Dalhousia atlantica McIntosh 1885

Dataset
Revision of Leocrates Kinberg, 1866 and Leocratides Ehlers, 1908 (Annelida, Errantia, Hesionidae): Rank
SPECIES

Classification

kingdom
Animalia: phylum
Annelida: class
Polychaeta: order
Phyllodocida: family
Hesionidae: genus
Dalhousia: species
Dalhousia atlantica

description

Description. Largest non-type specimen (MNHN CENTOB Thalassa 1973 - 417), complete, tapered, slightly damaged, tentacular and dorsal cirri broken, most notochaetal bundles broken, bent laterally and ventrally. Body colorless, stomach darker in some specimens (Fig. 9 A), 29 mm long, 5 mm wide, 16 chaetigers; right parapodium of chaetiger 8 removed for observing parapodial features. Eyes blackish, posterior prostomial projections blackish; feebly pigmented areas include areas around eyes, projected anteriorly into palpophores and along lateral ciliated bands (Fig. 10 B), darker in other specimens (Fig. 9 D, E). Prostomium as long as wide, wider anteriorly. Lateral antennae longer than prostomium, slightly longer than palps; palpophores slightly longer than palpostyles. Median antenna missing, scar inserted centrally between eyes (other large specimens with median antenna surpassing anterior prostomial margin). Eyes blackish, anterior ones emarginate, twice larger and slightly more separated than posterior reniform eyes; in lateral view, eyes distinct. Nuchal organs lobes blackish, slightly longer than wide, pigment spot medially indented, lobes subrectangular, slightly divergent; lateral ciliated areas visible dorsally (Fig. 9 B, E). Lateral cushions swollen, entire anteriorly, bifid posteriorly, longitudinal striae visible. Peristomial dorsolateral tubercles low, oval, barely projected, ventrolateral tubercles indistinct. Pharynx evert- ed, anterior margin ciliated, lateral vesicles not swollen, left one slightly more projected; basal ring smooth. Jaws brownish, upper jaw double, lower jaw transverse with exposed region semicircular, almost transparent (Figs 5 A – C, 9 C, F). Longest tentacular cirri without tips, reaching chaetiger 6. Dorsal cirri broken, shorter than body width. Chaetigers 1 – 3 without notochaetae, notochaetae present along chaetigers 4 – 16, mostly broken (abundant, about 50 per bundle in another large specimen), subdistally denticulate, denticles fine. Notacicular lobes triangular, tapered (Fig. 9 G), or blunt (Fig. 10 G); neuracicular lobes as long as wide, blunt. Neurochaetae brownish, handle and basal portion of blades pigmented, about 50 per bundle, blades denticulate, decreasing in size ventrally, 3 – 20 times longer than wide (Fig. 10 H, I), tips of longest blades difficult to be seen, guards approaching subdistal tooth. Posterior region tapered; prepygidial segment with dorsal cirri 3 times longer than ventral ones; pygidium with anus terminal, anal cirri missing (other large specimens with broken cirri, reaching chaetiger 13). Gonads visible inside parapodia; oocytes not seen. Variation. Five presumptive topotype specimens (MNHN A 71) with body grayish, twisted, most cirri missing, many chaetae broken, eyes and nuchal organs brownish to blackish (Fig. 10 A, E). Body obconic, 20 – 32 mm long, 3 – 4 mm wide, 16 chaetigers. Lateral antennae shorter than prostomium or palps, broken in several specimens; palpophores slightly longer than palpostyles, bent ventrally (Fig 10 B, F). Median antenna short, not reaching prosto- mial anterior margin, inserted between eyes. Nuchal organs lobes partially covered by anterior margin of tentacular belt, parallel, blackish; lateral ciliated bands wide, visible dorsally. Pharynx exposed; jaws with exposed portions hyaline, transverse to pharynx; upper jaw double, separated, lower jaw double, fused as a transverse plate (Fig. 10 C). Dorsal cirri broken, shorter than body width (excluding parapodia). Notochaetae present along chaetigers 4 – 16; notacicular and neuracicular lobes conical, three times longer than wide, tapered (Fig. 10 D, G). Notochaetae about 30 per bundle, subdistally denticulate, denticles fine. Neurochaetae golden, 30 – 40 per bundle, blades bidentate, 8 – 18 times longer than wide, guards approaching subdistal tooth. Posterior region tapered into a blunt cone; prepygidial segment without cirri, pygidium with anus terminal, anal cirri missing. Gonads with spermatids; ovaries seen in parapodia by transparency, oocytes about 100 µm in diameter (Fig. 10 G).

description

Figures 4, 5 A – C, 9, 10

discussion

Remarks. The holotype of Dalhousia atlantica McIntosh, 1885 is lost (E. Sherlock, 2018 in email). Pettibone (1970) redescribed and illustrated the type specimen, although she included another species from Indonesia, D. indica (Horst, 1921) n. comb., as a junior synonym. As indicated in the key above and in the corresponding redescription, they are different. The above description, as well as the variation, are based upon topotype and non-type specimens.

