Aega, LEACH, 1815

Bruce, Niel L., 2004, Reassessment of the isopod crustacean Aega deshaysiana (Milne Edwards, 1840) (Cymothoida: Aegidae): a worldwide complex of 21 species, Zoological Journal of the Linnean Society 142 (2), pp. 135-232 : 138-151

GENUS AEGA LEACH

Restricted synonymy

AEga Leach, 1815: 369 ; 1818: 549; Schioedte & Meinert, 1879: 334.

Aega – Brusca, 1983: 7; Kussakin, 1979: 231; Kensley & Schotte, 1989: 116.

Pterelas Guérin-Méneville, 1836 : pl. 20 (not paginated).

Aegacylla Dana, 1854: 176 (‘aegathoid’ or juvenile).

Aegiochus Bovallius, 1885: 4 .

Remarks

The genus has most recently been diagnosed by Brusca (1983) and Kensley & Schotte (1989). The present contribution deals with a subset of the species and it is not appropriate to revise the diagnosis. The genus, with 75 species, occurs throughout marine environments from the polar regions to the tropics, with the greatest number of species being recorded from the continental shelf and slope to depths of 1000 m, occasionally greater.

Brusca (1983) established two subgenera, the nominate subgenus and Ramphion. These have not been consistently accepted, being used by some (e.g. Wetzer, 1990) but not by others ( Bruce, 1988, 1996; Kensley & Chan, 2001). Some of the critical and ‘key’ characters are not present in all species placed within the respective subgenera. In the context of species related to A. deshaysiana ( Aega (Aega) of Brusca) most species lack the expanded antennule peduncle articles 1 and 2, the eyes while large are not always united, the terminal article of the maxilliped palp often lacks ‘recurved spines’ (= hooked robust setae), several species lack a propodal lobe to the palm of pereopods 1–3 and the exopod of pleopod 1 is consistently distally narrowly rounded rather than quadrate. These inconsistencies do not necessarily negate the validity of the subgenera but rather indicate the need for a refinement of the defining characters and reassessment of the distribution of the species between the two subgenera.

Characters of the Aega deshaysiana group

Head with large eyes, either narrowly separated or wholly united; anterior of head with a small anteriorly directed acute median rostral point. Antennule peduncular articles 1 and 2 appear somewhat flattened in dorsal view, but are triangular in cross-section, never strongly expanded (as in, for example, A. komai or A. monophthalma ), with a short flagellum that is always shorter than the peduncle and does not extend beyond the anterior margin of pereonite 1. Antenna peduncle article 2 often with ventral suture or groove; peduncle article 4 often with longitudinal dorsal ridge and groove; articles 4 and 5 often compressed with blade-like posterior edge, but never expanded. Frontal lamina anvil-like. Mandible molar minute or absent. Pereopods robust, anterior pereopods (1–3) always with obvious robust setae; posterior pereopods (4–7) inferior margins of ischium-propodus with relatively long robust setae (in comparison to those of species such as A. magnifica , A. semicarinata or A. monophthalma ). Pleopod 1 exopod distally narrow; pleopods 3–5 endopods always with distomedial point; pleopod 2 with appendix masculina shorter than endopod. Uropods always with endopod lateral margin characteristically indented, usually strongly so, occasionally weakly; rami never extending beyond pleotelson apex; uniquely within the genus the exopod is not coplanar to the endopod but at an angle of 145–160∞, somewhat similar to that of Rocinela .

Characters useful in identifying species similar to Aega deshaysiana

Head: the size and shape of the eye are reliable indicators, although some slight variation is present. Some species have eyes that almost fill the entire dorsal surface of the head; in others, the eyes are large and just separate. There are, between some species, obvious differences between the anterior clear fields (without ommatidia) and the posterior clear fields. The frontal lamina is critical in making species determinations and is a reliable species-specific character.

Coxae: coxal plates are rather uniform within this group. It is, however, necessary to determine: (1) the presence or absence of a posteroventral point on pereonite 1 and coxae 2–4 and (2) the shape of coxae as acutely pointed, rectangular or rounded.

Antennule and antenna: generally rather similar. Antennule peduncular article 2 may be with or without a small anterodistal lobe. There is a distinct difference in the relative lengths of the antennule and antennal flagellum between some species.

