Diapontonia maranulus Bruce, 1986

Fransen, Charles H. J. M., 2014, A second discovery of Diapontonia maranulus Bruce, 1986 (Crustacea: Decapoda: Palaemonidae) in the Caribbean, Zootaxa 3881 (6), pp. 591-596 : 591-595

Diapontonia maranulus Bruce, 1986

( Figs. 1 , 2A , 3 )

Diapontonia maranulus Bruce, 1986: 57–68 , figs 1–7.

Material examined. 2 ovigerous females (pocl 1.8 and 2.1 (GenBank acc. nr. KM 921671 )) RMNH. CRUS.D.56690; stn COA.24, Curaçao Substation, Curaçao, Netherlands Antilles, 12.084542ºN 68.898222ºW, 220 m, 8 November 2013, Curasub submersible, on Paleopneustes tholoformis , collected by Adriaan (Dutch) Schrier, Bruce Brandt, Charles H.J.M. Fransen, Sancia E. T. van der Meij and Bastian T. Reijnen.— 6 ovigerous females (pocl. 1.75–2.30), 4 males (pocl. 1.50–1.75), 1 juvenile (pocl. 1.43) RMNH. CRUS.D.56691; Curaçao Substation, Curaçao, Netherlands Antilles, 12.084542ºN 68.898222ºW, 214 m, 31 March 2014, Curasub submersible, on Paleopneustes tholoformis , collected by Adriaan (Dutch) Schrier, Cessa Rauch, Bert W. Hoeksema and Kaj van Tienderen.—1 non-ovigerous female paratype (pocl 3.5) RMNH. CRUS.D.36341; off Wood Cay, West End, Grand Bahama Island, 26º42.55'N, 79º01.72'W, 244–309 m, 14 June 1983, Johnson Sea Link Dive JSL-I-1357, on Paleopneustes tholoformis (as Palaeopneustes tholoformis ), collected by Miller, Askew, Hendler, and Chulamanis.

Material for comparison. Periclimenes ingressicolumbi Berggren & Svane, 1989: 1 male (pocl 2.4) and 1 ovigerous female (pocl 2.3) paratypes RMNH. CRUS.D.37738; off San Salvador Island, 24º02.91'N 74º32.7'W, 579 m, l May 1987, Johnson Sea Link Dive no. 2039, on Paleopneustes tholoformis (as Palaeopneustes tholoformis ) and Heterobrissus hystrix (A. Agassiz, 1880) (as Archaeopneustes hystrix Agassiz, 1880 ).— Periclimenes milleri Bruce, 1986: 1 female paratype (pocl 2.8) RMNH. CRUS.D.36342; off San Salvador Island, Bahama Islands, 24º02.75'N, 74º32.53'W, 527 m, 22 October 1983, Stn Johnson Sea Link SL-1500, on Heterobrissus hystrix (A. Agassiz, 1880) , collected by Askew, Kier, Hall and Miller, bottom temp 17.9°C.— Altopontonia disparostris Bruce, 1990: 1 ovigerous female paratype (pocl 3.1) RMNH. CRUS.D.37690; Station CP/45 (Biocal), New Caledonia, 22°47'S 167°15'E, 430–485 m depth, 30.viii.1985, collected by Richer de Forges, donated by the Museum National d'Histoire Naturelle, Paris through Alain Crosnier.— 1 ovigerous female (pocl 2.8 (GenBank acc. nr. KM 921672 )) RMNH. CRUS.D.51028; NORFANZ stn. 20/60 or 69, North Norfolk Ridge, 29°41.84'S 168°02.61'E; 322–337 m depth, beam trawl, 14.v.2003, NMNZ CR. 9991; don. A.J. Bruce.

Comparison with type-material. Specimens (pocl 1.4–2.3) from Curaçao are somewhat smaller than the four females of the type-series (pocl 3.5–5.1) .

The specimens from Curaçao have 7–10 (usually 8 or 9) small teeth on the dorsal margin of the rostrum ( Fig. 1A, B ) of which 2 or 3 are situated postorbitally; the ventral margin of the rostrum has 1 or 2 subdistal teeth. The smaller female (pocl 1.8) of RMNH. CRUS.D.56690 has the ventral margin devoid of teeth ( Fig. 1B ). The paratypes have 7–9 teeth on the dorsal margin of the rostrum of which 0–3 are situated postorbitally; the ventral margin of these specimens always has a subdistal tooth although minute in the small males. Carapace and anterior appendages ( Fig. 1B, C ) are as described for the type-specimens .

Abdomen, caudal fan ( Fig. 1D ) and pereiopods are as described for the type specimens. The configuration and ornamentation of the teeth on the flexor margin of the dactylus as well as the unguis and ventral and distoventral spines of the propodus of the third pereiopod ( Fig. 2A ) is as in the female paratype figured by Bruce (1986: Fig. 5A). Both third and fourth pereiopods with one distoventral spine on lateral surface and two on medial surface as figured by Bruce (1986: Fig. 5D).

Coloration. Uniform brown ( Fig. 3 ).

Host. Paleopneustes tholoformis Chesher, 1968 (Echinodermata: Echinoidea: Asterostomatidae ) ( Fig. 3 ). It was observed that one echinoid could host up to 10 specimens of the shrimp species.

