Myriochele olgae Blake, 2000

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 : 533-536

Myriochele olgae Blake, 2000

( Figures 2 , 3A, C, D , 4C , 6 , 7C , 8 , 9 , 12 , 13 ; Tables I, II)

Myriochele olgae Blake 2000, p 111 –113, Figure 5.5 .

Myriochele heeri Malmgren 1867, p 101 –102, Table 7, Figure 37; Blake and Dean 1973, p 37, Figure 2 ; Parapar 2003a, p 283 –284 [pro parte].

Myriochele heeri: Nilsen and Holthe 1985, p 21 –22, Figures 3 , 4 , 11c–e [? pro parte].

Type material

National Museum of Natural History. North Pacific Ocean, USA, California, Santa Maria Basin, off Point Sal , 145 m (holotype; USNM 186431 ) .

Additional material

Icelandic Museum of Natural History. BIOICE sample 2575 (five spms; IMNH 4105); sample 2700 (three spms; IMNH 4106).

Museo Nacional de Ciencias Naturales. BIOICE sample 2065 (five spms; MNCN 16.01 / 10536); sample 2080 (four spms; MNCN 16.01 /10537); sample 2081 (one spm; MNCN 16.01 /10538); sample 2100 (nine spms; MNCN 16.01 /10539); sample 2152 (13 specimens; MNCN 16.01 /10540); sample 2167 (three spms; MNCN 16.01 /10541) ;

sample 2364 (seven spms; MNCN 16.01/10542); sample 2480 (one spm; MNCN 16.01/ 10543).

Description based on Icelandic specimens

Body short, 5–10 mm length and 0.5 mm wide, 18–23 chaetigers. First two body chaetigers uniramous; third biramous ( TF 51:0-1:0-1:1), first and second shorter than wide and third longer than wide, with increasing length ( RLTC 51-1(1.5)-3) ( Figures 4C , 8A, F , 12 ). Fourth to sixth chaetigers (second to fourth abdominal) elongated and of similar length; fourth about two (1.5) times as long as the sum of three previous chaetigers. Following chaetigers decreasing in length. Notopodia with long capillary chaetae and short acicular chaetae ( Figure 8B, G ); neuropodial hooks with two apical teeth located one above the other ( Figure 8C ); pygidium with two low lateral lobes ( Figure 8D ).

As in M. heeri , ciliated fields associated with head and mouth distinct ( Figure 8F, J–L ); a dense ciliated anal field observed at the pigidium ( Figure 8D, E ); food remains, possible diatom frustules, present inside the mouth of one specimen ( Figure 8H, I ).

Tube with cylindrical middle part and long tapering ends, covered by sponge spicules or sand grains depending on bottom nature ( Figure 13 ).

Distribution

Myriochele olgae was originally described from the East Pacific coast of North America (California) and is now reported from Iceland. In Icelandic waters, the species seems to be restricted to sector a on the north coast ( Figure 2 ) at a wide depth (198–1136.5 m) and temperature (20.6–5.1 ° C) range ( Figure 6 ).

Remarks

The investigation of the holotype of Myriochele olgae ( USNM 186431) showed that the general body shape, size, number of chaetigers, and thoracic formula of the specimen are completely in agreement with the Icelandic specimens (Table II). The only difference was in the relative length of the anterior biramous chaetigers; in the holotype chaetiger 3 is about four times longer than the uniramous chaetigers (chaetigers 1 and 2) and chaetiger 4 is the longest of the body, the following being shorter. In Icelandic specimens chaetiger 3 is about three times longer than uniramous chaetigers and an increasing length is observed from the fourth to sixth chaetigers. In both cases chaetiger 4 is about two times longer than the first three chaetigers combined. In my opinion, those differences are not significant enough to describe a new species.

Specimens named Myriochele aff. olgae from BIOICE samples 2423 and 2424 ( Figure 9 ) show some abnormal characters such as: (1) asymmetrical second biramous chaetiger with left neuropodial hooks partially piercing the epidermis ( Figure 9A–C ); (2) anterior end broken or in process of regeneration ( Figure 9D, F ); (3) a supernumerary second biramous chaetiger ( Figure 9G ); and (4) last chaetigers without notopodia ( Figure 9E ). Cilia associated with pygidial lobes were also seen ( Figure 9H, I ).

