. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. DEFENSIVE SECRETIONS OF O. BOREALIS 395. FIGURE 1. Scanning electron micrograph of Onchidella borealis, showing marginal papillae (arrow) where repugnatorial glands are located. small. In Barkley Sound, populations were found on most coasts with moderate exposure. Surprisingly, the highest population density we have encountered is in a very protected cove of Grappler Inlet. There, O. borealis occurred abundantly on rocks in the middle intertidal zone, but also on Ulva sp. and cobbles overlying mud in the lower intertidal. Co
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. DEFENSIVE SECRETIONS OF O. BOREALIS 395. FIGURE 1. Scanning electron micrograph of Onchidella borealis, showing marginal papillae (arrow) where repugnatorial glands are located. small. In Barkley Sound, populations were found on most coasts with moderate exposure. Surprisingly, the highest population density we have encountered is in a very protected cove of Grappler Inlet. There, O. borealis occurred abundantly on rocks in the middle intertidal zone, but also on Ulva sp. and cobbles overlying mud in the lower intertidal. Comparable habitats in the San Juan Islands never supported populations of O. borealis. On rocky shores at low tide, O. borealis primarily occupy crevices, empty barnacle shells, and holdfasts of Hedophyllum sessile and Laminaria spp. On rainy or foggy days, many individuals leave their shelters and wander over the rock. Figure 2 shows the vertical distribution of O. borealis, several co-occuring limpets, and the predatory starfish Leptasterias hexactis. The precise tide level occupied by O. borealis varies from site to site, but is always between about m and + m above MLLW. This zone overlaps the distribution of L. hexactis, though the two populations do not always peak at the same level. At most sites, large starfish were found lower on the shore than O. borealis, and the asteroids primarily occupied the larger crevices. Small starfish also ocur in crevices, but live in relatively large numbers in holdfasts of//. sessile and various laminarians as well. At Eagle Point, all individuals of both species were counted within 10 cm quad- rats. There was a non-significant, though negative correlation between the occurrence of the two species. In general, no L. hexactis were found in quadrats containing high densities of O. borealis. The same held true for H. sessile holdfasts. At Pile Point, San Juan Island, two sites, one more exposed than the other, were examined in detail.
Size: 1810px × 1380px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
