Polychaetous Annelids of the Oil Platform Areas from the Southeastern Gulf of Mexico: Orbiniidae and Cossuridae

BULLETIN OF MARINE SCIENCE, 61(3): 549–557, 1997

POLYCHAETOUS ANNELIDS OF THE OIL PLATFORM AREAS FROM THE SOUTHEASTERN GULF OF MEXICO: ORBINIIDAE AND COSSURIDAE

Alejandro Granados-Barba and Vivianne Solís-Weiss

ABSTRACT The distribution and composition of families Orbiniidae and Cossuridae were analyzed from the oil platforms area in the Campeche Sound, southeastern Gulf of Mexico. The orbiniids were common in the study area; 108 specimens were identified in three genera and six species. The cossurids were a “dominant” family in terms of abundance and frequency; however all 829 specimens belong to only one species: Cossura delta Reish which is found here to be a senior synonym of C. soyeri Laubier, based on similari- ties between both species and discussion of the literature on the subject.

The Campeche Sound, in the southeastern Gulf of Mexico, is an area of important commercial and industrial activities; it is the most important shrimp fishery zone in Mexico and where the country’s largest concentration of off-shore oil platforms is found. How- ever, its fauna is poorly known which is why, since 1988, we have been involved in important regional projects whose objectives have been to study the composition of the benthic communities as well as the influence of the environmental factors upon their presence, abundance and distribution. The recent creation in Mexico of the National Commission for the study of Biodiversity (CONABIO) has helped (as part of the government policy), in the development of large projects focusing on the study of biodiversity. As part of one of these projects and because the annelid polychaetes are one of the most important benthic groups world-wide, the present study objectives are to address, over a long time scale, two fundamental issues: The composition and distribution of the polychaete fauna in the off-shore oil platforms region to facilitate future comparative work, and the study of the community structure, in time and space. The first objective is nearly complete (Granados-Barba, 1994) and this paper is the first of a series presenting the taxonomic results. The families Orbiniidae and Cossuridae collected during a 3-yr period in the area are presented in this time. Previous taxonomic studies on the polychaetes of the area include Granados-Barba and Solís-Weiss (1994), Granados-Barba (1994), Solís-Weiss, et al. (1994a) and Solís-Weiss et al. (1995).

STUDY AREA

The study area is located in the Campeche Sound, between 18° 46'-20° 03' N and 91° 33'-92° 34' W, covering the oil platforms area and part of the continental shelf down to about 200 m depth (Fig. 1). The climate is warm humid and sub-humid with summer rains (García, 1987), with three cli- matic seasons: (1) “dry” season from March to May, (2) “rainy” season from June to October and (3) “nortes” season, from November to February. A cyclonic circulation, mainly associated with the transport variations from the Yucatan channel is present in the Campeche Bay (Molinari and Morrison, 1988). Monreal-Gómez and Salas de León (1990) remarked on the presence of a cyclonic gyre in February and March which tends to weaken in April resulting in a change in the current direction. In May the gyre disappears com- pletely so the circulation is directed from East to West. In July, a small cyclonic gyre begins to form

549 550 BULLETIN OF MARINE SCIENCE, 61(3): 549–557, 1997

Figure 1. -Map of the study area; sample stations. over the West coast of Yucatan, which intensifies over the following months and persists until De- cember. The sediment in the oil platforms area is mainly mud, although there are some isolated patches of sandy mud. This is a zone of intense human action in that industrial activities that “Petróleos Mexicanos” (PEMEX) has been performing has lasted for 20 yrs. The area is exposed to constant perturbations such as hydrocarbon spills and direct discharge of human wastes to the sea. The coupling of industrial and commercial use and potential degradation of the area with its potentially high diversity in natural resources, makes it a very important site to study the benthic fauna.