Pereopods: the ornamentation of the palm of the propodus of pereopods 1–3 is consistent within species and is a significant character; the pattern, relative size and number of robust setae on the inferior margin of the merus also differ consistently between species. pereopods 4–7 are less obviously different, though there is a substantial difference between those species with long acute robust setae (e.g. A. musorstom sp. nov. and A. hamiota sp. nov.) and those with stout and short robust setae (e.g. A. deshaysiana and A. alazon sp. nov.). The relative proportions of the articles and the pattern and relative numbers of robust setae is consistent within species.

Pleopods: of little discriminatory value.

Pleotelson: shape is often similar between species but does vary with regard to length, general shape of the lateral margins (strongly convex to nearly straight). In addition, the number of robust setae should be noted. As the apex of the pleotelson is frequently damaged the number of robust setae is a difficult character of which to make reliable use.

Uropods: shape, setation and relative proportions all vary between species. Immediate points to observe include: (1) whether or not the exopod apex falls short of, or extends beyond, the endopod apex; (2) the relative proportions and shape of the exopod (a character that varies widely); (3) relative position of the notch on the endopod lateral margin; (4) numbers of marginal robust setae on both rami, and (5) the relative number of robust setae distal to and proximal to the excision on the lateral margin of the uropodal endopod.

AEGA ANTILLENSIS SCHIOEDTE & MEINERT, 1879

( FIGS 1–4 , 61 )

AEga Antillensis Schioedte & Meinert, 1879: 360 , pl. 8, figs 10-13.

AEga antillensis – Richardson, 1901: 521; 1905: 170, fig. 149.

Aega antillensis – Gerstaecker, 1882: 265; Menzies & Frankenberg, 1966: 5; Menzies & Kruczynski, 1983: 62, fig. 19; Kensley, 2001: 226 (part).

Aega deshaysiana – Nierstrasz, 1931: 182 (part).

Aega (Aega) antillensis – Brusca, 1983, fig. 1F.

Aega (Aega) deshaysiana – Kensley & Schotte, 1989: 117 [not Aega deshaysiana ( Milne Edwards, 1840) ].

Aega (Aega) deshayesiana – Kensley & Schotte, 1989: fig. 51A [not Aega deshaysiana ( Milne Edwards, 1840) ].

Not Aega antillensis of all other authors (= various species).

Material examined

Holotype: ♂ (38 mm), Cuba, Grundlach ( ZMB 4046 ).

Non-type: ♂ (32 mm), Gulf of Mexico, 25∞N, 84∞W, 14.vii. 1965, 128 m, coll. M.L. Jones ( USNM 278240). ♀ (non-ovig. 30 mm), Gulf of Mexico, 29∞50¢N, 86∞30¢W, 21.iii.1954, 91 m, coll. Oregon ( USNM 97891). Manca (13.7 mm), Gulf of Mexico, off Florida, 26∞45¢42≤N, 84∞00¢08≤W, 1.vii.1980, 89.8 m, coll. M.L. Jones ( USNM 232928). ♂ (36 mm), off Havana, Cuba, 23∞10¢51≤N, 82∞19¢03≤W, 17.i. 1885, 298 m, Albatross stn. 2323 ( USNM 9494). ♀ (non-ovig. 38 mm), off Havana, Cuba; 23∞10¢36≤N, 82∞20¢30≤W, 1.v. 1884, 358 m, Albatross stn. 2166 ( USNM 7757). ♀ (non-ovig. 34 mm), West Indies, stn.?283 ( USNM 20375). ♀ (non-ovig. 38 mm), south of Cozumel, Mexico, 20∞19¢10≤N, 87∞03¢30≤W, 29.i. 1885, 422 m, Albatross stn. 2359 ( USNM 9564, Brusca, 1983). HOURGLASS CRUISE (material examined by Menzies & Kruczynski, 1983). 2 ♀ (non-ovig. 29, 30 mm), off Florida western coast, Gulf of Mexico, 26∞24¢N, 83∞43¢W, 8.viii.1967, 70– 73 m, crushed shell, dead bryozoans and calcareous algae, coll. R. Presley on R.V. Hernan Cortez ( FSBC I-18383). ♂ (15.0 mm + half specimen), of Florida western coast, Gulf of Mexico, 4 miles west of Egmont Key, 27∞35¢N, 82∞50¢W, 5.ii.1967, 6 m, quartz sand and crushed shell, riverine influence, coll. R. Presley on R.V. Hernan Cortez ( FSBC I-18382). ♂ (18.5 mm), off Florida western coast, Gulf of Mexico, 7 miles west of Egmont Key, 27∞37¢N, 84∞13¢W, 3.vii.1966, 6 m, rushed shell, dead bryozoans and calcareous algae, coll. R. Presley on R.V. Hernan Cortez ( FSBC I-18381). ♀ (non-ovig. 38 mm), off Florida western coast, Gulf of Mexico, 26∞30¢N, 83∞40¢W, 8.v.1967, station depth 69.4–75.2 m, taken from grouper during fishing trip, coll. Lewis H. Bullock on R.V. White Lightning ( FSBC I-18877).

