Mursia spiridonovi Karasawa, 2018

Ng, Suvarna S. Devi Appukuttannair Biju Kumar Peter K. L., 2020, Redescription of the shallow water calappid Mursia spiridonovi Karasawa, 2018 (Brachyura: Calappidae) from India, Nauplius (e 2020015) 28, pp. 1-9 : 2-9

publication ID	https://doi.org/10.1590/2358-2936e2020015
persistent identifier	https://treatment.plazi.org/id/039387DF-3101-A164-FC4C-2D36FCB1FD02
treatment provided by	Felipe
scientific name	Mursia spiridonovi Karasawa, 2018
status

Treatment

Mursia spiridonovi Karasawa, 2018 View in CoL

( Figs. 1–4 View Figure 1 View Figure 2 View Figure 3 View Figure 4 )

Mursia bicristimana View in CoL – Laurie, 1906: 355; Galil, 1993: 356 (part); figs. 1f, 3j, k, 5c, d (not Mursia bicristimana Alcock and Anderson, 1894 View in CoL ).

Mursia minuta Spiridonov and Apel, 2007: 2870 View in CoL View Cited Treatment , figs. 2G, H, 4E, F, 8C, 10A–D, 11A, B, 12A, B; Trivedi et al., 2018: 32; Suvarna Devi et al., 2019: 493 (name preoccupied by fossil calappid Mursia minuta Karasawa, 1993 View in CoL )

Mursia spiridonovi Karasawa, 2018: 587 View in CoL View Cited Treatment (replacement name).

Material. 1 male (23.9 × 14.6 mm) ( ZRC 2019.0492 View Materials ), bycatch at Colachel port, approximately 12 km north of Muttom , Tamil Nadu, India, coll. Suvarna S. Devi, 4 March 2019 ; 1 ovigerous female (26.7 × 16.1 mm) ( ZRC 2019.0511 View Materials ), 1 ovigerous female (28.4 × 18.1mm) ( DABFUK), Jeppiaar fishing harbour, Muttom, Kanyakumari district , Tamil Nadu, India, coll. Suvarna S. Devi, 30 January 2019 .

Comparative material. Mursia bicristimana Alcock and Anderson, 1894 — 1 male (37.2 × 19.6 mm), 1 female (43.2 × 23.2 mm) ( ZRC 2017.0134 View Materials ), Kollam port, Kerala, southern India, coll. fishermen, 20 March 2017 ; 1 male (76.4 × 46.2 mm), 1 ovigerous female (62.1 × 36.4 mm) ( ZRC 2018.0880 View Materials ), Kollam harbour, Kerala, southern India, coll. fishermen, 20 March 2017 ; 3 males (75.7 × 43.9 mm, 80.1 x 47.4 mm, 78.9 x 46.9 mm) and 2 females (68.2 × 42.1 mm, 70.1 × 38.2 mm) ( DABFUK 2018 ), Kollam harbour, Kerala, southern India, coll. fishermen, 2 February 2018 ; 2 males (82.2 × 49.6 mm, 73.5 x 41.8 mm) ( ZRC 2017.0885 View Materials ), Tuticorin , Tamil Nadu, India, coll. trawl fishermen, March 2017 ; 1 male (75.0 × 42.2 mm) ( ZRC 1999.0086 View Materials ) [holotype of Mursia xianshengi Lai and Galil, 2006 ], trawled from the Andaman Sea , off southern Thailand-Burma coast, 06º41.7’N 97º58.2’E, 342 m, coll. fishing vessels, 20 March 1989 GoogleMaps .