MATERIALS AND METHODS

Sampling was done aboard the R/V JUSTO SIERRA, as part of the interdisciplinary projects IMCA and DINAMO during expeditions IMCA-1, 2 and 3 (March and September 1988 and March 1989) and DINAMO-1 and 2 (March and November 1990). The polychaetes were collected with a 0.1 m2 Smith-McIntyre grab. At each station, about 40 L of sediment were taken, screened through a 0.5- mm sieve and fixed in 10% formalin. In the laboratory, the organisms were washed again, sorted and transferred to 70% alcohol. Depth, salinity and temperature were recorded at each station with a Niels Brown C.T.D. The organic content of the sediment was determined as percent of organic carbon by the Gaudette and Flight (1974) method. A dichotomic reversible key was made for the orbiniid species, modified from Taylor (1984). For each species, selected synonyms with descriptions and figures from other studies are included. Data for each species included the date of collection, the station number and the number of specimens per station, this last in parenthesis. The habitat and worldwide reported distribution are also included. The environmental factors measured in this study are cited with the following abbrevia- tions: D = depth (m); T = temperature (°C); S = salinity (‰); OM = organic matter in the sediment (% organic carbon) and DO = dissolved oxygen (ml L-1). The identified species are deposited in the GRANADOS-BARBA AND SOLÍS-WEISS: GULF OF MEXICO ORBINIIDAE AND COSSURIDAE 551 collection of the Instituto de Ciencias del Mar y Limnología (CPICML) at the Laboratorio de Ecología Costera (poliquetos), Universidad Nacional Autónoma de México (UNAM).

Family ORBINIIDAE Hartman, 1942

Orbiniids are polychaetes with intermediate characteristics between the “errantiate” and “sedentariate” groups: they have distinct body regions but do not construct perma- nent tubes (Taylor, 1984). The family is represented by about 11 genera and 200 species (Pettibone, 1982). In this study, the orbiniids were not very abundant (2.1% of the total sample); however, they were very frequent since they appear in 75% of the stations in the study by Granados-Barba (1994) done in the study area. Orbiniids were represented by six species, a low specific richness considering the average of 8.4 found (Granados-Barba, 1994). In this family, apart from the undescribed Naineris species, there were no taxonomic problems that limited identification, except for a variation in the setiger where the branchiae first appear and the presence of ventral papillae in some species.

KEY TO ORBINIID SPECIES IN THE VICINITY OF OIL PLATFORMS

1a.- Prostomium rounded; branchiae from first to third abdominal setigers; abdominal neuropodia with broad lobes and bulbous ending ...... Naineris sp. A 1b.- Prostomium bluntly to sharply pointed anteriorly; thoracic neurosetae include other kind of setae in addition to crenulate setae; no broad hooded spines or spear-shaped acicular setae ...... 2 2a(1b).- Posterior thoracic neuropodia and some anterior abdominal setigers with more than 4 subpodal and ventral papillae ...... Orbinia...3 2b(1b).- Posterior thoracic neuropodia with up to 4 subpodal and ventral papillae .....Scoloplos...4 3a(2a).- Branchiae from setiger 9; more than 10 subpodal and ventral papillae from setigers 13 to 15; thorax with 19 to 21 setigers ...... O. riseri 3b(2a).- Branchiae from setiger 6; with 8 to 10 subpodal papillae in the middle of the neuropodia; without ventral papillae; thorax with 17 setigers ...... O. americana 4a(2b).- Branchiae from first or second abdominal setigers; setigers 1-9 with acicular spines arranged in two rows, thereafter arranged in one row; thorax with 15 to 20 setigers ...... S. treadwelli 4b(2b).- Branchiae from a thoracic segment ...... 5 5a(4b).- Branchiae from setiger 6; thorax with 15 to 17 setigers ...... S. rubra 5b(4b).- Branchiae from setigers 15-16; thorax with 16 to 17 setigers ...... S. capensis

Naineris sp. A Taylor, 1984

Naineris sp. A Taylor, 1984:1.5, fig. 1.2a-f.- Granados-Barba, 1994:29, pl. 3D.

Material Examined. —8 specimens.- September 1988: sta. 6(1); March 1989: sta. 7(1), 9(1), 11(1); October-November 1990: sta. 6(1), 7(1), 9(1), 10(1). Additional Material Examined: —2 specimens from BLM # 2423C-7/76 B-23-1.

