PROC. BIOL. SOC. WASH. 
97(4), 1984, pp. 792-800 
GENERIC REVISION OF MASTOBRANCHUS AND 
PERESIELLA (POLYCHAETA: CAPITELLIDAE) WITH 
DESCRIPTIONS OF TWO NEW SPECIES FROM THE 
GULF OF MEXICO AND ATLANTIC OCEAN 
R. Michael Ewing 
Abstract.— Tv^o new species of capitellid polychaetes from the Gulf of Mexico 
and Atlantic Ocean are described: Mastobranchus variabilis and Peresiella spath- 
ulata. Emended diagnoses for these genera are proposed. Two species currently 
assigned to Mastobranchus, M. dollfusi Fauvel, 1936, and M. indicus Southern, 
1921, are considered incertae sedis. Keys to the species of Mastobranchus Eisig, 
1887, and Peresiella Harmelin, 1968, are presented. 
From 1975 to 1981 the Bureau of Land Management (BLM; now Mineral 
Management Services) funded several large scale benthic studies of the Gulf of 
Mexico outer continental shelf The polychaete fauna from these benthic collec- 
tions was examined in great detail in a taxonomic standardization program con- 
ducted by Barry A. Vittor and Associates, Mobile, Alabama; an atlas of Gulf of 
Mexico polychaetes was pubhshed by this firm in mid- 1984. The BLM-OCS 
samples yielded numerous undescribed taxa in several polychaete families. Two 
of the new species of Capitellidae encountered during the polychaete standard- 
ization program are described in this paper; these capitellids were collected from 
the MAFLA (Mississippi, Alabama and Florida) and SOFLA (Southwest Florida) 
study areas. In the course of examining the BLM material, additional specimens 
of these new taxa were found in benthic samples collected by Interstate Electronics 
Corporation (lEC) at dredged material disposal sites off Florida, North Carohna, 
and Puerto Rico. Several specimens of one of these species, collected near Hutch- 
inson Island, Florida by the Florida Department of Natural Resources, were also 
examined. 
Description of these species necessitated generic revisions of Mastobranchus 
Eisig, 1887, and Peresiella Harmehn, 1968. The generic diagnoses and dichoto- 
mous keys provided in this paper reflect only adult characters. 
Type-specimens are deposited in the National Museum of Natural History 
(USNM), Smithsonian Institution, Washington, D.C., and the Allan Hancock 
Foundation (AHF), University of Southern Cahfomia, Los Angeles, California. 
Family Capitellidae Grube, 1862 
Genus Mastobranchus Eisig, 1887, emended 
Type- species.— Mastobranchus trinchesii Eisig, 1887. 
Diagnosis.— i:\ior2iy. with achaetous peristomium and 11 setigerous segments. 
First setiger with or without neurosetae. Setigers 1-9 with capillary setae only; 
last 2 thoracic segments with capillary setae only or hooded hooks only. Two or 
VOLUME 97, NUMBER 4 - 793 
more abdominal notopodia with mixed fascicles of capillary setae and hooded 
hooks; abdominal neuropodia with hooks only. 
Remarks.— Gallardo (1 968) noted that the two species added to Mastobranchus 
after its original description, M. dollfusi Fauvel, 1936, and M. indicus Southern, 
1921, have combinations of characters clearly not within this genus. 
Mastobranchus dollfusi is described as having an achaetous peristomium, fol- 
lowed by an incomplete first setiger with capillary setae in notopodia only, 12 
thoracic setigers with capillary setae only in both rami and a transitional segment 
(setiger 14) with capillary notosetae and neuropodial hooded hooks; however, 
there are no abdominal segments with mixed fascicles of capillary setae and hooks 
in the notopodia, an important diagnostic character of the genus Mastobranchus. 
The setal pattern of M. dollfusi fits that of the genus Leiocapitella; in fact, its 
specific setal formula is presently occupied by another species, L. glabra Hartman, 
1947. However, the palmate branchiae characteristic of M. dollfusi (see Fauvel 
1936, fig. 11) are not known in Leiocapitella. For these reasons, M. dollfusi is 
herein considered incertae sedis. 