Diagnosis. Small species, females ovigerous at 28.4 × 18.1 mm. Dorsal carapace surface with numerous prominent granules with regions well defined ( Figs. 1A View Figure 1 , 2E, F View Figure 2 ); gap between last two distal spines on merus of cheliped relatively narrow, acute ( Fig. 2G View Figure 2 ); third short spine present on merus of cheliped ( Fig. 2G View Figure 2 ); anterolateral teeth clearly defined( Fig.2F View Figure 2 ); granules on posterolateral margin and the median lobe on posterior carapace margin distinct, relatively larger ( Fig. 2F, H View Figure 2 ); granules on outer surface of chela, prominent granules with subventral ridge more undulating, rounded, with 2 clear lobes ( Fig. 3E, F View Figure 3 ); outer surface of ambulatory merus distinctly granulated ( Fig. 2H View Figure 2 ); male telson as long as broad ( Fig. 3G View Figure 3 ); median lobe on male pleonal somite 2 convex ( Fig. 3H View Figure 3 ); G1 relatively stouter, curved, tip sharper, opening very narrow, distal ( Fig. 4H–J View Figure 4 ); distal part of G2 (flagelliform part) twisted twice with the extremity tapering laterally ( Fig.4K–N View Figure 4 ).

Description of males. Carapace transversely ovate, broader than long; dorsal surface unevenly convex, regions well defined by grooves, distinctly granular all over, granules on lateral and posterior parts proportionately larger; mesogastric region with 2 low larger median granules; metagastric, urogastric, cardiac and intestinal regions with 4 low median tubercles; branchial region with 4–6 low tubercles ( Figs. 1A View Figure 1 , 2E, F View Figure 2 ). Median frontal lobe broadly triangular with low, slightly acuminate to gently rounded lateral lobes; supraorbital margin deeply concave, with deep, prominent median fissure; external orbital tooth low, rounded; anterolateral margin with 10 or 11 distinct acuminate granules or teeth (excluding external orbital angle), those on distal two-thirds more dentiform, wider; lateral carapace spine prominent, slightly directed obliquely and posteriorly, surface covered with small granules and short spinules, distinctly less than half-width of carapace at base of spines; posterolateral margin sinuous, proximal third with 3 low, uneven lobes, rest of margin finely denticulate; posterior carapace margin with 2prominent triangular lateral lobes and median, posteriorly directed intestinal protuberance shorter than lateral teeth ( Figs. 1A View Figure 1 , 2F View Figure 2 ). Eye short, peduncle stout, cornea large; completely covered by short, rounded orbits when retracted ( Fig. 1C View Figure 1 ). Suborbital margin with deep, U-shaped cleft ( Fig. 1C View Figure 1 ); suborbital and pterygostomial regions mostly smooth, separated by granulated ridge ( Fig. 1C View Figure 1 ).

Chelipeds almost symmetrical, right slightly larger; outer surface covered with low tubercles and numerous small granules, inner surface smooth ( Figs. 1A, C–E View Figure 1 , 2E View Figure 2 ). Merus short, with 3 laterally directed, stout, spinule-covered spines on distal margin, outermost spine largest, innermost spine smallest, outer 2 spines separated by relatively narrow gap ( Fig. 2G View Figure 2 ). Carpus subtriangular, outer surface with 3–5 low tubercles and numerous granules, inner distal angle with low triangular, non-spiniform tooth ( Figs. 1A, C View Figure 1 , 2E View Figure 2 ). Palm of chela with 9 lobiform teeth of various sizes on dorsal margin; Inflated on median part, with 5 tubercles of different sizes, subventral ridge gently undulating, rounded, with 2 clear sections, posterior section larger, with hook-like tubercle basally; ventral margin lined with sharp granules, serrated ( Figs. 1C–E View Figure 1 , 3E, F View Figure 3 ). Right chela with distinct basal cutting teeth at base of propodus and dactylus, rest of cutting margins with blade-like teeth; dorsal margin of dactylus usually with low protuberance. Left chela similar to right chela except basal cutting teeth absent ( Figs. 1C–E View Figure 1 , 3E, F View Figure 3 ).

Ambulatory legs relatively short, laterally compressed. Merus with cristate margins, without subdistal spine; outer surface distinctly granular, especially on proximal ventral part ( Fig. 2H View Figure 2 ). Carpus and propodus also with cristate margins, surface weakly granular. Dactylus distinctly longer than propodus, gently curved, slender, unarmed ( Figs. 1A View Figure 1 , 2E, H View Figure 2 ).

