Sthenolepis ruffi, Cruz-Gómez & Blake, 2024

Cruz-Gómez, Christopher & Blake, James A., 2024, Description of new species of deep water Sthenolepis Willey, 1905 and Neoleanira Pettibone, 1970 (Annelida, Sigalionidae) from off Northern California, with the redescription of Sthenolepis spargens Fauchald, 1972, Zootaxa 5507 (2), pp. 224-244 : 229-235

Sthenolepis ruffi new species

Figs. 3–5 , Table 1

urn:lsid:zoobank.org:act:DF33C5EF-F24B-4C17-84A4-AF380D5A3858

Sthenolepis sp. — Suárez-Morales et al. 2024: 55, figs. 1A, C (as host of a mesoparasitic copepod).

Material examined. Holotype. Eastern Pacific Ocean, Continental slope off northern California. W of Farallon Island, SF-DODS Benthic Monitoring Program , Sta. 52, 23 Jun 2015, 37.71686°N, 123.46695°W; 2350 m (LACMAHF-Poly 14396).

Paratypes and additional material. Eastern Pacific Ocean , Continental slope off northern California. W of Farallon Islands, SF-DODS Benthic Monitoring Program, Sta. 11, 23 Sep 2017, 37.6499°N, 123.5166°W, 3109 m, 1 paratype ( LACM-AHF Poly 14397) . Sta. 16, 28 Aug 2016, 37.6335°N, 123.4499°W, 2753 m, 2 paratypes ( CASIZ 236805 ) . Sta. 16, 20 Oct 2018, 37.633°N, 123.450°W, 2500 m, 2 paratypes ( CASIZ 236806 ) . Sta. 17, 07 Nov 2007, 37.635°N, 123.468°W, 2753 m, 1 paratype ( LACM-AHF Poly 14398) . Sta. 17, 20 Jun 2015, 37.634°N, 123.467°W, 2675 m, 4 paratypes ( LACM-AHF Poly 14399) . Sta. 19, 07 Nov 2007, 37.634°N, 123.500°W, 3030 m, 1 paratype ( LACM-AHF Poly 14400) . Sta. 19, 28 Aug 2016, 37.633°N, 123.500°W, 3064 m, 1 paratype ( CASIZ 236807 ) . Sta. 27, Nov 7, 2007, 37.686°N, 123.535°W, 2832 m, 1 paratype ( LACM-AHF Poly 14401) . Sta. 27, 27 Jun 2015, 37.667°N, 123.534°W, 2750 m, 4 paratypes ( MCZ IZ 169539 ) . Sta. 27, 28 Sep 2017, 37.683°N, 123.533°W, 2819 m, 4 paratypes ( LACM-AHF Poly 14402) . Sta. 92, 21 Jun 2015, 37.750°, 123.583°W, 2800 m, 2 paratypes ( MCZ IZ 169540 ) . Sta. 116, 07 Jul 2007, 37.750°N, 123.484°W, 2908 m, 1 paratype on SEM Stub ( LACM-AHF Poly 14403) . Sta. 137, 08 Aug 2016, 37.550°N, 123.483°W, 3253 m, 1 paratype on SEM stub ( LACM-AHF Poly 14404) . Sta. 19, 07 Oct 1998, 37.633°N, 123.5°W, 3030 m, 1 paratype ( LACM-AHF 14418 ) . Sta. 27, 2016, 37.666N, 123.53W, 2805 m, 5 non-types ( LACM-AHF Poly 14416) . Sta. 6, 27 Sep 2006, 37.650°N, 123.1166°W, 2732 m, 6 non-types ( LACM-AHF Poly 14405) . Sta. 6, 22 Sep 2006, 37.400°N, 123.127°W, 2697 m, (6, LACM-AHF Poly 14419) . Sta. 16, 11 Jul 2007, 37.616°N, 123.433°W, 2699 m, 2 non-types ( LACM-AHF Poly 14446) . Sta. 19, 11 Jul 2007, 37.633°N, 123.5°W, 3100 m, 1 non-type ( LACM-AHF Poly 14407) . Sta. 23, 13 Jul 2007, 37.6166°N, 123.4833°W, 2995 m, 2 non-types ( LACM-AHF Poly 14408) . Sta. 23, 26 Sep 2002, 37.3695°N, 123.2901°W, 2954 m, (1, LACM-AHF Poly 14417) . Sta. 64, 13 Jul 2007, 37.60°N, 123.55°W, 3115 m, 3 non-types ( LACM-AHF Poly 14409) . Sta. 23, 21 Jul 2015, 37.616°N, 123.483°W, 3000 m, 1 non-type ( LACM-AHF Poly 14410) . Sta. 92, 27 Aug 2016, 37.733°N, 123.583°W, 2820 m, 1 non-type ( LACM-AHF Poly 14411) . Sta. 57, 27 Aug 2016, 37.70°N, 123.533°W, 2815 m, 1 non-type ( LACM-AHF Poly 14412) . Sta. 64, 29 Aug 2016, 37.60°N, 123.533°W, 3221 m, 3 non-types ( LACM-AHF Poly 14413) . Sta. 116, 28 Jun 2015, 37.583°N, 123.483°W, 2850 m, 2 non-types ( LACM-AHF Poly 14414) . ― Eastern Pacific , Continental slope off northern California. Baseline Survey at U. S. Navy Ocean Disposal Site, July 1991, R/ V Wecoma, coll. J.A. Blake. Sta. B-1, 18 Jul 1991, 37.657°N, 123.500°W, 2955 m, 4 non-types ( MCZ IZ 169541 ) . Sta. B-2, 19 Jul 1991, 37.668°N, 123.466°W, 2701 m, 1 non-type ( MCZ IZ 169542 ) . Sta. B-4, 20 Jul 1991, 37.641°N, 123.501°W, 3055 m, 2 non-types ( MCZ IZ 169543 ) . Sta. B-5, 20 Jul 1991, 37.649°N, 123.480°W, 2925 m, 2 non-types ( MCZ IZ 169544 ) . Sta. B-6, 21 Jul 1991, 37.646°N, 123.4201°, 2720 m, 1 non-type ( MCZ IZ 169545 ) . Sta. B-12, 22 Jul 1991, 37.571°N, 123.472°W, 2700 m, 1 non-type ( MCZ IZ 169546 ) . Sta. B-13, 22 Jul 1991, 37.545°N, 123.413°W, 2400 m, 2 non-types ( MCZ IZ 169547 ) . Sta. B-14, 22 Jul 1991, 37.549°N, 123.4701°W, 3000 m, 1 non-type ( MCZ IZ 169548 ) . Sta. B-15, 23 Jul 1991, 37.5395°N, 123.435°W, 2750 m, 3 non-types ( MCZ IZ 169549 ) . Sta. B-19, 23 Jul 1991, 37.523°N, 123.413°W, 2425 m, 1 non-type ( MCZ IZ 169550 ) .