Mastobranchus indicus was described from a single incomplete specimen. This 
species has 1 1 biramous thoracic setigers with capillary setae only; setigers 1 2 and 
1 3 are transitional with capillary notosetae and neuropodial hooded hooks; fol- 
lowing segments have hooks only in both rami. The specific setal arrangement of 
M. indicus does not fit that of any presently recognized capitellid genus. In the 
author's opinion it would be inadvisable to erect a new genus for a species de- 
scribed from a single, incomplete specimen; M. indicus is therefore regarded as 
incertae sedis. 
Mastobranchus variabilis, new species 
Fig. 1 a-e 
Mastobranchus STp. A.— E\Nmg, 1984: 14-35, figs. 14-30a-f 
Material Examined.-G\5l.¥0¥ MEXICO: off Alabama: MS 694, 30°04'14"N, 
87°53'50"W, 13.4 m, sand, 11/80, 1 spec; ofTHorida: IEC713TB-003, 27°37.1'N, 
82°54.0'W, 12 m, clean sand, 10/79, 1 spec.;IEC713TB-004,27°37.1'N,82°55.1'W, 
10 m, clean sand, 10/79, 5 spec; lEC 713TB-005, 27°38.1'N, 82°55.1'W, 12 m, 
clean sand, 10/79, 2 spec; lEC 713TB-006, 27°37.1'N, 82°58.0'W, 17 m, clean 
sand, 10/79, 5 spec; lEC 723TB-003, 27°37.1'N, 82°54.0'W, 12 m, clean sand, 
1/80, 3 spec; lEC 723TB-004, 27°37.1'N, 82°55.1'W, 10 m, clean sand, 1/80, 3 
spec (Paratypes, AHFPoly 1369); lEC 723TB-006, 27°37.1'N, 82°58.0'W, 17 m, 
clean sand, 1/80, 1 spec; lEC 723TB-007, 27°36.5'N, 82°55.8'W, 12 m, clean 
sand, 1/80 (Holotype, USNM 81993); SOFLA 2, 26°45.84'N, 82°45.18'W, 24 m, 
medium sand, 5/81,2 spec. (USNM 75248); SOFLA 14, 25°46.01'N, 82°23.82'W, 
26 m, fine sand, 7/81,1 spec (USNM 75244); SOFLA 28, 24°47.1 1'N, 83°13.08'W, 
58 m, fine sand, 11/80, 1 spec (USNM 75249); MAFLA 2318, 29°05'00.8"N, 
83°45'00.0"W, 20 m, medium sand, 1/76, 1 spec; MAFLA 2419, 29°46'59.8"N, 
84°05'00.2"W, 10 m, fine sand, 8/77, 1 spec; same location, 1 1/77, 1 spec. (USNM 
75152); MAFLA 2528, 29°54'58.6"N, 86°04'58.5"W, 37 m, coarse sand, 9/75, 2 
spec; MAFLA 2531, 29°47'58.9"N, 86°09'28.9"W, 45 m, coarse sand, 2/76, 1 
spec; same location, 8/77, 2 spec; MAFLA 2855, 30°08'02.1"N, 86°30'00.0"W, 
794 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON 
40 m, medium sand, 8/77, 1 spec; ATLANTIC OCEAN: off Florida: Hutchinson 
Island: HI-290, sta. 5, 27°22'22'08"N, 80°13'46"W, 10.3 m, coll. by D. Beauma- 
riage, P. Camp and R. Gallagher, 5/10/72, 2 spec. (Paratypes, USNM 81994); 
HI-785, same coordinates, 9.7 m, coll. by C. Futch, W. Jaap and R. Gallagher, 
7/9/73, 2 spec; off North Carolina: lEC 733WL-010, 33°43.8'N, 78°01.0'W, 10 
m, clean sand, 7/80, 1 spec 
Description.— Length of holotype approximately 47 mm, width 0.6 mm, 116 
setigerous segments. Lengths of 8 additional complete specimens range from 1 6 
to 73 mm, widths 0.4 to 1.3 mm, setigers 50 to 112. 
Color light tan to reddish brown in alcohol; juveniles with dark brown pigment 
spots scattered over most of body. Thorax slightly inflated through setiger 4 (Fig. 
la). Thoracic epithelium smooth to faintly tesselate through setiger 4, thereafter 
smooth except for wrinkles of contraction. Abdominal segments smooth with 
glandular parapodial tori. 