distribution

Distribution. Originally described from off the Canary Islands, in deep water sediments (2745 m), it can be found from the Faroe Islands to Western Africa, in 760 – 1470 m depth. There is a surface record, in a drifting object by Fauvel (1914); the specimen (MOM 180995) matches the species and it is herein regarded as a mislabeled specimen. Other records for shallow water in Western Africa by Fauvel (1950: 349, 1953 a: 18) cannot be confirmed because his specimens were not available; additional records correspond with Paralamprophaea greeffiana (Augener, 1918) n. comb. (see below).

materials_examined

Type material. Western Africa. Holotype (BMNH 1885: 12: 1: 139), HMS Challenger, Sta. 3, SW off Canary Islands (25 ° 45 ’ N, 20 ° 14 ’ W), 2745 m, Feb. 1873 (type lost; E. Sherlock in email, 2018). Additional material. Western Africa. Five specimens (MNHN A 71), R / V Talisman, combined from three stations by Louis Roule, but two are Dalhousiella carpenteri McIntosh, 1901. Field data after Vaillant (1888) as follows: 4 specimens, dredge 20 (33 ° 43 ’ N, 11 ° 22 ’ W), off Mazagan (El Yadida), Morocco, 1105 m, sand and sponges, 14 Jun. 1883; 1 specimen, dredge 46, between Lanzarote (Canary Islands) and Morocco, 1153 m, yellow sand, 26 Jun. 1883; and 2 specimens, dragage 49, off Lanzarote (Canary Islands), 865 – 927 m, yellow sand, date not indicated (used for variation as topotypes). One specimen (MNHN A 420), Albert 1 er de Monaco Expeditions, Sta. 198 (38 ° 26 ’ 25 ” N, 28 ° 38 ’ 55 ” W), off South of Fayal, 800 m, sand and mud, 25 Jul. 1888 [19 mm long, 2.3 mm wide]. One specimen (MOM 180771), Albert 1 er de Monaco Expeditions, Sta. 1116 (31 ° 43 ’ 30 ” N, 10 ° 46 ’ 45 ” W), off Esauria, Morocco, 2165 m, pink sand with globigerinans, 11 Jul. 1901 [19 mm long, 4 mm wide]. Cabo Verde Islands. One specimen (MOM 180817), Albert 1 er de Monaco Expeditions, Sta. 1203 (15 ° 54 ’ 00 ” N, 22 ° 54 ’ 45 ” W), 6.2 km off SW Boa-Vista Island, 91 m, rocky bottom, 18 Aug. 1901. Açores. 11 specimens (MOM 180228), Albert 1 er de Monaco Expeditions, Sta. 198 (38 ° 26 ’ 25 ” N, 28 ° 38 ’ 55 ” W), 800 m, sandy mud, 25 Jul. 1888 [16 – 30 mm long, 3 – 5 mm wide]. One specimen (MOM 180401), Albert 1 er de Monaco Expeditions, Sta. 578 (38 ° 26 ’ 00 ” N, 26 ° 30 ’ 45 ” W), 1165 m, sandy mud, 14 Jul. 1895 [26 mm long, 3.5 mm wide]. 11 specimens (MOM 181144 a), Albert 1 er de Monaco Expeditions, Sta. 584 (38 ° 30 ’ 30 ” N, 26 ° 50 ’ 15 ” W), 845 m, rock, 16 Jul. 1895 [13 – 33 mm long, 2 – 4 mm wide]. Two specimens (MOM 181144 b), Albert 1 er de Monaco Expeditions, Sta. 584 (38 ° 30 ’ 30 ” N, 26 ° 50 ’ 15 ” W), 845 m, rock, 16 Jul. 1895 [very poor condition]. Two specimens (MOM 180414), Albert 1 er de Monaco Expeditions, Sta. 587 (36 ° 36 ’ 40 ” N, 27 ° 17 ’ 15 ” W), 793 m, sand, 18 Jul. 1895 [12 – 22 mm long, 3 – 4 mm wide]. One specimen (MOM 180433), Albert 1 er de Monaco Expeditions, Sta. 597 (38 ° 27 ’ 00 ” N, 28 ° 03 ’ 25 ” W), close to Prainha de Pico, 523 m, rock, 23 Jul. 1895 [16 mm long, 2.5 mm wide]. One specimen (MOM 180445), Albert 1 er de Monaco Expeditions, Sta. 616 (38 ° 46 ’ 35 ” N, 28 ° 17 ’ 20 ” W), close to Rosales or São