Remarks. —This species can be distinguished from other related species by the region of the body in which the branchiae emerge. They start in the abdominal region and not in the thorax as in most of Naineris species so far described. Another important character- istic is the shape and size of the abdominal neuropodia: there are prominent, digitiform and broadly rounded distally bearing long slender capillary setae oriented dorsally. 552 BULLETIN OF MARINE SCIENCE, 61(3): 549–557, 1997

Habitat. —15 to 45 m, in fine sand and clay (Taylor, 1984). In this study N. sp. A was collected in mud and sandy mud, D = 15-33; T = 28; S = 35.59-36.94; OM = 0.59-1.65. Distribution: Gulf of Mexico (Taylor, 1984; Granados-Barba, 1994).

Orbinia americana Day, 1973

Orbinia americana Day, 1973:89, fig. 12c-g.- Taylor, 1984:1.26, fig. 1.26a-e.- Granados-Barba, 1994:30, pl. 3H.

Material Examined.—1 specimen.- March 1990: sta. 13(1).

Remarks. —The specimen identified fits Taylor’s (1984) description. Habitat. —47 to 122 m, in clay, clayey and silty sand, and fine to coarse sand (Taylor, 1984). In this study O. americana was collected in mud, D = 74.5; OM = 1.47. Distribution. —North Carolina (Day, 1973); Northern Gulf of Mexico (Taylor, 1984; Granados-Barba, 1994).

Orbinia riseri (Pettibone, 1957)

Scoloplos (Scoloplos) riseri Pettibone, 1957:163, fig. 2a-d.- 1963:288, fig. 74e-f. Orbinia riseri.- Day, 1973:90, fig. 12h-l.- Taylor, 1984:1.25, fig. 1.24a-e.- Hernández-Alcántara, 1992:67.- Granados-Barba, 1994:31, pl. 3G.

Material Examined. —47 specimens.- March 1988: sta. 8(1); September 1988: sta. 2(1), 8(5), 9(1); March 1989: sta. 6(2), 8(13), 9(16); March 1990: sta. 7(1); October-November 1990: sta. 8(1), 9(6).

Remarks. —The number of ventral papillae on posterior thoracic segments vary widely (from 9 to 16) and is size related; they start from setigers 15 to 17. In some instances, a separation between subpodal and ventral papillae could be seen; in others only a single row emerge from the neuropodial bases. Habitat. —Intertidal to 160 m, in sand (Day, 1973; Taylor, 1984); fine to medium sand, D = 29-50; T = 14-22; S = 34.92-35.51; OM = 3.6-5.5; DO = 1.03-5.4 (Hernández- Alcántara, 1992). O. riseri was here collected in mud and sandy mud, D = 16; T = 25; S = 37.06; OM = 0.36. Distribution. —New England (Pettibone, 1957); North Carolina (Day, 1973); Gulf of California (Hernández-Alcántara, 1992); Gulf of Mexico (Taylor, 1984; Granados-Barba, 1994).

Scoloplos (Leodamas) rubra (Webster, 1879)

Aricia rubra Webster, 1879:253, pl. 9, fig. 123-126. Scoloplos (Leodamas) rubra Hartman, 1951:74, pl. 20, fig. 1-6.- 1957:291, pl. 32, fig. 1-6.- Day, 1973:91.- Granados-Barba, 1994:31, pl. 3A. Scoloplos rubra Taylor, 1984:1.29, fig. 1.28a-d.

Material Examined. —42 specimens.- March 1988: sta. 8(1); September 1988: sta. 8(1), 9(4), 16(2); March 1989: sta. 1(1), 8(2), 9(9), 10(1), 16(1); March 1990: sta. 3(1), 8(1), 9(7); October-November GRANADOS-BARBA AND SOLÍS-WEISS: GULF OF MEXICO ORBINIIDAE AND COSSURIDAE 553

1990: sta. 8(5), 9(4), 10(2).

