Using external morphology as a proxy for stomach size in Hemigrapsus sanguineus

Area of Science:

• Marine Biology
• Crustacean Ecology
• Functional Morphology

Background:

• Stomach morphology is linked to diet in many species, but assessing it requires sacrificing animals.
• External crab carapace measurements, specifically the progastric region, have shown potential for predicting stomach size and diet quality.
• This non-invasive method could streamline diet studies in crabs if it accurately reflects individual diet preferences and specialization.

Purpose of the Study:

• To investigate if external progastric region size can predict internal stomach size in the invasive Asian shore crab, Hemigrapsus sanguineus.
• To determine if this relationship holds true across different latitudes and times of year.
• To evaluate the potential of using external morphology as a proxy for internal stomach size in individual crabs.

Main Methods:

• Collected Asian shore crabs (Hemigrapsus sanguineus) across various latitudes and times of year.
• Measured external progastric region width and internal stomach width for each individual.
• Analyzed the relationship between progastric region size, stomach size, body size, latitude, and time of year.

Main Results:

• Progastric region width increased at a faster rate with body size than stomach width.
• The trends of progastric region width across sites and time differed from those of stomach width.
• External progastric region size did not consistently predict internal stomach size across individuals.

Conclusions:

• The external progastric region size is not a reliable proxy for internal stomach size in Hemigrapsus sanguineus.
• Latitude and time of year influence the relationship between external and internal morphology.
• The use of external morphology to assess individual diet quality and consumption in crabs is not supported by this study.