Physalia physalis physiology: axes, cormidia, and you can zooid items

Abilities and you may Discussion

Siphonophores add lots of functionally authoritative zooids which might be homologous so you can free-living polyps otherwise medusae twenty-seven (Fig. step one ). Physalia physalis is part of Cystonectae, a clade that is sibling to other siphonophores 8 . During the long-stemmed cystonects (the cystonects except for Physalia physalis) gastrozooids (eating polyps) arise due to the fact buds on the anterior of one’s colony and are usually carried to the posterior by the a keen elongating stem, if you find yourself gonodendra (reproductive formations) appear independently across the stalk twenty eight . In every cystonects, the latest gonodendra is compound structures, that has had gonophores (less medusae, bearing a beneficial gonad), palpons (derived gastrozooids, that use up all your tentacles inside cystonects), and you will nectophores twenty seven . P. physalis gonodendra has these types of zooids, as well as ‘jelly polyps’ which might be faster nectophores off undecided mode 22 , twenty six .

Than the most other siphonophore species, including other cystonects, Physalia physalis is unusual in terms of the colony team (Figs step one and you will ? anddos). dos ). P. physalis is also really the only siphonophore species where in actuality the gastrozooid, the main serving zooid, does not have a beneficial tentacle to have sufferer grab. Really the only difference is the protozooid (the original gastrozooid to create while in the advancement), which is generally an everyday siphonophore gastrozooid, having a mouth, tentacle and you will small basigaster part 26 , 29 . Aside from the protozooid, during the P. physalis the fresh new tentacle is borne on an effective pulla 26 . Most other article authors make reference to sometimes the fresh new zooid or even the connected tentacle as the a good dactylozooid 10 , 13 , 21 , 29 – the word dactylozooid keeps typically been used on palpons various other siphonophore varieties but is perhaps not already made use of, and dactylozooids try authoritative palpon-such protective zooids various other hydrozoans 30 – 33 . To quit dilemma about the homology associated with the zooid, i suggest that the word dactylozooid should not be utilized, once we think of this zooid having arisen de novo during the P. physalis that will be unlikely homologous in order to dactylozooids in other hydrozoans (come across less than). In addition, the definition of ampulla is also commonly from the terminal vesicle of the tricornuate tentillum from agalmatids twenty seven . I favor reviving Haeckel’s ‘tentacular palpon’ to mention to that particular zooid 34 , hence not merely has precedence, in addition to matches this new more than likely hypothesized supply with the zooid (discover below).

Cystonects is actually dioecious, and all the fresh gonodendra during the a colony bear gonophores from merely one intercourse

Colony direction for the siphonophores. An excellent – anterior, P – rear, D – dorsal, V – ventral, L – remaining, R – right. (A) Schematic from a mature colony of your siphonophore Nanomia bijuga. Changed to incorporate axes so you can an attracting from Nanomia bijuga by FreyaGoetz ( subscribed lower than CC By-SA step three.0 ( (B) Schematic out-of a creating Physalia physalis larva. Drawing based on pic of the Linda Ianniello. (C) Schematic out-of a mature Physalia physalis nest.

Haeckel in depth a couple of you can easily hypotheses towards the origin of tentacular palpons – the original theory, advertised of the Huxley, is because they are not zooids, but they are instead additional diverticula toward the base of tentacle you to setting much like ampullae in echinoderm pipe foot 34 , thirty five . About 2nd theory, modification and subfunctionalization out-of an enthusiastic ancestral gastrozooid gave rise to one or two separate zooids – an effective gastrozooid in place of good tentacle and you will a good tentacular palpon having a tentacle. Totton recommended a change in the initial hypothesis, and you can suggested the ‘ampulla’ was an effective hypertrophied basigaster (aboral area for a gastrozooid you to definitely performs a working character when you look at the nematogenesis) who has got split up from the other countries in the gastrozooid twenty six . However, we like the next hypothesis, based on findings of the gastrozooid and you will tentacular palpon (Figs 3 – six ; Second video clips step one , dos ). The latest gastrozooid and you https://datingmentor.org/escort/chico/ can tentacular palpon are borne to your separate peduncles (Figs 5A,B and you can ? and6A; 6A ; Second films dos ), and create from distinctive line of, independent buds (Figs 3A,B , ? ,4; 4 ; Secondary films step 1 ). Therefore, this new tentacular palpon try a good derived gastrozooid, book in order to Physalia physalis, who may have an enlarged tentacle, no lips, that’s functionally certified to own nematocyst creation. The latest gastrozooids inside the P. physalis are also derived gastrozooids with destroyed tentacles and generally are functionally official to have feeding only. The fresh subfunctionalized gastrozooid hypothesis is even even more parsimonious versus almost every other hypotheses, due to the fact modification and you can subfunctionalization of zooids is common in siphonophores – palpons, instance, are thought to-be derived, altered gastrozooids you to routinely have a diminished tentacle twenty seven .