. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. DEVELOPMENT OF SQUID ESCAPE RESPONSE 219. 7*jl^v«X>W, Figure 12. Fully developed adult-like interplay of giant and non- giant motor systems in escape responses of a 5-day post-hatching Sc/n- Kti'iilhis. (A) An electrical stimulus (•) to the side of the head produces an escape jet at a latency of —500 ms that is driven only by small motor axons. (B) A stronger stimulus to the same site produces a delayed escape jet driven by both small axons and giant axons acting in concert. Non- giant activity precedes giant axon activat
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. DEVELOPMENT OF SQUID ESCAPE RESPONSE 219. 7*jl^v«X>W, Figure 12. Fully developed adult-like interplay of giant and non- giant motor systems in escape responses of a 5-day post-hatching Sc/n- Kti'iilhis. (A) An electrical stimulus (•) to the side of the head produces an escape jet at a latency of —500 ms that is driven only by small motor axons. (B) A stronger stimulus to the same site produces a delayed escape jet driven by both small axons and giant axons acting in concert. Non- giant activity precedes giant axon activation. Lower trace shows an ex- pansion of the record around the giant fiber spike. (C) Stimulation on the ventral surface of the head just anterior to the eye produces a multiple cycle escape response at a long latency. The first cycle is driven by the small axon motor system acting alone, whereas the second also involves the giant axon pathway. (Fig. 3B) or neurophysiologically (Fig. 10A)], time to peak mantle contraction (Fig. 3B), and rate of contraction (Fig. 3C). The time course of this improvement, beginning at stage 28-29, coincides closely with the anatomical ap- pearance and maturation of the third-order giant motor axons in the more posterior stellar nerves that control jetting. Performance peaks at hatching. Presumably this is a valuable capability, because the embryonic squid must jet vigorously to escape from the confines of the egg mass in order to hatch. At present it is not known how the neural portions of these giant and non-giant motor systems are associated with the two types of circular muscle fibers in adult squid mantle (Bone el 1981; Mommsen el ai, 1981). De- veloping embryos and hatchlings would provide a valuable system in which to pursue this question, because the two motor systems do not develop in perfect synchrony. We have not carried out an anatomical analysis of the muscle fiber types in these young animals. Although the overall picture o
Size: 1512px × 1652px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
