Magelona paulolanai, Magalhães & Bailey-Brock & Watling, 2018

Magalhães, Wagner F., Bailey-Brock, Julie & Watling, Les, 2018, Four new species of Magelona (Annelida: Magelonidae) from Easter Island, Guam and Hawaii, Zootaxa 4457 (3), pp. 379-396 : 387-390

Magelona paulolanai sp. nov.

Figures 2 (F‒H) and 5

Material examined. Holotype: Hawaii, Oahu, Mamala Bay, Sand Island outfall, Sta. B6R5, 21°17'04.7" N, 157°53'25.3" W, Aug/1992, 39 m ( USNM 1494159). Paratypes: Same locality, Sta. B6R5, 21°17'04.7" N, 157°53'25.3" W, Aug/1992, 39 m (1 af, USNM 1494160); Sta. ZR2, 21°16'53.4" N, 157°54'21" W, Aug/1992, 40 m (1 af, BPBM-R 3872); B4R2, 21°17'01.4" N, 157°54'23.8" W, Aug/1991, 30 m (1 af, USNM 1494161); Sta. B1R3, 21°17'30.2" N, 157°55'44" W, Aug/1990, 33 m (1 af, BPBM-R 3873). Additional material examined: Mariana Islands, Guam, Northern District outfall, 13°29'14" N, 144°44'54" E, Jan/2007, 40‒ 52 m, Sta. N1R1 (1 af); Sta. N2R2 (2 af); Agana outfall, 13°33'08" N, 144°48'25" E, Jan/2007, 65‒ 100 m Sta. A1R2 (1 af), Sta. A1R3 (1af); A3R2 (1 af).

Diagnosis. Prostomium longer than wide, with rudimentary prostomial horns. Notopodia of chaetigers 1‒8 with elongate foliaceous postchaetal lamellae with smooth upper edges. Superior processes present from chaetigers 1‒8, more elongate in the posterior thorax. Chaetiger 9 with only simple bilimbate capillaries. Abdominal hooded hooks tridentate. Posterior abdominal lateral pouches (C configuration) present from chaetiger 36 of holotype, paired and absent on last 7 chaetigers.

Description. Holotype: complete specimen, both palps attached; prostomium 0.40 mm long, 0.37 mm wide; thorax 2.31 mm long (including prostomium), 0.31 mm wide; abdomen 0.27 mm wide; total length 15.66 mm for 67 chaetigers. Paratypes: all incomplete, (three with palps attached) measured; prostomium 0.34‒0.66 mm long, 0.33‒0.59 mm wide; thorax 2.57‒4.04 mm long (including prostomium), 0.35‒0.38 mm wide; abdomen 0.35‒0.46 mm wide; total length 5.91‒11.6 mm for 23‒54 chaetigers.

Prostomium slightly longer than wide (L:W ratio 1.03‒1.12), rounded triangular; anterior margin smooth rounded, with rudimentary prostomial horns ( Figs 2F ; 5A, F ). Two pairs of prominent longitudinal dorsal ridges, thin; outer pair, reaching further basally and approaching achaetous segment; inner pair diverging half way toward prostomial tip and posteriorly towards prostomial base, with slight medial gap ( Fig. 5A, F ); prostomium with lateral round markings on either sides of ridges. Burrowing organ partially everted in two paratypes, oval and with longitudinal ridges. Palps arising ventro-laterally from base of prostomium and extending to chaetiger 15 ( Fig. 5A ); palps measuring 6.79 mm long in holotype and ranging from 2.54‒4.97 mm long in paratypes; non‒papillated region very short, extending to chaetigers one or two ( Fig. 5A ). Papillae short proximally ( Fig. 5B ) but long for majority of length, elongate ( Fig. 5C, D ); proximally and distally with two rows of papillae and medially with four rows ( Fig. 5B‒D ). Achaetous segment twice as long as chaetiger one ( Fig. 5A ).

Thoracic segments slightly longer than wide; chaetigers 1‒8 similar; parapodia biramous; notopodia with low prechaetal lamellae confluent with foliaceous postchaetal lamellae of similar size throughout thorax and becoming slightly broader on chaetiger 8 ( Fig. 5H‒K ); notopodial lamellae distally smooth. Prechaetal superior processes present (DML), digitiform on chaetiger one ( Fig. 5G ) and elongate on subsequent thoracic chaetigers ( Fig. 5I, J ). Neuropodial pre- and postchaetal lamellae as low ridges; ventral lobes (VNL) lobes elongate, as long as notopodial lamellae from chaetigers 1‒7 ( Fig. 5H‒J ). Chaetiger nine shorter and slightly constricted ( Fig. 5K ): notopodial prechaetal lamellae low, rounded, postchaetal lamellae triangular and slightly shorter than preceding thoracic chaetigers; superior processes (DML) absent. Neuropodia of chaetiger nine with digitiform prechaetal lobes and triangular postchaetal lamellae. Chaetae of thoracic chaetigers 1‒9 simple bilimbate capillaries ( Fig. 5E ); number of capillaries similar throughout thorax, 8‒10 per rami.

