Galathea aegyptiaca

Galathea aegyptiaca Paul’son, 1875

(Figs 5, 115 B, C)

Galathea australiensis.— Balss, 1913b: 2 (Red Sea).— Laurie, 1926: 123 (Amirante, Saya De Malha Bank, Cargados Carazos, 37–146 m).— Barnard, 1958: 4 (Delagoa Bay).

Galathea aegyptiaca Paul’son, 1875: 94, pl. 12, figs 1, 1a–b (Red Sea).— Nobili, 1906: 126, fig. 8, pl. 7, fig. 3 (Red Sea).— Lewinsohn, 1969: 98, fig. 18 (Red Sea, 0–3 m).— Garth et al., 1987: 252 (list).—Baba, 1990: 952 (Madagascar, intertidal to 50 m).— Tirmizi & Javed, 1993: 61, fig. 27 (N Madagascar and Mozambique Channel, 1.5–62 m).—Baba et al., 2008: 64 (in part, compilation).— Macpherson & Cleva, 2010: 58, color figs 3A, B (Mayotte and Madagascar, 0–25 m).— Poore et al., 2011: 332, pl. 10B (color photo, Madagascar).—Poupin, 2013: 12, fig. 6a–b (color) (Mayotte, 3–30 m).

Dubious identifications:

Galathea aegyptiaca. — Haig, 1974: 447 (Western Australia).— Baba, 1977a: 244 (near Timor, Obi, Talaud and Holandia Bay, New Guinea, 0–10 m).— Baba, 1979b: 645 (Marsegu Island and Gorong Island, subtidal).— Baba, 1982b: 59 (Palau Islands and Yap Island, subtidal).— Kamezaki et al., 1988: 95, with color fig. (Okinawa).— Wu et al., 1998: 88, figs. 8, 12E (Taiwan).— Davie, 2002: 60 (no record).—Baba et al., 2008: 64 (in part, compilation); 2009: 107, figs. 86–87 (Taiwan).— Dong & Li, 2010: 2 (South China Sea, intertidal to 50 m).

Material examined. Red Sea. Gulf of Aqaba. 5 m, 12 July 1995: 1 M 2.8 mm (SMF).—Stn AQ127, 5 m, 22 July 1995: 2 M 2.9–3.4 mm (SMF).—Stn AQ129, 5 m, 22 July 1995: 2 F 2.7–4.0 mm (SMF). Sudan, Al Bahr al Ahmar. Stn SAN166, 5 m, 21 September 1992: 1 F 2.4 mm (SMF).—Stn SAN173, 5 m, 21 September 1992: 1 M 2.2 mm (SMF).—Stn SAN138, 1 m, 29 September 1992: 3 ov. F 4.0– 4.6 mm, 1 F 2.7 mm (SMF).—Stn SAN168, 5 m, 29 September 1992: 1 M 2.8 mm, 1 ov. F 3.9 mm (SMF).—Red Sea. No locality: 4 M 4.4–4.8 mm, 6 ov. F 4.8–5.2 mm (SMF 4577). Djibouti, Moucha Island, Maskali Bank, 11.6992°N, 43.1432°E, 7–17 m, 27 September 2012: 2 M 2.0–3.0 mm (UF33346).— Djibouti, NE Gulf of Tadjoura, E of Obock, 11.9737°N, 43.3358°E, 4–6 m, 28 September 2012: 1 M 3.0 mm (UF32802), 1 F 3.0 mm (UF32797), 1 M 2.0 mm, 2 ov. F 3.2—3.4 mm (UF33072).— Djibouti, NE Gulf of Tadjoura, E of Obock, 11.976°N, 43.365°E, 8–13 m, 29 September 2012: 1 M 3.4 mm (UF32828). Saudi Arabia, 22.2646°N, 39.0263°E, 1–20 m, 8 October 2012: 1 ov. F 2.9 mm (UF32997).— 22.2741°N, 39.0512°E, 2–20 m, 10 October 2012: 1 M 3.7 mm (UF32999); 1 M 4.0 mm, 1 F 2.2 mm (UF33063).— 18.2206°N, 41°3244°E, 5–15 m, 6 March 2013: 1 M 2.5 mm (UF36154), 1 ov. F 3.4 mm (UF36675).— 18.0731°N, 40.8859°E, 7–9 m, 8 March 2013: 1 M 4.1 mm (UF36010), 1 M 2.8 mm (UF36822).— 22.4268°N, 38.9963°E, no depth, 18 March 2013: 1 F 4.2 mm (UF37107).— 27°47'65"N, 35°07'48"E, 3–5 m, 23 June 2013: 1 ov. F 3.6 mm (SMF).—Abulat, No date: 1 M 4.1 mm (MNHN-Ga751, MNHN-IU-2013-9694).— Ras Al-Ubayd. 26.7361°N, 36.0443°E, 4 m, 26 September 2013: 1 M 2.1 mm, 1 ov. F 2.9 mm (UF36403).—Jaz'air, 27.6384°N, 35.3062°E, 10 m, 27 September 2013: 1 M 2.3 mm (UF36438).—Gulf of Aqaba, 28.4039°N, 34.7407°E, 7–8 m, 29 September 2013: 1 M 2.8 mm, 1 F 2.4 mm (UF38067).—Gulf of Aqaba, 28.3991°N, 34.7373°E, 2 m, 30 September 2013: 1 M 3.2 mm (UF38132).