Remarks. —The number of thoracic segments was variable, and probably size related since the largest specimen has one or two thoracic segments more than the smallest. The transition between thorax and abdomen is inconspicuous; we based the separation of the two regions on neuropodial setal changes. Habitat. —Intertidal to 200 m, in silty clay and sands (Taylor, 1984). S. rubra was here collected in mud and sandy mud, D = 16-17; T = 25; S = 37.06, OM = 0.36-0.39. Distribution. —From North Carolina to Florida (Day, 1973); Gulf of Mexico (Taylor, 1984; Granados-Barba, 1994).

Scoloplos (Scoloplos) capensis (Day, 1961)

Scolaricia capensis Day, 1961:480, fig. 1p-s. Scoloplos capensis Day, 1973:90, fig. 12m-q.- Taylor, 1984:1.37, fig. 1.36a-e. Scoloplos (Scoloplos) capensis Granados-Barba, 1994:32.

Material Examined. —2 specimens.- March 1989: sta. 9(2).

Remarks. —The specimens identified fit Taylor’s (1984) description. Habitat. —15-200 m, in sandy mud and fine sand (Taylor, 1984). S. capensis was here collected in mud, D = 17. Distribution. —Southern Africa (Day, 1961); North Carolina (Day, 1973); Gulf of Mexico (Taylor, 1984; Granados-Barba, 1994).

Scoloplos (Scoloplos) treadwelli Eisig, 1914

Scoloplos cirrata Treadwell, 1931:4. Scoloplos treadwelli Eisig, 1914:405.- Hartman, 1957:283.- Maciolek and Holland, 1978:163. Scoloplos (Scoloplos) treadwelli.- Granados-Barba, 1994:33, pl. 3B-C.

Material Examined. —5 specimens.- March 1988: sta. 8(1); March 1989: sta. 8(2); March 1990: sta. 7(1); October-November 1990: sta. 8(1).

Remarks. —Scoloplos treadwelli is very similar to S. texana; however, the former has two rows of acicular neuropodial spines, instead of only one row as in the latter. S. texana lacks branchiae on the thorax whereas in S. treadwelli they occur on the two last thoracic segments or begin on the first two or three abdominal setigers (Maciolek and Holland, 1978). Habitat. —Intertidal to 220 m, in sand and mud, with fragments of shells and coral (Hartman, 1957). S. treadwelli was here collected in mud and sandy mud, D = 16, T = 25, S = 37.06. Distribution. —Puerto Rico, Jamaica and Curazao (Treadwell, 1901; Maciolek and Holland, 1978); Gulf of Mexico (Granados-Barba, 1994). 554 BULLETIN OF MARINE SCIENCE, 61(3): 549–557, 1997

Family COSSURIDAE Day, 1963

Cossurids are very common in several habitats, from shallow waters to abyssal depths. They are considered motile burrowers (Fauchald and Jumars, 1979) and probably detrital feeders (Fauchald, 1977; Orensanz, 1976). The family includes two genera and about 15 species (Ewing, 1984). The cossurids were a “dominant” family in terms of abundance and frequency because they represent 16.5% of the total of specimens collected in this area (Granados-Barba, 1994), where they were collected at all stations at one time or another. Their specific richness was found to be below the average of 8.4. The only species collected was Cossura delta Reish, 1958.

Cossura delta Reish, 1958

Cossura delta Reish, 1958:53, figs. 1-2. Cossura soyeri Laubier, 1963: 833, fig. 1.- Gardiner and Wilson, 1979:169, fig. 4.- Ewing, 1984:4.6, fig. 4.- Granados-Barba, 1994:36, pl. 4A-D.

Material Examined. —829 specimens. March 1988: sta. 8(13), 9(1), 12(2); September 1988: sta. 1(5), 2(4), 3(1), 4(3), 5(4), 7(1), 9(1), 13(1), 14(6); March 1989: sta. 1(3), 5(1), 6(3), 7(4), 8(98), 9(144), 11(3), 12(1), 13(5), 15(1); March 1990: sta. 1(1), 3(7), 5(5), 7(22), 8(133), 9(175), 10(1), 13(3), 14(1), 16(2); October-November 1990: sta. 1(1), 3(2), 5(2), 7(18), 8(38), 9(103), 11(1), 13(1), 14(5), 15(2), 16(1). Additional Material Examined. —Holotype of Cossura delta U.S.N.M. No. 28706. sta. 328, off the Mississippi River Delta.

