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

Efficiency and you will Discussion

Siphonophores put loads of functionally authoritative zooids that will be homologous to free-living polyps otherwise medusae 27 (Fig. step 1 ). Physalia physalis falls under Cystonectae, a great clade that is sister to most other siphonophores 8 . When you look at the long-stemmed cystonects (every cystonects with the exception of Physalia physalis) gastrozooids (giving polyps) arise while the buds on anterior of nest as they are transmitted into rear of the an enthusiastic elongating stalk, while you are gonodendra (reproductive formations) appear separately along side stalk twenty-eight . In every cystonects, this new gonodendra is actually compound formations, that has gonophores (quicker medusae, impact good gonad), palpons (derived gastrozooids, one use up all your tentacles in cystonects), and you can nectophores twenty-seven . P. physalis gonodendra features these types of zooids, plus ‘jelly polyps’ which might be less nectophores off undecided setting twenty two , twenty six .

Than the almost every other siphonophore variety, plus other cystonects, Physalia physalis try unusual regarding its colony providers (Figs step one and ? and2). 2 ). P. physalis is additionally the only siphonophore types where gastrozooid, an important eating zooid, doesn’t have a great tentacle getting victim get. The actual only real different ‘s the protozooid (the first gastrozooid in order to create during the advancement), that’s essentially a consistent siphonophore gastrozooid, that have a mouth, tentacle and you will short basigaster region twenty-six , 29 . Apart from the protozooid, from inside the P. physalis the tentacle are borne into an excellent pulla twenty-six . Other people refer to either new zooid or perhaps the connected tentacle as the a dactylozooid ten , thirteen , 21 , 31 – the definition of dactylozooid features over the years started used on palpons various other siphonophore varieties but is maybe not currently used, and you will dactylozooids are formal palpon-such as for example defensive zooids in other hydrozoans 30 – 33 . To eliminate misunderstandings about the homology for the zooid, i suggest that the expression dactylozooid shouldn’t be utilized, while we think of this zooid getting developed de- novo for the P. physalis which can be unlikely homologous so you can dactylozooids in other hydrozoans (find lower than). At the same time, the definition of ampulla is additionally are not from the terminal vesicle of your own tricornuate tentillum away from agalmatids twenty seven . I prefer reviving Haeckel’s ‘tentacular palpon’ to refer to that particular zooid 34 , which besides have precedence, and also matches new probably hypothesized source of zooid (come across below).

Cystonects is actually dioecious, as well as the gonodendra inside the a colony happen gonophores out-of just you to definitely intercourse

Nest orientation within the siphonophores. Good – anterior, P – posterior, D – dorsal, V – ventral, L – left, R – proper. (A) Schematic regarding an adult colony of siphonophore Nanomia bijuga. Altered to incorporate axes so you’re able to a drawing away from Nanomia bijuga because of the FreyaGoetz ( licensed around CC Of the-SA step three.0 ( (B) Schematic out of a creating Physalia physalis larva. Drawing predicated on photo by the Linda Ianniello. (C) Schematic away from an older Physalia physalis nest.

Haeckel detail by detail one or two you’ll be able to hypotheses into supply away from tentacular palpons – the first theory, advertised of the Huxley, is because they aren’t zooids, however they are as an alternative additional diverticula at chrzeЕ›cijaЕ„ska strona randkowa com the base of your own tentacle you to definitely form much like ampullae from inside the echinoderm tubing legs 34 , thirty-five . Regarding second hypothesis, modification and you will subfunctionalization out of a keen ancestral gastrozooid gave rise so you’re able to a couple of independent zooids – a beneficial gastrozooid in the place of a tentacle and you may good tentacular palpon with a beneficial tentacle. Totton proposed a change in the original hypothesis, and you will ideal the ‘ampulla’ is actually an effective hypertrophied basigaster (aboral area for an effective gastrozooid you to performs a working character in the nematogenesis) who may have broke up on the rest of the gastrozooid twenty-six . not, i prefer the next hypothesis, centered on findings of gastrozooid and tentacular palpon (Figs 3 – six ; Secondary video clips 1 , 2 ). The latest gastrozooid and tentacular palpon was borne to the independent peduncles (Figs 5A,B and ? and6A; 6A ; Supplementary video 2 ), and develop out-of type of, independent buds (Figs 3A,B , ? ,4; cuatro ; Second video step one ). Ergo, brand new tentacular palpon are a beneficial derived gastrozooid, novel so you’re able to Physalia physalis, who has an expanded tentacle, no mouth, which will be functionally specialized to have nematocyst creation. The gastrozooids into the P. physalis are also derived gastrozooids which have lost tentacles and are functionally official to have giving only. The newest subfunctionalized gastrozooid hypothesis is also more parsimonious compared to most other hypotheses, since amendment and you will subfunctionalization off zooids is typical in the siphonophores – palpons, eg, are thought to get derived, modified gastrozooids you to routinely have less tentacle twenty seven .