(Crustacea: Amphipoda) as a distinct species, with a ...

J. Mar. Biol. Ass. U.K. (2006), 86, 1389^1399 Printed in the United Kingdom

doi: 10.1017/S0025315406014421

Re-establishment of Orchomenella crenata (Crustacea: Amphipoda) as a distinct species, with a ¢rst record of its occurrence in the British Isles Niamh M. Kilgallen*P, Alan A. MyersO and David McGrath* *Department of Life Sciences, Galway ^ Mayo Institute of Technology, Ireland. ODepartment of Zoology, Ecology & Plant Science, University College Cork, Ireland. PCorresponding author, e-mail: n __ [email protected]

Orchomenella crenata is recorded for the ¢rst time from the Irish Sea. Some authors have previously questioned the validity of this taxon due to its morphological similarity with Orchomenella nana and have placed it in the synonymy of O. nana. The question of its validity is resolved by the re-description and comparison of both species.

INTRODUCTION During a recent sampling expedition in the Irish Sea, a number of amphipod specimens were taken which were subsequently identi¢ed as Orchomenella crenata Chevreux & Fage, 1925. This represents the ¢rst record of the species from the Irish Sea. The species is morphologically very similar to Orchomenella nana (Kryer, 1846). As a result some authors have questioned the validity of O. crenata as a distinct species and have placed it in the synonymy of O. nana. This paper re-describes the two species and determines the speci¢c validity of Orchomenella crenata. Orchomenella crenata was described from Villefranche, on the Mediterranean coast of France, by Chevreux & Fage (1925). It appears to be a rarely recorded species, but two notable records from outside the Mediterranean are those of Chevreux (1925) and Reid (1951), both of whom identi¢ed specimens from the coast of tropical West Africa. Orchomenella nana, originally described from the Kattegat by Kryer (1846), is, however, a widely recorded species from southern Norway to Spain and Senegal (Lincoln, 1979; Diviacco & Ru¡o, 1989) and the Mediterranean. Karaman’s (1973) discussion on the variability of Adriatic specimens of O. nana questioned the validity of O. crenata as a distinct species. After examining O. crenata and O. nana material deposited in the Muse¤um National d’Histoire Naturelle (MNHN) (both determined by Chevreux), he remarked that he could ¢nd no di¡erences between the two materials. However, he noted that specimens of O. crenata exhibit all variations of the epimeron 3 from smooth to crenated. He also noted that the specimens labelled O. nana appeared to have a very variable shape of the 3rd epimeron, from rounded to subacute or acute (‘pointed’). He concluded that O. crenata must be synonymous with O. nana, but ‘on the other hand, it seems that O. nana is one very variable species’. Ledoyer (1977) recorded both O. crenata and O. nana from the north-west Mediterranean. While noting the observations of Karaman (1973), he chose to retain Journal of the Marine Biological Association of the United Kingdom (2006)

O. crenata as a separate species, using the notched epimeron 3 as the distinguishing character. However, he did not discuss the matter further and the specimens were not illustrated for comparison. In their descriptions of lysianassoid species from the Mediterranean, Diviacco & Ru¡o (1989) followed Karaman (1973), and placed O. crenata in the synonymy of Orchomenella nana. Diviacco & Ru¡o’s illustrations, however, show what appear to be at least two distinct species, di¡ering in the form of the 3rd epimeron. The illustrations show one specimen with an entirely smooth posterior margin of the epimeron; one with two distinct notches in the same margin, which the authors call O. nana (forma crenata); and one which appears to be intermediate between the others, having very slight, widely spaced notches on the epimeron margin. The latter of these they determined to be O. nana and was taken from Banyuls-surMer. In order to resolve this issue, we have examined a number of specimens of both O. nana and O. crenata from the North Atlantic and Mediterranean, including those recorded by Chevreux (1925), Reid (1951) and Ledoyer (1977). Unfortunately the type material of both species appears to be lost and, thus, cannot be studied for comparison.