Description. Holotype complete with 81 segments, 35.5 mm long, 9 mm to segment 30, 4.5 mm wide. Body slender, tapered at both ends; pale orange ( Fig. 3A ). Mid-dorsal line smooth, some elytra remain, venter smooth. Elytrophores on segments 2, 4, 5, 7, then alternate segments to 25, then present in all segments. Elytrophores bulbous, longer and thinner in posterior segments.

Prostomium pale orange, whitish on cerebral lobes; oval, wider than long. Eyes lacking. Lateral antennae short, inconspicuous, inserted on inner dorsal side of tentacular segment. Median antenna with ceratophore, slightly shorter than prostomial length; style 7× as long as ceratophore length; inserted on anterior margin of the prostomium.Auricles reniform, half as long as ceratophore; inserted basally and laterally on ceratophore. Tentacular segment uniramous, chaetae verticillate. Dorsal tentacular cirri 5× longer than tentacular neuropodia, ventral tentacular cirri very short, 2× as long as tentacular neuropodia ( Figs. 3B , 5A ). Inner tentacular lobes half as long as inner palpal sheaths. Palps reaching segment 12. Inner palpal sheaths twice as large as outer palpal sheaths ( Figs. 3C , 5C ). Buccal cirri slightly longer than the remaining ventral cirri. Buccal ctenidial pads, slightly enlarged, inserted anterolaterally on buccal aperture ( Figs. 3C , 5B–C ). Ctenidial pads from segment 1; segment 1 with 1 dorsal ctenidial pad, succeeding segments with 4–5 ctenidial pads: 2 large and bulbous pads placed on dorsolateral surface of the segment; 1 smaller pad, half as large as dorsolateral ones, placed on dorsal side of notopodia; 0–1 small pad, placed on anterior inner side of parapodia; and 1 truncated pad, inserted ventrally. Branchiae from segment 2, small becoming larger from segment 7, filiform with cilia ( Fig. 3E ). Nephridial papillae not observed.

First right elytron small, oval ( Fig. 3A , upper inset). Median elytron larger, oblong ( Fig. 3A , lower inset). Posterior elytra larger, distally expanded ( Fig. 3A , upper inset). All elytra with smooth surfaces and margins; due to their fragility and delicate texture, elytral surface may appear corrugated under microscope.