Prostomium long, broadly conical in dorsal view, binannulate; pair of nuchal 
slits at proximal margin; conspicuous elongate ocular patches on dorsal surface. 
Achaetous peristomium wider than long, approximately same length as following 
segment. Eversible pharynx bulbous, smooth on entire surface. Setigers 1-3 about 
3 times wider than long, thereafter segments gradually increase in length to end 
of thorax (Fig. la). Anterior notopodia dorsolateral, well separated, but approach 
middorsally by setiger 10-11; neuropodia ventrolateral in position throughout 
thorax. 
Number of setae per fascicle proportional to body size; setiger 1 with 4-6 
capillary setae per fascicle, thereafter increasing to as many as 20 per fascicle in 
last thoracic segment. Nephridial apertures (1 pair on each segment) located in 
segmental groove following each of last 5 thoracic and first abdominal segments. 
Lateral organs present on all thoracic setigers as a minute ciliated pore between 
noto- and neuropodium, increasing in size toward abdomen; appearing as conspic- 
uous ovoid tuft of cilia just beneath notopodial tori in abdominal segments. 
Transition from thorax to abdomen distinct, marked by change in notopodia from 
capillary setae to mixed fascicles and in neuropodia from capillary setae to hooded 
hooks (in adults), slight broadening of segments, and appearance of glandular 
neuropodial tori. 
Anterior abdominal segments approximately same length as those of posterior 
thorax, gradually lengthening to midabdominal region where they are 2 to 3 times 
as long as wide; thereafter segments becoming increasingly shorter; far posterior 
segments usually strobiliform. 
Branchiae from mid- to posterior abdominal region (about setiger 67 in holo- 
type) as eversible palmate tufts of 5-8 digitate filaments emerging posterior to 
notopodial tori (Fig. lb). 
Abdominal notopodia with mixed fascicles of 10-20 capillary setae and 3-8 
hooded hooks through all or most of abdomen; notopodia in posterior third of 
abdomen often with hooks only. Occasionally notosetae absent in last few seg- 
ments. Abdominal neuropodia with hooks only on slightly elevated glandular tori; 
hook rows separated by shallow midventral groove; first abdominal segment with 
6-10 hooks per fascicle, increasing in number to as many as 35 hooks per fascicle 
and then decreasing to 1-2 hooks in far posterior setigers. Hooded hooks mul- 
VOLUME 97, NUMBER 4 
795 
Fig. 1 . Mastobranchus variabilis: a, Lateral view of anterior end showing thorax and first 2 ab- 
dominal segments; b, Dorsal view of midabdominal segment showing everted branchiae; c-d, Lateral 
and frontal views of neuropodial hooded hook from abdomen; e, Lateral view of pygidium. Scales = 
0.5 mm for a, b, e; 0.035 mm for c, d. 
tidentate, consisting of main fang surmounted by 7-8 teeth arranged in 3 rows (Fig. 
Ic, d); hooks in notopodia and neuropodia similar in crown structure and total 
length although shafts of notopodial hooks frequently extend further out of body, 
giving appearance that these setae are longer. Subtle variations in structure of 
these hooks were observed (i.e., relative sizes and location of denticles). 
Pygidium conical with 3-4 digitiform caudal cirri (Fig. le). 
Remarks.— Consider dihlQ variations from the thoracic setal arrangement of adults 
were observed in small specimens of Mastobranchus variabilis. Mixed setal fas- 
cicles or hooded hooks only rarely appeared in the last 1-2 notopodia. Neuropodia 
of the last 4 thoracic segments were found with capillary setae only, hooks only, 
or mixed setal fascicles. 
796 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON 
Mastobranchus variabilis has a first setiger without neuropodia. The other two 
species o^ Mastobranchus, M. trinchesii Eisig, 1887, and M. loii Gallardo, 1968, 
have both noto- and neuropodia on setiger 1. 
Etymology.— Tht specific name refers to the size-related differences in the tho- 
racic setal arrangement of Mastobranchus variabilis (Latin "variabilis" meaning 
variable or changeable). 
Distribution. —Mastobranchus variabilis was collected from sandy sediments in 
the northeast Gulf of Mexico off" Alabama and Florida and in the Atlantic Ocean 
off" Florida and North Carolina; known depth range 9.7 to 58 m. 
