New symbiotic association in marine annelids: ectoparasites of comb jellies

Abstract

A new genus of ectoparasitic marine annelids living on ctenophores, Ctenophoricola gen. nov., is described and its feeding behaviour, reproduction and developmental stages are discussed. Its unusual morphology challenged its placement within the known marine families. However, analyses of mitochondrial and nuclear sequence data showed the new genus as member of the Alciopini, a group of holopelagic annelids included within the Phyllodocidae. Ctenophoricola masanorii sp. nov. from Japan and Ctenophoricola rousei sp. nov. from the Canary Islands (Spain) are described. A third species from the Gulf of California is not formally described because the specimens are in poor condition. The new genus is characterized by having: 1) two distinctive body regions, the anterior with reduced parapodia lacking chaetae, and the posterior with long parapodia and chaetae and 2) a pair of large, elongate lensed eyes. These eyes are here described using histology and 3D reconstruction based on a Californian specimen. The two new species mainly differ in colour pattern, shape of parapodia, number of chaetae and body ciliation.

Morphological convergence and adaptation in cave and pelagic scale worms (Polynoidae, Annelida)

“…Most notably, Alciopidae, with their greatly enlarged, lensed eyes and thin, long, often transparent bodies 1 . Likely also evolved from a shallow water ancestor, alciopids are only known from the epi- and mesopelagic zones, retaining their eyes, as have their sister group, the newly described Ctenophoricola 3 . Similarly, lopadorrhynchids, tomopterids and iospilids have eyes, suggesting that eyes are an important feature for pelagic annelids.…”

“…Their mystery lies in their original discovery, which in most cases, dates back several centuries and are based on single observations of often incomplete or damaged specimens 1 . Yet, annelids are not uncommon throughout the oceanic water column, the midwater, with several groups containing only holopelagic species, including Lopadorrhynchidae, Iospilidae, Typhloscolecidae, Tomopteridae 2 , Alciopini, and Ctenophoricola 3 . Among the obligate holopelagic groups, evolution has driven numerous morphological specializations, including well-developed eyes (Alciopini), transparent bodies (Tomopteridae), specialized feeding and reproductive modes (Lopadorrhynchidae, Ctenophoricola ) and creative defensive strategies (Alciopini 4 , 5 ; Swima 6 ).…”

“…Holopelagic species are found within several other annelid families too, and are assumed to have evolved by opportunistic colonization events within otherwise benthic lineages. Such examples include Poeobius and Flota , two unrelated holopelagic genera within the otherwise benthic Flabelligeridae 7 , Swima and Teuthidodrilus within Acrocirridae 8 , Alciopini and Ctenophoricola within Phyllodocidae 3 and C haetopterus pugaporcinus Osborn, Rouse, Goffredi & Robison, 2007 within the tube dwelling Chaetopteridae 9 . Several other annelid representatives can be found in the water column, but distinguishing truly pelagic forms from late stage larvae, or species with periodic swimming has proven challenging given the limited amount of direct observations available.…”

Planktonic Ctenophora of the Madeira archipelago (Northeastern Atlantic)

“…Compared to other marine organisms, information on gelatinous zooplankton's functional roles in all marine ecosystems is still sparse. With such a lack of knowledge, more research is needed given the fact that (i) recent studies highlighted the importance of the so-called "jelly web" in planktonic oceanic food webs (Chi et al 2020) and their role in pelagic-benthic coupling (Sweetman et al 2014;Sweetman & Chapman 2015); (ii) some ctenophores present a foreseeable invasive behaviour and proliferation potential; (iii) ctenophores can host different parasites (Martorelli 2001;San Martín et al 2021) that might negatively affect other organisms and higher trophic levels. In this context, the present study takes place to increase our knowledge of gelatinous zooplankton in the Macaronesia region and particularly in the Madeira Archipelago (Gueroun et al 2021).…”

On the Diversity of Phyllodocida (Annelida: Errantia), with a Focus on Glyceridae, Goniadidae, Nephtyidae, Polynoidae, Sphaerodoridae, Syllidae, and the Holoplanktonic Families

“…Alciopini (Figure 15b,c) are usually classified as macrophagous visual hunters that feed on copepods, euphausiids and zooplankton, although some small-sized members also feed on diatoms and other phytoplanktonic organisms [12,239]. The recently described genus Ctenophoricola San Martín, Álvarez-Campos et al 2021 (including two species) shows a characteristic parasitic behavior, feeding and living on ctenophores [240]. Most species are epipelagic, with a limited range of vertical migration [239].…”