Mayotte Island. BENTHEDI, Stn 16R, 12°45.2'S; 45°16.7'E, 3–8 m, 22 March 1977: 2 ov. F 2.7–2.8 mm; 2 F 1.9–2.0 mm (MNHN-IU-2013-8009).

Madagascar. ATIMO VATAE, Stn TS2, 25°01.3'S, 47°00.5'E, 18 m, 29 April 2010: 3 F 1.6–3.0 mm (MNHN- IU-2013-8016).— Stn TB1, 24°59.8'S, 47°05.7'E, 22 m, 30 April 2010: 1 F 2.9 mm (MNHN-IU-2013-8013).—Stn TB2, 25°01.3'S, 47° 00.5'E, 18 m, 0 1 May 2010: 3 M 2.6–3.4 mm, 1 ov. F 4.4 mm, 4 F 2.2–4.8 mm (MNHN-IU- 2013-8010, MNHN-IU- 2010-2739).—Stn TB3, 25°01.3'S, 47° 00.5'E, 18 m, 0 1 May 2010: 1 M 4.1 mm, 3 ov. F 3.0– 3.6 mm, 1 F 2.6 mm (MNHN-IU-2013-8011).—Stn TB5, 25°02.2'S, 47°00.4'E, 23 m, 0 7 May 2010: 1 ov. F 3.1 mm (MNHN-IU- 2010-2742).—Stn TB9, 25°02.3'S, 46°59.6'E, 6–7 m, 10 May 2010: 1 ov. F 3.9 mm (MNHN- IU- 2010-2744).—Stn TA1, 25°09.5'S, 46°45.3'E, 7–14 m, 12 May 2010: 1 M 4.8 mm (MNHN-IU-2013- 8019).—Stn DW3606, 25°48.4'S, 44°51.1'E, 44–46 m, 13 May 2010: 1 ov. F 2.8 mm, 1 F 2.7 mm (MNHN-IU- 2010-2740).— Stn TB12, 25°01.5'S, 47°00.0'E, 4–5 m, 14 May 2010: 1 ov. F 2.7 mm, 1 F 2.0 mm (MNHN-IU- 2013-8012).—Stn TB13, 25°01.5'S, 47°00.0'E, 2–4 m, 15 May 2010: 1 ov. F 4.0 mm (MNHN-IU-2013- 8015).—Stn BS1, 25°28.2'S, 44°56.4'E, 12–14 m, 25 May 2010: 1 M 4.4 mm (MNHN-IU-2013-8014).—Stn BB4, 25°26.9'S, 44°55.9'E, 14–18 m, 30 May 2010: 1 ov. F 4.2 mm (MNHN-IU-2013-8018).—Stn BS4, 25°26.9'S, 44°55.9'E, 14–18 m, 30 May 2010: 1 M 4.2 mm (MNHN-IU-2013-8017).

