment and Cold Storage
Presenter(s): Makayla Gallimore, Francisco Ernesto Loayza Davila, Matthew Garcia
Advisor(s): Dr. Hagop S. Atamian, Dr. Anuradha Prakash
Harvested apples often get stored under cold refrigeration for months before they are released into the market. During this prolonged storage, apples are vulnerable to physiological disorders as well as fungal fruit decay and various pests. Irradiation is commonly used for phytosanitary purposes before storage to kill some of the most destructive apple pests such as Oriental fruit moth, codling moth, fruit flies, and light brown apple moth. According to the recent findings from Prakash lab, irradiation was shown to be very effective in mitigating the superficial scald incidence in stored “Granny Smith” apples. Superficial scald is a very common physiological disorder in stored apples characterized by skin browning, which can lead to product waste due to decrease in shelf-life and consumers’ unwillingness to purchase defective apples. The objective of this project is to investigate the overall apple transcriptome changes due to irradiation and possibly explain the molecular mechanisms underlying the irradiation-mediated protection of apples against superficial scald. Apple peels were collected from irradiated and control apples on day zero and after 90 days of refrigeration. Total RNA was extracted from three biological replicates per treatment and RNA-Seq libraries were constructed. The libraries were pooled together and subjected to 150 bp single-end sequencing on Illumina HiSeq4000 machine. A total of 582 million high quality reads were mapped to the apple genome and differential gene expression analysis was conducted. Compared to 90 day stored control apples, the irradiated and 90 day stored apples showed 1,182 differentially expressed genes. Our results will provide the first step towards understanding the molecular responses in apples to irradiation treatment.
Identification of Genes Involved in Chia PAMP-Triggered Immune Responses
Presenter(s): Cailyn Sakurai
Advisor(s): Dr. Hagop S. Atamian
Salvia hispanica (commonly known as chia) is a re-emerging crop that belongs to the mint family (Lamiaceae). Chia is gaining popularity worldwide as a healthy food supplement. Chia seed contains 34.4% total dietary fiber, 31% total lipids, 16% protein, 5.8% moisture, and high amounts (335–860 mg/100 g) of calcium, phosphorus, potassium, and magnesium. Chia is gaining popularity both nationally and internationally. The US import of chia seeds increased 7.5 times since 2011. With an estimated annual import of 15,000 tons, USA is the largest market for chia. With the expected increase in chia seed demand, the crop will be planted worldwide and consequently will be exposed to diseases and insect pests that cause economic losses in agricultural crops. However, being a re-emerging crop, nothing is known about chia immune responses to plant pathogens. Plant immune system is divided into main branches. The first line of immune responses is triggered by plant cell receptors that recognize pathogen associated molecular patterns (PAMPs), signatures that are widely conserved among certain pathogen clades such as bacterial flagellin. This is known as PAMP-triggered immunity. The second plant immune response is stronger and more specific and is triggered upon recognition of pathogen effectors by specialized plant receptors called resistance (R) genes. The objective of this project is to identify the genes involved PAMP-triggered immune responses in chia. Chia seeds were germinated on nutrient media for two weeks. The seedlings were floated on water overnight and subjected to bacterial flagellin for one hour. As control, similar number of seedlings were subjected to distilled water. RNA was extracted and sequenced using the Illumina high throughput sequencing platform. We expect to find an increase in the expression of hundreds of genes that play important roles in the chia PAMP-triggered immunity. Our study will identify the repertoire of chia genes involved in the first line of defense against pathogen infection.