Description

Body 3.5 times as long as greatest width, dorsal surfaces smooth, widest at pereonite 5, lateral margins subparallel. Rostral point projecting anteriorly, not ventrally folded. Eyes large, medially united, anterior clear field 15% length of head, posterior clear field 53% length of head; each eye made up of ~20 transverse rows of ommatidia, each row with ~7–10 ommatidia; eye colour dark brown. Pereonite 1 and coxae 2–3 each with posteroventral angle rounded; coxae 5–7 with entire oblique carina. Pleon with pleonite 1 visible in dorsal view; pleonite 4 with posterolateral margins extending to but not beyond posterior margin of pleonite 5; pleonite 5 with posterolateral angles free, not overlapped by lateral margins of pleonite 4. Pleotelson 1.0 times as long as anterior width, dorsal surface without longitudinal carina; lateral margins sinuate, smooth, posterior margin with elongate medial point, with 10–12 RS.

Antennule peduncle articles 1 and 2 flattened, article 2 without anterodistal lobe; articles 3 and 4 0.7 times as long as combined lengths of articles 1 and 2, article 3 2.7 times as long as wide (¥ LW); flagellum with 7 articles, extending to posterior margin of eye. Antenna peduncle article 2 inferior surface without distinct longitudinal suture; article 4 2¥ LW, 1.5 times as long as combined lengths of articles 1–3, without deep longitudinal groove, inferior margin with 1 plumose seta, and 0 short simple setae; article 5 not markedly wider or flatter than article 4, 0.9 times as long as (¥ L) article 4, 2.5¥ LW, inferior margin with 1 plumose seta, anterodistal angle with cluster of 5 short simple setae; flagellum with 11 articles, extending to posterior of pereonite 1.

Frontal lamina flat, as wide as long, lateral margins converging posteriorly, posteriorly rounded, anterior margin rounded, with small median point, posterior margin not abutting clypeus.

Mandible molar process present, small distinct flat lobe; palp article 2 with 7 distolateral setae (2 large and 5 small), palp article 3 with 20 setae. Maxillule with 6 terminal RS (falcate). Maxilla medial lobe with 3 RS (and 1 simple seta); lateral lobe with 4 RS. Maxilliped endite with 1 apical seta; palp article 2 with 2 RS; article 3 with 5 recurved RS (and 3 simple setae); article 4 with 3 hooked RS (massive); article 5 articulating with article 4, with 4 RS.

Pereopod 1 basis 2.2 times as long as greatest width; ischium 0.5¥ L basis, inferior margin with 0 RS, superior distal margin with 2 RS (acute); merus inferior margin with 3 RS, set as 2 groups (of 1 and 2), superior distal angle with 2 RS; carpus 0.8¥ L merus; inferior margin with 0 RS; propodus 1.3 times as long as proximal width, inferior margin with 0 RS, propodal palm with small distal lobe (rectilinear, with single simple seta), dactylus smoothly curved, 1.4¥ L propodus. P2 ischium inferior margin with 1 RS, superior distal margin with 2 RS; merus inferior margin with 5 RS, set as single row (distal RS overridden by flange), superior distal margin with 2 acute RS; carpus similar in size to that of P1, inferodistal angle with 0 RS, propodus without large club-shaped distal RS. P3 similar to P2 (but propodal lobe narrower); propodus without large club-shaped distal RS. P6 similar to P7 (but longer, inferior margins with longer acute RS). P7 basis 2.8 times as long as greatest width, inferior margin with 6 palmate setae; ischium 0.7¥ L basis, inferior margin with 6 RS (set as 1, 2, 2 and 1), superior distal angle with 5 RS, inferior distal angle with 5 RS; merus 0.7¥ L ischium, 2¥ LW, inferior margin with 4 RS (set as 2 and 2), superior distal angle with 4 RS, inferior distal angle with 4 RS; carpus 0.9¥ L ischium, 5¥ LW, inferior margin with 3 RS (set as 1 and 2), superior distal angle with 4 RS, inferior distal angle with 6 RS; propodus 0.6¥ L ischium, 4.5¥ LW, inferior margin with 1 RS, superior distal angle with 2 slender plumose setae, inferior distal angle with 3 RS.

