on medusae that are large enough to allow its feeding apparatus to function effectively.
Figure 3.16 Feeding behavior of Pelagia noctiluca on motile prey. (a) When the prey touches a marginal tentacle, there is an immediate nematocyst discharge, followed by a tentacle contraction after 2–3 seconds; (b) the stiff tentacle bends toward the nearest oral arm, at the same time the oral arm moves upward, turns slightly, and draws its endodermic layer near the food; (c) the stiff tentacle releases the prey and moves upward, going away from the oral arm; (d) the oral arm grasps the prey completely and starts the peristaltic and mucous movements, which drive the food to the oral arm groove, to the manubrium, and finally to the gastric cavity. The inset figure is a transverse section of “d.”
Source: Rottini‐Sandrini and Avian (1989), figure 1 (p. 52). Reprinted by permission from Springer Nature Customer Service Centre GmbH Springer‐Verlag, Marine Biology, Feeding mechanism of Pelagia noctiluca (Scyphozoa: Semaeostomeae), Rottini‐Sandrini and Avian, 1989.
Table 3.1 Tentacular encounter zones and deployment patterns, tentacle length, volume, and density, and prey types of some medusae and siphonophores.
Source: Adapted from Madin (1988), table 2 (p. 423).
| Species | Encounter zone – shape of space | Tentacle deployment a pattern (see Figure 3.17) | Encounter zone – volume (cm3) | Tentacular length (m) | Tentacular volume (cm3) | Tentacle densityb (ppm) | Prey types |
|---|---|---|---|---|---|---|---|
| Medusae | |||||||
| Calycopsis typa | Disc | 3.17A | 850 | 12 | 0.0942 | 110.20 | Large prey – types unknown |
| Stomotoca pterophylla | Sphere | 3.17B | 900 000 | 2.4 | 0.0033 | 0.00 | Medusae, other gelatinous spp. |
| Aequorea macrodactyla | Cone | 3.17C | 1 500 000 | 200 | 0.7697 | 0.53 | Salps, ctenophores, pteropods, forams, medusae |
| Laodicea undulata | Disc | 3.17C | 175 | 18 | 0.0088 | 50.00 | Small crustacea, larval fish |
| Dichotomia cannoides | Cone | 3.17C | 50 | 7.5 | 0.0019 | 36.80 | Small crustacea types unknown |
| Liriope tetraphylla | Sphere | 3.17B | 220 000 | 3 | 0.0052 | 0.02 | Heteropods, appendicularia, larval crustacea, juvenile fish |
| Solmundella bitentaculata | Cylinder | 3.17B | 2 | 0.1 | 0.0118 | 5000.00 | Gelatinous species |
| Aeginopsis laurentii | Cone | 3.17D | 100 | 0.2 | 0.0471 | 476.20 | No data |
| Somaris spp. | Cone | 3.17D | 2 | 0.3 | 0.0001 | 40.00 | Small motile species, types unknown |
| Pelagia noctiluca | Cone | 3.17C | 8 700 000 | 24 | 0.1794 | 0.21 | Salps, ostracods, ctenophores, polychaetes, copepods, fish |
| Siphonophores | |||||||
| Sulculeolaria spp. | Cylinder | 3.17E,F | 257 000 | 243.2 | 1.0400 | 4.10 | Copepods |
| Forskalia spp. | Cylinder | 3.17E | 434 000 | 88.2 | 0.2400 | 0.56 | Copepods, amphipods, chaetognaths, molluscs, fish, fish eggs |
a See Figure 3.17 for cross‐reference to arrangement patterns of deployed tentacles.