Remarks. —A certain amount of confusion prevails in C. delta’s original description: Reish (1958) declares that the first setiger is biramous while in the illustration it is clearly represented as uniramous. Thus, anyone following the key and the description would conclude that the specimen is C. soyeri, while following the same key but looking at the illustrations the conclusion would be that it is C. delta. This prompted us to compare both species with the following results: In C. soyeri the description says, there are two achaetous segments following the prostomium, the middorsal tentacle is inserted in the posterior margin of setiger 2, and the first parapodium is uniramous. In C. delta, according to the original description, there is one achaetous segment following the prostomium, the middorsal tentacle is inserted in the posterior margin of setiger 2, and the first parapodium is biramous. The examination of C. delta’s holotype by on of us (VSW) made it clear that the first segment is biannulated and the setiger is biramous. C. soyeri’s has been not available for loan; however, the original description and the illustrations fit perfectly C. delta’s holotype. Our specimens are the same species as C. delta’s holotype. Also, these organisms fit Ewing’s (1984) description and illustration of C. soyeri. In another study, Fournier and Petersen (1991) separated the Cossurids in three groups depending on the setiger where the middorsal tentacle is inserted and the number of thoracic segments. Based on the original descriptions, these authors separate C. soyeri and C. delta because in the former the middorsal tentacle is inserted in setiger 2 with 30-31 GRANADOS-BARBA AND SOLÍS-WEISS: GULF OF MEXICO ORBINIIDAE AND COSSURIDAE 555 thoracic segments, and in the latter it is inserted in setiger 3 with 15-18 thoracic setigers. Furthermore C. soyeri is said to be distributed in the Mediterranean while C. delta is found in the Gulf of Mexico. In this study we could not find a clear separation between thorax and abdomen even though we analyzed more than 200 organisms with at least 49 setigers. We doubt the validity of a separation based on this feature. Ewing (1984) for his part identified his specimens from the northern Gulf of Mexico as C. soyeri despite the fact that some of his organisms come from stations located, in part, in front of the Mississippi delta, the type locality of C. delta. All previously identified specimens from the Gulf of Mexico, in excess of 1000 organisms (Granados-Barba, 1994; Solís-Weiss, et al., 1994b) in addition to Ewing’s specimens have been identified as C. soyeri. In spite of the fact that the holotype of C. soyeri was not available for loan, we feel the evidence is strong enough to synonymize both species; the valid name of this taxon would be Cossura delta Reish, 1958. Habitat. —Intertidal to 189 m, clay to coarse sand (Ewing, 1984). In this study C. soyeri was collected in mud and sandy mud, D = 15-151; T = 20-28; S = 35.51-37.09; OM = 0.2-1.51. Distribution. —Mediterranean (Laubier, 1963), North Carolina (Gardiner and Wilson, 1979) and Northern Gulf of Mexico (Ewing, 1984; Granados-Barba, 1994).

ACKNOWLEDGMENTS

We would like to thank all the participants of the projects IMCA-DINAMO as well as the R/V JUSTO SIERRA crew for their help in the field. DGAPA-UNAM and CONABIO financed part of this study for which we are grateful. K. Fauchald kindly allowed us to examine the holotype of C. delta, for which he is thanked. M. Petersen and J. Blake provided useful comments for which we are grateful.

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DATE ACCEPTED: October 6, 1995.

ADDRESS: Laboratorio de Ecología Costera (poliquetos) Instituto de Ciencias del Mar y Limnología, U.N.A.M. Apdo. Postal 70-305. México, D.F. 04510, Mexico. Voice (525) 622-58-33, Fax (525) 616- 07-48.