Segment 3 ( Fig. 3E ). Notopodia ovate, slightly shorter than neuropodia. Notacicula thick, not protruding from body wall. Notochaetae with up to 20 simple verticillate chaetae, smallest 3× as long as notopodia ( Fig. 3E , lower inset), longest 5× as long ( Fig. 3E , upper inset). Neuropodia conical. Prechaetal lobe entire, with a few dendritic stylodes. Postchaetal lobes differentiated, divided by a deep notch, without stylodes. Neuracicula thick, inserted in the prechaetal lobe, protruding from body wall. Neurochaetae only spinigers ( Fig. 3D ). Upper group (unit A) with 6 chaetae, handles slender with a subdistal row of small denticles, blades medium-sized, 24× as long as wide. Upper middle group (unit B) with 10 chaetae, blades long, 35× as long as wide. Middle group (unit C), 8 chaetae, blades short, 15× as long as wide. Lower middle group (subunit 1) with 8 chaetae, blades long, 29× as long as wide. Lowest group (unit D) with 5 chaetae, blades medium-sized, 18× as long as wide. Ventral cirri 1/3 as long as neuropodia.

Segment 20 (middle segment) ( Fig. 4A–D ): Notopodia conical, with a few small subdistal dendritic stylodes, barely shorter than notopodia. Notacicula thick. Notochaetae with up to 15 simple verticillate chaetae ( Figs. 4D , inset, 5F), smallest barely shorter than notopodia, longest 2× longer than notopodia. Neuropodia conical. Prechaetal lobe entire, with a few small dendritic stylodes along lateral external margin. Postchaetal lobes well differentiated, without stylodes. Neuracicula thick, inserted in prechaetal lobe, protruding from body wall. Neurochaetae only spinigers ( Figs. 4E , 5H ). Upper group (unit A) with 3 chaetae, handles slender with a medial small subdistal tooth, and two smaller ones laterally, blades medium-sized to long, 16–30× as long as wide. Upper middle group (unit B) with 10 chaetae, handles thick with a medial small subdistal tooth, and two smaller ones laterally, blades long, 39–47× as long as wide. Middle group (unit C) with 8 chaetae, blades long, 26× as long as wide. Lower middle group (subunit 1) with 5 chaetae, blades short, 14× as long as wide. Lower group (subunit 2) with 2 chaetae, blades medium-sized, 24× as long as wide. Lowest group (unit D) with 7 chaetae, blades short, 15× as long as wide. Ventral cirri 1/3 as long as parapodia ( Fig. 4D ).

Pygidium half as large as regular posterior segments. Pygidial cirri not observed, large ctenidial pads inserted dorsally. Anus terminal ( Figs. 3A , inset, 5D).

Remarks. In the Northeastern Pacific, there are two Sthenolepis species: S. fimbriarum ( Hartman, 1939) and S. spargens , both described from the Gulf of California. Although these species and the newly described Sthenolepis species are morphologically similar, they can be easily distinguished based on the size of the median antennae and auricles, as well as on the type of neurochaetae and elytra ( Table 1 ).

Sthenolepis ruffi n. sp. differs from S. fimbriarum in lacking eyes, having smaller auricles and a long median antenna, smooth elytra without fimbriae on its margins, and canaliculate blades. In contrast, S. fimbriarum has two pairs of eyes, large auricles, as long as the median antennal ceratophore, a short median antenna, slightly longer than the prostomium, elytra with a few fimbriae on one of its margins, and non-canaliculate blades ( Hartman 1939: 70, Pl. 18, 217–225). Hartman (1939) originally described her species in the genus Leanira , but noted that it resembles Sthenelais Kinberg, 1856 ; however, she kept her species in Leanira because it only has spinigers. Later she transferred the species to Sthenolepis with no comment on the decision ( Hartman 1965). The other genus that has spinigers is Eusthenelais McIntosh, 1876 (sensu Barnich & Van Haaren 2021), but even in this latter genus, falcigers are present. Further, Eusthenelais presents dorsal tentacular crests and nuchal organs, features lacking in S. frimbriarum . We recommend the revision of Sthenolepis , and its comparison with other morphologically close genera such as Eusthenelais and Horstileanira . This issue is beyond the scope of the present paper.

Sthenolepis spargens seems closer morphologically to S. ruffi n. sp., both lack eyes and have small auricles and canaliculate blades. However, the two species differ in the size of the palps and tentacular cirri and the composition of neurochaetae ( Table 1 ). Sthenolepis ruffi n. sp. has long palps reaching segment 12 and short tentacular cirri, five times as long as tentacular parapodia. Meanwhile, S. spargens has longer palps reaching segment 20 and long tentacular cirri, 12 times as long as the tentacular parapodia. Further, S. ruffi n. sp. has upper neurochaetal handles with a small median subdistal tooth, and two barely noticeable smaller ones on the sides. In comparison, S. spargens has handles with an enlarged medial subdistal tooth but no additional teeth on the sides. Another difference between these species is the nature of the neurochaetal blades. Sthenolepis ruffi n. sp., bears noticeably longer blades, for instance, blades from the upper middle group (unit B) can reach up to 47 times longer than wide, and blades from the lowest group (unit D) may be non-canaliculate. While S. spargens has blades from the upper middle group (unit B) shorter, ½ as long as the ones in S. ruffi n. sp., being about 23 times longer than wide, and all blades are canaliculate, including the lowest group (unit D).

