Morphogenesis and motility of the Astyanax mexicanus gastrointestinal tract

Damen

Aspiras

et al. 2019

Preprint

Self Cite

The gastrointestinal tract has evolved in numerous ways to allow animals to optimally assimilate energy from different food sources. The morphology and physiology of the gut is plastic and can be greatly altered by diet in some animals. In this study, we investigate the evolution and plasticity of gastrointestinal tract morphology by comparing laboratory raised cave-adapted and river-adapted forms of the Mexican tetra, Astyanax mexicanus reared under different dietary conditions. In the wild, river-dwelling populations (surface fish) consume plants and insects throughout the year, while cavedwelling populations (cavefish) live in a perpetually-dark environment dependent on nutrient-poor food brought in by bats or seasonal floods. We find that multiple cave populations converged on a reduced number of digestive appendages called pyloric caeca and that some cave populations have a lengthened gut while others have a shortened gut.Moreover, we identified differences in how gut morphology and proliferation of the epithelium respond to diet between surface fish and cavefish. Using a combination of quantitative genetic mapping, population genetics, and RNA sequencing we implicate molecular and genetic changes influencing cell proliferation, cell signaling, and immune system function in the evolution of gut morphology.

Section: Discussionmentioning

confidence: 65%

Evolution of gastrointestinal tract morphology and plasticity in cave-adapted Mexican tetra, Astyanax mexicanus

Damen

Aspiras

et al. 2019

Preprint

Self Cite

“…Morphological changes to the gut could influence carotenoid accumulation by altering digestion or absorption. For example, Pachón cavefish have altered gut motility at post-larval stages that results in slower transit of food; an adaptation that could increase nutrient absorption (Riddle, Boesmans, Caballero, Kazwiny, & Tabin, 2018). We found that length of the gut is not linked with fat color in surface/Tinaja F2 hybrids, however we identified a candidate gene that could influence development of intestinal cell types: DTX2.…”

Section: Discussionmentioning

confidence: 70%

Genetic architecture underlying changes in carotenoid accumulation during the evolution of the Blind Mexican cavefish,Astyanax mexicanus

Aspiras

Damen

et al. 2019

Preprint

Self Cite

Research Highlights• Cavefish accumulate carotenoids in the visceral adipose tissue (VAT)• Genetic mapping reveals candidate genes associated with yellow VAT • Carotenoid accumulation is linked with decreased expression of carotenoidprocessing genes AbstractCarotenoids are yellow to orange pigments produced by plants, bacteria, and fungi. They are consumed by animals and metabolized to produce molecules essential for gene regulation, vision, and pigmentation. Cave animals represent an interesting opportunity to understand how carotenoid utilization evolves. Caves are devoid of light, eliminating primary production of energy through photosynthesis and therefore limiting carotenoid availability. Moreover, the selective pressures that favor carotenoid-based traits, like pigmentation and vision, are relaxed. Astyanax mexicanus is a species of fish with riveradapted (surface) and multiple cave-adapted populations (i.e. Tinaja, Pachón, Molino).Cavefish exhibit regressive features such as loss of eyes and melanin pigment, and constructive traits, like increased sensory neuromasts and starvation resistance. Here we show that unlike surface fish, Tinaja and Pachón cavefish accumulate carotenoids in the visceral adipose tissue (VAT). Carotenoid accumulation is not observed in Molino cavefish indicating that it is not an obligatory consequence of eye loss. We used quantitative trait loci mapping and RNA sequencing to investigate genetic changes associated with this trait.Our findings suggest that multiple stages of carotenoid processing may be altered in cavefish, including absorption and transport of lipids, cleavage of carotenoids into unpigmented molecules, and differential development of intestinal cell types involved in carotenoid assimilation. Our study establishes A. mexicanus as a model to study the genetic basis of natural variation in carotenoid accumulation and how it impacts physiology.

“…The fluorescent signal is only visible in the fish incubated with primary antibody. We have used this protocol to successfully label neurons 10 (Figure 1) and pancreatic cells 6 at stages up to 12.5 dpf in both surface and cave morphotypes.…”

Section: Representative Resultsmentioning

confidence: 99%

“…Rotifers are much smaller than Artmeia nauplii (160 vs. 400 microns), making them easier for the fish to capture and swallow. Post-larval surface fish and cavefish consume rotifers in similar quantities suggesting no difference in preference or ability to capture the rotifers 10 .…”

Section: Discussionmentioning

confidence: 98%

“…The Mexican tetra, Astyanax mexicanus, is a single species of fish that exists as river-dwelling populations (surface fish) and a number of cave-dwelling populations (cavefish) named for the caves they inhabit ( i.e., Tinaja, Molino, Pachón). A growing number of researchers are using A. mexicanus to investigate the genetic and developmental bases of behavioral 1,2,3,4 , metabolic 5,6,7,8 , and morphological evolution 9,10,11 . Available resources for studies of A. mexicanus include a sequenced and annotated genome 12 ; transcriptome 13 ; developmental staging table 14 ; and methods for breeding 15,16,17 , creating transgenics 18 , and editing genes 19 .…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Raising the Mexican Tetra <em>Astyanax mexicanus</em> for Analysis of Post-larval Phenotypes and Whole-mount Immunohistochemistry

Martineau

Peavey

et al. 2018

JoVE

River and cave-adapted populations of Astyanax mexicanus show differences in morphology, physiology, and behavior. Research focused on comparing adult forms has revealed the genetic basis of some of these differences. Less is known about how the populations differ at post-larval stages (at the onset of feeding). Such studies may provide insight into how cavefish survive through adulthood in their natural environment. Methods for comparing post-larval development in the laboratory require standardized aquaculture and feeding regimes. Here we describe how to raise fish on a diet of nutrient-rich rotifers in non-recirculating water for up to two-weeks post fertilization. We demonstrate how to collect post-larval fish from this nursery system and perform whole-mount immunostaining. Immunostaining is an attractive alternative to transgene expression analysis for investigating development and gene function in A. mexicanus. The nursery method can also be used as a standard protocol for establishing density-matched populations for growth into adults.