Majella Ortmann, 1893

Ng, Peter K. L., Lee, Bee Yan & Forges, Bertrand Richer de, 2021, Periclimenaeus djiboutensis Bruce 1970, Zoological Studies 60 (15), pp. 1-22 : 2-4

Genus Majella Ortmann, 1893

Majella Ortmann, 1893: 51 .

Majella – Sakai 1938: 301; Sakai 1965: 84; Sakai 1976: 235; Griffin and Tranter 1986: 218; Ng et al. 2008: 117.

Type species: Majella brevipes Ortmann, 1893 , by monotypy; gender feminine.

Comparative material. Choniognathus reini ( Balss, 1924) : 1 female (6.3 × 4.0 mm) ( ZRC 2020.0373), stn T 36, on mud, Cortes, Panglao, Bohol, Visayas, Philippines, 9°43.3'N 123°48.8'E, 123–135 m, coll. PANGLAO 2004, 24 June 2004; 1 female (poor condition) (9.1 × 6.2 mm) (KPM NH 0104599, part), Manazuru Town, Ashigarashimo District, Sagami Bay, Japan, coll. T. Sakai, 1962. Seiitaoides orientalis ( Sakai, 1961) : 2 males (8.1 × 5.1 mm; 5.5 × 3.2 mm), 2 females (7.5 × 5.0 mm; 7.3 × 4.8 mm) ( ZRC 2020.0374), stn T 36, sand on echinoderm bed, Cervera Shoal, West Pamilacan island, Bohol, Visayas, Philippines, 9°29.3'N 123°51.5'E, 95–128 m, coll. PANGLAO 2004, 4 July 2004. For comparative material of Eurynome and Kasagia , see Richer de Forges and Ng (2007) and Padate et al. (2019).

Diagnosis: Members all small species, adult females with eggs at cw 9–10 mm. Carapace pyriform, regions well defined by grooves or ridges, but normally obscured by setae; surface smooth or covered by numerous small granules, spines and short stiff and long soft setae, some setae hooked. Pseudorostral spines slender, long, diverging forming V- or broadly U-shaped cleft, with accessory spinules along margin, largest spinules on distal half or proximal third outer margin. Supraorbital eave relatively wide, anterior margin usually with sharp spines or spinules; antorbital spine visible as spine or spinule; intercalated supraocular spine short; postorbital spine longer than antorbital and intercalated supraocular spines in dorsal view, with accessory spinules, small sharp granule present on inner ventral margin, adjacent to suborbital tooth; suborbital tooth clearly separated from postorbital spine and basal antennal article by gaps or clefts. Hepatic lobe distinct, with 2 or 3 prominent spines, all with accessory spinules. Lateral margin with 4 large spines, 1 or 2 epibranchial spines present. Posterolateral margin separated by spine or spinule from posterior carapace margin. Posterior carapace margin with marginal and median spines or spinules; intestinal region not swollen; mesogastric region with 2 short spines, metagastric region with 1 distinct median spine; cardiac region with 1–3 median spines; branchial region with mix of spines, granules, tubercles and/or spinules. Ocular peduncle with sharp distal tubercle. Antennal basal article subquadrate, outer median part with low lobe with tubercles. Epistome subrectangular, wider than long; posterior margin of epistome with triangular lobe with median cleft, separated from sinuous lateral margin by deep cleft. Buccal cavity subtrapezoidal, distal part wider; anteroexternal angle with pterygostomial region marked by serrated flange which brackets anteroexternal angle of merus of third maxilliped when closed; third maxilliped ischium with outer margin lined with sharp tubercles; merus triangular, with anteroexternal angle strongly produced to form large auriculiform structure; exopod outer margin with sharp tubercles. Chelipeds not prominently elongate, not inflated, surfaces covered by short stiff and long soft setae; merus, carpus and chela covered with large and small spines, spinules, tubercles and granules. Ambulatory legs short, with short stiff and long soft setae; margins of merus not carinate, lined with sharp teeth spines or spinules; carpus with dorsal and outer surface lined with spinules or sharp tubercles; dactylo-propodal lock distinct; dactylus falciform, ventral margin usually with 2 sharp submedian granules. Thoracic sternum relatively transversely narrow; surfaces with punctae and small rounded granules; sternites 1 and 2 completely fused to form narrow subtriangular structure, separated from sternite 3 by prominent concave ridge; sternite 3 depressed, fused with sternite 4, demarcated only by lateral incisions, no visible groove present; anterior surface of sternite 4 depressed; sternites 5–8 progressively more narrow, surface of sternites 5–7 medially depressed; small part of sternite 8 visible when pleon closed; sutures between sternites 3–6 medially interrupted; sutures between sternites 6–8 complete; longitudinal groove present between sternites 6–8; sternopleonal cavity deep, reaching to middle part of sternite 4; margin adjacent to telson subcristate, granulate; tubercle of pleonal locking mechanism distinct, on median or distal third part of sternite 5; penis coxal, exiting P5 coxa anterior to condyle. Male pleon narrow; all somites and telson free; somite 1 wider than somite 2, with large median tubercle or spine, visible in dorsal view; somite 2 as wide as somite 3 with swelling on distal margin topped by 4 rounded granules; somite 3 with swelling on distal margin topped by 2 distinct rounded granules, with 1 low granule proximal to them; telson triangular. G1 relatively stout, sinuous or gently curved, groove for G2 on ventral surface; tip relatively sharp to truncate; subdistal setae may be long or absent; G2 very short, with short distal segment. Female pleon longitudinally ovate, all somites and telson free. Vulva large, median, directed obliquely anteriorly inwards towards median line, no vulvar cover.

