Research Article |
Corresponding author: Bee Yan Lee ( beeyan06@gmail.com ) Academic editor: Sammy De Grave
© 2020 Bee Yan Lee, Bertrand Richer De Forges, Peter K. L. Ng.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Lee BY, Richer De Forges B, Ng PKL (2020) Revision of the deep-water spider crab genus, Scyramathia A. Milne-Edwards, 1880, with the description of a new species from the Mediterranean and notes on Rochinia A. Milne-Edwards, 1875, and Anamathia Smith, 1885 (Crustacea, Decapoda, Brachyura, Epialtidae). Zoosystematics and Evolution 96(2): 537-569. https://doi.org/10.3897/zse.96.48041
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The taxonomy of the deep-water spider crabs of the genus Scyramathia A. Milne-Edwards, 1880, is revised and four extant species are recognised from the Atlantic and western Indian Ocean: S. carpenteri (Norman, in
deep-sea, Epialtidae, new species, revision, spider crabs, taxonomy
The deep-water epialtid spider crab genus, Scyramathia A. Milne-Edwards, 1880, was recently reinstated by
With a good series of Scyramathia specimens from various parts of Europe and Africa, including types, the genus is herein revised and diagnosed. Four species are here recognised, including a new species from the Mediterranean. These species are diagnosed and figured. To provide context and necessary comparisons, the genera Rochinia A. Milne-Edwards, 1875, and Anamathia Smith, 1885, are also diagnosed, and their type species figured.
The material examined are deposited in the Muséum national d’Histoire naturelle (
Measurements provided, in millimetres, are of the carapace length (excluding pseudorostral spine) and carapace width (to the base of the lateral spine). The maximum length and width of the merus of the ambulatory legs are measured following
With regard to the taxa named by Sir Charles Wyville Thomson, his family name has been cited as “Thomson” (see examples:
Superfamily Majoidea Samouelle, 1819
Family Epialtidae MacLeay, 1838
Rochinia
A. Milne-Edwards 1875 [in 1873–1880]: 86 (footnote);
Rachinia
[sic]:
Rochinia gracilipes A. Milne-Edwards, 1875, by monotypy; gender feminine. Monotypic.
The study by
Rochinia gracilipes
A. Milne-Edwards 1875 [in 1873–1880]: 86 (footnote) (type locality: Cape Corrientes, Argentina);
Rachinia
[sic] gracilipes: A. Milne-Edwards 1875 [in 1873–1880]: pl. 18 fig. 1–1d;
Paralectotypes
: 1 ♂ [dry] (20.0 × 15.0 mm, 1 ♀ (10.4 × 8.5 mm) (
No type specimen was designated when this species was described by A. Milne-Edwards (1875: 86 [footnote]) although various specimens from “la collection du Muséum” (i.e., the Muséum national d’Histoire naturelle (
Rochinia gracilipes was recorded from the coast of Africa near Gabon by
Currently only known from its type locality, Cape Corrientes (= Cabo Corrientes), Mar del Plata, Argentina (A. Milne-Edwards 1875), southeastern Brazilian coast (Spivak et al. 2019), South Shetland Islands (Griffiths et al. 2014); Antarctic Peninsula (De Melo, 1996; Tavares and Melo 2004).
A–D. Rochinia gracilipes A. Milne-Edwards, 1875, paralectotype male (20.0 × 15.0 mm) (
Scyramathia
A.
? Scyramathia:
Amathia carpenteri Norman, in
Carapace pyriform, with strong raised plate-like structures in large adult specimens (Figs
When establishing Scyramathia A. Milne-Edwards, 1880, A.
Scyramathia carpenteri (Norman, in
The species in Scyramathia s. str. have characteristic carapace plates that become more pronounced and lamelliform with age (see
Scyramathia s. str. is herein re-defined. With the transfer of S. hertwigi, as well as the description of a new species, S. tenuipes sp. nov., from the Mediterranean Sea, there are now four extant species and one fossil species in this genus.
1 | Pseudorostral spines long, slightly longer than or equal to half carapace length; basal antennal article with straight to gently convex outer margin | 2 |
– | Pseudorostral spines short, shorter than half carapace length; basal antennal article with convex outer margin | 3 |
2 | With weak or relatively distinct plates on carapace; lateral branchial spine sharp, pointing laterally, slightly upwards; pterygostomial region with plate-like granules on outer margins; P2 merus length 11.8–14.0 times width; P5 merus length 5.5–7.3 times width |
Scyramathia carpenteri (Norman, in |
– | With weak plates on carapace; lateral branchial spines sharp, pointing outwards; pterygostomial region with distinct granules on outer margins; P2 merus length 19.5–20.5 times width; P5 merus length 8.0–9.6 times width………….. | Scyramathia tenuipes sp. nov. |
3 | With distinct, slightly raised plates on carapace; fused L-shaped postorbital and hepatic plates directed upwards; lateral branchial plate slightly curved, pointed upwards in large males |
Scyramathia hertwigi Doflein, in |
– | With distinct, raised leaf-like plates on carapace; fused L-shaped postorbital and hepatic plates curved upwards; lateral branchial plate curved upwards in large males | Scyramathia umbonata (Stimpson, 1871) |
Amathia carpenteri
Norman, in
Scyramathia Carpenteri: A.