MATERIALS AND METHODS Material studied was from the collections of the Zoological Museum of the University of Copenhagen (ZMUC), the Museo Civico di Storia Naturale di Verona (MSNV), the Muse¤e Oceanographique, Monaco (MOM), and from the Irish Sea, taken by Day grab, 0.5 mm mesh, in November 2004 by Aquafact International. Specimens for illustration were dissected and mounted in Faure’s solution. Illustrations were made using a compound microscope with a drawing attachment. Descriptions were generated from a DELTA (DEscriptive Language for TAxonomy) database (Dallwitz et al., 1999).

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Orchomenella crenata, new to the British Isles

SYSTEMATICS Order AMPHIPODA Latreille, 1816 Suborder GAMMARIDEA Latreille, 1802 Family LYSIANASSIDAE Dana, 1849 Subfamily TRYPHOSINAE Lowry & Stoddart, 1997 Genus Orchomenella Sars, 1890 Orchomenella crenata Chevreux & Fage, 1925 (Figures 1^3) Orchomenella crenata Chevreux & Fage, 1925: 71, ¢gures 60^61. Chevreux, 1925: 288. Reid, 1951: 195. Ledoyer, 1977: 384. Orchomene nana. Karaman, 1973: 133, ¢gures 14^17 (in part). Orchomenella nana. Ledoyer, 1977: 384. Diviacco & Ru¡o, 1989: 525, ¢gure 527 (in part). Orchomene crenatus.Barnard & Karaman, 1991: 508. Type material

Presumed lost. Type locality

Villefranche, Mediterranean coast of France.

and delimited posteriorly by two robust setae; dactylus with accessory spine. Gnathopod 2 minutely chelate; carpus distinctly longer than propodus. Pereopods 3^4 propodus with locking robust setae at posterodistal corner. Coxa 5 produced into a slight posterior lobe; pereopod 5 basis distinctly longer than broad. Coxa 6 produced into a posterior lobe; pereopod 6 basis slender, much longer than broad; merus posterodistally produced to about 14 carpus length. Pereopod 7 basis longer than broad; merus produced posterodistally to less than 14 carpus length. Epimeron 1 anterodistal corner subquadrate to slightly obtuse; epimeron 3 posterodistal margin variable, with 1^3 distinct notches, with associated seta inserted into each notch. Urosomite 1 with deep dorsal depression and rounded distal carina. Uropod 1 rami subequal; uropod 2 rami subequal, inner ramus with slight marginal constriction; uropod 3 outer ramus 2-articulate, article 2 long (up to half length of article 1), rami distinctly unequal, with inner ramus extending slightly past article 1 of outer ramus. Telson longer than broad, cleft to about 70%. Length

2.5^3.5 mm.

Material examined

Description of adult male (sexually dimorphic characters)

Irish Sea: 2 females, 3^3.2 mm, 52837.78’N 06804.70’W, 23 m, 5 November 2004, collected by Aquafact International; 3 females, 2.5^3 mm, 52837.5’N 06806.31’W, 22 m, 6 November 2004, collected by Aquafact International. Banyuls-sur-Mer: 6 females, 1.7^2.4 mm, 42830’N 03812’E, 75^80 m, 12 September 1975. Gulf of Naples: 14 specimens, 1.4^3.2 mm, Gaiola sand banks, 15^20 m, 24 May 1955; 18 specimens, 1^3.2 mm, 2 miles from the buoy at Gaiola, 150 m, 1957. Marseille: 7 females, 2^3 mm, north of Ratonneau, 50^75 m, 14 April 1975; 6 females, 2.5^3.5 mm, north of Ratonneau, 80 m, 14 April 1975; female 2.8 mm, south-east of Planier, 90 m, 2 May 1975. West Africa: 2 females, 2.8^3 mm, 9288’N 14858’W, 45 m, 14 April 1946, ZMUC CRU-4990; 8 specimens, 2^3.5 mm, from Dakar, 1890, MOM 37 3149.

Antenna 1 shorter than antenna 2; antenna 2 between 50^70% of body length, calceoli present.