Penes opening flush with surface of sternite 7; penial openings separated by 6% of sternal width.

Pleopod 1 exopod 1.8¥ LW, distally narrowly rounded with strongly oblique medial margin (not markedly narrow), lateral margin weakly convex, medial margin strongly convex (tapering obliquely to lateral), with PMS from base; endopod 2¥ LW, distally subtruncate, lateral margin strongly concave, with PMS from distal half; peduncle 1.6 as wide as long (¥ WL), medial margin with 9 coupling hooks. Pleopod 2 appendix masculina with straight margins, 0.8¥ L endopod, distally narrowly rounded. Exopods of pleopods 1–5 each with distolateral margin not deeply serrate; endopods of pleopods 3–5 each with mediodistal point; pleopods 2–5 peduncle distolateral margin without prominent acute RS.

Uropod peduncle ventrolateral margin with 1–2 RS, posterior lobe about 0.5¥ L endopod. Uropod rami not coplanar, exopod at angle of about 135∞ to endopod, rami not extending beyond pleotelson, marginal setae in single tier, apices narrowly rounded. Endopod apically not bifid, lateral margin proximally convex, with prominent excision positioned about two-thirds along ramus, proximal lateral margin with 4 RS, distal lateral margin with 5 RS, medial margin weakly convex, with 5 RS. Exopod extending beyond end of endopod, 3 times as long as greatest width, apically not bifid; lateral margin weakly convex, with 9 RS; medial margin convex, with 5–6 RS.

Female

Similar to male with the exception of the sexual characters.

Variation

Robust setae: pleotelson apex frequently damaged, particularly in old specimens. Of the specimens examined only 5 were sufficiently intact to allow RS to be counted; owing to the uncertainty percentage figures are not given and, as far as could be discerned, the number of pleotelson RS ranges from 4 + 4 to 6 + 6. Uropod (n = 13) exopod medial margin 4 (65%), 5 (27%), lateral margin 9 (69%) or 10 (19%); uropod endopod (n = 11) medial margin 5 (19%) to 6 (65%), the lateral margin RS are highly variable with the proximal RS 2–5, distal RS 3–6, with 3 + 4 (15%), 4 + 4 (27%) and 4 + 5 and 5 + 5 (each 11.5%). 4 + 5 (10%), and 5 + 4 (5%). There is no discernible difference between males and females, nor does the number of RS increase with the size of the specimen.

P1–3 had highly consistent counts for the RS on the inferior margin of the merus: P1 with 3 (all), P2 and 3 with 5 (all).

Size

Males 15.7–36 mm (mean 26 mm), females 29–38 mm (mean 34 mm); mancas at 14 mm.

Remarks

The characters that best serve to identify A. antillensis are the large, medially united eyes, frontal lamina with a minute median point, pleotelson with a strongly produced medial point, pereopod 1 merus inferior margin usually with 3 robust setae, that of pereopod 2 with a single row of 5 robust setae and by the uropodal exopod being slightly longer than the endopod. Aega antillensis can be easily separated from other western Atlantic species by the deeply excised uropodal endopod lateral margin.

Differentiation of A. antillensis from A. deshaysiana is discussed in detail in the remarks for the latter species.

Prey

Only recorded prey is ‘grouper’, a species of Serranidae . The White Lightning specimen (FSBC I18877) was not examined by Menzies & Kruczynski (1983) and is the only prey record.

Distribution

Caribbean and Gulf of Mexico, including western Florida and Cuba. The species is probably more widespread than the present records indicate. At depths from 70 to 422 m, Menzies & Kruczynski (1983) cast doubt on the accuracy of their 6 m depth record, attributing it to mismatched data.

