Myrioglobula malmgreni, Parapar, 2006

Parapar, Julio, 2006, The genera Myriochele and Myrioglobula (Polychaeta, Oweniidae) in Icelandic waters with the revision of type material of Myriochele heeri Malmgren, 1867, and the description of a new species, Journal of Natural History 40 (9 - 10), pp. 523-547 : 536-541

Myrioglobula malmgreni sp. nov.

( Figure 2 , 6 , 10A–C , 11 , 12 ; Tables I, II)

Myriochele heeri: Parapar 2003a, p 283 –284 [pro parte].

Type material

Icelandic Museum of Natural History. Holotype ( IMNH 4112 ); 11 paratypes ( IMNH 4107 / 4111 and 4113) .

Museo Nacional de Ciencias Naturales. Eleven paratypes ( MNCN 16.01 /10544–47) .

Additional type material

Museo Nacional de Ciencias Naturales. Myrioglobula islandica Parapar, 2003 , five paratypes ( MNCN 16.01 /9023) ( Figure 10D, E ).

Type localities

Northern Icelandic coast: BIOICE sample 2080 (one paratype; IMNH 4107 ) . Iceland – Faeroe Passage : BIOICE sample 2364 (one paratype; IMNH 4108 ) . Southern coast– Reykjanes Peninsula: BIOICE sample 2167 (three paratypes; IMNH 4109 ) ; sample 2303 (four paratypes, one on SEM stub; IMNH 4110–4111 ) ; sample 2400 (holotype and two paratypes; IMNH 4112–4113 ) ; sample 2401 (one paratype on SEM stub; IMNH MNCN 16.01 /10544) ; BIOICE sample 2423 (three paratypes; IMNH MNCN 16.01 – 10545 ) ; sample 2424 (four paratypes, IMNH MNCN 16.01 /10546) ; BIOICE sample 2474 (three paratypes; IMNH MNCN 16.01 /10547) .

Diagnosis

First chaetiger uniramous; second and third biramous ( TF 51:0-1:1-1:1). Relative length of three anterior chaetigers ( RLTC) 1-1.5(2)-5, fourth to sixth (seventh) chaetigers of similar length, fourth about 1.5 times as long as three previous chaetigers. Following chaetigers decreasing in length. Notopodia with long capillary chaetae and short acicular chaetae; neuropodial hooks with two apical teeth located one above the other; pygidium with two low lateral lobes.

Description based on holotype ( Figure 10A, B )

Body short, 10 mm long and 0.6 mm wide, with 28 chaetigers, nearly cylindrical, and posteriorly tapered. A longitudinal mid-dorsal, ventral and lateral slit present along the body ( Figure 11H, J, L ). Head region rounded and distinctly set off from thorax by a constriction ( Figure 10A–C ). Eye-spots not visible. First chaetiger uniramous; second and third biramous ( TF 51:0-1:1-1:1) ( Figure 10A, B , 11A, H–J ), with relative length 1-1.5(2)- 5, followed by 25 biramous chaetigers. Fourth chaetiger 1.5 times as long as the sum of preceding chaetigers ( Figure 12 ). Fourth to sixth or seventh chaetigers of more or less similar length. Following chaetigers showing a progressive decrease in length. Notopodia with a dorsal bundle of capillary chaetae and a ventral bundle of short and smooth acicular chaetae from the third chaetiger ( Figure 11F, K ). Notopodial acicular chaetae about half the length of the capillaries ( Figure 11K ), with distal half abruptly tapered. Neuropodial tori narrow and nearly rectangular, with uncini arranged in three to four irregular rows in anterior segments ( Figure 11E ) to four to five in middle ones. Hooks with two long and slender teeth constantly arranged one above the other ( Figure 11G ). Posterior end distally tapered, with final segments highly compressed; pygidium consisting of two low lateral lobes.

Cilia associated with head (neck ciliated field and oral cilia) also present in specimens studied with SEM ( Figure 11B–D, I ).

Tube with cylindrical middle part and long tapering ends, covered with sand grains.

Distribution

Iceland. Although specimens of this new species were found in the three sectors studied, most were found in sector b off the southwest coast of the Reykjanes Peninsula ( Figure 2 ) in temperate waters (5.5–6.8 ° C) at moderate depths (535 and 812.5 m) ( Figure 6 ).