Key to the Species of Mastobranchus 
1 . Setiger 1 with notopodia only M. variabilis 
- Setiger 1 with both noto- and neuropodia 2 
2. Last 2 thoracic setigers with hooded hooks only in noto- and neuropodia 
M. loii 
- Thorax with capillary setae only M. trinchesii 
Genus Peresiella Harmelin, 1968, emended 
Type- species.— Peresiella clymenoides Harmelin, 1968. 
Diagnosis.— Thovdo^ with an achaetous peristomium and 11 setigerous seg- 
ments. First 3 setigers with capillary setae only; setiger 1 without neurosetae; 
following 2 setigers biramous; remaining thoracic segments (setigers 4-11) bira- 
mous with modified spatulate setae, capillary setae or hooded hooks. Abdominal 
parapodia with hooded hooks only in both rami. 
Peresiella spathulata, new species 
Fig. 2a-e 
Peresiella sp. A— Ewing, 1984:14-13, figs. 14-8a-e. 
Material Examined. -KTI^A^TIC OCEAN: off" Puerto Rico: lEC 724SJ-001, 
18°30.7'N, 66°09.0'W, 257 m, sandy mud, 1/80 (Holotype, USNM 81995); lEC 
724SJ-002, 18°30.7'N, 66°08.5'W, 261 m, mud, 1/80, 1 spec; lEC 724SJ-003, 
18°30.2'N, 66°09.0'W, 220 m, sandy mud, 1/80 (Paratype, USNM 81996); lEC 
724SJ-005, 18°31.2'N, 66°09.0'W, 279 m, mud, 1/80, 2 spec; lEC 724SJ-010, 
18°30.7'N, 66°11.6'W, 210 m, mud, 1/80, 1 spec; lEC 731SJ-003, 18°30.2'N, 
66°09.0' W, 220 m, sandy mud, 6/80, 1 spec; lEC 73 1 SJ-005, 1 8°3 1 .2'N, 66°09.0'W, 
279 m, mud, 6/80, 1 spec. GULF OF MEXICO: off"Horida: SOFLA 18, 25°45.37'N, 
83°42.22'W, 87 m, medium sand, 4/81, 1 spec (USNM 75252); MAFLA 2105, 
26°24'59.5"N, 83°49'57.6"W, 90 m, coarse sand, 6/75, 1 spec; MAFLA 2106, 
26°24'56.8"N, 84°15'00.0"W, 168 m, silty very fine sand, 5/75, 1 spec; MAFLA 
2212, 27°57'00.0"N, 84°47'59.6"W, 189 m, silty very fine sand, 8/77, 1 spec; 
same location, 11/77, 1 spec; MALFA 2426, 28°57'59.4"N, 85°23'00.2"W, 82 
m, fine sand, 6/75, 2 spec; MAFLA 2645, 29°35'00.5"N, 27°20'02.2"W, 106 m, 
coarse sand, 6/75, 1 spec. (USNM 75158). 
Description.— \lo\o\.yipQ an incomplete gravid female (18 ^m. ova), length ap- 
proximately 19 mm, width 0.5 mm, 40 setigerous segments. Lengths of 15 ad- 
VOLUME 97, NUMBER 4 
797 
Fig. 2. Peresiella spathulata: a, Lateral view of anterior end showing thorax and first 2 abdominal 
segments; b, Frontal view of spatulate seta; c, Lateral view of thoracic hooded hook; d-e, Lateral and 
frontal views of neuropodial hooded hook from abdomen. Scales = 0.5 mm for a; 0.025 mm for 
b-e. 
ditional incomplete specimens ranged from 4 to 8 mm, widths 0.3 to 0.5 mm, 
with up to 36 setigers. 
Color light tan in alcohol. Thorax slightly inflated through setiger 2 (Fig. 2a). 
Thoracic epithelium smooth to faintly tesselate with glandular ring around pos- 
terior half of setiger 1 1 . Entire surface of first 2-3 abdominal segments glandular 
in appearance (on unstained specimens), thereafter segments smooth anterior to 
setal fascicles and glandular on posterior margin. 