AEGA DESHAYSIANA ( MILNE EDWARDS, 1840)

( FIGS 5–8 , 61 )

Rocinela Deshaysiana Milne Edwards, 1840: 243 .

Aega Deshaysiana – Lütken, 1859: 75; Heller, 1866: 744.

AEga Deshayesiana – Schioedte & Meinert, 1879: 360, pl. 8, figs 7-9; Gourret, 1891: 8, pl. 3, figs 12, 13, pl. 4, figs 1–4.

Aega Deshayesiana – Gerstaecker, 1882: 250.

Aega (Rocinela) Deshayesiana – Gerstaecker, 1882: 255, 257.

Aega Schioedteana Bovallius, 1885: 5 , pl. 10, figs 1–10; Stebbing, 1893: 348.

AEga Deshaysiana – Norman, 1904: 343, pl. 12, figs 1– 4; 1905: 13.

Aega deshaysiana – Nierstrasz, 1931: 182 (part).

Aega (Aega) deshaysiana – Brusca, 1983: 11, 13 (part), figs 1E, 2E, H, J, K, 3A, D, F–H.

Aega deshayesiana – Rokicki, 1984: 72, fig. 2; 1985: 97, 103, 104, 108, fig. 1 (map); Kensley, 2001: 226 (part).

Not Aega deshaysiana of all other authors (various species).

Type locality

Mediterranean ( Milne Edwards, 1840), possibly northwestern Africa. Brusca (1983) stated that a label jar read ‘ Palerme ’, possibly the Sicilian coastal town of Palermo. Schioedte & Meinert (1879) stated ‘ ad Panorum captus.’ I have seen no convincing evidence that restricts the type locality to something less precise than the Mediterranean in general.

Material examined

Holotype: ♂ (23 mm), Mediterranean ( MNHN Is.903) . Holotype of Aega schioedteana , ♀ (non-ovig. 17.5 mm), Adriatic, #3736, coll. Wessel ( SMNH 5785 ) .

Non-types: MEDITERRANEAN. ♂ (25 mm), Formentera , Balearic Islands, Spain, 1871, 40 fv (= c. 73 m), coll. F. Sonderlund ( SMNH 6513 ) . ♀ (non-ovig. 20 mm), Cadaqués , Spain (BMNH 1955.2.28.328–29) . ♂ (22 mm), Bonifacio , Corsica, 41∞22¢15¢N, 06∞47¢E, no. 24, 16.vii.1881, 50– 60 m, coll. Travailleur ( MNHN Is. 958) . Manca (13.0 mm), Skerki Bank, Bay of Tunis, Tunisia, coll. HMS Porcupine ( BMNH 1882.14 ) . ♂ (23 mm), Bona Bay , Algeria, specimen reported by Norman (1904) ( BMNH 1903.5.20.74) . 2 ♀ (non-ovig. 32, 34 mm), off Tripoli coast, Libya, 27.v.1986, from pharynx of Pomatomus saltator ( BMNH 1991.14.2) .

NORTH-EASTERN ATLANTIC: ♀ (non-ovig. 31 mm), Fayal , Azores, 30–80 fv (= c. 55–146 m), coll. Exped. Joseph ( SMNH 4985 ) . Manca (10.5 mm), Biacores, 30.x.1971, stn. 143, 61– 74 m, coarse sand, coll. Jean Charcot ( MNHN Is. 762) . ♂ (21 mm), Canary Is., 28∞49¢N, 16∞13¢W, 28.vi. 1883. 120 m, sand and rock, coll. Talisman ( MNHN Is. 959) . ♂ (17.0 mm), Madeira (BMNH, 1876.2). ♂ (23 mm), Madeira ( BMNH 1858.30 ) . 2 ♀ (non-ovig. 28, 36 mm), Arrerife , Lanzarote Is. (BMNH 1956.5.2.129–30). Specimen (damaged, gender not ascertained, 30 mm), 32∞38–47¢N, 18∞55¢W, 10.viii. 1882, 100 m, coral rocks, coll. Travailleur ( MNHN Is. 957) . ♀ (non-ovig. 17.5 mm), off coast of Morocco, 23∞43¢N, 11∞22¢W, before Mazagan, Africa , Stn 20, about 1105 m, 14.vi.1883, Str. Talisman ( USNM 40839 , Brusca, 1983) . ♀ (36 mm), off West Sahara , c. 23∞N, 17∞W, 5.xi.1978, trawled ; 2 ♀ (nonovig. 35, 19.0 mm), 4 (dried, not sexed, 20, 23, 24, 29 mm), off coast of West Sahara and Mauritania, depth and precise location not recorded (private collection of J. Rokicki, reported by Rokicki, 1985) . ♂ (22 mm), SE Leton Bank, 15∞40.0¢N, 23∞05.1¢W, 71 m, Gazelle Expedition (specimen reported by Studer, 1884; ZMB 5492).

