PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON 114(1):207-218. 200L

A new species of Ectinosoma Boeck, 1865 (Copepoda: : Ectinosomatidae) from northwestern Mexico

Samuel Gomez and Sybille Seifried

(SG) Institute de Ciencias del Mar y Limnologia, Unidad Academica Mazatlan, Universidad Nacional Autonoma de Mexico, Joel Monies Camarena s/n, Ap. Postal 811, Mazatlan 82040, Sinaloa, Mexico, Limburgs Universitair Centrum, Dept. SBG, Researchgroup Zoology, Universitaire Campus Building D, B-3610, Diepenbeek, Belgium (SS) FB7/AG Zoosystematic and Morphologie, University of Oldenburg, 26111 Oldenburg, Germany

Abstract. —A new species of harpacticoid , Ectinosoma mexicanum (Harpacticoida: Ectinosomatidae), is described from a coastal lagoon in north- western Mexico (Sinaloa state). Ectinosoma mexicanum appears to be allied to E. porosum (Wells, 1967) by sharing a robust endopod on P2 and P4 and a strong setae on the first and second endopodal segment of P2 and P4. The new Mexican ectinosomatid also has the seta next to the outermost seta of exopod of P5 barely longer than the exopod inner edge as in E. porosum and E. mediterraneum Kunz, 1975.

In 1991 a one-year study on the impact investigation. Observations and drawings of organic enrichment on the distribution were made from the whole and then dis- and abundance of meiofauna in a coastal sected specimen mounted in glycerin, at lagoon in the southeastern Gulf of Califor- 1250X using a Leitz Periplan phase con- nia (Mexico) was undertaken (G6mez-No- trast light microscope equipped with a guera & Hendrickx, 1997). During this drawing tube. The terminology proposed by study 63 harpacticoid taxa were identified, Huys & Boxshall (1991) for the general most of which turned out to be new to sci- morphological description, Koomen (1992) ence. Ectinosomatidae was by far the most and Seifried & Durbaum (2000) for U- abundant family throughout the study pe- pores, Seifried (1997) and Seifried & Diir- riod (39.4%), and was represented by spe- baum (2000) for the somitic ornamentation cies of Lang, 1965, Hastig- (palisades), and Moore (1976) for hyaline erella Nicholls, 1935, Pseudectinosoma frill, were adopted. Abbreviations used in Kunz, 1935 and Ectinosoma Boeck, 1865. the text and tables: P1-P6, first to sixth leg; This contribution deals with the description EXO, exopod; END, endopod; ae, aesthe- of the only species of Ectinosoma found in tasc. the sediment samples taken in Ensenada del Pabellon lagoon (northwestern Mexico). Family Ectinosomatidae Sars, 1903

Genus Ectinosoma Boeck, 1865 Materials and Methods Ectinosoma mexicanum, new species Figs. 1-6 Quantitative triplicate sediment samples were taken in Ensenada del Pabellon lagoon Type material. —A single dissected female (Sinaloa, northwestern Mexico). The sam- (holotype) catalogued EMUCOP-020591-17, ple strategy was described in G6mez-No- deposited in the collection of the Institute of guera & Hendrickx (1997). Harpacticoids Marine Sciences and Limnology, Mazatlan were stored in 70% ethanol prior to further Marine Station. 208 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON

