Diplocirrus Haase, 1915

Salazar-Vallejo, Sergio I. & Buzhinskaja, Galina, 2011, Revision of Diplocirrus Haase, 1915, including Bradiella Rullier, 1965, and Diversibranchius Buzhinskaja, 1993 (Polychaeta, Flabelligeridae), ZooKeys 106, pp. 1-45 : 5-8

Diplocirrus Haase, 1915

Diplocirrus Haase 1915:194; Day 1967:664-666; Fauchald 1977:116; Darbyshire and Mackie 2009:93.

Saphobranchia Chamberlin 1919:397; proposed for Stylarioides longisetosa vonMarenzeller, 1890.

Bradiella Rullier 1965:188.

Diversibranchius Buzhinskaja 1994:231.

Type species.

Trophonia glauca Malmgren, 1867, by original designation.

Diagnosis.

Body clavate or subcylindrical, often anteriorly swollen. Cephalic cage variably developed. Body papillae abundant, short giving a velvety appearance, or very long, giving a hirsute outlook, sometimes adhering sediment particles. All chaetae multiarticulated capillaries; neurochaetae thicker, sometimes falcate. Branchiae sessile, 4 pairs, distal branchiae thicker, often shorter, proximal branchiae thinner, often longer, sometimes basally lamellate. Gonopodial papillae present in chaetiger 4 or 5, or a series of paired ventrolateral gonopores along some anterior chaetigers.

Remarks.

Haase (1915) proposed Diplocirrus for those species formerly included in Stylarioides having two different sizes of branchiae, and multiarticulated capillaries only. Some species currently included in the genus had been previously described in either Trophonia or Stylarioides . However, as an independent genus, it differs by having two different sizes of branchiae, and all chaetae are multiarticulated capillaries.

Webster and Benedict (1887: 730) proposed Zorus , with Zorus sarsi as the type and only species. They indicated that it had a body anteriorly swollen, becoming thinner posteriorly, only with capillary chaetae, and stated that branchiae and palps arise from an eversible stalk but gave no details on the size relationship of branchiae. Hartman (1961:122) regarded Zorus as a junior synonym of Piromis Kinberg, 1867. However, because of the body form and chaetal features, it rather resembles Diplocirrus , because Piromis has few papillae arranged in longitudinal rows and sometimes bifid neurohooks, which were not found in Zorus . Webster (1879:46) had already stated the differences among capillary chaetae and ventral hooks when he described another flabelligerid; so, there is no room for any such confusion. The only illustration provided by Webster and Benedict (1887, Pl. 5, Fig. 67), shows a cross section of a middle segment with very long chaetae, and long papillae. These features resemble Diplocirrus hirsutus (Hansen, 1879), which is comm in the Bay of Fundi ( Appy et al. 1980:32). However, because there is no type material, the generic definition did not include a size relationship of branchial filaments, and the description and illustration lack critical information, Zorus sarsi has been regarded as indeterminable ( Salazar-Vallejo et al. 2008).

The record by Langerhans (1881:102-103, Figs. 14 a–d) of Brada inhabilis apparently belongs to Diplocirrus , but the illustrations and characters are not clear enough to assign it to any species. The record of Diplocirrus longisetosus by Rullier (1964:1094) off Cameroon belongs in Pycnoderma Grube, 1877b, likewise Diplocirrus erythroporus Gallardo, 1968, includes Diplocirrus glaucus orientalis Gibbs, 1971 (:181, no figures; orange globular papillae below each neuropodium in chaetigers 4-14(16)), and might also include the Indian Ocean record of Diplocirrus glaucus by Fauvel (1932:186-187, Fauvel 1953:353, Fig. 184 a–d).

As stated above, Diplocirrus capensis Day (1961:509, Fig. 9 a–f, South Africa), was described as lacking cephalic cage, with branchiae of a single kind, and with distally hooked neurochaetae (against generic diagnosis, cf Fauvel, Støp-Bowitz). The same different group might include Diplocirrus sp A Milligan (1984). The records of the former, originally described from Southern Africa ( Day 1967:666, Figs. 32.4 e–j; Fauchald 1972:4120), for North Carolina ( Day 1973:105-107), and the Gulf of Mexico ( Milligan 1984:47.9-11, Figs. 47.5-6), require confirmation to define if they belong to the same species. As stated above, Darbyshire and Mackie (2009) have clarified the branchial features for Diplocirrus capensis , whereas the other records remain unsolved.