Systematic position. At present three species of deep water echinoid associated pontoniine shrimps have been described from the tropical West Atlantic: Diapontonia maranulus , Periclimenes milleri Bruce, 1986 , and Periclimenes ingressicolumbi Berggren & Svane, 1989 . These three species were until now only known from a few records in the vicinity of the Bahama Islands ( Bruce, 1986a,b; Berggren & Svane, 1989). The recently described deep water species Periclimenes bathyalis Anker, Pachelle & Tavares, 2014 , collected off Espírito Santo, Brazil, at a depth of 360 m, is morphologically similar to P. milleri and P. ingressicolumbi . It is only known from the holotype male specimen and its host is unknown.

Diapontonia maranulus differs from the three Periclimenes species in the absence of a hepatic tooth, an important character often used in the delimitation of genera in Pontoniinae . Morphological differences between the three species of Periclimenes are mainly found in the ventral rostral dentition, antennular peduncle, scaphocerite, major second pereiopod, size and position of the hepatic tooth, propodi and dactyli of the third to fifth pereiopods, telson, number of setae and spines on the endopod of the first pleopod, and the size and number of spines on the appendix masculina ( Berggren & Svane, 1989; Anker et al., 2014)

It is interesting to note that Berggren & Svane (1989) collected seven specimens from the echinoid Paleopneustes tholoformis , identified by them as belonging to P. milleri , of which two were lacking the hepatic tooth and in one specimen a very small hepatic tooth was present.

The three Caribbean species are very similar and share several apomorphic characters, most conspicuous in the armature of the ambulatory propodi and dactyli ( Fig. 2A–C ) like (1) the distally strongly serrulate ventral and distoventral spines of the propodi, (2) the presence of three distoventral spines on the propodi of the third and fourth pereiopods of which one situated laterally and two medially, (3) the presence of a series of 8–10 acute ventral teeth on the flexor margin of the dactylus, and (4) with the ventral border of the unguis minutely crenulate or denticulate. The presence of minute crenulation on the ventral margin of the unguis in P. milleri was not described by Bruce (1986b) nor by Berggren & Svane (1989) but observed in the paratype female (RMNH.CRUS.D.36342) as is shown in figure 2C. These characters have not been described for P. bathyalis .

The most closely related species from the Indo-West Pacific seems Altopontonia disparostris Bruce, 1990 . Specimens of this species have been collected from depths of 322–503 m off New Caledonia, the Loyalty Islands and the North Norfolk Ridge ( Bruce, 1990, 1991, 1996, 2005). Its host is unknown, although its resemblance to Diapontonia suggests it might be associated with echinoids ( Bruce, 1990). The species is generally similar to the three Atlantic species mentioned above. It shares the presence of the strongly serrulate ventral and distoventral spines on the propodi ( Fig. 2D ) of the ambulatory pereiopods with the three Atlantic species. It has the absence of a hepatic tooth in common with Diapontonia maranulus . It differs from the three Atlantic species principally in the form of the major chela and in having the flexor margin of the dactyli of the ambulatory pereiopods devoid of teeth.

Species of the recently described Indo-West Pacific deep-water, possibly echinoid associated genus Echinopericlimenes ( Marin & Chan, 2014) share several characters in the rostrum, chelae and dactyli of the ambulatory pereiopods with Diapontonia and Altopontonia , though differ in having a distinct hepatic tooth like Periclimenes milleri and P. ingressicolumbi have. With Diapontonia they share the denticulation of the flexor margin of the unguis of the ambulatory dactyli and the irregular dentition of the dactylar accessory tooth. They differ in having the flexor margin of the dactyli entire while it is denticulate in Diapontonia . With Altopontonia they share the entire flexor margin of the dactyli of the ambulatory pereiopods. However. Altopontonia does not show the denticulate accessory tooth nor a denticulate flexor margin of the unguis.

Mitochondrial DNA COI barcodes were obtained for the species of Diapontonia and Altopontonia . Unfortunately, DNA extraction of paratype specimens of Periclimenes milleri (RMNH.CRUS.D.36342) and P. ingressicolumbi (RMNH.CRUS.D.37738) failed. The genetic distance between Diapontonia and Altopontonia is 0.25, which is substantial. COI barcodes of the four Echinopericlimenes species were used by Marin & Chan (2014) to show the molecular distinction between these species. Unfortunately these COI barcodes are not yet available on GenBank for comparison with the present material.

Figures

FIGURE 1. Diapontonia maranulus Bruce, 1986, RMNH.CRUS.D.566905. A, carapace and anterior appendages, lateral view; B, anterior appendages, dorsal view; C, carapace, lateral view; D, tailfan, dorsal view, setae omitted. A,B, D, ovigerous female, pocl. 1.8; C, ovigerous female, pocl. 2.1. Scale bar A–C = 2; D = 1 mm.

FIGURE 2. Dactylus right third pereiopod, median aspect. A, Diapontonia maranulus Bruce, 1986, ovigerous female pocl. 1.8, RMNH.CRUS.D. 566905; B, Periclimenes milleri Bruce, 1986, female pocl. 2.8, RMNH.CRUS.D.36342; C, Periclimenes ingressicolumbi Berggren & Svane, 1989, ovigerous female, pocl. 2.3, RMNH.CRUS.D.37738; D, Altopontonia disparostris Bruce, 1990, ovigerous female paratype, pocl. 3.1, RMNH.CRUS.D.37690. Scale bar = 0.5 mm.

FIGURE 3. Host echinoid Paleopneustes tholoformis Chesher, 1968, with Diapontonia maranulus Bruce, 1986 shrimps (indicated by circles) photographed with Curasub at 220 m depth off the SE coast of Curaçao. Photo by Adriaan (Dutch) Schrier.