Acromegalomma schwindtae, Tovar-Hernández, María Ana, León-González, Jesús Ángel De & Bybee, David R., 2017

Tovar-Hernández, María Ana, León-González, Jesús Ángel De & Bybee, David R., 2017, Sabellid worms from the Patagonian Shelf and Humboldt Current System (Annelida, Sabellidae): Phyllis Knight-Jones’ and José María Orensanz’s collections, Zootaxa 4283 (1), pp. 1-64 : 16

Acromegalomma schwindtae sp. nov.

( Figs 5 , 31 C)

Material examined. Type material: ARGENTINA, Holotype ( UANL 8042 ) and two paratypes ( UANL 8043 ), Puerto de San Antonio Este , Provincia de Rio Negro, 40°49´29.98´´S, 64°44´59.56´´W, dock piling fouling, 9 m depth, 10 October 2005, coll. E. Schwindt. Additional material : ARGENTINA, Campaña COMP IV, UANL 8044 , St. 65, 38°23’S, 58°01’W, 25 m depth, medium sand, 21 March 1964, 1 specimen . URUGUAY, Campaña Akademik Knipovich , UANL 8045 , St. 1073, 35°10.5’S, 52°42.5’W, 115–117 m depth, 1967, coll . V.N. Semenova & V. Scarabino, 1 specimen .

Description. Trunk length 17 mm (13.5– 22 mm), width 1.5 mm (1–2 mm). Branchial crown length 5 mm (4– 5 mm), as long as thorax, with 14 pairs of radioles (13–15 pairs). Eight thoracic and 46 (45–56) abdominal segments. Branchial lobes semi-circular. Outer surfaces of radioles quadrangular basally, rounded distally. Subdistal compound eyes spherical, present only in dorsal-most pair of radioles ( Fig. 5 H). Except for dorsal-most radioles, all other radioles with short tips, as long as 3 pinnules ( Fig. 5 I). Dorsal collar margins V-shaped, fused to faecal groove ( Fig. 5 A, B). Dorsal lappets absent. Dorsal pockets present ( Fig. 5 A, B). Ventral lappets triangular, overlapping or separate, as long as collar ventral shield ( Fig. 5 D). Anterior peristomial ring exposed below dorsal pockets ( Fig. 5 A, B). Lateral collar margins not covering bases of radioles ( Fig. 5 C). Dorsal lips erect, triangular, about 1/4 length of branchial crown, with radiolar appendages. Two to three dorsal pinnular appendages. Ventral lips about 1/4 length of dorsal lips, broadly rounded with ventral radiolar appendages. Ventral sacs present ( Fig. 5 E). Caruncle and keel absent. Ventral shield of chaetiger 1 with rounded anterior margin, with anterior medial incision. Body plump, cylindrical, pale with ventral shields cream colored. Tori in chaetigers 2–8 not contacting shields. Notopodial fascicles with superior group of elongate, narrowly hooded chaetae; inferior group of chaetae Type A (chaetae with distal end narrowing abruptly, see remarks) ( Fig. 5 F, J). Thoracic uncini with main fang surmounted by 8–10 rows of numerous minute teeth, handles two times longer than main fang. Companion chaetae with teardrop-shaped membranes. Abdominal neurochaetae broadly hooded ( Fig. 5 G); chaetae in posterior rows longer than in anterior rows. Abdominal uncini with main fang surmounted by 8–10 rows of numerous minute teeth. Pygidium broadly rounded. Pygidial eyespots absent. Tubes unknown.

Type locality. Puerto de San Antonio, Argentina, 9–117 m depth, as dock piling fouling, into hard sediment matrix and medium sand.

Etymology. The species is named after Dr. Evangelina Schwindt, in recognition for her research on polychaetes and invasive species, and especially because she collected the specimens used in this description.

Remarks. Five nominal species of Acromegalomma have eyes only in the dorsalmost radiolar pair: A. bioculatum ( Ehlers, 1887) , A. gesae ( Knight-Jones, 1997) , A. modestum (de Quatrefages, 1866) , A. pigmentum ( Reish, 1963) , and A. kaikourense ( Knight-Jones, 1997) . Acromegalomma schwindtae sp. nov., and A. modestum have the dorsal collar margins fused to the faecal groove, whereas in A. bioculatum , A. gesae , A. kaikourense , and A. pigmentum the dorsal collar margins are not fused to grove.

The major differences between A. modestum and A. schwindtae sp. nov., are the following: dorsal collar margins V-shaped in A. schwindtae sp. nov., (squared in A. modestum ); ventral lappets triangular in A. schwindtae sp. nov., (rounded in A. modestum ); anterior peristomial rig exposed dorsally in A. schwindtae sp. nov., (not exposed in A. modestum ); lateral collar margins not covering the bases of radioles in A. schwindtae sp. nov., (covering bases in A. modestum ); and A. modestum has abdominal chaetae narrowly hooded (broadly hooded in A. schwindtae sp. nov.).

The unique set of distinguishable features in A. schwindtae sp. nov. are: eyes only in dorsal most radioles (spherical); dorsal margins of collar fused to faecal grove, V-shaped, forming broad pockets; anterior peristomial ring visible above dorsal margins of collar; abdominal chaetae broadly hooded and thoracic chaetae Type A. Type A includes those chaetae with distal end narrowing abruptly according to the classification proposed by Capa & Murray (2009).

Figures

FIGURE 5. Acromegalomma schwindtae sp. nov. A, B) Base of branchial crown and anterior thoracic segments in dorsal view, C) same, lateral view, D) same, ventral view, E) ventral lappets and ventral sacs (arrows), F) thoracic notochaetae, G) abdominal neurochaetae, H) sub-distal compound eye from dorsal-most radiole, I) tip of ventral radiole, J) inferior thoracic notochaetae, Type A. Scale bars: A – E 0.5 mm, F 30 µm, G, J 10 µm, H, I 100 µm. A – E Stain: A – J Shirla. Specimens: A – J Holotype, UANL 8042.

FIGURE 31. Distribution of some sabellid species in South America. A) Chone orensanzi sp. nov., B) Jasmineira crumenifera Hartmann-Schröder, 1986, C) Acromegalomma schwindtae sp. nov. (star denotes type locality).