Description

Body 3.2 times as long as greatest width, dorsal surfaces smooth, widest at pereonite 5, lateral margins weakly ovate. Rostral point projecting anteriorly, not ventrally folded. Eyes large, not medially united, separated by about 4% width of head; each eye made up of ~21 transverse rows of ommatidia, each row with ~10– 12 ommatidia; eye colour dark brown. Pereonite 1 and coxae 2–3 each with posteroventral angle rounded; coxae 5–7 with entire oblique carina. Pleon with pleonite 1 visible in dorsal view; pleonite 4 with posterolateral margins extending clearly beyond posterior margin of pleonite 5; pleonite 5 with posterolateral angles overlapped by lateral margins of pleonite 4. Pleotelson 1.0–1.1 times as long as anterior width, dorsal surface without longitudinal carina; lateral margins sinuate, smooth, posterior margin with elongate medial point, with 8–10 RS.

Antennule peduncle articles 1 and 2 flattened, article 2 without anterodistal lobe; articles 3 and 4 0.6 times as long as combined lengths of articles 1 and 2, article 3 2.9¥ LW; flagellum with 8 articles, extending to midpoint of eye. Antenna peduncle article 2 inferior surface with indistinct groove; article 4 1.8¥ LW, 1.1 times as long as combined lengths of articles 1–3, without deep longitudinal groove, inferior margin with 1 plumose seta, and 2 short simple setae; article 5 not markedly wider or flatter than article 4, 0.9¥ L article 4, 2.7¥ LW, inferior margin with 2 plumose setae, anterodistal angle with cluster of 4 short simple setae; flagellum with 14 articles, extending to middle of pereonite 1.

Frontal lamina flat, as wide as long, lateral margins converging posteriorly, posteriorly rounded, anterior margin with median indentation (small), without small median point, posterior margin not abutting clypeus.

Mandible molar process absent; palp article 2 with 2 distolateral setae, palp article 3 with 24 setae. Maxillule with 7 terminal RS (4 falcate, distalmost 3 simple). Maxilla medial lobe with 3 RS; lateral lobe with 4 RS. Maxilliped endite with 1 apical seta (acute RS); palp article 2 with 4 RS; article 3 with 4–5 recurved RS; article 4 with 3 hooked RS; article 5 partly fused to article 4, with 3 RS.

Pereopod 1 basis 1.9 times as long as greatest width; ischium 0.3¥ L basis, inferior margin with 0 RS, superior distal margin with 2 RS; merus inferior margin with 4 RS, set as 2 groups (of 1 and 3), superior distal angle with 2 RS; carpus 0.9¥ L merus, inferior margin with 4 RS (3 small, 1 large); propodus 1.3 times as long as proximal width, inferior margin with 0 RS, propodal palm with small distal lobe (posteriorly convex, distal margin convex, provided with 1 simple seta), dactylus smoothly curved, 1.6¥ L propodus (distally strongly curved). P2 ischium inferior margin with 0 RS, superior distal margin with 2 RS; merus inferior margin with 6 RS, set as 2 rows, superior distal margin with 1–2 acute RS; carpus similar in size to that of P1, inferodistal angle with 0 RS, propodus without large club-shaped distal RS. P3 similar to P2; propodus without large club-shaped distal RS. P6 similar to P7 (but more robust, with more and longer RS). P7 basis 3.1 times as long as greatest width; ischium 0.6¥ L basis, inferior margin with 4 RS (set as 1, 2 and 1), superior distal angle with 4 RS, inferior distal angle with 4 RS; merus 0.7 ¥ L ischium, 1.9¥ LW, inferior margin with 5 RS (set as 3 and 3 RS), superior distal angle with 7–9 RS, inferior distal angle with 5–6 RS; carpus 0.9 ¥ L ischium, 3.2 ¥ LW, inferior margin with 3 RS (set as 1 and 2), superior distal angle with 4–6 RS, inferior distal angle with 4–6 RS; propodus 0.7 ¥ L ischium, 4.3¥ LW, inferior margin with 2 RS (single cluster), inferior distal angle with 3 RS.