Remarks

Myrioglobula malmgreni n. sp. differs from Myrioglobula islandica Parapar, 2003 , a species recently described from Icelandic waters, in: (1) head of M. islandica larger and quadrangular instead of rounded ( Figure 10D, E ); (2) body shape large and robust in M. islandica , small and slender in M. malmgreni , which is very similar in general appearance to Myriochele heeri and M. olgae ; (3) body dorso-ventrally flattened in M. islandica (as in M. japonica ) especially in posterior chaetigers, and rounded in M. malmgreni ; (4) dorsal chaetae more numerous in M. islandica than in M. malmgreni ; (5) both absolute and relative length of anterior chaetigers different, longer in M. islandica .

Curiously, Myrioglobula malmgreni n. sp. is, regarding its general body shape, much more similar to the Icelandic specimens of Myriochele olgae and Myriochele heeri than to Myrioglobula islandica , the biramous organization of chaetiger 2 being the only relevant character that separates it from the two Myriochele species.

Etymology

This species is named in honour of A. J. Malmgren, Finnish zoologist of the second half of the 19th century, pioneer in the study of taxonomy of Icelandic polychaetes, who originally described Myriochele heeri , type species of the genus.

Key to species of Oweniidae

Nilsen and Holthe (1985) described a new oweniid species ( Galathowenia fragilis as Myriochele ) for Boreo-Arctic waters, and presented emended descriptions of all four species known from the area up to that date: Owenia fusiformis Delle Chiaje, 1842 , M. heeri , Myriochele danielsseni Hansen, 1879 , and Galathowenia oculata ( Zachs, 1923) (as Myriochele ). Parapar (2003a), from material collected during the BIOICE expeditions, confirmed the presence of all of them in Icelandic waters and described a new species, Myrioglobula islandica . In the present work, the description of Myriochele heeri is emended and one new species is described.

Although a key for Icelandic oweniids was recently presented by Parapar (2003a), the important additions and changes to Oweniid taxonomy in Arctic and East Atlantic boreal waters presented in this work and in Koh et al. (2003), which reinstated the taxon Owenia assimilis ( Sars, 1851) and described the two new Owenia Delle Chiaje, 1842 species ; O. polaris Koh, Bhaud and Jirkov, 2003 and O. borealis Koh, Bhaud and Jirkov, 2003 , justify the presentation of a new key. Owenia fusiformis is not included because its geographical distribution, according to these authors, is probably more meridional (Mediterranean Sea). Koh et al. (2003) differentiated this species from O. polaris and O. borealis , among other characteristics, by a larger tentacle crown, with a ‘‘length of crown’’ to ‘‘length of thorax’’ ratio of 1:1 instead of 1: 2 in both new species.

Key to species of Oweniidae from Arctic and East Atlantic boreal waters

1. Cephalic region with tentacular crown.......... Owenia 2

– Cephalic region without tentacular crown............ 4

3. Collar oblique and without angle at level of lateral notch. Owenia assimilis ( Sars, 1851)

Figures

Figure 2. Distribution maps of species. Sectors and BIOICE sampling sites of Myriochele heeri sensu lato and Myrioglobula islandica taken from Parapar (2003a).

Figure 6. Relationship between bottom water temperature and water depth at sampling sites where Myriochele and Myrioglobula species were found. Data from M. heeri sensu lato and Myrioglobula islandica obtained from Parapar (2003a).

Figure 10. Anterior end of two Myrioglobula species studied in this work. (A, B) M. malmgreni n. sp. in lateral (left) and ventral view (holotype, IMNH 4112); (C) M. malmgreni n. sp. (paratype, IMNH 4107) in latero-ventral view; (D, E) M. islandica Parapar, 2003 (paratype, MNCN 16.01/9023) in ventral and lateral (left) view. In (B), notochaetae of chaetigers 3 and 4 are concealed by the body. Scale bars: 0.5 mm.

Figure 11. (A–G) Myrioglobula malmgreni n. sp. BIOICE 2401 (paratype, MNCN 16.01/10544): (A) anterior end, ventral view; (B) mouth opening with oral ciliary field; (C) detail of oral cilia; (D) detail of mouth ciliary fold; (E) first and second neuropodia; (F) notopodia of segment 6; (G) hooks from fourth chaetiger. (H–L) Specimen from BIOICE 2303 (paratype, IMNH 4110): (H) anterior end, lateral (right) view; (I) detail of head; (J) anterior chaetigers, lateral view; (K) notopodia of chaetiger 5; (L) lateral slit at fourth chaetiger. In (A) and (E), chaetae of first chaetigers numbered. no1–4, notochaetae of chaetigers 1 to 4; ne2–4, neurochaetae of chaetigers 2 to 4; ncf, neck ciliated field; ocf, oral ciliated field.

Figure 12. Schematic diagrams of anterior end organization, in ventral view, of species studied in this work, showing chaetal composition and relative length of anterior chaetigers. Drawings not at same scale.