Prostomium conical in dorsal view, tapering to bluntly rounded tip, often partly 
withdrawn under peristomium; paired nuchal slits at posterolateral margin; eyes 
absent. Achaetous peristomium slightly longer than wide, approximately twice as 
long as first setigerous segment. Eversible pharynx bulbous, sparsely papillate on 
distal half, smooth proximally. Setigers 2-3 approximately 3 times as wide as 
long, thereafter segments increase in length with last thoracic setiger about as wide 
as long (Fig. 2a). 
Anterior 3 setigers with 4-6 capillary setae per fascicle. Remaining thoracic 
setigers (of holotype) with 6-8 modified setae per fascicle in both rami; modified 
798 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON 
setae elongate, spatula-shaped with truncate hood and short arista (often broken 
off) extending from end of shaft through hood aperture (Fig. 2b). In smaller 
individuals last thoracic segment (setiger 11) may have mixed noto- and neuro- 
podial fascicles of 4-6 spatulate setae and hooded hooks or hooks only. These 
thoracic hooks (Fig. 2c) transitional in structure between spatulate setae of pre- 
ceding segments and typical capitellid-like hooks on following abdominal seg- 
ments: hood usually slightly truncate rather than rounded; hood aperture distal 
to, rather than at right angle to shaft; crown not well developed, with reduced 
main fang and minute, barely discernible denticles; length of shaft intermediate 
between that of elongate spatulate setae and shorter abdominal hooks. Nephridial 
apertures and lateral organs not observed. Transition from thorax to abdomen 
marked by noticeable change in setal type (or structure of hooded hooks) and 
slight increase in number of neurosetae per fascicle. 
First 1-2 abdominal segments approximately same length as last thoracic seg- 
ment, thereafter segments gradually increasing in length. Branchial structures 
presumably absent. Pygidium not observed. 
Abdominal parapodia with multidenate hooded hooks only in both rami, 
emerging from slightly elevated glandular ridges; notopodia dorsal in position 
with 6-8 notosetae per fascicle on narrowly separated tori; neuropodia ventro- 
lateral with 7-11 hooks per fascicle. Under ordinary light microscopy hooded 
hooks appear to consist of large main fang surmounted by 10-13 teeth arranged 
in 3-4 rows (Fig. 2d, e). SEM reveals microstructure of these hooks more complex, 
with at least 20 teeth in numerous rows above main fang; in posterior view these 
hooks have many additional, irregularly arranged minute denticles (micrographs 
not shown). With the exception of minor differences in the number of teeth in 
the crown area of the hook, these setae do not vary in structure throughout the 
abdomen. 
Remarks.— In an earlier study the author noted that this species (reported as 
Peresiella, sp. A; Ewing, 1984) had hooded hooks only in the last thoracic 
setiger. Later examination of additional material revealed that the largest speci- 
men, an ovigerous female, had spatulate setae only on this segment and that 
smaller individuals had mixed setal fascicles or "transitional" hooks only on the 
last thoracic segment. The suggestion is, of course, that these hooks (on setiger 
11) are present only in juveniles and are then replaced by modified spatulate setae 
during growth of the individual. 
Peresiella spathulata differs considerably from the other two known species of 
Peresiella, P. clymenoides Harmelin, 1968, and P. acuminatobranchiata Tho- 
massin, 1970. The type-species, P. clymenoides, has a thorax with capillary setae 
on setigers 1-3 and spatulate setae on the following 8 segments (setigers 4-11); 
this thoracic setal arrangement is identical to that of P. spathulata. However, the 
anterior end of P. clymenoides differs sharply from the usual pattern of the Cap- 
itellidae, i.e., the first and second segments are obliquely flattened, resembling the 
cephalic plate of many maldanids (see Harmelin 1968: pi. II). Peresiella spathulata 
is further distinguished from P. clymenoides in that the latter has neuropodial 
hooks on setigers 12-13 with a slender, extremely curved main fang, noticeably 
different from other abdominal hooks; noto- and neuropodial hooks are similar 
in structure throughout the abdomen of P. spathulata. 
Peresiella acuminatobranchiata has two thoracic segments with modified setae. 