Penes opening flush with surface of sternite 7.

Pleopod 1 exopod 1.9¥ LW, distally narrowly rounded with strongly oblique medial margin, lateral margin straight, medial margin strongly convex (tapering obliquely to lateral), with PMS from base; endopod 2.3¥ LW, distally subtruncate, lateral margin sinuate, with PMS from distal half, medial margin with PMS from on distal margin only; peduncle 1.5¥ WL, medial margin with 10 coupling hooks. Pleopod 2 appendix masculina with straight margins, 0.8¥ L endopod, distally bluntly rounded. Exopods of pleopods 1–5 each with distolateral margin not deeply serrate; endopods of pleopods 3–5 each with mediodistal point; pleopods 2–5 peduncle distolateral margin without prominent acute RS.

Uropod peduncle ventrolateral margin with 2 RS (and 6 simple setae), posterior lobe about one-half L endopod. Uropod rami not coplanar, exopod at angle of about 135∞ to endopod, rami not extending beyond pleotelson, marginal setae in single tier, apices narrowly rounded. Endopod apically not bifid, lateral margin straight, with prominent excision positioned about two-thirds along ramus, proximal lateral margin with 4 RS, distal lateral margin with 4 RS, medial margin weakly convex, with 4–5 RS. Exopod not extending to end of endopod, 4.1 times as long as greatest width, apically not bifid; lateral margin weakly convex, with 9 RS; medial margin convex, with 3–5 RS.

Female

Similar to the males except for the sexual characters.

Size

Males 17–25 mm (mean 22 mm), females 17–36 mm (mean 29 mm), mancas at 11 and 13 mm.

Variation

Robust setae: pleotelson apex frequently damaged, particularly in old specimens. Of the 25 specimens examined only 7 were sufficiently intact to allow the RS to be counted; owing to the uncertainty, percentage figures are not given and, as far as could be discerned, the number of pleotelson RS ranges from 3 + 3 to 4 + 4, possibly 5 + 5. Uropod (n = 13) exopod medial margin 3 (65%), 4 (31%), 5 (once), lateral margin 7 (15%) 8 (19%), 9 (58%) and 10 (once); uropod endopod (n = 11) medial margin varied from 4 (41%) or 5 (59%), lateral margin with 3 + 4 (10%), 4 + 4 (61%). 4 + 5 (10%), and 5 + 4 (5%). There is no discernible difference between males and females, nor does the number of RS increase with the size of the specimen.

P1–3 had highly consistent counts for the RS on the inferior margin of the merus: P1 with 3 + 1 (all), P2 had 2 rows of 3 + 3 RS (all) and P3 the same with one instance of 3 + 4.

Remarks

The characters that best serve to identify A. deshaysiana are the large, narrowly separated eyes, the frontal lamina with a median anterior indentation, pleotelson with a strongly produced medial point, pereopod 1 merus inferior margin usually with 4 robust setae (set as 1 + 3), the merus of pereopods 2 and 3 each with a double row of 6 robust setae and by the uropodal exopod not extending to the endopod apex.

The separate identities of A. deshaysiana and A. antillensis , two large and distinctive aegids, have long been obscured, originally by the lack of detailed descriptions and then by the consequent misidentification of the species from around the world’s oceans. Brusca (1983) synonymized these two species along with A. excisa Richardson, 1910 and A. schioedtiana Bovallius, 1885 . Brusca’s (1983) redescription and figures were based on material from the East Pacific (Cocos Island), north-western Pacific ( Japan), central North Pacific (Hawaii), Caribbean (holotype of A. antillensis ) and the East Atlantic (holotypes of A. deshaysiana and A. schioedtiana ). The pooling of these specimens effectively established the concept of a highly variable species whereas re-examination of that material shows that the eight specimens included by Brusca (1983) under the name A. deshaysiana belong to five species: A. antillensis , A. deshaysiana , A. excisa , A. sp. (Hawaii), A. sp. (Cocos Is.) and A. japonica sp. nov.