Remarks: Ortmann (1893: 51) established Majella , differentiating it from Maja Lamarck, 1801 , by having a serrate orbital margin, the merus of the third maxilliped being triangular with the external angle prominently produced, and the carpus and palm of the cheliped short and spiny. Only one species was included, Majella brevipes Ortmann, 1893 , from Japan. In this paper, two more species are described from the western Indian Ocean. Majella is a very distinctive majid because of its small size, with female adult specimens ovigerous at carapace widths less than 9–10 mm.

Ng and Richer de Forges (2015) revised Maja Lamarck, 1801 , and recognised 10 genera, and the differences noted by Ortmann (1893) are still valid. All the genera allied to Maja have the supraorbital eave entire, the merus of the third maxilliped is never projected and the chela is always smooth and unarmed. In addition, the members of these genera have a different arrangement of hepatic, lateral and branchial spines. In addition, the outer margin of the ischium and exopod of the third maxilliped are never spinate like in Majella .

In the Majidae , Majella superficially resembles species of Eurynome Leach, 1814 , Seiitaoides Griffin & Tranter, 1986 , and Kasagia Richer de Forges & Ng, 2007 , especially in the general form of the cheliped (see also Sakai 1965). Eurynome , however, differs from Majella in that the carapace is covered by plates and fungiform tubercles with the margins lined with teeth and spines, the pseudorostral spine is dorsoventrally flattened without accessory granules or spinules, the hepatic lobe marked by a prominent lobe, the basal antennal article is triangular with the margins swollen, the anteroexternal angle of the merus of the third maxilliped is less projecting, the male anterior thoracic sternum is proportionately shorter with the sternopleonal cavity reaching to almost the margin between sternites 3 and 4, and the G1 does not have a subdistal accessory projection (cf. Richer de Forges and Ng 2007: figs. 4B, D, 5A).