Thoracic sternum transversely narrow, surface generally smooth; sternites 1 and 2 completely fused, separated from fused sternites 3 and 4 by shallow sinuous suture; sternite 7 partially visible when pleon closed but sternite 8completely covered; sternopleonal cavity deep, reaching to imaginary line joining anterior margins of coxae of chelipeds, but extending beyond edge of telson as shallow longitudinal channel reaching to suture between sternite 2 and 3 ( Fig. 1B View Figure 1 ). Pleonal locking mechanism present as low tubercle on anterior edge of sternite 5. Pleon relatively narrow; somite 1 mostly hidden under posterior edge of carapace; somite 2 with distal part prominently lamellate, trilobed with margin of median lobe distinctly convex ( Figs. 1B View Figure 1 , 3G, H View Figure 3 ); somites 3–5 fused, somites 3 and 4 demarcated by short lateral cleft, somites 4 and 5 marked by deeper, longer fissure ( Fig. 3G View Figure 3 ); telson as long as broad, almost equilateral in shape ( Fig. 3G View Figure 3 ).

G1 stout, distinctly curved, distal third almost straight, with sharper tip, narrow opening distally ( Fig. 4H–J View Figure 4 ). G2 longer than G1; distal segment as long as basal segment, distal part flagelliform, prominently twisted twice with extremity tapering laterally ( Fig. 4K–N View Figure 4 ).

Females. Similar to males except that the pleon is ovate and covers most of the thoracic sternum. In ovigerous females, the egg mass is large and extends laterally beyond the base of the ambulatory legs ( Fig. 1F View Figure 1 ). When freshly obtained, the eggs are small, less than 1.0 mm in diameter and bright red in color ( Fig. 1F View Figure 1 ).

Color in life. The carapace is entirely orange on the dorsal surface, with a white longitudinal stripe medially in males ( Fig. 1A View Figure 1 ), but in females, the white stripe is reduced to a spot. The inner margins of the mandibles are bright red ( Fig. 1C View Figure 1 ). The upper half of the chela has the granules orange to red, with the subventral ridge and outer lower surfaces all white ( Fig.1D View Figure 1 ); the inner surface of the chela has a bright red rim at the base of the dactylus ( Fig. 1E View Figure 1 ). The thoracic sternum and abdomen are white with patches of pink ( Fig. 1B View Figure 1 ).

Remarks. Mursia spiridonovi (as M. minuta ) was described on the basis of the holotype male (28.0 × 17.1 mm) and a paratype female (25.4 x 16.8 mm) from the Gulf of Mannar in Sri Lanka as well as four other complete males (20.5 × 13.0 mm – 32.4 × 19.5 mm) and an ovigerous female (25.4 × 16.8 mm) from the Laccadives ( Lakshadweep) and Gulf of Aden (see also Suvarna Devi et al., 2019). As the name Mursia minuta of Spiridonov and Apel (2007) was preoccupied by that of a fossil species, Karasawa (1993) provided a replacement name, M. spiridonovi . Spiridonov and Apel (2007: 2870) characterized the species by its small adult size (carapace width not exceeding 32.4 mm), hence its specific name. They commented that the juvenile material identified as M. bicristimana by Laurie (1906) and Galil (1993) is actually M. spiridonovi .

In contrast to almost all other Mursia species that occur in depths over 300 m (see Galil, 1993), M. spiridonovi appears to prefer shallower waters. Spiridonov and Apel (2007) noted that their specimens from the Gulf of Aden occurred on muddy sand bottom at depths of 83–87 m, while the Laccadives ( Lakshadweep) material was collected from sandy and stony substrates at depths of 124– 271 m. The two type specimens from the Gulf of Mannar were almost certainly from shallow waters as they were collected from pearl oyster banks. The present materials from Tamil Nadu were all obtained from waters shallower than 200 m. They were not collected with M. bicristimana which invariably comes from depths exceeding 200– 300 m.