Type locality. —Ensenada del Pabellon transverse rows of palisades and evenly dis- lagoon (24°19'-24°35'N, 107°28'- tributed depressions and U-pores; ventral 107°45'W). Leg. S. Gomez, May 1991. surface plain, with U-pores; P6 represented Diagnosis. —Ectinosomatidae. Rostrum by 2 setae, genital pore located in proximal relatively large and fused to cephalothorax. half; hyaline frill of first post genital ab- Antennule six-segmented. Armature for- dominal somite as in sixth thoracic somite. mula of P1-P4 (EXO/END): 0.1.123/ Second and third post genital abdominal 1.1.221; 1.1.223/1.1.221; 1.1.323/1.1.221; somites ornamented with 3 and 4 rows of 1.1.323/1.1.221. First and second endopo- palisades; second post genital abdominal dal segment of P2-P4 with one strong spi- somite with U-pores and with denticulate nulose seta. Endopod of P2-P4 robust, first hyaline frill; third post genital abdominal endopodal segment of P2 and P3 as long as somite without U-pores, with protruded wide, first endopodal segment of P4 wider pseudoperculum dorsally, reaching to distal than long. Seta next to the outermost seta third of anal segment, with entire striated of exopod of P5 barely longer than inner hyaline frill ventrally (Fig. 2C). Anal seg- edge of exopod. Setae I and VI of caudal ment (fourth post genital abdominal somite) rami spine-like. with palisades and U-pores. Caudal rami Description. —Habitus (Fig. lA-B, 2A- about 1.5 times longer than broad, with 7 C), fusiform. Length 773 |xm including ros- elements. Posterior dorsal edge of caudal trum and caudal rami. Rostrum (Fig. lA) rami terminating as an acuminate lappet; relatively large, fused with cephalothorax. rami with 1 ventral proximal row of small The latter about Vs of total body length, with palisades, and 2 sets of ventrolateral spi- denticulate hyaline frill and sensilla; integ- nules at base of elements I and II; setae I ument ornamented with tiny depressions ar- and VI developed as spines. ranged longitudinally and perforated by U- Antennule (Fig. 3A), six-segmented. Sur- pores. Surface of third to fifth thoracic so- face of segments smooth. Armature formula mites with tiny depressions arranged as in 1.10.3+ae.0.3.3+ae. cephalothorax; U-pores present. Third tho- Antenna (Fig. 3B): basis massive, with 2 racic somite without palisades, fourth and inner long elements (indicated in Fig. 3B). fifth thoracic somites with 2 and 4 trans- Endopod two-segmented; first segment verse rows of palisades, respectively; third bare; second segment ornamented with to fifth thoracic somites with denticulate strong and short proximal spinules and with hyaline frill, that of the fifth one deeper longer spinules at base of 2 inner lateral than that of the third and fourth thoracic spines; with 6 distal spines. Exopod three somites. Fifth thoracic somite with 1 trans- segmented; first segment as long as third verse row of small palisades and 3 trans- and about 2.3 times longer than second one, verse rows of long palisades. P5 bearing- with one seta; second segment with 1 spine; somite (sixth thoracic somite) ornamented third segment with 2 spines and ornamented with 3 transverse rows of small palisades with subapical set of spinules, one of them and 1 row of long palisades, and with even- markedly stronger. ly distributed tiny depressions (possibly Mandible (Fig. 3C): gnathobase of coxa pores) and U-pores; with denticulate hya- with a strong spinulose distal spine on cut- line frill. W:L ratio of genital double-so- ting edge, 1 strong and 4 smaller teeth; ba- mite, 1.19 (width measured in the proximal sis large with 2 long and slender inner setae wider part of seventh thoracic somite); dor- and 1 thickened and spinulose inner ele- sal surface with remains of ancestral sub- ment. Endopod one-segmented, with 8 se- division between seventh thoracic somite tae, 2 each of distal 4 fused at base forming and first post genital abdominal somite (in- 2 pairs of elements. Exopod one-segment- dicated in Fig. lA-B) and ornamented with ed, small, with 1 lateral and 2 distal setae. VOLUME 1 14, NUMBER 1 209

100pm

Fig. 1. Ectinosoma mexicanum. new species. Holotype, female, EMUCOP-020591-17 A habitus B, dorsal- surface ornamentation of fourth to seventh thoracic somites and first post genital abdominal somite.' 210 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON

B

100Mm

Fig. 2. Ectinosoma mexicanum, new species. Holotype, female, EMUCOP-020591-I7. A, urosome, ventral

(first urosomite omitted); B, urosome, lateral, (first urosomite omitted); C, part of anal segment and left caudal ramus, ventral. VOLUME 1 14, NUMBER 1 211

lOOMm 100pm

Fig. 3. Ectinosoma mexicanum, new species. Holotype female, EMUCOP-020591-17. A, antennule, third

segment separated from second and fourth; B, antenna; C, mandible; D, maxillule; E, maxilla; F, maxilliped (endopodal setae lost during dissection). 212 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASfflNGTON

Fig. 4. Ectinosoma mexicanum, new species. Holotype female, EMUCOP-020591-17. A, PI, anterior; B, P2, anterior. VOLUME 1 14, NUMBER 1 213

Fig. 5. Ectinosoma mexicanum, new species. Holotype female, EMUCOP-020591-17. A, P3, anterior; B, P4, anterior. 214 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON

50 pm

Fig. 6. Ectinosoma mexicanum, new species. Holotype female, EMUCOP-02059I-17, Fifth leg, anterior.

