Evolution of interstitial Polychaeta (Annelida)

Abstract

An update of the systematics is given for the eight most important interstitial polychaete families: Diurodrilidae, Nerillidae, Protodrilidae, Protodriloididae, Saccocirridae, Parergodrilidae, Polygordidae and Psammodrilidae. Additional information and new observations are presented for the Diurodrilidae, Nerillidae and Psammodrilidae. Three new supplementary evolutionary hypotheses for these families are here suggested: (I) basal position of Diurodrilidae in Polychaeta, (2) evolution of Nerillidae in mud, and (3) evolution from meio-to macrofaunal forms of Psammodrilidae. Hydrobiologia (2005) 535

The Evolution of Annelids Reveals Two Adaptive Routes to the Interstitial Realm

“…For these four archiannelid taxa, a close relationship to Errantia or its subtaxon Eunicida had been proposed based on morphological data, again assuming progenesis [4,10]. For example, Dinophilidae and Diurodrilidae were considered progenetic Eunicida due to their resemblance to eunicidan polytroch larvae [3,4,8,9,[13][14][15]. Such a relationship is not supported by our data and was significantly rejected by hypothesis testing (Table S1).…”

“…These also include various annelid taxa, which among others comprise the so-called archiannelids (Protodrilida, Polygordiidae, Dinophilidae, Diurodrilidae, Nerillidae, and Apharyngtus) [8,9]. Hypotheses regarding evolution of interstitial species can be categorized into three scenarios [3].…”

“…Progenesis is currently assumed for all archiannelid taxa (taxa labeled with an A in Figure 1) [3,4,8,9,[13][14][15]. However, the conclusion of progenesis based on morphological data alone entails the risk of circular reasoning [4].…”

Nerillidae (Annelida) from the Corona lava tube, Lanzarote, with description of Meganerilla cesari n. sp.

“…1). Nerillidae, favoring the coarse sandy subtidal interstitial environment offshore (Worsaae and Kristensen 2005;Westheide 2008), here exhibit the highest diversity among the annelid families. Two of the four nerillids recorded here, Mesonerilla armoricana and Meganerilla cesari n.…”

“…Another four species of Nerillidae have previously been described from anchialine and marine cave systems in the Atlantic: Leptonerilla prospera Sterrer and Iliffe, 1982; Longipalpa saltatrix Worsaae, Sterrer and Iliffe, 2004;Nerilla marginalis Tilzer, 1970;and Troglochaetus beranecki Delachaux, 1921. Neither Mesonerilla nor Meganerilla have been reported previously from anchialine environments, but both nerillid genera have been found in fine silty sediments and dirty coarse gravel similar to sediments of the Corona lava tube (see, e.g., Müller et al 2001;Worsaae and Kristensen 2005;Worsaae and Rouse 2009).…”