Raricirrus Hartman, 1961

Magalhães, Wagner F., Linse, Katrin & Wiklund, Helena, 2017, A new species of Raricirrus (Annelida: Cirratuliformia) from deep-water sunken wood off California, Zootaxa 4353 (1), pp. 51-68 : 53

Genus Raricirrus Hartman, 1961

Type species: Raricirrus maculatus Hartman, 1961

Diagnosis (emended after Dean 1995). Prostomium rounded, eyes absent, nuchal organs shallow ciliary pits, postero-lateral, rounded or elongate. Peristomium not obviously delimited from prostomium and chaetiger 1 dorsally; ventral cilia may be present on peristomium and first few segments; first segment complete chaetiger. Tentacles absent. Branchiae present on several segments, filiform or club-like distally. Notochaetae short and long serrate capillaries anteriorly and modified chaetae posteriorly as acicular spines, coarsely serrate forms and short pectinate falcigers. Neurochaetae short serrate capillaries and/or modified chaetae such as acicular spines, falcate and finely pectinate, and coarsely serrate chaetae. Simple enlarged spines may be present in one or two posterior end segments. Heart body enlarged dorsal vessel present in variable number of anterior and middle segments. Pygidium simple lobe, anal aperture usually dorsal; posterior region distinct with few segments wider than preceding ones. Asexual reproduction via architomy. Sexual reproduction may occur; epitoke individuals, hermaphroditism, seminal vesicle and reproductive stylet may be present.

Remarks. The genus Raricirrus Hartman, 1961 was originally proposed as part of the Cirratulidae and differed from the known genera by the absence of dorsal tentacles and branchiae limited to a few mid-body segments ( Hartman 1961). Petersen & George (1991) transferred Raricirrus to the family Ctenodrilidae based on the absence of feeding tentacles at all stages of development and redefined the ctenodrilids to include Raricirrus while excluding Zeppelina Vaillant, 1890 . The close morphological affinities between Raricirrus and Raphidrilus led Petersen & George (1991) to include Raricirrus within the subfamily Raphidrilinae Hartmann-Schröder, 1971. The differences between these two genera were elucidated in Magalhães et al. (2011), listing as the main differing characters the types of chaetae, position and extent of the heart body and shape of the posterior end segments. Based on molecular data, Ctenodrilus Claparède, 1863 , the type genus of the Ctenodrilidae , has been shown to belong to a clade that includes the Cirratulidae and shows close affinities to the cirratulid genus Dodecaceria ( Bleidorn et al. 2003; Rousset et al. 2007; Magalhães et al. 2016; Weidhase et al. 2016). Weidhase et al. (2016) suggested that the genus Raricirrus , represented by sequences of R. beryli , belonged within the Cirratulidae as a sister taxon to a clade composed of multitentaculate cirratulid genera Cirratulus , Cirriformia and Timarete . The diagnosis of Raricirrus is herein emended to include the presence of acicular spines as seen in R. jennae sp. nov., a character only previously known in most multitentaculate cirratulid genera. The absence of tentacles as in all ctenodrilid genera was speculated to represent a juvenile character (Weidhase et al. 2016) but further phylogenetic analysis taking into consideration molecular and morphological data should be performed to understand the relationships between ctenodrilid and cirratulid genera and the evolution of the feeding tentacles. Raricirrus is herein defined as genus belonging to a clade that includes the Cirratulidae , lacking dorsal tentacles, having filiform branchiae limited to a few anterior and mid-body segments, posterior end with a few widened segments, and having diverse types of chaetae, including short and long serrated capillaries, acicular spines, falcate and finely pectinate chaetae, coarsely serrate chaetae and simple enlarged genital spines limited to a few posterior end segments in male individuals.

Two subfamilies had been proposed for the Ctenodrilidae : Ctenodrilinae Kennel, 1882 , including those ctenodrilids with a short body, without branchial filaments and reproducing exclusively asexually (genera Ctenodrilus and Aphropharynx Wilfert, 1974 ) and Raphidrilinae Hartmann-Schröder, 1971 for those ctenodrilids with long bodies, branchial filaments present, and reproducing both sexually and asexually (genera Raricirrus and Raphidrilus ). The genus Ctenodrilus was shown to be related to the bidentaculate genus Dodecaceria (e.g. Magalhães et al. 2016; Weidhase et al. 2016) and Raricirrus to be related to the multitentaculate genera Cirratulus Lamarck, 1818 , Cirriformia Hartman, 1936 and Timarete Kinberg, 1866 (Weidhase et al. 2016). Molecular data on Aphropharynx is unlikely to become available as this species was collected from an aquarium and it has not been reported again in the literature. The genus Raphidrilus was recently reviewed by Magalhães et al. (2011) and its relationship with Raricirrus is limited to the absence of feeding tentacles (which seems to be very labile within the Cirratulidae ) and the presence of filiform branchiae (also present in most cirratulid genera). The genus Raphidrilus has species with only serrated capillaries and lacking modified chaetae. The only other cirratulid genus sharing these characters is Protocirrineris Czerniavsky, 1881 , but differs from Raricirrus in the presence of dorsal tentacles. The genus Aphelochaeta Blake, 1996 also lacks modified chaetae but the capillaries are fimbriated. Presently, the validity of the subfamilies Ctenodrilinae and Raphidrilinae cannot be fully assessed because of the lack of molecular data for the genera Raphidrilus and Aphropharynx and lack of a cladistics analyses for the cirratulid genera. Further phylogenetic analysis should be performed to verify if all Ctenodrilidae genera belong within the Cirratulidae . Here we provide a key to all cirratulid and ctenodrilid genera plus a key to species of Raricirrus .