Abdominal segments longer than thoracic ones; DML and VML present, digitiform. Abdominal parapodia with foliaceous lateral lamellae, basally constricted, well-separated; low postchaetal extension of lateral lamellae behind chaetal rows in anterior abdomen ( Fig. 5L ). Abdominal chaetae tridentate hooded hooks of similar size throughout; two same-sized teeth above main fang ( Fig. 5G ); a pair of internal arcuate chaetae present sensu Fiege et al. (2000) in abdominal chaetigers. Hooks in two groups, outer group with usually an additional hook than inner group, hooks of similar size, main fangs vis–à–vis ( Fig. 5L ). Anterior abdominal segments with 4‒5 hooks per ramus.

Anterior abdominal lateral pouches (Σ configuration) absent and posterior abdominal lateral pouches (C configuration) present from chaetiger 36 of holotype, paired and absent on last 7 chaetigers; all specimens with paired interparapodial glandular regions on anterior abdominal segments.

Pygidium with a pair of short ventral cirri ( Fig. 5M ).

All preserved specimens lacking pigmentation, pale yellow.

Methyl Green Staining. Anterior end not distinctly stained. Dark green speckles present as transverse bands on anterior end of every segment in thorax and abdomen ( Fig. 2G ). Ventral region of chaetiger four with dense green speckles ( Fig. 2H ). Abdominal region staining intensely as interparapodial patches ( Fig. 2G, H ).

Remarks. Magelona paulolanai sp. nov. is most similar to M. pitelkai Hartman, 1944 , M. berkeleyi Jones, 1971 and M. dakini Jones, 1978 by the shape of the prostomium having weakly-developed (rudimentary) prostomial horns, shape of parapodial lamellae from chaetigers 1‒8 and presence of tridentate abdominal hooks. It differs from M. pitelkai by the absence of modified chaetae on chaetiger nine. Magelona berkeleyi differs from M. paulolanai sp. nov. in the shape of the prostomium, prostomial longitudinal ridges and methyl green staining pattern. The prostomium of M. berkeleyi is wider than long with short but distinct frontal horns whereas M. paulolanai sp. nov. has a prostomium that is longer than wide and the prostomial horns that are not distinctly separated from prostomium; the inner pair of prostomial dorsal ridges in M. berkeleyi is completely separated and short while in M. paulolanai sp. nov. only a slim gap is present. The methyl green staining pattern of M. berkeleyi was described in Blake (1996) as having intense staining on the first 4‒5 chaetigers. Magelona paulolanai sp. nov. is stained in same region, but only chaetiger four had the darkest stain. Magelona dakini was described as having finely unilimbate capillaries on chaetiger nine and Jones (1978) suggested that it had a narrowly pennoned aspect. Other species with rudimentary prostomial horns include Magelona sp. F sensu Uebelacker & Jones (1984), M. longicornis Johnson, 1901 and M. phyllisae Jones, 1963 but all three possess bidentate abdominal hooks.

Etymology. This species is named after Dr. Paulo da Cunha Lana, a polychaete researcher whose publications on polychaetes have had great impact on the scientific growth of the first author (WFM). Dr. Lana also kindly introduced this author to the study of polychaetes back in 2007 during a short but fruitful meeting.

Distribution. This species is known from Mamala Bay, Oahu, Hawaii and Guam in the Mariana Islands,

30‒100 m.

Figures

FIGURE 2. A-B, Holotype of Magelona alexandrae sp. nov. A; prostomium stained with Shirlastain A, dorsal view, B, Methyl Green Staining Pattern (MGSP) dorsolateral view, arrows indicate distinctive staining regions of thorax and abdomen; C-E, Paratype of M. cinthyae sp. nov., D, prostomium stained with Shirlastain A; D and E, MGSP, dorsal and ventral views, respectively with arrows indicating distinctive staining regions of thorax and abdomen; F-H, Holotype of M. paulolanai sp. nov., A, prostomium stained with Shirlastain A; G and H, MGSP, dorsal and ventral views, respectively, with arrows indicating distinctive staining regions of thorax and abdomen.

FIGURE 5. Magelona paulolanai sp. nov. A, anterior end and thoracic region, dorsal view, holotype; B, basal region of palp, lateral view; C, medial region of palp, lateral view; D, distal region of palp, lateral view; E, thoracic simple bilimbate capillaries; F, anterior end showing prostomium and anterior region of chaetiger 1 of holotype, dorsal view; G, tridentate notopodial abdominal hooks, frontal and lateral views; H, parapodium of chaetiger 1, anterior view; I, parapodium of chaetiger 4, anterior view; J, parapodium of chaetiger 8, anterior view; K, parapodium of chaetiger 9, anterior view; L, parapodium of chaetiger 30, anterior view; M, posterior end and pygidium. Abbreviations: ch, chaetiger; pa, palp; ph, prostomial horn; pr, prostomium.