Other less abundant groups (<1%) such as siphonophores
, medusae, cladocerans, heteropods, appendicularians and echinoderm larvae showed a negative correlation (-0.64 < r < -0.28; P < 0.05).
On the other hand, no chemotactic cross-reactivity exists in the siphonophore
species examined, for which contact with seawater in the absence of attractants is sufficient to activate sperm motility (Cosson, 1990).
So its mouth could nip off bits of prey that the siphonophores
get tangled in their frizz.
According to pioneering midwater explorer Bruce Robison, a biologist at the Monterey Bay Aquarium Research Institute (MBARI) in Moss Landing, California, ignorance of these animals "meant that we probably underestimated the biomass of the sea by a third." The deep ocean's midwaters, he adds, "contain the largest animal communities on Earth." And within these communities, siphonophores
rule, consuming so much food that they compete with big, hard-bodied carnivores such as sharks and whales.
These figures generally underestimate the biomass of gelatinous zooplankton, formed by jellyfish, siphonophores
, ctenophores, pteropod mollusks, and thaliaceans or salps.
Many of the dives found swarms of gelatinous animals known as siphonophores
. The otherworldly creatures have long bodies ringed by pulsing bells for propulsion, and up to thousands of elastic tentacles for catching and drawing in prey.
For instance, based on the spatial distribution of siphonophores
and neustonic communities off Northern and Southern Ice Field channels in southern Chile, Palma et al.
Sato, "Ocean sunfish rewarm at the surface after deep excursions to forage for siphonophores
," Journal of Animal Ecology, vol.
The functions of nematocysts in prey capture by epipelagic siphonophores
Mr Bastian added: "Portuguese Man-O-War are colonial siphonophores
, so not a true jellyfish.
Other hydrozoans called siphonophores
include species like the Portuguese man-o-war that may grow up to several feet long, but are actually colonies made up of many smaller bells chained together.
Some of the other factors that have been suggested to have at least some influence on rockfish recruitment include adult spawning biomass (Mason, 1998), increased predation by siphonophores
and chaetognaths on larval stages during years of high sea temperature (Yoklavich et al., 1996), turbulence (Ainley et al., 1993), and diet of juvenile rockfishes (Reilly et al., 1992).