Diagnosis

Maxilliped outer plate reaching to tip of palp article 2; coxa 1 slightly tapering posterodistally; pereopod 5 basis distinctly longer than broad; epimeron 3 posterior margin with 1^3 distinct notches. Description of adult female

Antenna 1 subequal to antenna 2, less than 40% of body length; £agellum article 1 distinctly elongate, with 2-¢eld callynophore. Calceoli absent. Eyes large, suboval. Lateral cephalic lobes subacute. Mouthparts forming a quadrate bundle. Mandible with palp attached slightly proximal to molar, molar triturative. Maxilliped palp 4-articulate, reaching well beyond outer plate; inner plate well developed, greater than half the length of outer plate; outer plate reaching to extremity of article 2 of palp. Gnathopod 1 subchelate; coxa 1 large, almost as long as coxa 2, very slightly tapering posterodistally; ischium short, about 1.5 times as long as broad; carpus short (only slightly longer than broad), of subequal length to propodus; propodus margins sub-parallel, palm acute Journal of the Marine Biological Association of the United Kingdom (2006)

Distribution

North Atlantic (coast of Sierra Leone, Senegal, Irish Sea (new record)); Mediterranean. Depth

15^150 m. Remarks

Orchomenella crenata di¡ers from O. nana in form of the third epimeron, which is notched in O. crenata, but smooth in O. nana. This may, however, be quite hard to distinguish in some specimens. This is particularly true of those specimens with only one notch along the posterior margin. Other diagnostic features include the pereopod 5 basis, which in O. nana is subequal in length and breadth, but in O. crenata is distinctly longer than broad, and the outer plate of the maxilliped which reaches to the tip of the second palp article in O. crenata, but reaches beyond the end of the second palp article in O. nana. Finally, there appears to be a slight di¡erence in the form of the ¢rst coxa, being slightly narrower and tapering in O. crenata, but more subrectangular with a slightly concave anterior margin in O. nana. A variety of Orchomenella material from various localities was examined including that of Chevreux (1925), Reid (1951) and Ledoyer (1977). Both Reid’s and Chevreux’s West Africa material, determined by these authors as Orchomenella crenata, is identical to the newly recorded material from the Irish Sea. Although the type material for O. crenata appears to be lost, the specimens in question correspond well to the original illustrations of Chevreux & Fage (1925). Despite small variations in the number of notches on the posterior margin of epimeron 3, all of the Mediterranean


N.M. Kilgallen et al. 1391

Figure 1. Orchomenella crenata Chevreux & Fage, 1925. Female, 2.8 mm, from Irish Sea (52837.5’N 06806.31’W, 22 m). (A) Entire; (B) uropod 1; (C) uropod 3; (D) head and antennae; (E) epimeron 3 and urosome; (F) telson; and (G) uropod 2. Scale bars: (a) 0.8 mm (Figure 1A), 0.2 mm (Figure 1B,C,F&G); (b) 0.4 mm (Figure 1D&E). Journal of the Marine Biological Association of the United Kingdom (2006)

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Figure 2. Orchomenella crenata Chevreux & Fage, 1925. Female, 2.8 mm, from Irish Sea (52837.5’N 06806.31’W, 22 m). (A) Antenna 1; (B) maxilla 2; (C) right maxilliped; (D) maxilla 1; (E) gnathopod 1; (F) gnathopod 1 propodus palm and dactylus; and (G) right mandible. Scale bars: (a) 0.2 mm (Figure 2A,C,E&G), 0.1 mm (Figure 2D&F); (b) 0.2 mm (Figure 2B). Journal of the Marine Biological Association of the United Kingdom (2006)



Figure 3. Orchomenella crenata Chevreux & Fage, 1925. Female, 2.8 mm, from Irish Sea (52837.5’N 06806.31’W, 22 m). (A) Pereopod 6; (B) pereopod 5; (C) pereopod 4; (D) gnathopod 2; (E) gnathopod 2 propodus and dactylus; (F) pereopod 3 propodus and dactylus; and (G) pereopod 7. Scale bars: (a) 0.2 mm (Figure 3E&F); (b) 0.2 mm (Figure 3A^D&G). Journal of the Marine Biological Association of the United Kingdom (2006)

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Figure 4. Orchomenella crenata Chevreux & Fage, 1925. Female, 2.9 mm, from Marseille, 90 m. (A) Pereopod 5; and (B) epimeron 3. Scale bar: 0.2 mm.

material examined was also determined to be conspeci¢c to both the West Africa and Irish Sea material. This included the specimens collected by Ledoyer (1977) from Marseille. No di¡erence was found between the specimens labelled as Orchomenella nana and those labelled as Orchomenella crenata by Ledoyer. However, as we have not examined all of Ledoyer’s (1977) material it is impossible to say if this is the case for all specimens determined by him as O. nana.