Comparisons between specimens of markedly different sizes are always difficult as we do not know the ontogenetic changes that take place during growth. Fortunately, we have on hand two small specimens of M. bicristimana that allow us to make suitable comparisons with M. spiridonovi . The differences are clear. Mursia bicristimana differs in possessing a relatively smoother carapace, with the granules and regions less marked and prominent ( Fig. 2A, B View Figure 2 ) (versus the granules on the carapace are large and strong, and the regions are better defined in M. spiridonovi ; Fig. 2E, F View Figure 2 ); the gap between the last two distal spines on the merus of the cheliped is relatively wider ( Fig. 2C View Figure 2 ) (versus it is narrower and acute in M. spiridonovi ; Fig. 2G View Figure 2 ), a small third spine is visible on the merus of the cheliped in M. spiridonovi which is absent in M. bicristimana ( Fig. 2C, G View Figure 2 ); the anterolateral teeth of the carapace are low and poorly defined ( Fig. 2B View Figure 2 ) (versus they are clearly defined in M. spiridonovi ; Fig. 2F View Figure 2 ); the granules on the posterolateral margin and the median lobe on the posterior margin of the carapace are low ( Fig. 2B, D View Figure 2 ) (versus the granules and the median lobe are prominently larger in M. spiridonovi ; Fig. 2F, H View Figure 2 ); the granules on the outer surface of the chela are small with the subventral ridge, which is distinct and sharp, forming only one lobe distally and the rest is almost entire ( Fig. 3A, B View Figure 3 ) (versus the granules are prominent and the subventral ridge is more undulated and rounded, with two clear lobes in M. spiridonovi ; Fig. 3E, F View Figure 3 ); the outer surface of the ambulatory merus is smooth ( Fig. 2D View Figure 2 ) (versus it is distinctly granulated in M. spiridonovi ; Fig. 2H View Figure 2 ); the male telson is distinctly longer than broad ( Fig. 3C View Figure 3 ) (versus it is as long as broad in M. spiridonovi ; Fig. 3G View Figure 3 ); the median lobe on the male pleonal somite 2 is truncate ( Fig. 3D View Figure 3 ) (versus it is rounded and more convex in M. spiridonovi ; Fig. 3H View Figure 3 ); the G1 is more slender with the distal part straighter, and the tip has a distinct, ovate subdistal opening ( Fig. 4A–C View Figure 4 ) (versus the G1 is relatively stouter and more curved, with a sharper tip, and the opening is very narrow and situated distally in M. spiridonovi ; Fig. 4H–J View Figure 4 ); and the distal section of the G2 flagelliform part is gently curved with a distinctly narrowed extremity which is directed downwards ( Fig. 4D–G View Figure 4 ) (versus it is twisted twice with the extremity tapering laterally in M. spiridonovi ; Fig.4K–N View Figure 4 ). The G1 and G2 structures of M. spiridonovi agree very well with those figured by Spiridonov and Apel(2007: fig. 4D–F) (as M. minuta ).

Mursia spiridonovi is thus a species clearly smaller than M. bicristimana . The two small females of M. spiridonovi on hand (26.7 × 16.1 mm, ZRC 2019.0511 and 28.4 × 18.1 mm, DABFUK) are ovigerous, while a female of M. bicristimana measuring 43.2 × 23.2 mm ( ZRC 2017.0134) is still immature, with the pleon relatively narrow and the pleopods not developed.

The gonopods of a young male of M. bicristimana are figured here for the first time ( Fig. 4A–G View Figure 4 ). The structures on the gonopods are not clearly developed, being not fully chitinized, and relatively soft, and most of the setae are absent. The G1 of the young specimen differs from that of adult specimens in being distinctly less curved ( Fig. 4A–C View Figure 4 versus Kumar et al., 2013: fig. 6). The G2 of the young specimen has the tip of the flagellum less dilated and not bilobed with the median part not dilated or spinose ( Fig. 4D–G View Figure 4 versus Kumar et al., 2013: fig. 7). The gonopods of “ M. bicristimana ” reported from the Gulf of Aden by Spiridonov and Apel (2007): fig. 4A–C) have been referred to those of another species, M.arabica (see Kumar et al.,2013).