VOLUME 97, NUMBER 4 ' 799 
which according to original illustrations (Thomassin 1970: fig. 3) resemble blunt- 
tipped, slightly curved acicular spines enveloped by a hood; P. acuminatobran- 
chiata also has nonretractile, acuminate branchial processes beginning on anterior 
abdominal segments. Peresiella spathulata has 7-8 setigers with modified, spatula- 
shaped setae and no apparent parapodial (branchial) extensions. 
Etymology.— The specific name refers to the shape of the modified thoracic 
setae (Latin "spathulata" meaning spatulate). 
Distribution.— Peresiella spathulata was collected in the Gulf of Mexico off 
Florida and in the Atlantic Ocean off Puerto Rico at depths of 87-279 m. The 
species is known to inhabit a wide range of sediment types from mud to coarse 
sand. 
Key to the species of Peresiella 
1. Two thoracic segments with modified setae; branchial structures present 
P. acuminatobranchiata 
- At least 7 thoracic segments with modified setae; branchiae absent .... 2 
2. Anterior end modified like an oblique cephalic plate; abdominal hooks of 
2 distinct types P. dymenoides 
- Anterior end capitellid-like, not modified; all abdominal hooks similar in 
structure P. spathulata 
Acknowledgments 
Material examined in this study was provided by Interstate Electronics Cor- 
poration (contract no. 68-01-4610 from the Environmental Protection Agency) 
and Barry A. Vittor and Associates, Inc. (contract no. DACW01-80-C-0427 from 
the U.S. Army Corps of Engineers, Mobile District, and contract no. 14-12-0001- 
29091 from Mineral Management Services). Additional specimens of Masto- 
branchus variabilis were provided by Thomas H. Perkins of the Florida Depart- 
ment of Natural Resources, Marine Research Laboratory. The author gratefully 
acknowledges all of the above for the opportunity to examine this material. 
I would like to thank Dr. Keith Carson and Vera Wong of the Electron Mi- 
croscopy Laboratory, Department of Biological Sciences, Old Dominion Uni- 
versity, for assistance in the preparation of specimens for scanning electron mi- 
croscopy. 
I am especially grateful to Dr. Kristian Fauchald of the Smithsonian Institution 
for his constant assistance and for a constructive review of this manuscript. 
Literature Cited 
Eisig, H. 1887. Die Capitelliden des Golfes von Neapel.— Fauna und Flora des Golfes von Neapels 
16:1-906. 
Ewing, R. M. 1984. Family Capitellidae. Chapter 14. In J. M. Uebelacker and P. G. Johnson, eds., 
Taxonomic guide to the polychaetes of the northern Gulf of Mexico. Prepared for the U.S. 
Department of the Interior, Minerals Management Services, Metairie, Louisiana, by Barry A. 
Vittor and Associates, Mobile, Alabama. 47 pp. 
Fauvel, P. 1936. Contribution a la faune des Annelides polychetes du Maroc. — Memoirs Societe des 
Sciences Naturelles et Physiques du Maroc Zoologie 43:1-143. 
800 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON 
Gallardo, V. A. 1968. Polychaeta from the Bay of Nha Trang, South Viet Nam.— NAGA Report 
4(3):35-279. 
Grube, A. E. 1862. Noch ein Wort iiber die Capitellen und ihre Stellung im Systeme der Anneliden. — 
Archiv fiir Naturgeschichte (Berlin) 28:366-378. 
Harmelin, J. G. 1968. Note sur trois Capitellidae (Annelides polychetes) recoltes en Mediterranee, 
avec description d'un nouveau genre: Peresiella. — Kecueil des Travaux de la Station Marine 
d'Endoume 59:253-259. 
Hartman, O. 1947. Polychaetous annelids. Part VII. Capitellidae.— Allan Hancock Pacific Expedi- 
tions 10:391-481. 
Southern, R. 1921. Polychaeta of the Chilka Lake and also of fresh and brackish waters in other 
parts of India.— Memoirs of the Indian Museum Calcutta 5:563-659. 
Thomassin, B. 1 970. Contribution a I'etude des polychetes de la region de Tulear (SW Madagascar). 
Sur les Capitellidae des sables coralliens. — Recueil des Travaux de la Station Marine d'En- 
doume, Supplement 10:71-101. 
Department of Biological Sciences, Old Dominion University, Norfolk, Virginia 
23508.