In the triangular and strongly auriculiform merus of the third maxilliped, Majella resembles Kasagia Richer de Forges & Ng, 2007 , which is represented by two species from the Philippines and Arabian Sea ( Richer de Forges and Ng 2007; Padate et al. 2019). Majella , however, differs from Kasagia in several key characters: the dorsal surface of the carapace is covered with large spines and sharp tubercles ( Figs. 2B, 3, 4B) (vs. covered with rounded granules and tubercles without long spines in Kasagia ; cf. Richer de Forges and Ng 2007: fig. 3A; Padate et al. 2019: figs. 2B, 5B); the supraobital eave is spinate with a strong antorbital spine ( Figs. 2B, 3, 4B) (vs. supraobital eave not spinate with no antorbital spine in Kasagia ; cf. Richer de Forges and Ng 2007: fig. 3A; Padate et al. 2019: figs. 2B, 5B); the postorbital spine is lobiform in Kasagia ; cf. Padate et al. 2019: figs. 2B, 5B); the hepatic region has 3 prominent spines ( Figs. 2B, 3, 4B) (vs. with only a distinct lobe in Kasagia ; cf. Richer de Forges and Ng 2007: fig. 3A; Padate et al. 2019: figs. 2B, 5B, E); the lateral margin has 4 large spines ( Figs. 2B, 3, 4B) (vs. lateral spines are small and low in Kasagia ; cf. Richer de Forges and Ng 2007: fig. 3A; Padate et al. 2019: figs. 2B, 5B); the basal antennal article is more quadrate with the distal part narrower and has distal tubercles ( Fig. 5B) (vs. triangular and unarmed in Kasagia ; cf. Richer de Forges and Ng 2007: figs. 3C, 4A; Padate et al. 2019: figs. 2C, 5C); the auriculiform anteroexternal process of the merus of the third maxilliped is more projected ( Fig. 6B) (vs. relatively shorter and lower in Kasagia ; cf. Padate et al. 2019: figs. 2C, 5F); the male anterior thoracic sternum and telson are proportionately shorter ( Fig. 4F) (vs. more elongate in Kasagia ; cf. Richer de Forges and Ng, 2007: figs. 3C, 4A; Padate et al. 2019: figs. 2D, F, 5D); the male chelipeds are short ( Figs. 3B, 4A, 5F, G) (vs. elongate in Kasagia ; cf. Richer de Forges and Ng 2007: fig. 2A; Padate et al. 2019: figs. 2A, E, 5A, G); the dorsal margin of the ambulatory merus is not carinate ( Fig. 5H–K) (vs. distinctly carinate in Kasagia ; cf. Padate et al. 2019: figs. 2G, 5H); and the G1 is sinuous to curved with the distal part simple ( Fig. 6H–J) (vs. G1 curved with distal part expanded and bifid in Kasagia ; cf. Richer de Forges and Ng 2007: fig. 5B, C; Padate et al. 2019: fig. 3A, B); and the G2 has a short distal segment ( Fig. 6K) (vs. without a distal segment in Kasagia ; cf. Padate et al. 2019: fig. 3C, D).

Two West Pacific species previously placed in Eurynome were separated into a new genus, Seiitaoides , by Griffin and Tranter (1986: 251) as their carapaces are different. Seiitaoides shares with Majella a pseudorostral spine that has accessory granules and spinules, a serrated supraorbital eave, a merus of the third maxilliped that is expanded, and a simple G1 without projections or flanges. Seiitaoides , however, has a short pseudorostrum, prominent gastric, cardiac, intestinal and lateral plates, no hepatic and lateral spines, the merus of the third maxilliped is not strongly expanded, and adult males have proportionately longer chelipeds (cf. Sakai 1961: pl. 4 fig. 2; Sakai 1976: text-fig. 119, pl. 76 fig. 1; Griffin and Tranter 1986: fig. 69b).

Choniognathus Rathbun, 1932 , species have previously been placed in Eurynome , but members of this genus are very unusual in that the merus and ischium of the third maxilliped are fused (cf. Sakai 1976: text-fig. 120b). Like, Majella , its members are all small, but Choniognathus species can be distinguished by the pseudorostrum being short, the anteroexternal angle of the merus of the third maxilliped is not expanded, the carapace regions and margins are lined with rounded tubercles and granules, not spines, the hepatic lobe is not spinate, and the chelipeds are short and the chela is not armed (see Balss 1924: pl. 1 fig. 3; Yokoya 1933: text-fig. 57; Sakai 1976: text-fig. 120, pl. 78 fig. 2; Ho et al. 2004: fig. 3F).