This species has three ontogeny stages before it reaches its adult stage: 1)
Ammocoete (subcutaneous eyes, oral opening with folded lips, without marginal papillae, gill area arranged as furrow with seven undeveloped openings, and a brown colored body), 2) Macroftalmia (developed eyes, inner mouth with fleshy lips and supra and infraoral dental lamina, gill openings exposed to the outside and a dark silver dorsal and ventral body coloration), 3) Hypermetamorphic (semicircular mouth opening, with oral and supra-oral odontoid pieces well-developed, eyes relatively small and covered by translucent membrane, gill opening with folds on each edge, developed dorsal fins, a silver body coloration and a bluish pigmentation on the fins) (Ruiz & Marchant, 2004).
Fish codes: MD = Millicoma Dace; SD = Speckled Dace; CRS = Coastrange Sculpin; RT = Rainbow Trout; RS = Riffle Sculpin; CT = Cutthroat Trout; CO = Coho Salmon; SKB = Threespine Stickleback; RSS = Redside Shiner; SU = Largescale Sucker; LAM = lamprey
ammocoete. See text for scientific names.
At 4 inches, though, the offering is more representative of an immature lamprey (
ammocoete), especially when fished in pop-and-drop fashion, snapped off the bottom and then allowed to fall on an almost slack line.
Bioecological data.--The
ammocoete of 126.5 mm TL from the lower Arroyo Santo Domingo (19-II-1995), was collected in a branch of the stream 5 m wide, 0.4 m deep, and over sand/gravel, with salinity of 0.3 ppt.
Like most lampreys (family Petromyzontidae), both of these species have complex life cycles that include an extended larval stage (the
ammocoete stage) and a relatively brief adult stage (Hardisty, 2006).
Species Collection Site Petromyzontidae Lampetra appendix, American 49 (adult); 26, 27, brook lamprey 42, 49, 67 (
ammocoete) Ichthyomnyzon unicuspis, 1, 4, 11 (adult); 49, silver lamprey 51, 53, 64 (
ammocoete) Polyodontidae Polyodon spathula, paddlefish 7 Acipenseridae Scaphirhynchus platorynchus, 1, 3, 4, 7, 8, 10 shovelnose sturgeon Lepisosteidae Lepisosteus oculatus, 62 spotted gar L.
In vertebrates, however, the mouth in
ammocoete larvae, which are also suspension feeders, is exclusively innervated by efferent fibers (maxillomandibular nerve) from the CNS (Kuratani et al., 1998).
The expression pattern of lamprey neural crest homologs was examined from late gastrulation (E4) through early
ammocoete larval stages (Fig.
For example, Lacalli and West (1993) propose that the distinctive multipolar cells of echinoderm circumoral ciliary bands are homologous with similar neurons in the ciliary bands of the hemichordate tomaria, as well as with those in the dorsal nerve cord of
ammocoete larvae of the lancelet Branchiostoma.