Chagos Islands. Great Chagos Bank, Brothers Island. Stn CH 0594, 8–12 m, Febuary 2012: 1 M 2.6 mm (OUMNH).

Description. Carapace: As long as broad; cervical groove distinct, but anterior cervical groove indistinct; transverse ridges on dorsal surface with numerous non-plumose setae setae, and some thick long iridescent and plumose setae, in particular forming median tuft between epigastric spines and on median convexity of anterior protogastric ridge. Seven ridges on gastric region: 1 epigastric ridge with 2 submedian spines, medially interrupted; 2 protogastric ridges, anterior ridge strongly convex medially, uninterrupted, with 1 parahepatic spine on each side, posterior ridge short, scale-like and placed medially; 2 mesogastric ridges, anterior ridge uninterrupted, extending laterally to anteriormost branchial marginal spine, posterior ridge scale-like; 2 metagastric ridges uninterrupted and sometimes fused with anterior branchial ridges. Mid-transverse ridge uninterrupted, preceded by shallow cervical groove, followed by 5 transverse ridges, 3 or 4 ridges uninterrupted. Lateral margins medially convex, with 7 spines: 2 spines in front of, and 5 spines behind, indistinct anterior cervical groove; first spine at anterolateral angle well-developed, at same level of lateral limit of orbit; second, small, at midlength between anterolateral spine and anteriormost spine of branchial margin, accompanying another spine ventral to between first and second; 2 spines on anterior branchial margin, last small, and 3 spines on posterior branchial margin, last small. External limit of orbit ending in small spine; infra-orbital margin with a strong spine. Rostrum broadly triangular, as long as or slightly longer than broad, length 0.5 of, breadth 0.4 of carapace, distance between distalmost lateral incisions 0.25 distance between proximalmost lateral incisions, dorsal surface nearly horizontal in lateral view, with some thick long plumose setae; lateral margin with 4 sharp teeth.

Pterygostomian flap rugose, anterior margin ending in well-developed spine; no facial spine.

Sternum: 0.8 times as long as broad, lateral limits divergent posteriorly.

Abdomen: Somites 2–4 each with 2 uninterrupted transverse ridges on tergite, with or without short scales between those transverse ridges; somite 5 and 6 each with 2 ridges, some of them medially interrupted; posteriomedian margin of somite 6 distinct. Males with G1 and G2.

Eyes: Ocular peduncles 1.1 times longer than broad, maximum corneal diameter 0.5 rostrum width.

Antennule: Article 1 with 3 well-developed distal spines, distodorsal larger. Ultimate article twice longer than broad, with tuft of fine setae on distodorsal margin.

Antenna: Article 1 hardly visible from dorsal view, with depressed distomesial process slightly exceeding distal margin of peduncle. Article 2 with distomesial spine smaller than distolateral, exceeding midlength of article 3. Article 3 with small, distinct distolateral spine. Article 4 unarmed.

Mxp3: Ischium with well-developed distal spine on flexor margin; extensor margin unarmed; crista dentata with 20 or 21 denticles. Merus shorter than ischium, with 2 strong spines of subequal size on flexor margin, proximal one located at midlength, distal one at terminal end; extensor margin with distal spine. Carpus spineless.

P1: 2.0–4.0 times carapace length, relatively slender, subcylindrical, with numerous short setae and some scattered long plumose setae on dorsal surface and along lateral and mesial margins of all articles. Merus as long as or slightly shorter than carapace, 1.3–1.7 times as long as carpus, with rows of spines, mesial and distal spines strong. Carpus 0.8 length of palm, 1.9–2.2 times longer than broad, lateral and mesial margins subparallel, dorsal surface with small spines in 2 longitudinal rows; mesial surface with row of well-developed spines; and row of small spines along lateral margin. Palm 2.3 times longer than broad, lateral and mesial margins subparallel; spines arranged in inrregular longitudinal rows on dorsal, mesial and lateral surfaces; lateral row continued onto whole lateral margin of fixed finger. Fingers 0.6–0.8 as long as palm, each finger distally with 2 rows of teeth, spooned; mesial margin of movable finger unarmed.

