Presentation Title

Partial Hatching in the California Grunion, Leuresthes tenuis

Faculty Mentor

Karen Martin

Start Date

17-11-2018 12:30 PM

End Date

17-11-2018 2:30 PM

Location

HARBESON 4

Session

POSTER 2

Type of Presentation

Poster

Subject Area

biological_agricultural_sciences

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 embryos partially hatch with their egg membrane, the chorion, still on their heads. Partial hatching has not 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. Incubation in aerated and still sea water was tested against the control of sand to assess effects of oxygen availability and boundary layers at normal (control) and elevated incubation temperatures, 20 ℃and 30℃, respectively. A Chi-Square analysis of the data showed that all experimental conditions led to a higher percentage of partial hatchlings than the controls. These conditions may cause changes in chorion composition, embryonic development, or both, and thereby hinder complete hatching. This has implications for the development of other fish species whose eggs incubate in air such as Fundulus heteroclitusand Austrofundulus limnaeus. Further study will examine environmental effects on development with cartilage and bone stains on preserved hatchlings incubated in each environmental condition to assess abnormalities.

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Nov 17th, 12:30 PM Nov 17th, 2:30 PM

Partial Hatching in the California Grunion, Leuresthes tenuis

HARBESON 4

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 embryos partially hatch with their egg membrane, the chorion, still on their heads. Partial hatching has not 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. Incubation in aerated and still sea water was tested against the control of sand to assess effects of oxygen availability and boundary layers at normal (control) and elevated incubation temperatures, 20 ℃and 30℃, respectively. A Chi-Square analysis of the data showed that all experimental conditions led to a higher percentage of partial hatchlings than the controls. These conditions may cause changes in chorion composition, embryonic development, or both, and thereby hinder complete hatching. This has implications for the development of other fish species whose eggs incubate in air such as Fundulus heteroclitusand Austrofundulus limnaeus. Further study will examine environmental effects on development with cartilage and bone stains on preserved hatchlings incubated in each environmental condition to assess abnormalities.