An additional difference observed between the three similar species, S. spargens and S. ruffi n. sp. were found in deep water (2,350 –3,400 m), while S. fimbriarum occurs in shallow water (18.2 m).

Biology. Specimens of Sthenolepis ruffi n. sp. were collected from throughout the SF-DODS disposal area including the boundary of the actual disposal site and from numerous reference locations well outside the site (see Blake et al. 2009: fig. 2). In addition, the species was collected in samples from the US Navy baseline survey prior to any dredged material disposal. As such the species is likely widespread along the continental slope off California.

Sedimentary parameters determined by subsamples from the box cores and sediment profile images (SPI) from surveys from 1996–2003 indicate that S. ruffi n. sp. occurs in sediments with fine grains (silt + clay) of 90–98% and total organic carbon (TOC) of 2.97–3.09% at distant reference stations (64 and 92) not influenced by dredged material (DM) disposal and where it was not detected in the SPI images. In contrast, Stations 17 and 19 on the boundary of the disposal site had sediments with 45–77% silt + clay, TOC values of 1.3–2.6%, and DM depths of 2.35–7.0 cm (Sta. 17, 7 surveys) and 2.1–5.7 (Sta. 19, 5 surveys) ( Blake et al. 2009).

In addition, S. ruffi n. sp. was recently recorded as a host of a mesoparasitic copepod. The copepod was found attached to the anterior region of the body; apparently the prevalence is low since only one of more than 60 specimens was parasitized ( Suárez-Morales et al. 2024).

Etymology. This species is named after the late Robert Eugene Ruff in recognition of his many efforts in the exploration of deep-sea and collections of marine invertebrates, especially polychaetes.Also, he made the first round of identification of these specimens. The species name is a noun in the genitive case ( ICZN 1999, Art. 31.1.2).

Distribution. Northeast Temperate Pacific, lower continental slope off northern California, 2,350 –3,253 m.

Figures

FIGURE 3. Sthenolepis ruffi n. sp. Holotype (LACM-AHF-Poly 14396). A. Complete specimen, inset: 1st right elytron, medium right elytron, posterior right elytron, and pygidium, ventral view. B. Drawing of anterior end, dorsal view. C. Drawing of anterior end, ventral view. D. Neurochaetae from segment 3. E. Parapodium from segment 3, anterior view, inset: close-up of notochaetae from lower and upper position. Abbreviations: au= auricle, ct= ctenidia, dtu= dorsal tubercle, dtc= dorsal tentacular cirrus, ftu= facial tubercle, ipas= inner palpal sheath, itl= inner tentacular lobe, lan= lateral antenna, man= median antenna, opas= outer palpal sheath, pa= palp, S1= lower middle group, UA= upper group, UB= upper middle group, UC= middle group, UD= lowest group. Scale bars: A: 5 mm, B, C: 1 mm, D: 50 µm, E: 200 µm.

FIGURE 4. Sthenolepis ruffi n. sp. Holotype (LACM-AHF-Poly 14396). A. Drawing of parapodium from segment 20, anterior view. B. Drawing of same, posterior view. C. Diagrammatic of same, lateral view, color lines indicate the insertion of neurochaetal groups, color scheme following that shown in E. D. Parapodium from segment 20, anterior view, inset: close-up of notochaetae. E. Neurochaetae from segment 20. S1= lower middle group, S2= lower group, UA= upper group, UB= upper middle group, UC= middle group, UD= lowest group. Scale bars: A–C: no scale, D: 200 µm, E: 50 µm.

FIGURE 5. Sthenolepis ruffi n. sp. SEM images of paratypes (LACM-AHF-Poly 14403 and 14404). A. Anterior end, dorsal view. B. Anterior end, frontal view. C. Anterior end, ventral view. D. Posterior end, pygidium. E. Parapodia from median segments. F. Notochaetae from same. G. Ventral ctenidium. H. Neurochaetae, upper group.Abbreviations: an= anus, au= auricle, br= branchia, ct= ctenidia, dtu= dorsal tubercle, dtc= dorsal tentacular cirrus, ipas= inner palpal sheath, itl= inner tentacular lobe, lan= lateral antenna, man= median antenna, mo= mouth, opas= outer palpal sheath, pa= palp, st= stylode, vc= ventral cirrus, vtc= ventral tentacular cirrus. Scale bars: A–E: 100 µm, F: 10 µm, G: 50 µm, H: 20 µm.