Maxillule (Fig. 3D): arthrite of praecoxa exopod with 2 seta, endopod with 6 setae, with 4 apical spines and 2 bare setae; coxa 2 each fused at base to form 3 pairs of se- and basis fused, the latter with 3 setae; ex- tae. opod and endopod not articulating at base; Maxilla (Fig. 3E): syncoxa with 3 en- VOLUME 1 14, NUMBER 1 215

50 Mm

''''' ^^^"^' «°^°^^P^ ^-^^^ ^--^ ^--y Muscu. (London)- 1967.8.4.21.6?8.4'2, Prrr:.L^~Endopod of P4 216 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON

Table 1. formula of legs (Pl- —Armature swimming dian anterior, and 1 distal and 1 median P4) of Ectinosoma mexicanum. posterior U-pore; inner baseoendopodal ex-

EXO END pansion reaching middle of exopod. Exo- pod wider than long, basal limit only visible PI I-O; I-l; in, II, 1 0-1; 0-1; I, n, 2 on posterior face; with 4 marginal setae and P2 I-l; I-l; III, II, 2 0-1; 0-1; I, II, 2 ornamented with row of long spinules in P3 I-l; I-l; III, II, 3 0-1; 0-1; L n, 2 at P4 I-l; I-l; III, n, 3 0-1; 0-1; L n, 2 the middle and the base of the three larg- est marginal elements; outermost seta about 3.5 times longer than adjacent one, the lat- dites, proximal endite with 3, middle endite ter barely longer than inner edge of exopod; with 2, distal one with 3 setae; allobasis seta adjacent to innermost seta about 1.8 with 3 setae medially. Endopod one-seg- times longer than innermost element, the mented, with 2 long spines and 5 setae. latter about 1 .2 times longer than outermost Maxilliped (Fig. 3F): badly damaged; the seta of baseoendopod. endopodal setae missing. Basis with 2 par- Remarks.—At present about 35 species allel rows of spinules. of Ectinosomatidae (apart from E. mexican- PI (Fig. 4A), with massive coxa orna- um new species), have been attributed to mented with distal spinules. Basis with out- the genus Ectinosoma. The and er seta and inner strong spine, with spinules phylogeny of this genus has been obscured at base of exo- and endopod and close to by poor descriptions that in most cases lack inner spine. Rami three-segmented, orna- sufficient detail. Moreover, no revisions of mented with strong spinules; exopod barely the genus are available and nothing is reaching beyond second endopodal seg- known about the phylogenetic relationships ment. Inner seta of second endopodal seg- of this taxon (Seifried, 1997; Seifried & ment spinulose at tip. Armature formula as Diirbaum, 2000). in Table 1. Ectinosoma mexicanum and E. porosum P2-P4 (Fig. 4B, 5A-B), with massive (Wells, 1967), seem to be related by the fol- coxa ornamented with row of spinules in lowing synapomorphies: strong spinulose outer distal corner. Basis ornamented with seta on the first and second endopodal seg- strong spinules at base of exopod and with ment of P2 and P4, and by the robust en- minute ones at base of endopod and in dis- dopod of P2 in which the first segment is tal inner comer, the latter with dentiform as long as wide. Unfortunately, Wells process. Rami three-segmented, ornament- (1967) illustrated only the third exopodal ed with spinules as in PI. Exopod of P2 segment of P3, and did not discuss the gen- barely reaching beyond second endopodal eral morphology of P4. In order to check segment, of P3 and P4 reaching middle of the general morphology of P3 and P4 of E. third endopodal segment. Endopods robust; porosum, the only material available (Ho- first endopodal segment of P2 and P3 as lotype 1967.8.4.21) was borrowed from the long as wide, of P4 wider than long; first Natural History Museum (London). Unfor- and second endopodal segment of P2-P4 tunately, the only slide on which the dis- with strong curved setae ornamented with sected holotype of E. porosum was mount- 2 rows of spinules. Armature formula as in ed was badly damaged during transit and Table 1. only the mouth parts, PI, P2, P4, P5 and P5 (Fig. 6): baseoendopod with 2 inner abdomen were successfully recovered. setae, innermost about 1.8 times longer than The general morphology of P4 of E. po- outer one; inner expansion of baseoendo- rosum (Fig. 7) showed that the robust rami pod ornamented with fine spinules at base constitutes a synapomorphy for E. porosum of both setae, and with strong ones along and E. mexicanum. On the other hand, the inner margin of posterior face; with 1 me- general morphology of P2-P4 of E. mexi- —

VOLUME 1 14, NUMBER 1 217 canum shows that the robust condition of (project SCH 352/19-2) is gratefully ac- the rami and the strong spinulose seta of the knowledged. first and second endopodal segment is con- stant in these three swimming legs. This is Literature Cited the case also for P2 and P4 of E. porosum Boeck, A. 1865. Oversigt over de ved Norges Kyster and in all probability for the third swim- Copepoder henhorende til Calanidemes, Cyclo- ming leg. pidemes eg Harpactidemes Familier.—Forhan-

Some Bradya Boeck, 1872, Pseudobrad- dlinger i Videnskabsselskabet i Kristiana 1864: ya Sars, 1904, and Halectinosoma Lang, 226-282.

