Scoloplos cryptospinigerus, Dean, Harlan K. & Blake, James A., 2015

Dean, Harlan K. & Blake, James A., 2015, The Orbiniidae (Annelida: Polychaeta) of Pacific Costa Rica, Zootaxa 3956 (2), pp. 183-198 : 195

Scoloplos cryptospinigerus n. sp.

Figures 5 (H–I), 6 (D–G)

Material examined. Gulf of Nicoya, Sta. 22, 9°48′25″N, 84°52′40″W, 22 m, muddy sand, 11 Jul 1980, Holotype, ( MCZ 50379); STA. 29, 9°54′55″N, 84°45'15″W, 18 m, muddy sand, 7 Jun 1981, Paratype ( MCZ 50380).

Description. Both specimens incomplete; holotype 38 setigers, 7.18 m long, 0.41 cm maximum thoracic width. Paratype 19 setigers, 3.60 cm long, 0.47 cm maximum thoracic width. Prostomium sharply conical; lacking eyespots; paired nuchal organs located dorso-laterally at posterior border ( Figs. 5 H, 6D). Peristomium subequal in length to prostomium. Thorax with 17 setigers in holotype, 15 setigers in paratype, widest in middle setigers. Branchiae from first abdominal setiger as short digitate process, thereafter increasing in size and subequal to notopodial lamellae in mid-body segments ( Fig. 6 F).

Thoracic notopodial and neuropodial postsetal lobes digitate to triangular, beginning at setiger 3 as small papillae, reaching two-thirds setal length in posterior thoracic setigers; notopodial postsetal lobe longer than that of neuropodium ( Fig. 6 E). Subpodial lobes and stomach papillae lacking. Abdominal notopodial postsetal lobes triangular, subequal in length to branchiae ( Fig. 6 F). Neuropodial post-setal lobes weakly bilobed, becoming narrow and elongate posteriorly, slightly shorter than notopodial lobe; emergent, slightly hooked, acicula present.

Thoracic neurosetae densely packed camerated capillaries accompanied by an antero-ventral row of slightly curved, serrate spines ( Figs. 5 I, 6E) with a thin, translucent hood ( Fig. 6 G); up to 4‒6 spines present per segment from setigers 1–15 in the 17 setiger thorax of the holotype and 1–12 in 15 setiger thorax of paratype. Thoracic notopodial setae camerated capillaries, fewer in number than in neuropodia. All abdominal setae crenulated capillaries. Notopodial furcate setae absent.

Remarks. The presence of few serrate uncini among numerous capillary setae in the thoracic neuropodia is similar to Scoloplos normalis ( Day, 1977) from Australia, originally described in the genus Leitoscoloplos as no spines were seen in the neuropodia. Mackie (1987) later examined the type material and found neuropodial uncini in thoracic setigers and therefore transferred this species to the genus Scoloplos . All specimens examined by Mackie (1987) had 15 setigers in the thoracic region and single neuropodial spines in the first three setigers except for a smaller specimen that had spines to setiger 11. De León-González & Rodriguez (1996) later reported S. normalis from Baja California ( Mexico) but saw no spines in their specimens and retained them within the genus Leitoscoloplos . Díaz-Castañeda et al. (2005) later reported specimens of L. normalis from the Pacific coast of Baja California, Mexico presumably also lacking neuropodial spines. In the review of the Orbiniidae of Mexico by Solís-Weiss et al. (2009), Scoloplos normalis was reported from Pacific Mexico (presumably referring to the above mentioned citations) with a single weakly serrate spine in the second setiger (see their Fig. 4 a) with no further explanation presented. It is thus unclear whether this report of Scoloplos normalis from the tropical eastern Pacific is the same species as that described by Day (1977).

S. normalis and S. cryptospinigerus n. sp. have similar numbers of thoracic setigers, 15–16 and 15–17 respectively, and the branchiae occur from the first or second abdominal setiger in both species. While S. normalis has single, blunt uncini with small dentitions in the first few thoracic neuropodia, S. cryptospinigerus n.s p. has 1‒5 more strongly toothed spines in all thoracic setigers but the final two ( Fig. 5 I). The postsetal lobes of the thorax are longer and more digitate than the shorter, more triangular, postsetal lobes seen in S. normalis . Additionally, the abdominal notopodial postsetal lobe is medially enlarged and the neuropodial postsetal lobe is bifid with large subequal branches giving an anvil-like appearance in S. cryptospinigerus n. sp. ( Fig. 6 F). Based on the descriptions of Day (1977) and Mackie (1987), the abdominal notopodial lobe of S. normalis is not enlarged and, according to Day (1977), the neuropodial postsetal lobe is bifid but with an inner arm three times as long as the outer arm. Also, notopodial furcate setae were reported for S. normalis by Day (1977), Mackie (1985) and Díaz-Castanea et al. (2005) but none were observed in S. cryptospinigerus n. sp..

Other species of Scoloplos with similar numbers of thoracic setigers include Scoloplos cylindrifer Ehlers, 1904 and S. simplex ( Hutchings, 1974) . These species differ from S. cryptospinigerus n. sp. by the presence of dendritically branched branchiae in S. cylindrifer and the presence of thoracic branchiae in S. simplex .

Etymology. The species name refers to the spines in the anterior thoracic neuropodia which are often hidden from view by the numerous capillary setae.

Distribution. Gulf of Nicoya, Pacific Costa Rica, in muddy sand from 18‒ 22 m.

Figures

FIGURE 4. Leitoscoloplos multipapillatus: A, Setigers 17 – 19, ventral view. Leodamas hamatus n. sp.: B, Paratype XXX Anterior region, lateral view; C, Anterior thoracic spines, setiger three, mid-neuropodial region; D, Posterior thoracic spines, setiger 15, mid-neuropodial region; E, Posterior thoracic spines, upper neuropodial region; F, Furcate notosetae, posterior abdominal region; G, Posterior emergent neuroaciculum, posterior abdominal region. Scale bars: A = 200 µm, B = 500 µm, C ‒ E, F, G = 10 µm. h = hoods, stp = stomach papillae.

FIGURE 5. Leodamas treadwelli: A, Station 28 Oct, Gulf of Nicoya specimen, anterior and midbody, lateral view; B, Station 28 Jun, Gulf of Nicoya specimen, notopodial furcate seta. Naineris setosa: C, Playa Blanca specimen, anterior end, dorsal view; D, Playa Blanca specimen, thoracic parapodia, posterior view; E, Playa Blanca specimen, anterior abdominal parapodia, posterior view; F, Playa Blanca specimen, posterior abdominal parapodia, posterior view; G, Playa Blanca specimen, notopodial furcate seta. Scoloplos cryptospinigerus n. sp.: H, Holotype, anterior end, dorsal view; I, Holotype, posterior thoracic neuropodial spines. Scale bars: A, D ‒ E, H = 500 µm, B, G, I = 10 µm, C, F = 1000 µm. s = neuropodial spines.

FIGURE 6. Leitoscoloplos pugettensis: A, Station 9, Bahia Culebra specimen, thoracic setiger, anterior view; B, Station 9, Bahia Culebra specimen, posterior notopodial flail setae. Leodamas treadwelli: C, Station 28 Jun, Gulf of Nicoya specimen, posterior abdominal setiger, anterior view; Scoloplos cryptospinigerus n. sp.: D, Holotype, anterior end, dorsal view; E, Holotype, thoracic parapodia, posterior view; F, Paratype, abdominal parapodia, anterior view; G, Paraytpe, thoracic neurosetal spines. Scale bars: A, F = 50 µm, B = 10 µm, C, E = 100 µm, D = 500 µm, G = 20 µm.