Unlike mormyrids, not all gymnotiformes have a separate larval and adult electric organ. The species I am focusing on, Brachyhypopomus gauderio, has a larval organ that extends during development. Monophasic electrocytes are produced within the first week of hatching that remain throughout adulthood; however, at a certain point in development the electrocytes that arise have the adult morphology and are biphasic. These adult electrocytes are continually produced at the tip of the tail as the fish grows, eventually swamping out the larval monophasic electrocytes in the anterior and producing a biphasic head to tail EOD that has the same amplitude in P1 and P2; see images below.
I am interested in the transcriptional network that promotes electrocytes, and how larval versus adult electrocytes are specified, both as cell types and within their location in the body. To understand this at some level, I am currently exploiting the regenerative capabilities of this species, where over 20% of the total body length can be removed and regrown within 3-4 weeks- even producing new electrocytes that integrate into the electric organ and eventually return the electric organ discharge to the pre-injury state. I plan to investigate differentially expressed genes between the newly formed electrocytes at the tip of the regrowth and those that have reformed in the more proximal regenerated region to try and understand what genes/networks are involved in producing electrocytes de novo.
Another question with electric fish is the utility/function of the larval electrocytes. It is unclear if they serve a function, or if they are a vestigial remnant of electric organ development. I am currently producing F0 scn4aa mutants using CRISPR/Cas9, identifying those with a reduced EOD amplitude phenotype and I will be testing 2 hypotheses about larval EOD function. I plan to see if feeding or locomotion/movement are affected by the loss of the larval EOD amplitude.