Proceraea exoryxaesp. nov. (Annelida, Syllidae, Autolytinae), the first known polychaete miner tunneling into the tunic of an ascidian

Abstract

While studying organisms living in association with the solitary tunicate Phallusia nigra (Ascidiacea, Ascidiidae) from a shallow fringing reef at Zeytouna Beach (Egyptian Red Sea), one of the collected ascidians showed peculiar perforations on its tunic. Once dissected, the perforations revealed to be the openings of a network of galleries excavated in the inner tunic (atrium) by at least six individuals of a polychaetous annelid. The worms belonged to the Autolytinae (Syllidae), a subfamily that is well known to include specialized predators and/or symbionts, mostly associated with cnidarians. The Red Sea worms are here described as Proceraea exoryxae sp. nov., which are anatomically distinguished by the combination of simple chaetae only in anterior chaetigers, and a unique trepan with 33 teeth in one outer ring where one large tooth alternates with one medium-sized tricuspid tooth, and one inner ring with small teeth located just behind the large teeth. Male and female epitokes were found together with atokous individuals within galleries. Proceraea exoryxae sp. nov. constitutes the first known miner in the Autolytinae and the second species in this taxon known to live symbiotically with ascidians. The implications of finding this specialized parasite are discussed considering that Phallusia nigra has been introduced worldwide, in tropical and sub-tropical ecosystems, where it has the potential of becoming invasive.

A novel symbiotic relationship between ascidians and a new tunic-boring polychaete (Annelida: Spionidae: Polydora)

“…However, only a few animals inhabit the ascidian tunic: mytilid mussels in the genera Mytilimeria and Musculus (Say 1822;White 1949;Lambert 2005;Morton & Dinesen 2011;Cañete & Rocha 2013) and amphipods in the genus Polycheria (Skogsberg & Vansell 1928;McClintock et al 2009). In annelids, Proceraea exoryxae is the only known polychaete tunic-borer that produces a network of burrows in the tunic of an ascidian species (Martin et al 2017). Polydora tunicola sp.…”

“…Despite the hundreds of symbiotic polychaete species, polychaete-ascidian symbiotic relationships are only known for two syllid species: Myrianida pinnigera (Montagu, 1808) and Proceraea exoryxae Martin, Nygren & Cruz-Rivera, 2017(Okada 1935Spooner et al 1957;Martin et al 2017). Proceraea exoryxae is the only polychaete known to bore into the tunic of an ascidian.…”

Spatial Variability in a Symbiont-Diverse Marine Host and the Use of Observational Data to Assess Ecological Interactions

“…In P. nigra, the tunic is smooth, and it readily separates from the body. The visceral mass (digestive and reproductive systems) and pharyngeal basket were carefully inspected because the location of ascidian faunal associates varied within the host according to symbiont species [46,47] (Figure 2). Using the number of associated animals per ascidian, symbiont diversity was quantified by calculating the Shannon-Wiener and Simpson indices for each collected host containing at least one associated species.…”

“…A diverse symbiont community has evolved to utilize this defended ascidian host around the world (Table 1). In the Red Sea alone, P. nigra hosts the amphipod Leucothoe furina (Savigny, 1816), a polychaete worm, and at least seven species of copepods that live within different parts of its body [44][45][46][47][48] (Table 1). Outside of this geographic area, five other amphipod symbionts have been reported from P. nigra in Belize, Cuba, Florida, Panama, Brazil and Venezuela (Table 1), although records of L. spinicarpa and L. wuriti from Brazil have been questioned [49,50].…”