P2–4: Moderately setose, sparsely with long setae on all articles. P2 1.6–1.8 times carapace length. Meri successively shorter posteriorly (P3 merus 0.9 length of P2 merus, P4 merus 0.9 length of P3 merus), equally broad on P2–4; P2 merus 0.5–0.7 carapace length, 3.2–3.5 times as long as broad, 1.5 times longer than P2 propodus; P3 merus 3.4 times as long as broad, 1.3 times length of P3 propodus; P4 merus 2.8 times as long as broad, 1.1 length of P4 propodus; extensor margins with row of 6–9 proximally diminishing spines on P2–3, unarmed on P4; lateral surface unarmed on P2–3, row of 4 proximally diminishing spines on P4; flexor margins each with strong terminal spine. Carpi each with 4 spines on extensor margin; lateral surface each with row of 2 or 3 small spines paralleling extensor row; flexor distal margins each with spine. Propodi subequal in length for one another in P3 and P4, slightly shorter in P2, equally broad in P2–4, and 3.5–4.0 times as long as broad; extensor margins each with 2 or 3 proximal spines in P2–4; flexor margins each with 4 slender movable spines in P2or 3, 3 in P4; 2 proximal spines on lateral surface on P2or 3, unarmed on P4. Dactyli subequal in length, 0.7 length of propodi, ending in incurved, strong, sharp spine; flexor margins each with prominent triangular subterminal tooth preceded by 4 or 5 low teeth, each tooth bearing robust setae.

Epipods present on P1, absent on P2–3.

Color. Base color reddish or greenish, with darker ridges on the carapace dorsal surface and abdomen, and darker stripes on pereopods; rostrum reddish or greenish; plumose setae on carapace reddish or whitish; some spines on carapace margins and pereopods with basis blue and distal point red; basis of P1 fingers bluish; distal part of P2–4 meri each with orange spot.

Remarks. Galathea aegyptiaca was described from two males collected in the Red Sea. Unfortunately the types were lost. The species is characterized by the uninterrupted mesogastric ridge between the left and right anteriormost branchial marginal spines and the presence of plumose stiff setae on the carapace and rostrum. However, the molecular data has revealed the existence of some closely similar species differenciated by subtle morphological characters: G. corbariae n. sp. from Japan to Vanuatu, G. homologa n. sp. from Vanuatu, G. imitata n. sp. from Western Australia and G. simulata n. sp. from New Caledonia.

Galathea aegyptiaca seems restricted to the western Indian Ocean, therefore, previous records from all localities in the western Pacific should belong to other species (see synonymy). The genetic divergences among G. aegyptiaca and the other related species are quite large (13.1–16.6% COI, 4.8–7.8% 16S rRNA, see Tab. 1). The specimens from Madagascar and Mayotte Islands show a divergence higher than 5% (COI) with those from the Red Sea (type locality) that could indicate the existence of two cryptic species. However, no morphological differences have been observed between the material from the two areas. Further analysis is necessary to establish the specific status of the population in Madagascar and adjacent waters.

Galathea aegyptiaca can be distinguished from G. corbariae, G. homologa and G. imitata by the presence of a short posterior median protogastric ridge and a short posterior median mesogastric ridge. These ridges are absent in the other species (sometimes one of them can be present). Galathea simulata can be differentiated from G. aegyptiaca by having the P2–3 propodi more elongate, 5 times longer than broad, whereas they are less slender, equal or less than 4 times longer than broad, in the other species.

Distribution. Eastern African coasts, from the Red Sea to Mozambique, Madagascar, Amirante, Saya De Malha Bank, Cargados Carajos, Chagos Islands, 0– 146 m. Specimens collected on Stylophora pistillata, Pavona decussata, and in dead Pocillopora.