Newly discovered associations between peritrich ciliates (Ciliophora: Peritrichia) and scale polychaetes (Annelida: Polynoidae and Sigalionidae) with a review of polychaete–peritrich epibiosis

Abstract

In this research, we report the presence of two ciliate protozoans of the subclass Peritrichia, Cothurnia amphicteis and C. peloscolicis, as epibionts on the chaetae of scaled polychaetes Malmgrenia lilianae, M. andreapolis (fam. Polynoidae) and Sthenelais boa (fam. Sigalionidae), from the north Adriatic (Mediterranean Sea). Both ciliate species are herein found for the first time after their original description and are redescribed, based on light and scanning electron microscopy analyses. This is the first record of an association between ciliates and polychaetes of the family Sigalionidae. Our results suggest that these host–epibiont relationships might be highly specific. We also present the first review of epibiosis between polychaetes and peritrich ciliates, indicating that this relationship is more diverse than previously thought. Forty taxa of peritrich ciliates from 12 genera and seven families are recorded as epibionts on polychaetes, while 48 polychaete taxa are known as their hosts. The relationship can be considered ectocommensalism, where the ciliates have the advantages of increased food availability. This association might be a more widespread phenomenon than currently known, because it could be easily overlooked or misinterpreted. It, therefore, deserves careful attention and further investigation.

Long forgotten: Eunice woodwardi Baird, 1869 (Annelida, Eunicidae) revisited, with an insight on internal anatomy

“…Epibiosis is a widespread phenomenon and marine annelids show a variety of ecological relationships with other organisms, including different symbiotic associations ( Martin & Britayev, 1998 ) and some have been reported as hosts (basibionts) of a large variety of other taxa ( Álvarez-Campos et al, 2014 ). Mikac et al (2019) states that this association can be considered as ectocommensalism because the annelid gets no harm from the epibiont. The presence of ciliophorans as epibionts on “polychaetes” has been reported previously in Onuphidae ( Arias, Anadón & Paxton, 2010 ), Syllidae ( Álvarez-Campos et al, 2014 ), Ampharetidae ( Parapar et al, 2018 ), Polynoidae and Sigalionidae ( Mikac et al, 2019 ).…”

“… Mikac et al (2019) states that this association can be considered as ectocommensalism because the annelid gets no harm from the epibiont. The presence of ciliophorans as epibionts on “polychaetes” has been reported previously in Onuphidae ( Arias, Anadón & Paxton, 2010 ), Syllidae ( Álvarez-Campos et al, 2014 ), Ampharetidae ( Parapar et al, 2018 ), Polynoidae and Sigalionidae ( Mikac et al, 2019 ). Ciliophorans have been found in E. woodwardi only on branchiae but in other species can be found also in other parts, such as body surface, prostomium, mouth opening, palps, chaetae, parapodial cirri and pygidium.…”

The Cost for Biodiversity: Records of Ciliate–Nematode Epibiosis with the Description of Three New Suctorian Species

“…Mikac et al [7] defined the association between peritrich ciliates and polychaetes as ectocommensalism-where the ciliates have the advantages of increased food availability but the polychaetes do not have any benefits and are not harmed. Authors stated that the major advantage which ciliates gain from being associated with a motile substratum is increased food availability, assured by the free transport to a variety of habitats, and by increased water flow.…”

“…Epibiotic relationships are rarely species-specific [1], nevertheless, that is not confirmed for polichaete-peritrich ciliate relationships since species-specific relationships were documented [7,13].…”

Diversity and Distribution Patterns of Hard Bottom Polychaete Assemblages in the North Adriatic Sea (Mediterranean)

“…With an average depth of 35 m, this semienclosed basin represents the most extensive region of shallow water in the Mediterranean [1,2], being one of the most productive areas too, due to high amount of nutrients loaded by the Po River [3]. It is also the coldest Mediterranean sector, together with the Gulf of Lion and the North Aegean Sea, thus inhabited by species of boreal affinity [4,5]. The Adriatic Sea and in particular its northern part, exhibits the highest species richness of invertebrates in the Mediterranean basin [6].…”