CALANOID COPEPODS OF THE GENUS AETIDEUS 

 FROM THE GULF OF MEXICOi 



Taisoo Park2 



ABSTRACT 



The copepod population known previously as belonging to Aciidcus annaius (Boeck) in 

 the Gulf of Mexico and Caribbean Sea is recognized as a separate species. The males of 

 Aetideus ciciiius Farran and Aciidciis giesbrechti Cleve are fully redescribed with figures. 



The genus Aetideus Brady, 1883, comprised 

 four species (A. armatus, A. bmdyi, A. aciitioi, 

 and A. giesbn'chti) when Sars (1925) estab- 

 lished the genus Enaetideus to distinguish the 

 last three species from the first. A new species 

 has since been added to each genus, A. pacificus 

 and E. ausfralis. Bradford (1971) reviewed the 

 genera Aetideus and Euaetideus on the basis 

 of specimens from the Atlantic and Pacific 

 Oceans. Having found a close similarity be- 

 tween the males, she proposed the merging of 

 the two genera. In agreement with her pro- 

 posal, the name Euaetideus is considered here 

 as a junior synonym of Aetideus. 



In the Gulf of Mexico, three species of 

 Aetideus (A. armatus, A. acutus, and A. gies- 

 brechti) have been recorded (Owre and Foyo, 

 1967; Park, 1970). During the examination of 

 plankton samples obtained from the Gulf of 

 Mexico by the RV Alamiuos in September 

 1971. all of these species were found, including 

 the males. 



A. armatus had been known to have world- 

 wide distribution (Vervoort, 1957) until Brad- 

 ford (1971) recognized a population in the 

 Southern Hemisphere and two in the North 

 Pacific as separate species. Bradford also noted 

 differences between the northern and southern 

 forms of A. armatus in the Atlantic, but the 

 differences were not considered as taxonomical- 

 ly significant. When examined in detail in the 

 light of Bradford's findings, the Gulf of Mexico 

 population of A. armatus, however, was found 

 to be significantly different from either the 

 northern or southern Atlantic form of the spe- 



' This study was supported bv National Science Founda- 

 tion Grant GA-27485. 



- Department of Marine Sciences, Texas A&M Uni- 

 versity, Galveston. TX 77550. 



cies, or from any other known species of the 

 genus. Therefore, it is described here as a new 

 species. 



A. acutus and A. giesbrechti found in this 

 study were in agreement with the descriptions 

 by Grice (1962) and Park (1968) for the Pacific 

 forms. The males of these species have not 

 been fully described, except for brief descrip- 

 tions by Giesbrecht (1892) and Bradford (1971). 



AETIDEUS MEXICAN US, 

 NEW SPECIES 



Type. — Holotype female, U.S. National Mu- 

 seum No. 143777; allotype male USNM No. 

 143778; 30 female and 7 male paratypes, 

 USNM No. 143779. Type locality, lat. 25°15'N, 

 long. 89°11'W, in the Gulf of Mexico (sam- 

 pling depth, about 500-0 m). 



Female. — Body lengths of 31 type specimens, 

 1.66-1.84 mm. Proportional lengths of pro- 

 some and urosome about 78:22. Viewed dorsal- 

 ly, body slender, with a round, slightly 

 produced forehead (Figure lA). Laterally, dor- 

 sal margin of forehead broadly vaulted at level 

 of mouth (Figures IB, D). Two rostral rami 

 separated by a U-shaped notch (Figure IG). 

 Distance between tips of rostral rami exceed- 

 ing depth of notch (1.07-1.15:1). Metasomal 

 process extending straight backward; although 

 variable in length, generally reaching about 

 distal end of genital segment. Dorsally, genital 

 segment (Figure IH) wider than long, with its 

 widest part close to its proximal end. Shape 

 of spermatheca (Figures IC, F) similar to 

 A. armatus as described by Bradford (1971), 

 with short wide neck connecting proximal and 

 distal sacs; space between two sacs slightly 



Manuscript accepted July 1973. 



FISHERY BULLETIN: VOL. 72. NO. I. 1974. 



215 



