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- Oct 19, 2003
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I am finding myself more and more intrigued by the Argonautoida; always has been a "pet" superfamily of sorts, but the more I read up on them, the more I find myself digging deeper and deeper. Just to illustrate:
From Ferrebeekeeper:
"From Marcie Orenstein’s Marine Animals of Bermuda: “These animals often form associations with gelatinous marine species, utilizing them for food, locomotion, and protection.” For example Argonauts are often found clutching the top of jellyfish and steering the latter around the ocean. The Argonaut eats through the jellyfish’s mantle into its digestive tract. It can thereafter rely on the jellyfish’s tentacles as a sort of fishing apparatus with which to catch prey (which it takes from inside the jellyfish’s gastral cavity). The jellyfish further serves as a protective shield, for the argonaut’s predators, such as tuna and dolphins, tend to shun such hydrozoans. Additionally the Argonaut gets a free ride for as long as its jellyfish remains alive.
Argonauta argo atop the jellyfish, Phyllorhiza punctata. Photographs Copyright ©, Thomas Heeger, University of San Carlos, Philippines"
From Orenstein and Woods' excellent "the cephalopod page":
"Association with Salps
One example of the argonaut’s thigmotactic tendencies is its association with salps. In the Gulf of Mexico, argonauts were observed residing within the branchial cavities of salps, their tentacles attached to the walls of the pharynx. The colonial salps harboring the juvenile argonauts were comprised of 40 to 60 individuals, and one male and one female argonaut were collected from separate salp chains. In addition to argonauts, the salps contained amphipods, copepods, and fish. After capture, the argonauts left their hosts, and no morphological damage to the salps was observed. It is believed that the association between salps and argonauts may allow argonauts to obtain food such as commensal amphipods, a means of floatation, and possibly camouflage. Protection is probably not a factor in the argonaut’s choice of host since perturbations via capture induced a fleeing response (Banas et al., 1982).
Association with Jellyfish
Salps are not the only gelatinous organisms with which argonauts associate. In the Phillipine archipelago, argonauts have been observed atop scyphomedusans with lateral and ventral arms gripping the exumbrella tightly. Aboral surfaces of these jellyfish are extremely damaged, and large pieces of mesoglea were missing. Two holes (20 by 10mm and 5 by 2mm) are believed to be bite marks from horny mandibles. Blue perimeters were noted near the surface of the bell. Five channels lead from these bite marks through the mesoglea to the gastral cavity, probably to extract food. In addition to food, the medusa-argonaut association could provide shelter, camouflage, or protection to the argonaut since argonaut predators like tunas, dolphinfishes, and swordfishes usually avoid scyphozoans as prey (Heeger et al., 1992).
Nematocysts are used to ward off potential predators of jellyfish, but interesting results were obtained in experiments on scyphomedusan contact with cuttlefish and catfish. When attached to jellyfish, the number of penetrated nematocysts on the surfaces of these two animals was counted. Fewer nematocysts discharged on the mantles of the cuttlefish than the surfaces of the catfishes, perhaps because cuttlefish mantles do not carry substances prone to trigger nematocyst release. These results might be extrapolated to other cephalopods, such as argonauts (Heeger et al., 1992)."
From Ferrebeekeeper:
"From Marcie Orenstein’s Marine Animals of Bermuda: “These animals often form associations with gelatinous marine species, utilizing them for food, locomotion, and protection.” For example Argonauts are often found clutching the top of jellyfish and steering the latter around the ocean. The Argonaut eats through the jellyfish’s mantle into its digestive tract. It can thereafter rely on the jellyfish’s tentacles as a sort of fishing apparatus with which to catch prey (which it takes from inside the jellyfish’s gastral cavity). The jellyfish further serves as a protective shield, for the argonaut’s predators, such as tuna and dolphins, tend to shun such hydrozoans. Additionally the Argonaut gets a free ride for as long as its jellyfish remains alive.
Argonauta argo atop the jellyfish, Phyllorhiza punctata. Photographs Copyright ©, Thomas Heeger, University of San Carlos, Philippines"
From Orenstein and Woods' excellent "the cephalopod page":
"Association with Salps
One example of the argonaut’s thigmotactic tendencies is its association with salps. In the Gulf of Mexico, argonauts were observed residing within the branchial cavities of salps, their tentacles attached to the walls of the pharynx. The colonial salps harboring the juvenile argonauts were comprised of 40 to 60 individuals, and one male and one female argonaut were collected from separate salp chains. In addition to argonauts, the salps contained amphipods, copepods, and fish. After capture, the argonauts left their hosts, and no morphological damage to the salps was observed. It is believed that the association between salps and argonauts may allow argonauts to obtain food such as commensal amphipods, a means of floatation, and possibly camouflage. Protection is probably not a factor in the argonaut’s choice of host since perturbations via capture induced a fleeing response (Banas et al., 1982).
Association with Jellyfish
Salps are not the only gelatinous organisms with which argonauts associate. In the Phillipine archipelago, argonauts have been observed atop scyphomedusans with lateral and ventral arms gripping the exumbrella tightly. Aboral surfaces of these jellyfish are extremely damaged, and large pieces of mesoglea were missing. Two holes (20 by 10mm and 5 by 2mm) are believed to be bite marks from horny mandibles. Blue perimeters were noted near the surface of the bell. Five channels lead from these bite marks through the mesoglea to the gastral cavity, probably to extract food. In addition to food, the medusa-argonaut association could provide shelter, camouflage, or protection to the argonaut since argonaut predators like tunas, dolphinfishes, and swordfishes usually avoid scyphozoans as prey (Heeger et al., 1992).
Nematocysts are used to ward off potential predators of jellyfish, but interesting results were obtained in experiments on scyphomedusan contact with cuttlefish and catfish. When attached to jellyfish, the number of penetrated nematocysts on the surfaces of these two animals was counted. Fewer nematocysts discharged on the mantles of the cuttlefish than the surfaces of the catfishes, perhaps because cuttlefish mantles do not carry substances prone to trigger nematocyst release. These results might be extrapolated to other cephalopods, such as argonauts (Heeger et al., 1992)."
venerable to tonmo, hope you'll enjoy yourself!