Anamathia Carpenteri:
Anamathia carpenteri:
Rochinia carpenteri:
Rochinia Carpenteri:
Scyramathia carpenteri:
Lectotype : ♂ (21.6 × 15.9 mm) (NHM 1907.8.28.3), stn 47, ‘Holtenia ground’, 59°34'N, 7°18'W, 958 m, coll. H.M.S. “Porcupine”, 1869. Paralectotypes: 1 ♀ (13.0 × 8.4 mm) (NHM 1911.11.8.377), same locality and collection data as lectotype; 1 damaged juvenile ♀ (5.4 × 3.0 mm) (NHM 1910.2.4.213), stn 48, ‘Holtenia ground’ 59°32'N, 6°59'W, coll. H.M.S. “Porcupine”, 1869. Other material: Scotland/North Sea • 1 ♂ (35.0 × 27.1 mm) (NHM 1981.108), stn 18, Sula Sgeir, 59°33.7'N, 06°49'W to 59°29.5'N, 06°43.3'W, 915–880 m, coll. A Wheeler, 16 July 1973; 2 ♂♂ (41.3 × 34.0 mm, 38.8 × 31.6 mm) (NHM 1983.449), 56°23'N, 09°18.2'W, 1010–1030 m, coll. W Wales, 20 October 1977; 7 ♂♂ (37.1 × 30.5 mm, 35.0 × 27.6 mm, 30.5 × 23.0 mm, 28.2 × 22.7 mm, 24.6 × 17.2 mm), 3 ♀♀ (37.1 × 30.6 mm, 33.5 × 27.5 mm, 22.4 × 17.2 mm), 1 ovigerous ♀ (35.8 × 29.0 mm) (NHM 1978.99), Atlantic Ocean, 56°33'N, 09°13'W to 56°30'N, 09°14'W, 750 m, coll. RW Ingle, 23 October 1977. Porcupine Seabight • 3 ♂♂ (25.0 × 18.9 mm, 15.5 × 11.1 mm, 9.0 × 6.2 mm), 1 ♀ (34.8 × 28.2 mm), 1 ♀ (with bopyrid; 15.6 × 11.6 mm) (National Oceanography Centre), stn 50601, 51°19.2'N, 11°41.1'W – 51°21.1'N, 11°42.9'W, 927–770 m, coll. H.M.S. “Discovery” Collection, 1 July 1979; 1 ♂ (23.9 × 18.4 mm), 3 ♀♀ (17.1 × 13.8 mm, 13.6 × 10.6 mm, 12.5 × 9.4 mm) (National Oceanography Centre), stn 9752 #1, 51°16.3'N, 11°42.5'W – 51°18.6'N, 11°42.8'W, 1010–1045 m, coll. H.M.S. “Discovery” Collection, 7 April 1978.
Carapace pyriform, strong diverging pseudorostral spines. Postorbital and hepatic spine fused, forming distinct L-shape plate on larger specimens. Carapace with 1 oblong mesogastric plate, 1 oblong cardiac plate, 2 metabranchial plates, 2 horseshoe-shaped epibranchial plates (Figs
A. Scyramathia carpenteri (Norman, in
Carapace covered by a thick tomentum of setae; with several plates and spines. Pseudorostral spines sharp, straight, diverging, slightly deflected. Supraorbital eave with sharp preorbital spine; sharp angle preorbital spine on juvenile specimens. Hepatic spine pointing upwards, fused with postorbital plate; proportionally longer on juvenile specimens (Figs
Illustration of Scyramathia carpenteri (Norman, in
Antennal flagellum shorter than pseudorostral spines, about half or nearly equal in length. Basal antennal article fused to carapace; longer than broad; straight to gently convex outer margin; blunt distal angle of article. Pterygostomial region with several granules on outer margin (Figs
Chelipeds long, slender; propodus longer than dactylus; dactylus curved, serrulated along entire length (Fig.
Male thoracic sternum with sternites 1–4 deep concave; sternites 1, 2 wider than long; sternites 3, 4 widest at base, lateral margin slightly constricted; sternites strongly defined (Figs
Illustration of Scyramathia carpenteri (Norman, in
The identity of Amathia carpenteri Norman, in
The three type specimens differ markedly from each other in many ways although they are all from Holtenia Ground. The lectotype male (21.6 × 15.9 mm, NHM 1907.8.28.3) selected here differs markedly from the other two paralectotypes in having a smoother carapace, without the distinct raised plate-like structures on the carapace and the branchial regions are also proportionately more inflated (Figs
Scyramathia carpenteri exhibits strong variation on the plate-like structures on the carapace of various sized specimens showed variation.