Orchomenella nana.Chevreux & Fage, 1925: 71, ¢gure 62. Chevreux, 1925: 288. Reid, 1951: 195. Diviacco & Ru¡o, 1989: 525, ¢gure 359 (in part). Dauvin & Sorbe, 1995: 443, 447, 449, tables 4^5, 456. Orchomene nana. G. Karaman, 1973: 133, ¢gures 14^ 18. Lincoln, 1979: 70, ¢gures 25a ^ g, 26e ^ h. Costello et al., 1989: 34. Dauvin et al., 1994: 550, table 3. Orchomene nanus. Barnard & Karaman, 1991: 509. Type material

Orchomenella nana (Kryer, 1846) (Figures 5^7)

Anonyx nanus Kryer, 1846: 30. ?Orchomenella ciliata. G.O. Sars, 1891: 69, pl. 25, ¢gure 2. Anonyx pinguis. (non Boeck, 1861) Della Valle, 1893: 821, pl. 28, ¢gures 22^35. Orchomenella nanus. Stebbing, 1906: 81. Journal of the Marine Biological Association of the United Kingdom (2006)

According to Dr Jrgen Olesen of the ZMUC, the type material of O. nana is lost (ex ZMUC CRU-7476). Type locality

The Kattegat. Material examined

The Kattegat, Skagerrak and the resund: 10 females, 3.6^5 mm, 7 males, 3.8^5.5 mm, ZMUC CRU-4999.



Figure 5. Orchomenella nana (Kryer, 1846). Female, 3.6 mm. (A) Telson; (B) antenna 2; (C) antenna 1; (D) head and antennae (male); (E) uropod 1; (F) uropod 3; (G) uropod 2; and (H) entire. Scale bars: (a) 0.2 mm (Figure 3A,B,C&F); 0.8 mm (Figure 3H); (b) 0.4 mm (Figure 3D); 0.2 mm (Figure 3E&G). Journal of the Marine Biological Association of the United Kingdom (2006)

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Figure 6. Orchomenella nana (Kryer, 1846). Female, 3.6 mm. (A) Gnathopod 2; (B) gnathopod 2 propodus; (C) maxilla 2; (D) left mandible; (E) left maxilliped; (F) gnathopod 1; (G) gnathopod 1 propodus; and (H) maxilla 1. Scale bars: (a) 0.4 mm (Figure 5A&F); 0.2 mm (Figure 5C,D,E&H); (b) 0.2 mm (Figure 5B&G). Journal of the Marine Biological Association of the United Kingdom (2006)



Figure 7. Orchomenella nana (Kryer, 1846). Female, 3.6 mm. (A) Pereopod 5; (B) pereopod 7; (C) pereopod 4; and (D) pereopod 6. Scale bars: (a) 0.4 mm (Figure 6A,B&D); (b) 0.2 mm (Figure 6C). Journal of the Marine Biological Association of the United Kingdom (2006)

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Diagnosis

Maxilliped outer plate reaching well beyond palp article 2; coxa 1 subrectangular with slightly concave anterior margin; pereopod 5 subequal in length and breadth; epimeron 3 posterior margin smooth without any notches or crenations. Description of adult female

