Morphology and systematics of some rooted cheilostome Bryozoa

Cook, Patricia L.; Chimonides, P.J.

doi:10.1080/00222938100770081

Cited by 36 publications

(30 citation statements)

References 22 publications

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“…The ancestrula of R. paucipora sp. nov. is similar, but a tatiform ancestrula does occur in Riscodopa parva, the Recent type species of Riscodopa Gordon (1989), as well as in R. cotyla (Cook and Chimonides, 1981a) and R. hyalina sp. nov. Whatever the characters of their frontal shields, the ancestrulae of all these species are inferred to have developed from a post-metamorphosi s binary complex, which included a rhizoid element in addition to a feeding zooid.…”

Section: Introductionmentioning

confidence: 80%

“…It is even probable that the earliest astogenetic stages of these 'sand fauna' species takes place below the surface of the seabottom, within the upper layers of sediment. This type of development is now known to occur in the genera Conescharellina, Sphaeropora and Parmularia (Cook and Downloaded by [McGill University Library] at 06:56 13 December 2014 Chimonides, 1981bChimonides, , 1985. In H. magna and M. ellerii, the ancestrula and primary zooids assume a semi-repent form, above the surface of the substratum .…”

Section: Discussionmentioning

confidence: 98%

“…In R. cotyla, fully developed ovicells occur in the fth generation, but there are only signs of early development in third and fourth generation zooids. This reversal of the usual astogenetic sequence in ovicell ontogeny is typical of the Petraliellidae (Cook and Chimonides, 1981a) . On the basal side of colonies, the ancestrula frequently shows a depression in the calci cation of the basal wall, which may mark the position of the inferred primary rhizoid element.…”

Section: Remarksmentioning

confidence: 90%

“…The curved proximal lamina is less robust, but similar to that occurring in some specimens of R. biincisa. It suggests that while the rest of the basal calci ed wall is an interior wall, the rhizoids of R. biincisa and R. paucipora may have had Downloaded by [McGill University Library] at 06:56 13 December 2014 a swollen origin surrounded by a rim of exterior calci ed wall, which included several septular pores, like those of Parastichopora (Cook and Chimonides 1981a …”

Section: Remarksmentioning

confidence: 96%

“…In addition, colonies with rhizoids can cover the surface of particulate sea-bottoms, and of sponges, both substrata inimical to the successful development of many other forms of bryozoan colony. Colonies of Petraliellidae may be unilaminar, with bilaminar expansions, or be tubular, with anastomosing branches (Marcus, 1921), or even be lunulitiform (Cook and Chimonides, 1981a) . Erect colonies frequently attain a large size, and may be more than 150 mm in height or breadth, tubular portions reaching a diameter of 7-10 mm.…”

Section: Introductionmentioning

confidence: 99%

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Notes on astogeny of some Petraliellidae (Bryozoa) from Australia

Cook¹,

Bock²

2002

Journal of Natural History

446

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Members of the bryozoan family Petraliellidae share the capacity to develop basal rhizoids, which anchor the unilaminar, semi-repent parts of the colonies above the substratum, and enable them to overgrow other, competing sessile forms. Little is known of the larval behaviour and settlement, or the early astogeny of species. Ancestrulate colonies of the Australian Tertiary lunulitiform species Smittia biincisa are referred to the genus Riscodopa, and together with Riscodopa paucipora sp. nov. are described and compared with the Recent species R. cotyla and R. parva from New Zealand, and with R. hyalina sp. nov. from New South Wales, Australia. All the Recent species are known to develop basal rhizoids, and an early astogeny similar to that of many other small, rooted bryozoans, comprising the post-metamorphosis development of a binary complex, including rhizoid and feeding elements, is inferred for Riscodopa. Observations on living Hippopetraliella magna from Queensland suggest that both the ancestrular morphology and early astogeny show a capacity for semi-repent growth, even though they do not include rhizoid development. Larvae metamorphose without direct attachment, and the ancestrula develops elongated, partially calci ed supporting processes, which raise the early stages of growth above the substratum. A similar kind of ancestrula has been found in preserved specimens of Mucropetraliella ellerii.

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Section: Introductionmentioning

confidence: 80%

Section: Discussionmentioning

confidence: 98%

Section: Remarksmentioning

confidence: 90%

Section: Remarksmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

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Notes on astogeny of some Petraliellidae (Bryozoa) from Australia

Cook¹,

Bock²

2002

Journal of Natural History

446

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Community assembly in a modular organism: the impact of environmental filtering on bryozoan colony form and polymorphism

Schack

Gordon²,

Ryan

2020

Ecology

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Understanding community assembly is a key goal in community ecology. Environmental filtering influences community assembly by excluding ill‐adapted species, resulting in communities with similar functional traits. An RLQ (a four‐way ordination) analysis incorporating spatial data was run on a data set of 642 species of cheilostomes (Bryozoa) from 779 New Zealand sites, and results were compared to trends in other sessile, epibenthic taxa. This revealed environmental filtering of colony form: encrusting‐cemented taxa were predominant in shallow environments with hard substrata (<200 m), while erect‐rooted taxa characterized deeper environments with soft substrata (>200 m). Furthermore, erect taxa found in shallow environments with high current speeds were typically jointed. Polymorphism also followed environmental gradients. External ovicells (brood chambers) were more common in deeper, low‐oxygen water than immersed and internal ovicells. This may reflect the oxygen needs of the embryo or increased predation intensity in shallow environments. Bryozoans with costae tended to be found in deeper water as well, while bryozoans with calcified frontal shields were found in shallow environments with a higher concentration of CaCO3. Avicularia did not appear to be related to environmental conditions, and changes in pivot bar structure with depth likely represent a phylogenetic signal. The importance of substratum type as a strict environmental filter suggests that anchoring structures, like rootlets, may be “key innovations” for other sessile, epibenthic taxa like sponges and ascidians.

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Comparative anatomical study of internal brooding in three anascan bryozoans (Cheilostomata) and its taxonomic and evolutionary implications

et al. 2006

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The anatomical structure of internal sacs for embryonic incubation was studied using SEM and light microscopy in three cheilostome bryozoans-Nematoflustra flagellata (Waters,1904), Gontarella sp., and Biflustra perfragilis MacGillivray, 1881. In all these species the brood sac is located in the distal half of the maternal (egg-producing) autozooid, being a conspicuous invagination of the body wall. It consists of the main chamber and a passage (neck) to the outside that opens independently of the introvert. There are several groups of muscles attached to the thin walls of the brood sac and possibly expanding it during oviposition and larval release. Polypide recycling begins after oviposition in Gontarella sp., and the new polypide bud is formed by the beginning of incubation. Similarly, polypides in brooding zooids degenerate in N. flagellata and, sometimes, in B. perfragilis. In the evolution of brood chambers in the Cheilostomata, such internal sacs for embryonic incubation are considered a final step, being the result of immersion of the brooding cavity into the maternal zooid and reduction of the protecting fold (ooecium). Possible reasons for this transformation are discussed, and the hypothesis of Santagata and Banta (Santagata and Banta1996) that internal brooding evolved prior to incubation in ovicells is rejected.

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Morphology and systematics of some rooted cheilostome Bryozoa

Cited by 36 publications

References 22 publications

Notes on astogeny of some Petraliellidae (Bryozoa) from Australia

Notes on astogeny of some Petraliellidae (Bryozoa) from Australia

Community assembly in a modular organism: the impact of environmental filtering on bryozoan colony form and polymorphism

Comparative anatomical study of internal brooding in three anascan bryozoans (Cheilostomata) and its taxonomic and evolutionary implications

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