On the Systematics and Biodiversity of the Opheliidae and Scalibregmatidae

Abstract

In this paper we review the systematics, diversity, and ecology of two related annelid families: Opheliidae Malmgren, 1867 and Scalibregmatidae Malmgren, 1867. Opheliids are deposit-feeders and that are mainly found as burrowers in sandy sediments. Morphologically, opheliids are characterized by the smooth cuticle, as well as the presence of a conspicuous ventral groove, reduced parapodia, and a tubular-shaped structure often projecting from the posterior end. Scalibregmatids are also deposit-feeders, but compared to opheliids, they have a characteristic arenicoliform body, a T-shaped anterior end and a glandular, reticulated epidermis. For each family, we summarize the available information about the evolutionary relationships, taxonomic history, geographical distribution, ecological preferences and diversity of life strategies along with the techniques most commonly used for their study. By highlighting the main gaps in knowledge on each of these topics, this review ultimately aims at stimulating further research into members of these two families in the future.

Annelid Diversity: Historical Overview and Future Perspectives

“…The current ranges of valid nominal species in the literature go from 14,000 to 20,000 [7,[86][87][88], and databases such as WoRMS currently considers 23,774 accepted species of extant annelids [89]. Recounting the number of species after the latest revisions, such as the Handbook of Zoology chapters [29][30][31] and the present special issue ( [90][91][92][93][94][95][96][97][98][99][100][101]), there seems to be around 20,000 currently accepted nominal species (Figure 3). There is a continuous documentation of new species and diversity patterns as new taxonomic surveys are carried out in poorly explored geographic areas and localities, in new environments, such as the deep-sea and, surprisingly, also in apparently well-known zones when using different collecting gear, sorting methods or identification techniques, such as SEM and molecular taxonomy.…”

“…com. [94]; Terebelliformia [93]; Arenicolidae [89]; Opheliidae [90], Salibregmatidae and Travisia [89,90]; Capitellida [89]; Spionida [103][104][105][106]; Sabellariidae [89,107]; Sabellida [99]; Siboglinidae [108]; Cirratuliformia [89,100]; Orbiniida [95]; Phyllodocida [101]; Eunicida [91]; Sipuncula [97]; Amphinomida [89].…”

“…For the present special issue, we aimed at gathering updated information and discuss the recent advances in different diversity aspects and in recent systematic revisions of some of the major Annelida clades, including Palaeoannelida, Sipuncula, Phyllodocida, Eunicida, Orbiniida, Cirratuliformia, Sabellida, Opheliida and Scalibregmatidae, Terebelliformia, and Clitellata [90,91,[93][94][95][96][97][99][100][101]. Other chapters take a more ecological approach, for example the papers on extreme or interstitial annelids [92,98].…”

The genus Ophelina Örsted, 1843 (Annelida: Opheliidae) in the coast of Kuwait (northern Indian Ocean), with the description of a new species

“…The family Opheliidae Malmgren, 1867 currently comprises 5-8 genera and ca 160 to 171 species (Parapar et al 2021b;Read & Fauchald 2022). Nevertheless, a comprehensive revision of this family is European Journal of Taxonomy 870: 1-29 (2023) needed given its confusing taxonomic history (Parapar et al 2021b), and the evidence of paraphyly in Ophelina Örsted, 1843 that is the most speciose genus (Paul et al 2010;Wiklund et al 2019;Blake & Maciolek 2020;Gunton et al 2021). Furthermore, taxonomic knowledge on opheliids from several geographic regions is still scarce or fragmentary, mostly across the Indian Ocean and large areas of the Indo-Pacific.…”

Still Digging: Advances and Perspectives in the Study of the Diversity of Several Sedentarian Annelid Families

“…Within this incomplete picture, there are several lineages whose relationships with the remaining Sedentaria remain particularly obscure, including Cossuridae Day, 1963 [5], Paraonidae Cerruti, 1909 [6], Siboglinidae Caullery, 1914 [7], Hrabeiella Pizl, 1984 [8], Aeolosoma Ehrenberg, 1828 [9], Potamodrilus Lastochkin, 1935 [10], Scalibregmatidae Malmgren, 1867 [11], and Travisiidae Hartmann-Schröder, 1971 [12], among many others. Many recent studies have reviewed the current knowledge of several of these sedentarian lineages [13][14][15][16], including several articles within this issue [17][18][19][20][21], while others have received less attention (See [4]). In this article we focus on the cirratuliform families Acrocirridae Banse, 1969 [22], Cirratulidae Ryckholt, 1851 [23], and Sternaspidae Carus, 1863 [24], as well as the families Longosomatidae [25], Paraonidae, and Cossuridae, with the goal of providing an updated overview of our current knowledge on their diversity and systematics.…”