Sperm morphology in the marine gastropodArchitectonica perspectiva (Mollusca): Unique features and systematic relevance

Healy, John M.

doi:10.1007/bf01320232

Cited by 11 publications

(15 citation statements)

References 21 publications

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“…2c). New ultrastructural data such as on osphradia and sperm were informative additional characters for resolving the phylogeny of several gastropod subgroups (Haszprunar 1985b, c;Healy 1991Healy , 2005. Nevertheless, structural characteristics are quite homogeneous within several euthyneuran subgroups on the one hand, whereas other organs had not yet been explored comparatively across taxa (Dayrat and Tillier 2002).…”

Section: Classification and Phylogenetic Concepts Of Opisthobranchia mentioning

confidence: 99%

Flashback and foreshadowing—a review of the taxon Opisthobranchia

et al. 2013

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Opisthobranchia have experienced an unsettled taxonomic history. At the moment their taxonomy is in state of dramatic flux as recent phylogenetic studies have revealed traditional Opisthobranchia to be paraphyletic or even polyphyletic, allocating some traditional opisthobranch taxa to other groups of Heterobranchia, e.g. Pulmonata. Here we review the history of Opisthobranchia and their subgroups, explain their traditionally proposed relationships, and outline the most recent phylogenetic analyses based on various methods (morphology, single gene and multiple gene analyses, as well as genomic data). We also present a phylogenetic hypothesis on Heterobranchia that, according to the latest results, represents a consensus and is the most probable one available to date. The proposed phylogeny supports the Acteonoidea outside of monophyletic Euthyneura, the basal euthyneuran split into Nudipleura (Nudibranchia plus Pleurobranchoidea) and the recently established taxon Tectipleura. The latter divides into the Euopisthobranchia, containing most of the major traditional opisthobranch clades, and the Panpulmonata, with a mix of the former opisthobranch, putative allogastropod and pulmonate taxa. This "new euthyneuran tree" rejects the traditional taxa Opisthobranchia and Pulmonata, and, in particular, has profound implications for preconceived textbook scenarios of opisthobranch and pulmonate evolution, which must now be reconsidered. In the absence of systematic barriers, research communities-which have traditionally investigated marine and non-marine heterobranchs separately-need to interact and finally merge for the sake of science.

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Section: Classification and Phylogenetic Concepts Of Opisthobranchia mentioning

confidence: 99%

Flashback and foreshadowing—a review of the taxon Opisthobranchia

et al. 2013

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“…In addition, paraspermatozoa (apyrene or oligopyrene sperm-common in caenogastropods, including the Janthinoidea) were shown to be absent from this species, and have yet to be observed in the family (see also Healy 1988aHealy , 1991. In addition, paraspermatozoa (apyrene or oligopyrene sperm-common in caenogastropods, including the Janthinoidea) were shown to be absent from this species, and have yet to be observed in the family (see also Healy 1988aHealy , 1991.…”

Section: Introductionmentioning

confidence: 99%

Ultrastructure of spermiogenesis in the gastropodHeliacus variegatus (Architectonicidae), with description of a banded periaxonemal helix

Healy

Jamieson

1991

Mar. Biol.

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Spermiogenesis and spermatozoa of the marine gastropod Heliacus variegatus Gmelin were examined using transmission electron microscopy (TEM). Mature spermatozoa are composed of an acrosomal vesicle, helical nucleus, elongate midpicce, annulus, glycogen piece and short end piece. The midpiece consists of a 9 + 2 axoneme, nine coarse fibres, and a banded helix, all enclosed by a continuous mitochondrial sheath (with multiple, helically coiled grooves). Anterior extensions of the mitochondrial sheath and banded helix form a double sheath around the basal half of the nucleus -an arrangement possibly unique in the Mollusca. During spermiogenesis, dense plaques delineating the anterior and posterior poles of the spermatid nucleus become attachment sites for the acrosomal vesicle and the axial complex (respectively). As the nucleus condenses and elongates, midpiece formation involves fusion of numerous, oblong mitochondria along the length of the axoneme. The coarse fibres and banded helix of the midpiece probably are derived through centriolar activity. Results of the study support inclusion of the Architectonicidae within the Heterobranchia, but in view of midpiece specializations, do not clarify the precise relationship of the family within this subclass.

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“…The axoneme of a mature flagellum consisted of 9 singlet outer units (course fibers, Healy, 1990Healy, , 1991Healy, , 1996 with 1 central course fiber; no paired microtubules were seen in the axoneme of A. californica sperm ( Figs 1F, 2A, B, C, E). The electron dense material composing the coarse fibers (peripheral or central) might have obscured their microtubule doublets.…”

Section: Resultsmentioning

confidence: 99%

“…Another vacuole develops either concurrent with the mitochondrial derivative, directly from it or just distal to its termination and it can overlap with the spiraled nucleus. This vacuole generally contains glycogen, is spiraled about the flagellum and is termed the glycogen helix (Healy, 1988(Healy, , 1991. In this paper, the spiraled nucleus and glycogen vacuole are termed nuclear and glycogen helices respectively.…”

Section: Discussionmentioning

confidence: 99%

“…Healy (1988) describes, however, that the glycogen helix in several pyramidellid gastropods developed concurrent with or just distal to the termination of the mitochondrial derivative. Healy (1991) reports the absence of a glycogen helix in the sperm of the gastropod, Architectonica perspectiva, while Beeman (1977) for A. californica and Kubo and Ishikawa (1981) for A. kurodai report not only the presence of a glycogen helix but also the presence of a second helical structure. Neither of the latter accounts shows a cross section of this secondary structure nor whether it is enclosed by microtubules, as is the case for the glycogen helix.…”

Section: Discussionmentioning

confidence: 99%

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Ultrastructure of the Sperm of Aplysia Californica Cooper

Prince

Cichocki

2015

MRAJ

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Abstract-The structure of the sperm of Aplysia californica was studied by both transmission and scanning electron microscopy. Aplysia californica, a species with internal fertilization, has the modified type of molluscan sperm structure. Spermatids had a glycogen helix spiraled about the flagellum, both enclosed by a common microtubular basket. A second vacuole helix was periodically seen only in spermatids and absent in spermatozoa. An additional basket of microtubules appeared to direct the elongation and spiraling of the nucleus about the flagellum/glycogen helix. A flat acrosome was present while the centriolar derivative was embedded in a deep nuclear fossa with strands of heterochromatin arranged nearly perpendicular to its long axis. The mitochondrial derivative consisted of small, frequently electron dense, closely spaced rods but individual mitochondria were also seen surrounding the axoneme of spermatids. The axoneme consisted of dense fibers that appeared to have a "C" shape substructure with a central dense fiber thus providing a 9+1 arrangement of singlet units; the typical 9+2 microtubule arrangement of flagella was absent. Flagella with two axonemes were frequently seen as well as an extra axoneme within the head of immature sperm.

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Sperm morphology in the marine gastropodArchitectonica perspectiva (Mollusca): Unique features and systematic relevance

Cited by 11 publications

References 21 publications

Flashback and foreshadowing—a review of the taxon Opisthobranchia

Flashback and foreshadowing—a review of the taxon Opisthobranchia

Ultrastructure of spermiogenesis in the gastropodHeliacus variegatus (Architectonicidae), with description of a banded periaxonemal helix

Ultrastructure of the Sperm of Aplysia Californica Cooper

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