Antenna 1 subequal to or slightly shorter than antenna 2; £agellum article 1 distinctly elongate, about equal to next three articles combined, with strong 2-¢eld callynophore. Antenna 2 less than 40% of body length; calceoli absent. Eyes large, suboval. Lateral cephalic lobes subacute to narrowly rounded. Mouthparts forming a quadrate bundle. Mandible with palp attached slightly proximal to molar, molar triturative. Maxilliped palp 4-articulate, reaching well beyond outer plate; inner plate well developed, greater than half the length of outer plate; outer plate reaching beyond article 2 of palp. Gnathopod 1 subchelate; coxa 1 large, about as long as coxa 2, subrectangular with slightly concave anterior margin; ischium short, about 1.5 times as long as broad; carpus short, of subequal length to propodus; propodus longer than broad, margins subparallel, palm slightly acute, margin posteriorly delimited by two large, robust setae. Gnathopod 2 minutely chelate; carpus distinctly longer than propodus. Pereopods 3^4 propodus with blunt, locking robust setae at posterodistal corner. Coxa 5 producing slight posterior lobe; pereopod 5 basis subequal in length and breadth. Coxa 6 producing posterior lobe, pereopod 6 basis longer than broad; merus posterodistally produced to less than 12 carpus length. Pereopod 7 basis longer than broad and rounded posteriorly. Epimeron 1 anterodistal corner obtuse or broadly rounded; epimeron 3 posterodistal corner subacute to subquadrate, posterior margin smooth. Urosomite 1 with dorsal depression and rounded dorsal carina posteriorly. Uropod 1 rami subequal; uropod 2 rami subequal, inner ramus with slight marginal constriction; uropod 3 outer ramus 2-articulate, article 2 long (up to half length of article 1), rami distinctly unequal with inner ramus extending slightly past article 1 of outer ramus. Telson distinctly longer than broad, cleft to about 70%. Length

3.5^5 mm. Male (sexually dimorphic characters)

Antenna 1 shorter than antenna 2; £agellum article 1 as long as remaining articles combined; accessory £agellum present. Antenna 2 approximately half of body length; calceoli present. Lateral cephalic lobes subacute, somewhat narrower than in female. Length about 3.8^5.5 mm. Distribution

North-east Atlantic, North Sea, Mediterranean Sea (?). Depth

Infralittoral to bathyal. Remarks

Table 1 outlines the distinguishing features of these two species. Journal of the Marine Biological Association of the United Kingdom (2006)

Mediterranean specimens examined here, previously identi¢ed as Orchomenella nana (Kryer) by various investigators, are in fact O. crenata Chevreux & Fage. No specimens of O. nana were found in the material examined from the Mediterranean. This species may occur in the Mediterranean, as Karaman (1973) noted specimens from the south Adriatic as lacking a crenated epimeron posterior margin, while Diviacco & Ru¡o (1989) illustrate a smooth epimeron margin in specimens from the Adriatic also. Karaman’s (1973) illustrations of Orchomene nana from Boka Kotorska correspond with our illustrations of Orchomenella crenata from the Irish Sea, having a notched 3rd epimeron, a pereopod 5 basis that is longer than broad and a slightly tapering coxa 1. Conversely, in the same publication, material illustrated from the Atlantic, at Brest, have the characteristics of O. nana including a smooth epimeron, a pereopod 5 basis that is subequal in length and breadth, and a more subrectangular coxa 1. Table 1. Outline of the main morphological di¡erences between Orchomenella nana and O. crenata.

Maxilliped outer plate Coxa 1

Pereopod 5 basis Epimeron 3 posterodistal corner

Orchomenella nana

Orchomenella crenata

Reaching beyond palp article 2 Subrectangular, anterior margin slightly concave As long as broad Smooth

Reaching to tip of palp article 2 Weakly tapering posterodistally Longer than broad With 1^3 notches

The authors wish to thank Dr Jrgen Olesen of the ZMUC, Professor Sandro Ru¡o of the MSNV and Ms Miche'le Bruni of the MOM for the loan of specimens from respective institutions.

