Alien worm in worm: a new genus of endoparasitic polychaete (Phyllodocidae, Annelida) from scale worms (Aphroditidae and Polynoidae, Annelida)

Jimi, Naoto; Ogawa, Akito; Kajihara, Hiroshi

doi:10.1080/14772000.2020.1785038

Cited by 2 publications

(1 citation statement)

References 22 publications

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“…In within-the-host-body commensal relationships, hosts provide a living space within their bodies for symbionts to reside for a part of or the entire duration of the symbionts’ lifespan [ 5 ]. Endosymbionts often undergo simplification of their body plan, including reductions in body size and appendages (e.g., [ 7 , 8 ]), which are likely adaptations to their host environment. These modifications mostly occur during the postembryonic development of symbiont species.…”

Section: Introductionmentioning

confidence: 99%

Postembryonic development and lifestyle shift in the commensal ribbon worm

Hookabe,

Ueshima,

Miura

2024

Front Zool

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Background Various morphological adaptations are associated with symbiotic relationships between organisms. One such adaptation is seen in the nemertean genus Malacobdella. All species in the genus are commensals of molluscan hosts, attaching to the surface of host mantles with a terminal sucker. Malacobdella possesses several unique characteristics within the order Monostilifera, exhibiting the terminal sucker and the absence of eyes and apical/cerebral organs, which are related to their adaptation to a commensal lifestyle. Nevertheless, the developmental processes that give rise to these morphological characteristics during their transition from free-living larvae to commensal adults remain uncertain. Results In the present study, therefore, we visualized the developmental processes of the internal morphologies during postembryonic larval stages using fluorescent molecular markers. We demonstrated the developmental processes, including the formation of the sucker primordium and the functional sucker. Furthermore, our data revealed that sensory organs, including apical/cerebral organs, formed in embryonic and early postembryonic stages but degenerated in the late postembryonic stage prior to settlement within their host using a terminal sucker. Conclusions This study reveals the formation of the terminal sucker through tissue invagination, shedding light on its adhesion mechanism. Sucker muscle development likely originates from body wall muscles. Notably, M. japonica exhibits negative phototaxis despite lacking larval ocelli. This observation suggests a potential role for other sensory mechanisms, such as the apical and cerebral organs identified in the larvae, in facilitating settlement and adhesive behaviors. The loss of sensory organs during larval development might reflect a transition from planktonic feeding to a stable, host-associated lifestyle. This study also emphasizes the need for further studies to explore the phylogenetic relationships within the infraorder Amphiporiina and investigate the postembryonic development of neuromuscular systems in closely related taxa to gain a more comprehensive understanding of ecological adaptations in Nemertea.

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Section: Introductionmentioning

confidence: 99%

Postembryonic development and lifestyle shift in the commensal ribbon worm

Hookabe,

Ueshima,

Miura

2024

Front Zool

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Hardly Venus’s servant—morphological adaptations of Veneriserva to an endoparasitic lifestyle and its phylogenetic position within Dorvilleidae (Annelida)

Tilic,

Rouse

2024

Org Divers Evol

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Endoparasitic annelids living inside another annelid host are known, particularly with regard to Oenonidae, but in general are poorly studied. The dorvilleid Veneriserva pygoclava is known from southern California, and its genus name (Latin = Venus’s servant) alludes to the close association with the host aphroditid scaleworm Aphrodita longipalpa. Little is known on fundamental questions on the biology of Veneriserva pygoclava. What is its mode of reproduction? How do they feed? How do they penetrate the host? We have studied multiple parasitized hosts and V. pygoclava specimens, using an integrative approach, combining µCT, histology, and electron microscopy. 3D reconstructions from µCT data of a parasitized Aphrodita show the exact position of the parasites in their natural condition within the host’s coelomic cavity. Ultrastructural investigations of the parasites revealed interesting adaptations to their lifestyle such as the complete reduction of their gut, despite the presence of a functional jaw apparatus and a modified epidermis enabling nutrient uptake from the host’s coelomic fluid. In addition to these, we also investigated spermatogenesis and oogenesis in V. pygoclava. Sperm morphology indicates an external fertilization of eggs within the coelomic cavity of the host. Mature male and female parasites living inside the same mature host and the presence of juvenile V. pygoclava within juveniles of Aphrodita suggest an obligate form of parasitism with a very early penetration of the hosts. In addition to our detailed morphological investigation, we conducted a phylogenetic analysis showing the position of Veneriserva within Dorvilleidae and its position was recovered nested among taxa of the Iphitime. Our phylogenetic analyses also show that the taxation Ophryotrocha puerilis siberti should be given full species rank and referred to as Ophryotrocha siberti. Finally, we publish here the full mitochondrial genome of V. pygoclava and discuss its novel gene order with reference to other annelids.

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Alien worm in worm: a new genus of endoparasitic polychaete (Phyllodocidae, Annelida) from scale worms (Aphroditidae and Polynoidae, Annelida)

Cited by 2 publications

References 22 publications

Postembryonic development and lifestyle shift in the commensal ribbon worm

Postembryonic development and lifestyle shift in the commensal ribbon worm

Hardly Venus’s servant—morphological adaptations of Veneriserva to an endoparasitic lifestyle and its phylogenetic position within Dorvilleidae (Annelida)

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