Presentation Title

Partial Hatching in the California Grunion, Leuresthes tenuis

Presentation Type

Poster

Department

Biology

Major

Biology B.S

Abstract

The California Grunion, Leuresthes tenuis,is a marine fish that is uniquely adapted to lay eggs in the sandy shore during high tides. Eggs incubate out of water in slightly moist sand between semilunar high tides before hatching is triggered by wave action. Hatchlings swim out to sea within the same wave that caused hatching, but sometimes larvae partially hatch with their egg membrane, the chorion, still on their heads. Partial hatching has not previously been defined, studied or its causes determined, but it puts grunion at an early disadvantage by hindering swimming and covering their gills. We tested environmental factors during incubation to see whether they increase the percentage of partial hatchlings. Groups of eggs were incubated in either still or aerated water (experimental) or in slightly damp sand (control) to assess effects of oxygen availability and boundary layers. Each group was held in normal (20 ℃) and elevated temperatures (30 ℃). Data analysis suggests that incubation in both aquatic conditions and in elevated temperature resulted in more frequent partial hatching. We also compared standard length and head-body ratios between hatched Grunion incubated in control and experimental conditions. Individuals incubated in water were significantly shorter with higher head-body ratios compared to those in sand. Grunion incubated in normal temperature were not significantly longer but had significantly lower head-body ratios than in elevated temperature. Results suggest that aerial incubation may be necessary for normal morphological development in Grunion and could imply effects on other aerially incubating species like Fundulus heteroclitus.

Terms

  1. Semilunar high tide: high tide caused by a new or full moon occurring every two weeks
  2. Partial hatching: a Grunion that has part of its body free from the egg and part still stuck to its chorion in some way for any amount of time
  3. Chorion: soft egg membrane covering a Grunion embryo as it develops and from which it hatches
  4. Boundary layers: layers of stagnant water that form around submerged objects and from which nutrients can be depleted
  5. Standard length: fish length measured from the tip of its snout to its last vertebra
  6. Aerially incubating species: fish whose eggs are laid out of water that stay there until hatching

Faculty Mentor

Dr. Karen Martin and Dr. Donna Nofziger-Plank

Funding Source or Research Program

Summer Undergraduate Research in Biology

Location

Waves Cafeteria

Start Date

29-3-2019 2:00 PM

End Date

29-3-2019 3:00 PM

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Mar 29th, 2:00 PM Mar 29th, 3:00 PM

Partial Hatching in the California Grunion, Leuresthes tenuis

Waves Cafeteria

The California Grunion, Leuresthes tenuis,is a marine fish that is uniquely adapted to lay eggs in the sandy shore during high tides. Eggs incubate out of water in slightly moist sand between semilunar high tides before hatching is triggered by wave action. Hatchlings swim out to sea within the same wave that caused hatching, but sometimes larvae partially hatch with their egg membrane, the chorion, still on their heads. Partial hatching has not previously been defined, studied or its causes determined, but it puts grunion at an early disadvantage by hindering swimming and covering their gills. We tested environmental factors during incubation to see whether they increase the percentage of partial hatchlings. Groups of eggs were incubated in either still or aerated water (experimental) or in slightly damp sand (control) to assess effects of oxygen availability and boundary layers. Each group was held in normal (20 ℃) and elevated temperatures (30 ℃). Data analysis suggests that incubation in both aquatic conditions and in elevated temperature resulted in more frequent partial hatching. We also compared standard length and head-body ratios between hatched Grunion incubated in control and experimental conditions. Individuals incubated in water were significantly shorter with higher head-body ratios compared to those in sand. Grunion incubated in normal temperature were not significantly longer but had significantly lower head-body ratios than in elevated temperature. Results suggest that aerial incubation may be necessary for normal morphological development in Grunion and could imply effects on other aerially incubating species like Fundulus heteroclitus.

Terms

  1. Semilunar high tide: high tide caused by a new or full moon occurring every two weeks
  2. Partial hatching: a Grunion that has part of its body free from the egg and part still stuck to its chorion in some way for any amount of time
  3. Chorion: soft egg membrane covering a Grunion embryo as it develops and from which it hatches
  4. Boundary layers: layers of stagnant water that form around submerged objects and from which nutrients can be depleted
  5. Standard length: fish length measured from the tip of its snout to its last vertebra
  6. Aerially incubating species: fish whose eggs are laid out of water that stay there until hatching