REFERENCES Barnard, J.L. & Karaman, G.S., 1991. Records of the Australian Museum. The Families and Genera of Marine Gammaridean Amphipods (except Marine Gammaroids), Supplement 13. Part 2. Boeck, A., 1861. Bemrkninger angaaende de ved de norske kyster forekommende Amphipoder. Forhandlinger ved de Skandinaviske Naturforskeres Ottende Mde i Kibenhavn, 8, 631^677. Chevreux, E., 1925. Voyage de la goe¤lette Melita aux Canaries et au Se¤ne¤gal (1889^1890). Amphipodes I. Gammariens. Bulletin de la Socie¤te¤ Zoologique de France, 50, 278^311. Chevreux, E. & Fage, L., 1925. Amphipodes. Faune de France. Paris: Librairie de la Faculte¤ des Sciences. Costello, M.J., Holmes, J.M.C., McGrath, D. & Myers, A.A., 1989. A review and catalogue of the Amphipoda (Crustacea) in Ireland. Irish Fisheries Investigations, Series B, Marine, 33, 1^70. Dallwitz, M.J., Paine, T.A. & Zurcher, E.J., 1999. User’s guide to the DELTA system. http://biodiversity.uno.edu/delta/. Dana, J.D., 1849. Synopsis of the genera of Gammaracea. AmericanJournal of Science and Arts, Series 2, 8, 135^140. Dauvin, J.-C., Iglesias, A. & Lorgere¤, J.C., 1994. Circalittoral suprabenthic coarse sand community from the western English Channel. Journal of the Marine Biological Association of the United Kingdom, 74, 543^562.

Orchomenella crenata, new to the British Isles Dauvin, J.C. & Sorbe, J.C., 1995. Suprabenthic amphipods from the Southern Margin of the Cap-Ferret Canyon (Bay of Biscay, north-eastern Atlantic Ocean): abundance and bathymetric distribution. Polskie Archiwum Hydrobiologii, 42, 441^460. DellaValle, A., 1893. Gammarini del Golfo di Napoli. Faune und £ora des golfes von Neapel und der angrenzenden MerresAcschnitte. Monographie, 20, XI + 48 pp., atlas (Atlante) of 61 pls. Diviacco, G. & Ru¡o, S., 1989. Family Lysianassidae. In The Amphipoda of the Mediterranean. Part 2. Gammaridea (Haustoriidae to Lysianassidae). Me¤ moires de l’Institut Oce¤ anographique (ed. S. Ru¡o), pp. 469^575, ¢gures 318^396. Monaco: Muse¤e Oce¤anographique. Karaman, G.S., 1973. On some new or very interesting Amphipoda of the Adriatic Sea (XLII contributions to the knowledge of the Amphipoda). Memorie del Museo Civico di Storia Naturale di Verona, 20, 99^147. Kryer, H.A., 1846. Karcinologiske Bidrag (Fortaettelse). NaturhistoriskTidsskrift, 2, 1^211. Latreille, P.A., 1802. Histoire naturelle ge¤ne¤rale et particulie're des Crustace¤ s et des Insectes. Paris: F. Dufart. Latreille, P.A., 1816. Crustacea. In Nouveau dictionnaire d’histoire naturelle. 6, pp. 570. Paris: Deterville.

Journal of the Marine Biological Association of the United Kingdom (2006)


Ledoyer, M., 1977. Contribution a' l’e¤tude de l’e¤cologie de la faune vagile profonde de la Me¤diterrane¤e nord occidentale. I. Les Gammariens (Crustacea^Amphipoda). Bolletino del Museo Civico di Storia Naturale di Verona, 4, 321^421. Lincoln, R.J., 1979. British marine Amphipoda: Gammaridea. London: British Museum (Natural History). Lowry, J.K. & Stoddart, H.E., 1997. Amphipoda Crustacea IV. Families Aristiidae, Cyphocarididae, Endevouridae, Lysianassidae, Scopelocheiridae, Uristidae. Memoirs of the Hourglass Cruises, 10, 1^148. Reid, D.M., 1951. Report on the Amphipoda (Gammaridea and Caprellidea) of the coast of tropical West Africa. Atlantide Report, 2, 189^291. Sars, G.O., 1890^1895. Amphipoda. An account of the Crustacea of Norway with short descriptions and ¢gures of all the species. Christiana and Copenhagen: A.L.B. Cammermeyers Forlag. Stebbing, T.R.R., 1906. Amphipoda 1. Gammeridea. Das Tierreich. Berlin: Verlag von R. Friedla«nder und Sohn.

Submitted 25 May 2006. Accepted 6 September 2006.