Jorge Point, 1022 m, gray sandy mud, 1 Aug. 1895 [14 mm long, 2 mm wide]. One specimen (MOM 180527), Albert 1 er de Monaco Expeditions, Sta. 837 (37 ° 55 ’ 00 ” N, 25 ° 24 ’ 15 ” W), 880 m, rock, 22 – 24 Jul. 1897 [17 mm long, 3 mm wide]. Two specimens (MOM 180888), Albert 1 er de Monaco Expeditions, Sta. 1344 (38 ° 45 ’ 30 ” N, 28 ° 07 ’ 45 ” W), 1095 m, volcanic sand, 18 Aug. 1901 [27 – 32 mm long, 4 – 5 mm wide]. One specimen (MOM 180995), Albert 1 er de Monaco Expeditions, Sta. 2214 (39 ° 26 ’ 10 ” N, 31 ° 21 ’ 30 ” W), drifting object with Amphinome pallasii de Quatrefages (probably mislabeled specimen), 1866, 2 Sep. 1904 [19.5 mm long, 2 mm wide]. Celtic Sea. Sixteen specimens (MNHN CENTOB Thalassa 1973 - 417), R / V Thalassa, Cruise 1973, Sta. Z 417 (48 ° 12 ’ 99 ” N, 09 ° 09 ’ 05 ” W), 865 m, corals, sand to muddy bottom, 21 – 29 Oct. 1973 [21 – 28 mm long, 2.5 – 4.0 mm wide]. Fifteen specimens (MNHN CENTOB Thalassa 1973 - 421), R / V Thalassa, Cruise 1973, Sta. Z 421 (48 ° 22 ’ 05 ” N, 09 ° 33 ’ 05 ” W), 950 m, calcareous green rocks, sand, 21 – 29 Oct. 1973 [12 – 38 mm long, 2 – 6 mm wide]. Sixteen specimens (MNHN CENTOB Thalassa 1973 - 452), R / V Thalassa, Cruise 1973, Sta. Z 452 (48 ° 41 ’ 05 ” N, 10 ° 53 ’ 00 ” W to 48 ° 39 ’ 00 ” N, 10 ° 52 ’ 02 ” W), 1420 – 1470 m, rocks, sand, corals, 21 – 29 Oct. 1973 [15 complete and one anterior fragment; 12 – 35 mm long, 2 – 5 mm wide]. Iberian Seas. One specimen (MNCN 16.01 / 121), Banco de Galicia (43 ° 07 ’ N, 12 ° 14 ’ W), no further field data [27 mm long, 3.5 mm wide]. One specimen (MNCN 16.01 / 10300), Campaña Fauna II, Sta. 171 A, E off Islas Sisargas, 89 – 96 m (strange depth, probably wrong), 27 Jun. 1991 [34 mm long, 3.5 mm wide]. One specimen (MNCN 16.01 / 10301), Campaña Fauna II, Sta. 172 A, Banco de Galicia (43 ° 07 ’ N, 12 ° 14 ’ W), 761 – 768 m, 28 Jun. 1991 [43 mm long, 7 mm wide]. 29 specimens (MNCN 16.01 / 10302), Campaña Fauna II, Sta. 173 A, Banco de Galicia (43 ° 07 ’ N, 12 ° 14 ’ W), 769 – 760 m, 28 Jun. 1991 [25 – 38 mm long, 2.5 – 4.0 mm wide]. 12 specimens (MNCN 16.01 / 10303), Campaña Fauna IV, Sta. 277 B 22, E side of Banco El Fidalgo, Islas Columbretas, Castellón, 25 m, 16 Jul. 1996 [29 – 36 mm long, 3 – 4 mm wide]. 10 specimens (MNCN 16.01 / 10304), Campaña Fauna II, Sta. 173 A, Banco de Galicia (43 ° 07 ’ N, 12 ° 14 ’ W), 769 – 760 m, 28 Jun. 1991 [16 – 27 mm long, 2.5 – 4.0 mm wide]. 18 specimens (MNCN 16.01 / 10305), Campaña Fauna II, Sta. 173 A, Banco de Galicia (43 ° 07 ’ N, 12 ° 14 ’ W), 769 – 760 m, 28 Jun. 1991 [29 – 37 mm long, 3 – 4 mm wide]. Faroe Islands. One specimen (NHMD 109402), BIOFAR, SW off Faroe Islands, Sta. 493 (60 ° 49.38 ’ N, 09 ° 53.27 ’ W), 800 m, mud, 24 Jul. 1989 [24 mm long, 3 mm wide]. Eight specimens (NHMD 109404), BIOFAR, SW off Faroe Islands, Sta. 515 (60 ° 41.8 ’ N, 11 ° 46.5 ’ W), 700 m, sand, mud, 26 Jul. 1989 [one polynoid without elytrae and posterior end; other specimens 16 – 31 mm long, 2 – 4 mm wide]. One specimen (NHMD 237478), Shamrock Canyon, Sta. 1883 / 1 (47 ° 48.9 ’ N, 08 ° 08.87 ’ W), 1350 m, 19 Apr. 1977, Shackelton, coll. [26 mm long, 4 mm wide].

Name

Homonyms: Dalhousia atlantica McIntosh 1885