"H. littorale" can breathe both with gills and through its intestines. However, intestinal respiration is not exhibited upon hatching, and the development of the respiratory intestine occurs throughout the juvenile period (up to 32 days old). Newly hatched larvae do not have the ability to breathe air through their intestines; however, it is possible that they absorb oxygen through their skin at this point, before the armor plates have developed. Soon after, between about 12–23 days of age, young have the capacity to breathe air, but their respiratory intestine has not finished developing. The respiratory intestine is well-developed between days 24 and 32.