Laminatubus joycebrooksae, Rouse & Kupriyanova, 2021

Rouse, Greg W. & Kupriyanova, Elena K., 2021, Laminatubus (Serpulidae, Annelida) from eastern Pacific hydrothermal vents and methane seeps, with description of two new species, Zootaxa 4915 (1), pp. 1-27 : 18-24

Laminatubus joycebrooksae n. sp.

Figures 12 –15

Material examined. Holotype: SIO-BIC: A8255, Mound 12, Costa Rica. For locality details see Table 2.

Paratypes: SIO-BIC: A8256A, Mound 12, Costa Rica, 1 spec. prepared for SEM; A8256 B, Mound 12, Costa Rica, 1 spec. ; MZUCR 1507-01 ex A10063, 1 spec. ; MZUCR 1508-01 ex A11296, 1 spec. Mound 12, Costa Rica (see Table 2 for details).

Additional material. SIO-BIC: A1315A, 1 spec.; A1315B, 1 spec. prepared for SEM; A1330 , 6 spec.; A1494, 1 spec. (All from Mound 12, Costa Rica; see Table 2 for details).

Description. TUBE: white opaque, semi-circular to circular in cross-section, without wide flaring peristomes, some growth rings distinct, attached to the substrate throughout its length ( Fig. 9 ). Smooth low, sometimes slightly undulating medial keel and flattened attachment flange lacking alveoli present ( Figs 12 , 13B ). External hyaline layer absent.

RADIOLAR CROWN: radioles not connected by inter-radiolar membrane, arranged into semicircles or incomplete spiral of up to two whorls ( Fig. 13A ). Stylodes and radiolar eyes absent.

PEDUNCLE: smooth cylindrical (circular in cross section), about twice as thick as normal radioles ( Fig. 13A ), gradually merging into opercular ampulla, constriction absent ( Fig. 13A, C ). Peduncle inserted on left side of radiolar crown, below line of radioles. Small distal latero-dorsal winglets proximal to opercular ampulla absent ( Fig. 13A, D ).

OPERCULUM: semi-transparent, completely globular or slightly flattened distally, opercular top slightly sclerotized, with more or less distinct endplate in some. May be enhanced by epibiotic growth of unknown nature ( Fig. 13C, D ). Others lack distinct endplate ( Fig. 13A, B ).

COLLAR AND THORACIC MEMBRANES: collar high, clearly trilobed, with longer and wider ventral lobe and smaller lateral ones and with entire edge, continuous with thoracic membranes as wide as thoracic tori, forming apron across anterior abdominal chaetigers ( Figs 13A, D , 14A, B ). Pairs of small, wart-like protuberances of collar chaetiger or elongated tonguelets between ventral and lateral collar parts absent ( Fig. 14B ).

THORAX: with collar chaetiger and six uncinigerous chaetigers ( Fig. 14A, B ), fascicle of collar chaetae not distinctly separated from first uncinigerous chaetiger by a gap. Thoracic tori of the same length, gradually converging posteriorly, forming distinct triangular depression, but not touching each other medio-ventrally ( Fig. 13A ). Collar chaetae limbate only, no Spirobranchus - type chaetae present ( Fig. 14C ). Subsequent chaetae limbate, of two sizes, Apomatus -chaetae absent ( Fig. 14D ). Uncini along entire thorax saw-shaped, with 6–7 curved teeth, anterior fang slightly rounded to pointed ( Fig. 14E ). Prostomial eyes absent.

ABDOMEN: with up to 80 abdominal chaetigers. Achaetous anterior abdominal zone absent, distinct chaetae with long shaft starting from first abdominal segment and continuing throughout entire abdomen ( Fig. 14B ). Tips of chaetae distinctly curved and hollow, made of two rows of pointed teeth, thus true trumpet-shaped ( Fig. 14F ). Distinctly longer capillary chaetae absent in posterior chaetigers. Uncini saw-shaped, with pointed fang and 6–7 teeth ( Fig. 14G ); posterior-most uncini rasp-shaped with 3–4 rows of teeth, bluntly pointed fang and 7–8 teeth in profile view posteriorly. Posterior glandular pad absent ( Fig. 14A ).

SIZE: length up to 35 mm. Radioles and operculum accounting for 2/5 of entire animal length.

COLOUR: white radiolar crown, yellowish body ( Figs 12 , 13 ).

Etymology. The species was named after Joyce Brooks in recognition of her commitment and support of the Scripps Oceanographic Collections, particularly the Benthic Invertebrate Collection.

Distribution. Mound 12 methane seep, Costa Rica margin (~ 1000 m).

Reproduction. A specimen from Alvin Dive 4502 released white spherical eggs ~ 150 µm in diameter ( Fig. 13E ).

Remarks. Using the techniques employed here, L. joycebrooksae n. sp. is morphologically indistinguishable to L. paulbrooksi n. sp. The two species are reciprocally monophyletic sister groups ( Fig. 2 ) and show a clear divergence in mitochondrial cytochrome b sequences ( Fig. 4 ). They also are found at different depths with L. joycebrooksae n. sp. only found at ~ 1000 m at Mound 12 ( Costa Rica), while L. paulbrooksi n. sp. was found from 1400–2400 meters off Costa Rica and Mexico. Assigning species status to L. joycebrooksae n. sp. is therefore warranted.

Figures

FIGURE 2. Maximum likelihood (ML) tree from the analysis of the combined sequences from CytB, 18S, and Histone H3. Numbers on nodes are those bootstrap scores above 50%. * indicates the holotypes for L. paulbrooksi n. sp. and L. joycebrooksae n. sp. respectively.

FIGURE 4. Combined haplotype networks from CytB data for Laminatubus paulbrooksi n. sp. (top) from Pacific Costa Rica margin and Gulf of California (Mexico) localities and L. joycebrooksae n. sp. (bottom) from Costa Rica. There was little variability among the L. joycebrooksae n. sp. sequences and a distinct break to L. paulbrooksi n. sp. This corresponds to a minimum 6.4% uncorrected distance. Laminatubus paulbrooksi n. sp. showed marked intraspecific variability with distinct breaks among the three main sites; Costa Rica (9°N), Pescadero (23°N) and Guaymas Basin (27°N). * indicates the holotypes for L. paulbrooksi n. sp. and L. joycebrooksae n. sp. respectively.

FIGURE 9. Photos of Laminatubus paulbrooksi n. sp. in situ. At Jaco Scar, Costa Rica. Photo credit: ROV SuBastian, Schmidt Ocean Institute.

FIGURE 12. Photos of Laminatubus joycebrooksae n. sp. A–C—animals in situ, Alvin dive 4501, Mound 12, Costa Rica, 1008 m; D—close-up views of tubes, Alvin dive 4502, Mound 12, Costa Rica, 1000 m. Photo credit: HOV Alvin, Woods Hole Oceanographic Institute.

FIGURE 13. Photos of Laminatubus joycebrooksae n. sp. A, B, C—SIO-BIC A1315, Alvin dive 4501, Mound 12, Costa Rica, 1008 m. D—SIO-BIC A8255, Mound 12, Costa Rica, 1001 m. E– eggs released by the animal.

FIGURE 14. SEM of Laminatubus joycebrooksae n. sp. (SIO-BIC A8256A). A—lateral view of a specimen without radiolar crown. B—close-up view of the thorax. C—collar chaetae. D—thoracic chaetae of the last thoracic chaetigerous segment. E—thoracic uncini. F—anterior abdominal true trumpet-shaped chaeta. G—anterior abdominal uncini.