Variation of plate-like structures on carapace on Scyramathia carpenteri (Norman, in
Superficially, S. carpenteri resembles S. umbonata (Stimpson, 1871) from the western Atlantic, which also appears to grow to a much larger size (57 mm maximum carapace length; see Tavares et al. 2015). There are, however, consistent differences, with S. carpenteri, which has relatively longer pseudorostral spines, and the outer margin of the basal antennal article is always straight or only slightly convex. The pseudorostral spines of S. umbonata are always proportionately shorter, even when similar sized specimens are compared, and the outer margin of the basal antennal article is always distinctly convex (cf. Tavares et al. 2015: figs 1, 2, 4, 5). These differences are reliable for specimens of similar sizes. As such both species are here recognised as separate taxa.
It is interesting to note that some studies (A.
Scyramathia carpenteri is known from the type locality, “sandy chalk of the Holtenia ground” [= between North Scotland and the Faeroe Islands] (
Scyramathia Hertwigi: Doflein, in
Scyramathia Hertwigi Doflein, 1904: 81–84, pl. 27 fig. 3, pl. 28 fig. 1 (type locality: off Cape Point and on Agulhas Bank).
Scyramathia hertwigi:
Rochinia carpenteri:
Rochinia hertwigi:
Lectotype
: ♂ (33.7 × 27.0 mm) (
Carapace pyriform, covered with short setae. Pseudorostral spine short, diverging. Supraorbital eave with sharp preorbital spine; postorbital lobe fused to hepatic plate on large size specimens. Carapace with plates: 1 hepatic plate pointing upwards, 1 short mesogastric spine above 1 oblong mesogastric plate, 1 large protogastric granule, 1 oblong cardiac plate, 1 large epibranchial plate, 1 mesobranchial plate, 1 posterior blunt spine, 1 lateral branchial plate curved upwards (Fig.
The author and year of publication for Scyramathia hertwigi has traditionally been cited as
The Atlas by
The specimens of “Scyramathia carpenteri” from off Cape Bajador, West Africa (= off Boujdour, Western Sahara) reported by
Scyramathia hertwigi is known from its type locality, off Cape Point and on Agulhas Bank, South Africa, as well as parts of the south Atlantic along the African coast. It is the only species that enters the southwestern-most edge of the Indian Ocean.
Scyra umbonata
Scyra umbonata: A. Milne-Edwards 1875 [in 1873–1880]: 87–88; A. Milne-Edwards 1880 [in 1873–1880]: pl. 31A fig. 5–5b; A.
Scyramathia umbonata: A.
Anamathia umbonata:
Rochinia umbonata:
Rochinia confusa
Paratype of Rochinia confusa Tavares, 1991: 1 ♂ (8.0 × 5.2 mm) (
Carapace pyriform, covered with short setae. Pseudorostral spine short, diverging. Supraorbital eave fused to carapace with sharp preorbital spine; postorbital lobe and hepatic spine fused, forming a L-shape plate-like structure, pointing upwards; plate-like structure not formed on juvenile specimens. Carapace with raised plates: 1 hepatic plate curved, pointing upwards, 1 short mesogastric granule above 1 oblong mesogastric plate, 1 oblong cardiac plate, 1 large epibranchial plate, 1 mesobranchial plate, 1 posterior blunt spine, 1 lateral branchial plate curved upwards (Fig.
A–C. Scyramathia umbonata (Stimpson, 1871), female (36.7 × 27.9 mm) (
Scyramathia umbonata was originally described as a species of Scyra by
Scyramathia umbonata is recorded from the North Carolina to Gulf of Mexico (United States of America), Nicaragua, Caribbean Island, and Brazil (
Scyramathia Carpenteri: A.
Rochinia Carpenteri:
Rochinia (Amathia) carpenteri:
Rochinia (Scyramathia) carpenteri:
Rochinia carpenteri:
Holotype
: ♂ (33.9 × 26.3 mm) (ICMD288), Mediterranean Sea, coll. 1994. Paratypes: 1 ovigerous ♀ (31.2 × 24.6 mm) (ICMD000708), Málaga, Mediterranean Sea, 36°31'19"N, 03°59'18"W, 650 m, coll. 1 May 2016; 1 ♀ (27.7 × 20.5 mm) (ICMD000712), Castell de Ferro, Mediterranean Sea, 36°39'19"N, 03°16'47"W, 638 m, coll. 5 May 2016; 1 ovigerous ♀ (32.2 × 25.8 mm) (
Carapace pyriform. Pseudorostral spines straight, almost half of carapace length. Supraorbital eave fused with carapace, with blunt preorbital spine; postorbital lobe fused with hepatic spine. Carapace with plates: 1 hepatic spine, 1 small granule above 1 oblong mesogastric plate, 1 protogastric granule, 1 epibranchial plate, 1 oblong cardiac plate, 1 metabranchial granule, 1 lateral branchial spine, 1 blunt posterior spine (Figs
The term “tenuis”, which means thin in Latin, is used for the slender ambulatory legs. The name is used as a noun in apposition.
