144 



R. BOTTGER-SCHNACK AND R. HUYS 



genital aperture on either side; covered by pattern of denticles as 

 shown in Fig. 4E; posterolateral corners protruding laterally so that 

 they are discernible in dorsal aspect (Fig. 4D). 



Spermatophore oval, of variable size according to state of matu- 

 rity (Fig. 4F); swelling of spermatophore during development not 

 affecting shape or relative size of genital somite. 



TAXONOMIC HISTORY 



Claus ( 1 863: 1 59) presented a concise original description of Antaria 

 mediterranea with some illustrations of both sexes. Later Claus 

 ( 1 866) identified two size groups upon re-examination of original 

 material from Messina: the large one [1.3 mm excluding CR setae] 

 being the one that was mentioned in the original description; the 

 small one [0.8-0.9 mm] which he also recorded from Nice; no 

 overlap was found between both size morphs from Messina. 



Lilljeborg (1875) recorded a single specimen from Mosselbay 

 (Spitsbergen), and Car ( 1 884) found it in plankton samples taken off 

 Trieste in the Adriatic Sea. Both authors, however, gave no descrip- 

 tions or figures and their records therefore remain unconfirmed. 



Bourne (1889) [as Onccea mediterranea] found 2 females in 

 surface waters off Plymouth. Giesbrecht ( 1 892) regarded this record 

 doubtful and pointed out the discrepancy between the text and 

 figures with regard to the CR/anal somite length ratio. Careful 

 comparison of this character is hampered by the fact that Claus 

 ( 1 863) only figured the female in lateral aspect and by the possibility 

 that the urosome is considerably telescoped in the specimen illustrated 

 by Bourne. Giesbrecht's statement that Bourne's and Claus' speci- 

 mens differ fundamentally in maxilliped structure is equivocal since 

 he compared the former with what he had identified as O. 

 mediterranea rather than with the original type material. On the 

 basis of Brady's (1883) illustrations [Challenger Expedition], Bourne 

 (1889) also tentatively regarded Oncaza obtusa (Dana) as a possible 

 synonym of O. mediterranea, however, as Giesbrecht (1892) and 

 subsequent authors suspected, the latter could as well be conspecific 

 with O. venusta Philippi. 



Giesbrecht (1892) reviewed the earlier literature on Antaria and 

 Oncaea, and summarized the synonymies of the respective species 

 known at that time. Dana's (1849) species Antaria obtusa and A. 

 crassimana were included under the synonymy of both O. venusta 

 and O. mediterranea, reflecting the author's undecisiveness on this 

 matter. Giesbrecht redescribed O. mediterranea on the basis of 

 material from Naples and distinguished two colour varieties flava 

 and rubra. 



Comparison of Giesbrecht's illustrations with Claus' original 

 description, however, raises some doubts as to the conspecificity of 

 the Messina and Naples specimens. The major obstacle in this 

 comparison lies in the form, position and size of the setae on the 

 maxillipedal basis which is usually considered as an important 

 discriminant in oncaeid systematics. The issue is even more compli- 

 cated by the discrepancy between text and figures in Claus' original 

 description. Claus (1863) stated that there are two ornated setae on 

 the palmar margin of the basis, yet in his figure (Tafel XXX, Fig. 6) 

 only one naked seta is illustrated. From the position of this seta, 

 being located halfway the inner margin, it is conceivable that Claus 

 has overlooked the proximal seta. This hints at the possibility that 

 Claus' O. mediterranea is related to the 'englishi species-group' 

 which includes O. ornata Giesbrecht, 1891, O. shmelevi Gordejeva, 

 1972, O. englishi Heron, 1977 and O. alboranica Shmeleva, 1979. 

 In these species the distal element is long, slender and minutely 

 pinnate, whereas the proximal one is spiniform and because of its 



small size easily overlooked or misinterpreted as a spinule. In 

 Giesbrecht's O. mediterranea, however, both elements are (1) of 

 about the same size and only half the length of the proximal seta in 

 the Messina material, and (2) positioned differently, i.e. the proxi- 

 mal one at 1/3 distance from the syncoxa-basis joint, the distal one 

 at 2/3 distance. A second possibility is that the long palmar seta in 

 Claus' original illustration is in fact a maxillary element superim- 

 posed on the maxilliped since Claus believed that both appendages 

 represented the rami of a single limb, i.e. the maxilliped. 



Other differences are found in the female leg 5 which is longer in 

 the original description and the shape of the genital double-somite in 

 lateral aspect which does not have the pronounced swelling anterio- 

 ventrally as shown in Giesbrecht's illustration (Taf. 4, Fig. 16). The 

 male of Claus' O. mediterranea shows an exceptionally long leg 5 

 exopod (his Taf. XXX Fig. 7) which might or might not be free. This 

 character has thus far been found in only a small number of Oncaea 

 species belonging to the notopus group, such as O. damkaeri Heron, 

 1977 and O. parila Heron, 1977 (Heron, 1977; Heron et ai, 1984) 

 which also display a very long leg 5 exopod in the females. Species 

 of the notopus group have a setation pattern on the female maxilliped 

 which is significantly different from that displayed in the englishi 

 group which raises the suspicion that Claus (1863) might well have 

 based males and females on different species. 



As a result of this comparison it is clear that Claus' original text 

 and drawings contain several internal inconsistencies and lack the 

 detail that is necessary to allow unequivocal identification. The 

 setation of the maxilliped is a potentially critical character in this 

 process as confirmation or refutal of Giesbrecht's identification 

 depends on whether more weight is given to the text statement or to 

 the illustration. Given the fact that Claus' figures of the other 

 cephalic appendages are similarly poor (setation elements are miss- 

 ing from every limb) it is preferred here to give more weight to the 

 text as this will lead to nomenclatural stability. Pending the rediscov- 

 ery of Claus' types (which are in all probability lost) this admittedly 

 subjective decision is the best course of action. In view of the grossly 

 fragmentary original description in which the sexes were based on 

 two different - but unidentifiable - species and in the absence of 

 formal holotype designation the taxonomic problem is in our opin- 

 ion unsolvable. Moreover, it is considered highly unlikely that 

 collection of topotype material from Messina would be informative 

 as 130 years have lapsed since Claus' discovery of the species in an 

 open pelagic environment that might have been subjected to major 

 changes since, such as the opening of the Suez Canal in 1869. 



O. mediterranea (Claus, 1863) sensu Bourne (1889) is clearly 

 different from the Mediterranean material and is regarded here as 

 species inquirenda in the genus. 



Other records of O. mediterranea. 



O. mediterranea has been recorded from a wide range of localities 

 such as the Antarctic (Heron, 1977) and the Red Sea (Bottger- 

 Schnack, 1988). Many of its records, however, remain unconfirmed 

 such as the Red Sea records of Cleve (1900, 1903) and Thompson 

 and Scott (1903) [compiled by Halim (1969)]. Since most authors 

 have followed Giesbrecht's identification and ignored Claus' origi- 

 nal description it is likely that at least one, as yet unnamed, species 

 became established in the literature under the wrong name O. 

 mediterranea. For example, re-examination of material collected 

 during the Terra Nova and Challenger expeditions (deposited in The 

 Natural History Museum) proved to belong to at least two distinct 

 species differening in several aspects from O. mediterranea. Scott 

 (1894) recorded this species ('1 or 2 females') from the Gulf of 

 Guinea, but re-examination of his illustrations leave little doubt that 