These differences prompted Day (1961:510), to propose a misfortunate redefinition of Diplocirrus , because the branchial features have been employed to establish it by Haase (1915:26, 194). Especially because the posterior row of branchiae are not just thicker than the anterior row filaments; rather, they tend to be closely packed, with each filament laterally fused forming a branchial wall. Further, the cirriform thinner branchiae are contractile, and if they were observed completely relaxed by Day, he might have had the impression that they were of about the same thickness. Later, Day (1973:106-107) modified the generic definition of Diplocirrus concluding that it would also include Ilyphagus Chamberlin, 1919. However, as stated above, this second emendation is problematic as well, because of marked differences in neurochaetae, because in the species of Ilyphagus neurochaetae are aristate neurospines whose handle is made of fused or anchylosed, short articles, and a hyaline fragile tip, whereas in Diplocirrus there are only multiarticulate, often falcate, neurochaetae.

Bradiella Rullier (1965:190) was compared with Diplocirrus and Brada Stimpson, 1854. The branchial features were incompletely described (see below); it was regarded as different from these two genera because of the branchiae, and because it lacks gonopodial lobes. The potential differences between Bradiella and Diplocirrus would be that in Bradiella there are no gonopodial lobes in chaetigers 4-5, but gonopodial lobes have not been recorded in some Diplocirrus species at all. Further, the surface of branchial filaments is very complex in Bradiella , because it is provided with lamellate complex filaments, in contrast to the cirriform or tapering filaments which might barely have some ciliated bands, but some Diplocirrus species have a complex lamellar structure along the branchial filaments bases. Spies (1975) studied specimens from the type locality, Moreton Bay, Queensland, Australia, but overlooking the paper by Rullier (1965), identified them as Diplocirrus cf. capensis Day, 1961. He noticed that the branchiae include eight filaments, not just two as stated by Rullier, with four cirriform and four lamellate filaments. Spies (1975, Pl. 6, Fig. 18) illustrated a (lateral) dorsal spoon-like branchia provided with a flat lateral lobe, and a series of independent branchial blades. Thus, because there are variations in the presence of gonopodial lobes and in the development of lamellar structures in branchial filaments, the only difference to separate the Bradiella -like species would be the presence of paired ventrolateral pores. However, because there is no other major difference in chaetal types, Diplocirrus and Bradiella are regarded as synonyms.

Because of the rediscovery of these peculiar branchial features, Buzhinskaja (1994) established Diversibranchius . However, she overlooked Rullier (1965) as well, and compared his specimens with Diplocirrus , stressing its resemblance with Diplocirrus cf. capensis. She found that branchiae were of two types, cirriform and prismatic, or cuneiform, provided with foliose projections, and illustrated that both have convoluted branchial lamellae giving the impression of a series of independent blades, as was illustrated by Spies (1975). Bradiella and Diversibranchius Buzhinskaja, 1994 resemble each other by having two different types of branchiae, short to long body papillae, and multiarticulated neurohooks. These two genera are herein regarded as junior synonyms to Diplocirrus , such that the type species are redescribed, and transferred and newly combined into Diplocirrus .

As herein redefined, Diplocirrus includes, besides the type species from Scandinavia, Diplocirrus branchiatus (Rullier, 1965) comb. n. from Queensland, Australia, Diplocirrus capensis Day, 1961 from South Africa, Diplocirrus erythroporus Gallardo, 1968 from Vietnam, Diplocirrus hirsutus (Hansen, 1882) from Arctic and subarctic regions, Diplocirrus incognitus Darbyshire & Mackie, 2009 from South Africa, Diplocirrus kudenovi sp. n. from off Western Mexico, Diplocirrus longisetosus (von Marenzeller, 1890) restricted to the Bering Sea, Diplocirrus micans Fauchald, 1972 from deep water off Oregon and Western Mexico, Diplocirrus nicolaji (Buzhinskaja, 1994) comb. n. from the Japan Sea, Diplocirrus normani (McIntosh, 1908) comb. n. reinst., from Scandinavia, Diplocirrus octobranchus (Hartman, 1965) from off New England, and Diplocirrus stopbowitzi Dabryshire & Mackie, 2009, from the Irish Sea.

Two of these species ( Diplocirrus incognitus and Diplocirrus stopbowitzi ), have been recently described and only their diagnosis and illustrations are included. On the other hand, three other currently undescribed species are informally characterized but not all have been included in the key because the quality of the materials; one is from Morocco, another one from off Sri Lanka, and the other from Antarctica. The species can be separated using several morphological features as stated below.

Key to species of Diplocirrus Haase, 1915