Scyramathia tenuipes sp. nov. is superficially similar to S. carpenteri, but there are several important differences between the two species. Firstly, all the adult specimens of S. tenuipes sp. nov. examined have relatively less distinct plates on the carapace (Figs
An unpublished genetic study by the first author comparing S. tenuipes sp. nov. with S. carpenteri, S. hertwigi, S. umbonata and other Rochinia species shows small but consistent differences that indicate we are dealing with a recent but separate species. A total of five genes, three mitochondrial genes: COI, 12S, 16S, and two nuclear genes: 18S and H3, were used for the molecular analysis in this unpublished work. The cytochrome oxidase I (COI) dendrogram for S. tenuipes sp. nov. and S. carpenteri shows a consistent 0.3% difference between them whereas the differences between the other Scyramathia and Rochinia species ranged from 1.3–10.9 %. Significantly, the phylogenetic tree from the Maximum Likelihood analysis shows an 87% support for S. tenuipes sp. nov. and S. carpenteri as separate clades.
The type locality of S. tenuipes sp. nov. is an interesting area in the Mediterranean. The Alboran Sea is at the western narrow part of Mediterranean that ends at the Strait of Gibraltar. The complex circulation of the waters through this very narrow strait of approximately 14 km, is known to play a key role in regulating the gene flow for a number of benthic species (
There are various records of S. tenuipes sp. nov. as “S. carpenteri”, and while A.
Scyramathia tenuipes sp. nov. is known from its type locality, the western Mediterranean Sea, with possible records from Algeria (
Dorsal view of P5. A, B. Scyramathia carpenteri (Norman, in
A–D. Scyramathia hertwigi Doflein, in
Amathia
Roux 1828: 8, 11, 12, pl. 3; H.
Pisa (Amathia) De Haan 1839: 78 (key), 84.
Anamathia
Amathia rissoana Roux, 1828, by monotypy, gender feminine.
Carapace pyriform with spines. Pseudorostral spines relatively long, straight, stout, cylindrical, slight diverging at approximately 20° angle or less. Supraorbital eave with blunt preorbital angle; weak postorbital lobe small, round anterior margin. Carapace with strong spines; 3 spines medially: metagastric, cardiac, intestinal; strong lateral branchial spines pointed outwards and downwards (Figs
The genus was first described as Amathia by
Amathia rissoana Roux, 1828: 2 unnumbered paes, pl. 3 (type locality: Mediterranean).
Amathia Rissoana: H.
Anamathia rissoana:
Rochinia rissoana:
Rochinia (Anamathia) rissoana:
North Atlantic Ocean • 1 ♂ (22.9 × 16.1 mm), 1 ♀ (23.5 × 16.5 mm) (
Carapace pyriform, covered with layer of setae, smooth when denuded (Figs
Carapace with 13 spines: 1 hepatic spine, 1 protogastric spine, 1 metagastric spine, 1 lateral epibranchial spine, 1 lateral branchial spine, 1 cardiac spine, 1 metabranchial spine, 1 strong intestinal spine near posterior of carapace (Figs
Antennal flagellum shorter than pseudorostral spines. Basal antennal article longer than broad, narrow; straight outer margin with blunt distal angle. Presence of granule at base of article. Buccal frame covered by third maxilliped, distal angle of buccal frame distinct, highly protruded, forming blunt angle. Pterygostomial region with 2 or 3 granules on outer margin; second granule biggest (Fig.
Chelipeds slender, palm longer than dactylus; carpus with 2 spines on distal edge; merus with sharp spine on distal angle. Ambulatory legs slender; distal angle of merus blunt; P2 longest (Figs
Male thoracic sternum slightly concave, constricted between sternites 1, 2 and 3, 4; sternites 3, 4 widest (Fig.
The morphology of this species is distinct from species of Rochinia in having distinct carapace spines (Figs
There are studies that report the prezoea and first zoea stage morphology for A. rissoana (
A new fossil species, Lessiniamathia bolcense Ceccon & De Angeli, 2018, was recently described (see
Madère (= Madeira), Açores (= Azores), Méditerranée (= Mediterranean) (
The authors would like to thank many colleagues and friends who have helped in making important specimens available for this study: Enrique MacPherson and Pere Abelló (ICMD); Laure Corbari, Paula Martin-Lefèvre and Sébastien Soubzmaigne (