Unlike M. heeri , in which the principal taxonomic characters (number of uniramous/ biramous anterior chaetigers and their relative length) seem to be consistent, the Icelandic specimens of Myriochele olgae show a high variability in the presence of asymmetric anterior chaetigers and differences in the relative chaetiger length (see above). This variability would correspond to decapitation due to predation or an asexual reproduction process by bipartition, a reproductive strategy previously reported by Parapar (2003a) in the BIOICE oweniids Galathowenia fragilis ( Nilsen and Holthe, 1985) and Galathowenia oculata ( Zachs, 1923) .

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 3. Anterior end in ventrolateral view of three Myriochele heeri Malmgren, 1867 syntypes from the Swedish Museum of Natural History identified in this work as M. aff. olgae (A, C, D) and M. heeri (B). (A, B) SMNH 5847 (S. C. Byers’ label 6518 # 905, specimens 1/3 and 3/3, respectively); (C, D) SMNH 5848 (S. C. Byers’ label 6517 # 906, specimen 2/2), in left and right view. vpo, ventral pharyngeal organ. Scale bar: 1 mm.

Figure 4. Anterior end of two Myriochele species studied in this work. (A, B) Myriochele heeri Malmgren, 1867 (BIOICE 2257) in lateral and ventral view; (C) Myriochele olgae Blake, 2000 (BIOICE 2152) in latero-ventral view (drawn without cover glass). In (B), the neck ciliated field is observed and notochaetae of chaetigers 4 and 5 are concealed by the body. Scale bars: 0.5 mm.

Figure 5. Myriochele heeri BIOICE 2423. (A) Anterior end, lateral view (right side); (B) chaetiger 13 with two types of notochaetae; (C) posterior end; (D) anterior end, latero-ventral view (left side); (E) head, showing mouth lips, glandular area, and the three ciliated fields; (F) detail of lateral ciliated field; (G) oral ciliated field inside mouth lips; (H) detail of oral cilia; (I) ventral hooks from chaetiger 17. In (A) and (D), first four chaetigers numbered. no1–5, notochaetae of chaetigers 1 to 5; ne4–5, neurochaetae of chaetigers 4 and 5; lno, long notochaetae; sno, short notochaetae; ncf, neck ciliated field; ga, glandular area; lcf, lateral ciliated field; ml, mouth lips; ocf, oral ciliated field.

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 7. Three specimens from Greenland (USNM 51164) from Blake and Dean (1973). (A) Myriochele heeri in ventro-lateral showing the dorsolateral folds; (B) Myriochele indet. with the anterior end in process of regeneration and with ventral pharyngeal organ everted; (C) Myriochele aff. olgae in lateral view. dlcf, dorsolateral ciliary folds; vpo, ventral pharyngeal organ. Scale bars: 0.5 mm (A, B); 1 mm (C).

Figure 8. Myriochele olgae BIOICE 2065. (A) Anterior end, anteroventral view (right side) of a contracted specimen; (B) notopodium of chaetiger 16 showing two types of notochaetae; (C) hooks of first neuropodium; (D) posterior end; (E) detail of cilia from anus ciliated field; (F) anterior end, ventral view of a noncontracted specimen; (G) detail of two types of notochaetae of chaetiger 6; (H) view of mouth with food remains; (I) detail of food (diatom frustules); (J) ventral view of three anterior chaetigers showing limit of neck ciliated field; (K) detail of cilia from neck ciliated field; (L) detail of cilia from mouth ciliated field. In (A) and (F), chaetae of first four chaetigers numbered. no1–4, notochaetae of chaetigers 1 to 4; ne3–4, neurochaetae of chaetigers 3 and 4; sno, short notochaetae; lno, long notochaetae; ncf, neck ciliated field; acf, anus ciliated field.

Figure 9. (A–C) Myriochele aff. olgae with asymmetric biramous second chaetiger BIOICE 2423: (A) anterior end, lateroventral view (left side); (B) first neuropod in second chaetiger; (C) detail of hooks of first neuropod piercing the epidermis. (D–I) Myriochele aff. olgae from BIOICE 2424: (D) anterior end of a recently broken specimen; (E) posterior end with only neuropodial hooks; (F) specimen regenerating anterior end; (G) anterior end in ventral view of a specimen with a supernumerary fourth chaetiger (arrow); (H) posterior end in lateral view; (I) pigidial ciliated field. In (A), chaetae of first chaetigers numbered. no1–3, notochaetae of chaetigers 1 to 3; ne2–3, neurochaetae of chaetigers 2 and 3; sno, short notochaetae; lno, long notochaetae; ncf, neck ciliated field, acf, anus ciliated field.

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.

Figure 13. Some examples of Myriochele heeri (2257–2700) and Myriochele olgae (2065–2700) tubes collected in different localities in the BIOICE project. Scale bar: 1 mm.