Aega deshaysiana and A. antillensis occur in the eastern and western North Atlantic, respectively. The two species are readily and consistently separated by A. deshaysiana , having distinctly separate eyes (united in A. antillensis ), the anterior margin of the frontal lamina indented (with minute point), pereopod 1 merus inferior margin with 3–4 robust setae (vs. 3) and pereopod 2 merus inferior margin with 6 robust setae set in 2 rows (vs. 5 robust setae set in a single row). The uropods are similar but differ in details of setation and also shape: the uropodal exopod of A. deshaysiana is shorter than the exopod (slightly longer in A. antillensis ), the endopod is distally narrower in A. deshaysiana than in A. antillensis and the medial margin has 4 (41%) or 5 (59%) robust setae compared to 5–6 (65%) in A. antillensis .

Differentiation of the remaining species misidentified as A. deshaysiana are discussed under the individual accounts for those species.

Prey

No reliable records. Rokicki (1985) recorded the species from the basking shark Cetorhinus maximus (Gunnerus, 1765) (as Cetorhinidae ) and an unidentified shark.

Distribution

Western Mediterranean at Corsica, Libya and Algeria with two Adriatic records at ‘Lesina’ in Italy ( Heller, 1866) and an unspecified location collected by the ‘naturalist-merchant Carl Wessel’ ( Bovallius, 1885) from the eastern Mediterranean; along the eastern Atlantic seaboard from the Azores, Canary Islands, Madeira and the coast Spain, southwards off North Africa from Morocco, Western Sahara, and to a recorded latitude of 15∞N off Senegal. The western extent of the range is not precisely known but Rokicki (1985) shows a record at approximately 38∞N, 25∞W.

Recorded depth range of 50–146 m, with one record at c. 1105 m.

Figures

Figure 1. Aega antillensis Schioedte & Meinert, 1879. A–D, holotype, ZMB 4046, remainder male 18.5 mm, Gulf of Mexico, FSBC I 18381. A, dorsal view. B, lateral view. C, head. D, frons. E, antennule. F, antenna. G, pleotelson apex, ventral view. H, penial openings.

Figure 2. Aega antillensis Schioedte & Meinert, 1879. Male 18.5 mm, Gulf of Mexico, FSBC I 18381. A, mandible. B, mandible palp article 3 detail. C, maxillule. D, maxillule apex. E, maxilliped. F, maxilliped palp article 5. G, maxilliped palp articles 2–5. H, maxilla.

Figure 3. Aega antillensis Schioedte & Meinert, 1879. Holotype, ZMB 4046. A–E, pereopods 1–3, 6 and 7, respectively (pereopod 3 basis omitted).

Figure 4. Aega antillensis Schioedte & Meinert, 1879. Male 18.5 mm, Gulf of Mexico, FSBC I 18381. A–E, pleopods 1–5, respectively. F, uropod exopod, ventral view. G, uropod.

Figure 5. Aega deshaysiana (Milne Edwards, 1840). Holotype, MNHN Is.903. A, lateral view. B, dorsal view. C, head. D, head, ventral view. E, pleonites. (All figures by Birgitte Rubaek, Zoologisk Museum, Copenhagen.)

Figure 6. Aega deshaysiana (Milne Edwards, 1840). Female, 36 mm, Canary Islands, BMNH 1956.5.2.129–30. A, antennule. B, antenna. C, mandible. D, maxillule. E, maxillule apex. F, maxilliped. G, maxilliped palp, article 5. H, maxilliped palp, distal articles. I, maxilla. J, maxilla apex.

Figure 7. Aega deshaysiana (Milne Edwards, 1840). Holotype, MNHN Is.903. A–F, pereopods 1–3, 4, 6 and 7, respectively (basis omitted in B and C. Pereopods 2, 3 and 6 drawn in situ).

Figure 8. Aega deshaysiana (Milne Edwards, 1840). A, B and H, holotype. I and J holotype of Aega schioedtiana, SMNH 5795, remainder female, 36 mm, Canary Islands, BMNH 1956.5.2.129–30. A–E, pleopods 1–5, respectively. F, uropod exopod, ventral view. G, uropod. H, uropod. I, pleotelson apex, ventral view. J, frons.

Figure 61. North Atlantic distributions of: Aega antillensis (•) and A. deshaysiana (-). Open squares are records specified to region only, namely Algeria and Adriatic.