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Myoanatomy and serotonergic nervous system of the ctenostome Hislopia malayensis: evolutionary trends in bodyplan patterning of ectoprocta.

Schwaha T, Wood TS, Wanninger A - Front. Zool. (2011)

Bottom Line: The apertural muscles show high similarity within Ectoprocta and always consist of two sets of muscles.Gymnolaemates and Phylactolaemates show clear differences within their digestive tract musculature, the former showing smooth and longitudinal muscles to a much greater extent than the latter.The complex musculature at the lophophoral base appears promising for inferring phylogenetic relationships, but sufficient comparative data are currently lacking.

View Article: PubMed Central - HTML - PubMed

Affiliation: University of Vienna, Department of Morphology, Althanstra├če 14, 1090 Vienna, Austria. thomas.schwaha@univie.ac.at.

ABSTRACT

Background: Ectoprocta is a large lophotrochozoan clade of colonial suspension feeders comprising over 5.000 extant species. Their phylogenetic position within the Lophotrochzoa remains controversially discussed, but also the internal relationships of the major ectoproct subclades -Phylactolaemata, Stenolaemata, and Gymnolaemata - remains elusive. To gain more insight into the basic configuration of ectoproct muscle systems for phylogenetic considerations, we analysed the adult myoanatomy and the serotonergic nervous system as well as myogenesis in budding stages of the ctenostome Hislopia malayensis.

Results: In adults, the serotonergic nervous system is restricted to the lophophoral base with a high concentration in the cerebral ganglion and serotonergic perikarya between each pair of tentacles. Prominent smooth apertural muscles extend from the basal cystid wall to each lateral side of the vestibular wall. The musculature of the tentacle sheath consists of regular strands of smooth longitudinal muscles. Each tentacle is supplied with two bands of longitudinal muscles that show irregular striation. At the lophophoral base several muscles are present: (i) Short muscle fibres that proximally diverge from a single point from where they split distally into two separate strands. (ii) Proximally of the first group are smooth, longitudinal fibres that extend to the proximal-most side of the lophophoral base. (iii) Smooth muscle fibres, the buccal dilatators, traverse obliquely towards the pharynx, and (iv) a circular ring of smooth muscle fibres situated distally of the buccal dilatators. Retractor muscles are mainly smooth with short distal striated parts. The foregut consists mainly of striated ring musculature with only few longitudinal muscle fibres in the esophagus, while the remaining parts of the digestive tract solely exhibit smooth musculature. During budding, apertural and retractor muscles are first to appear, while the parietal muscles appear at a later stage.

Conclusions: The apertural muscles show high similarity within Ectoprocta and always consist of two sets of muscles. Gymnolaemates and Phylactolaemates show clear differences within their digestive tract musculature, the former showing smooth and longitudinal muscles to a much greater extent than the latter. The complex musculature at the lophophoral base appears promising for inferring phylogenetic relationships, but sufficient comparative data are currently lacking.

No MeSH data available.


Phylogenetic system of the Ctenostomata, modified after (a) Jebram (1986) and (b) Todd (2000). (a) The phylogenetic reconstruction of Jebram is mainly based on cystid and muscle differentiation. (b) The work of Todd (b) has in particular included characters of fossil ctenostomes.
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Figure 1: Phylogenetic system of the Ctenostomata, modified after (a) Jebram (1986) and (b) Todd (2000). (a) The phylogenetic reconstruction of Jebram is mainly based on cystid and muscle differentiation. (b) The work of Todd (b) has in particular included characters of fossil ctenostomes.

Mentions: Hislopiid ctenostomes comprise only seven freshwater species and are the sole family within the superfamily Hislopioidea. The latter belongs to the paraphyletic 'carnosans', which are regarded as primitive within the Euctenostomata (sensu [25]), and which have retained a simple colonial morphology similar to the proposed cheilostome-like ancestor (see e.g. [5,9,22,25,28]). Their supposedly relatively basal position within Euctenostomata (Figure 1; [5,10,22,25]) renders the Hislopiidae an important model taxon for inferring ectoproct phylogeny and evolution. To gain more insight into the basic configuration of ectoproct muscle systems and to evaluate their potential use for phylogenetic studies, we analyzed the adult myoanatomy and serotonergic nervous system as well as myogenesis during budding in Hislopia malayensis Annandale, 1916.


