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Anatomical descriptions of developing hypoglossal motor neurons in the green frog, Lithobates clamitans, and bullfrog, Lithobates catesbeiana, through metamorphosis
Author(s) -
Anderson Curt W,
Carroll Andrew J
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.577.2
Subject(s) - metamorphosis , biology , lithobates , bullfrog , larva , tadpole (physics) , tongue , hypoglossal nerve , brainstem , anatomy , amphibian , zoology , ecology , neuroscience , linguistics , physics , philosophy , particle physics
During metamorphosis anuran amphibians undergo dramatic changes in the central nervous system to facilitate the transition from an aquatic to a semi‐terrestrial lifestyle. Dramatic remodeling of organs as well as the development of new structures takes place in a very short period of time. For example, these tadpoles undergo the process of metamorphosis where they transform from a herbivore dependent on a feeding apparatus consisting of scraping mouth parts that efficiently harvest algae for dietary consumption to a carnivorous diet where the animal actively captures prey with a protrusible tongue and jaw musculature. Prior to metamorphosis, tadpole larvae do not have a developed tongue. During metamorphosis the structures of the tongue are not developed, for instance the anlage of the tongue does not appear until stage 10 and is not fully developed until stage 24. Muscular contraction of the adult tongue in Ranid frogs is primarily directed by hypoglossal nuclei in adult models. Although the circuitry and descriptions of the hypoglossal complex has been described in adult models, the dramatic development during metamorphosis of these neurons has been not studied completely. Retrograde labeling and proliferation of cell development studies of hypoglossal motor nuclei in the brainstem of developing Lithobates catesbeiana and Lithobates clamitans larvae have revealed morphological changes including peripheral nerve disconnection from the brainstem in T/K stages XV‐adult. Additional morphological differences including size and distribution between larvae and adults are substantial. A nearly 1/3 increase in average cell number and a corresponding 2/3 loss in average cell area (μm 2 ) was observed. Significant alterations in the differentiation, morphology and distribution of the motor neurons were also observed. Cellular proliferation was characterized in the ventral horn of the brainstem with mitotic activity from stage XV‐until metamorphic climax. There is a distinct period of time during development where peripheral connections from the spinal cord are lost and the cells undergo significant restructuring. Support or Funding Information Idaho INBRE NIH Grant #P20 RR0116454