1965 species, exhibit more robust endopods . 1872. Nye Slaegter og Arter af Saltvands-Co-

pepoder. Forhandlinger i Videnskabsselskabet of P2—P4 than observed for most Ectino- — i Kristiana 1872:35-60. soma species, but E. mexicanum seems to Gomez Noguera, S. E., & M. E. Hendrickx. 1997. Dis- be unique within the genus Ectinosoma in tribution and abundance of meiofauna in a sub- the following derived characters: endopod tropical coastal lagoon in the South-eastern Gulf of P2-P4 robust, first endopodal segment of of California, Mexico.—Marine Pollution Bul- letin 34:582-587. P2 and P3 as long as wide, and first endo- Huys, R., & G. A. Boxshall. 1991. Copepod evolution. podal segment of P4 wider than long; first The Ray Society, London, 468 pp. and second endopodal segment of P2-P4 Koomen, R 1992. The integumental perforation pattern with strong curved setae equipped with 2 of the Euchirella messinensis female (Copepo- characteristic rows of spinules; exopod of da, Calanoida): corrections, additions, intraspe- cific variation, and a checklist of pore sites. P5 wider than long (not shared by any other Crustaceana 63:113-159. Bradya, Pseudobradya, Halectinosoma or Kunz, H. 1935. Zur Oekologie der Copepoden Schles- Ectinosoma species), and outermost but one wig-Holstein und der Kieler Bucht. —Schriften seta barely longer than inner edge of exo- des Naturwissenschaftlichen Vereins fiir Schles- pod. The latter is shared with E. mediter- wig-Holststein 21:84-132.

. 1975. Harpacticoiden (Crustacea, Copepoda) raneum Kunz, 1974, and E. porosum. The aus dem Kiistengrundwasser der franzosischen outermost but one seta of exopod of P5 is Mittelmeerkiiste. —Zoologica Scripta 3:257- much shorter than the inner edge of exopod 282. in E. obtusum Sars, 1920, and much longer Lang, K. 1965. Copepoda Harpacticoidea from the in all other Ectinosoma species. Californian Pacific coast.—Kungliga Svenska Vetenskapsakademiens Handlingar, Almquist & Wiksell, Stockholm 10:1-566. Acknowledgements Moore, C. G. 1976. The form and significance of the

hyaline frill in harpacticoid copepod taxono- The first author is indebted to Dr. Frank my.—Journal of Natural History 10:451-456. Fiers of the Koninklijk Belgisch Instituut Nicholls, A. G. 1935. from the interstitial fauna of a sandy beach. Journal of the Marine voor Natuurwetenschappen and Dr. Ernest — Biological Association of the United Kingdom Schockaert of the Limburgs Universitair 20:379-405. Centrum (Belgium) for their support during Sars, G. O. 1903. Copepoda Harpacticoida. Parts I & my stay in Belgium (1995-1998). The sec- n, Misophriidae, Longipediidae, Cerviniidae, ond author is very grateful to Professor H. Ectinosomidae (part.). An account of the Crus- tacea of Norway, with short descriptions and K. Schminke for the introduction in the figures of all the species.—Bergen Museum, world of copepods and phylogenetic sys- Norway 5:1-28 + pis. 1-16. tematics. This paper is a contribution to . 1904. Copepoda Harpacticoida. Parts III & IV. project G.0086.96 and was financed by the Ectinosomatidae, Harpacticidae (part.). An ac- Fund of Scientific Research-Flanders and count of the Crustacea of Norway, with short descriptions and all the Direccion General de Asuntos del Per- figures of the species. Bergen Museum, Norway 5:29-80 + pis. 17- sonal Academico of the National Autono- 32. mous University of Mexico. Also the sup- . 1920. Copepoda. An account of the Crustacea port of the German Science Foundation of Norway, with short descriptions and figures — —

218 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON

of ail the species.—Bergen Museum, Norway , & J. Diirbaum. 2000. First clear case of car- 7:1-121 + pis. 1-76. nivory in marine Copepoda Harpacticoida. Seifried, S. 1997. Three new species of Ectinosoma Journal of Natural History 34:1595-1618.

Boeck, 1865 (Harpacticoida; Ectinosomatidae) Wells, J. B. J. 1967. The littoral Copepoda (Crustacea) from Papua New Guinea and the Fiji Islands. of Inhaca Island, Mozambique.—Transactions

Microfauna Marina 1 1:35-58. of the Royal Society of Edinburgh 67:189-358.