Background

Chirostoma humboldtianum (Valenciennes, 1835) is the first ichthyic species scientifically described in Mexico. Diversification processes of the genus Chirostoma Swaison, 1839 are related to the specialization of its mandibular apparatus; yet few studies exist regarding the digestive system in Atherinopsidae. In particular, the anatomical aspects of its mandibular, branchial, and hyoid skeleton, mandibular and pharyngeal dentition, and visceral musculature are superficially described.

Goals

Analyze and describe the general organization of the digestive system of Chirostoma humboldtianum as part of its basic biology, in order to reveal the feeding processes useful for its conservation or culture.

Methods

Adult specimens, previously fixed with formaldehyde and preserved in ethyl alcohol, were obtained. Their visceral skeleton and musculature and digestive tract were analyzed by dissections.

Results

Major characteristics include presence of lower interpharyngeal cartilage, extensive expansion of levator operculi muscle over external opercular surface; presence of tendinous complex of A1 section of the adductor mandibulae muscle, which relates this section with the lacrimal and anguloarticular bones; presence of an additional section of pharyngoclavicularis externus muscle; insertion of retractor dorsalis muscle in vertebrae 2 to 4, absence of a stomach; and presence of a dental plate in each ceratobranchial 4.

Conclusions

The organization of the digestive system of C. humboldtianum corresponds to the Atherinomorpha anatomic pattern, because of the absence of a stomach, among other characteristics; it particularly corresponds to the Atherinopsidae anatomical pattern due to its visceral skeleton organization. This organization, in particular, of the mandibular and pharyngeal adult dentition is characteristic of a carnivorous fish that includes other teleosts in its diet.