Myoanatomy and serotonergic nervous system of the ctenostome Hislopia malayensis: evolutionary trends in bodyplan patterning of ectoprocta.

Schwaha T, Wood TS, Wanninger A - Front. Zool. (2011)

Phylogenetic system of the Ctenostomata, modified after (a) Jebram (1986) and (b) Todd (2000). (a) The phylogenetic reconstruction of Jebram is mainly based on cystid and muscle differentiation. (b) The work of Todd (b) has in particular included characters of fossil ctenostomes.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3117780&req=5

Figure 1: Phylogenetic system of the Ctenostomata, modified after (a) Jebram (1986) and (b) Todd (2000). (a) The phylogenetic reconstruction of Jebram is mainly based on cystid and muscle differentiation. (b) The work of Todd (b) has in particular included characters of fossil ctenostomes.
Mentions: Hislopiid ctenostomes comprise only seven freshwater species and are the sole family within the superfamily Hislopioidea. The latter belongs to the paraphyletic 'carnosans', which are regarded as primitive within the Euctenostomata (sensu [25]), and which have retained a simple colonial morphology similar to the proposed cheilostome-like ancestor (see e.g. [5,9,22,25,28]). Their supposedly relatively basal position within Euctenostomata (Figure 1; [5,10,22,25]) renders the Hislopiidae an important model taxon for inferring ectoproct phylogeny and evolution. To gain more insight into the basic configuration of ectoproct muscle systems and to evaluate their potential use for phylogenetic studies, we analyzed the adult myoanatomy and serotonergic nervous system as well as myogenesis during budding in Hislopia malayensis Annandale, 1916.

Bottom Line: The apertural muscles show high similarity within Ectoprocta and always consist of two sets of muscles.Gymnolaemates and Phylactolaemates show clear differences within their digestive tract musculature, the former showing smooth and longitudinal muscles to a much greater extent than the latter.The complex musculature at the lophophoral base appears promising for inferring phylogenetic relationships, but sufficient comparative data are currently lacking.

View Article: PubMed Central - HTML - PubMed

Affiliation: University of Vienna, Department of Morphology, Althanstra├če 14, 1090 Vienna, Austria. thomas.schwaha@univie.ac.at.

ABSTRACT

Background: Ectoprocta is a large lophotrochozoan clade of colonial suspension feeders comprising over 5.000 extant species. Their phylogenetic position within the Lophotrochzoa remains controversially discussed, but also the internal relationships of the major ectoproct subclades -Phylactolaemata, Stenolaemata, and Gymnolaemata - remains elusive. To gain more insight into the basic configuration of ectoproct muscle systems for phylogenetic considerations, we analysed the adult myoanatomy and the serotonergic nervous system as well as myogenesis in budding stages of the ctenostome Hislopia malayensis.

Results: In adults, the serotonergic nervous system is restricted to the lophophoral base with a high concentration in the cerebral ganglion and serotonergic perikarya between each pair of tentacles. Prominent smooth apertural muscles extend from the basal cystid wall to each lateral side of the vestibular wall. The musculature of the tentacle sheath consists of regular strands of smooth longitudinal muscles. Each tentacle is supplied with two bands of longitudinal muscles that show irregular striation. At the lophophoral base several muscles are present: (i) Short muscle fibres that proximally diverge from a single point from where they split distally into two separate strands. (ii) Proximally of the first group are smooth, longitudinal fibres that extend to the proximal-most side of the lophophoral base. (iii) Smooth muscle fibres, the buccal dilatators, traverse obliquely towards the pharynx, and (iv) a circular ring of smooth muscle fibres situated distally of the buccal dilatators. Retractor muscles are mainly smooth with short distal striated parts. The foregut consists mainly of striated ring musculature with only few longitudinal muscle fibres in the esophagus, while the remaining parts of the digestive tract solely exhibit smooth musculature. During budding, apertural and retractor muscles are first to appear, while the parietal muscles appear at a later stage.

Conclusions: The apertural muscles show high similarity within Ectoprocta and always consist of two sets of muscles. Gymnolaemates and Phylactolaemates show clear differences within their digestive tract musculature, the former showing smooth and longitudinal muscles to a much greater extent than the latter. The complex musculature at the lophophoral base appears promising for inferring phylogenetic relationships, but sufficient comparative data are currently lacking.

No MeSH data available.