A revision of the genus Prionocrangon (Crustacea: Decapoda: Caridea: Crangonidae) Author Kim, Jung Nyun Author Chan, Tin-Yam text Journal of Natural History 2005 2005-04-18 39 19 1597 1625 http://dx.doi.org/10.1080/00222930400016788 journal article 10.1080/00222930400016788 1464-5262 5214903 Prionocrangon ommatosteres Wood-Mason and Alcock, 1891 ( Figure 1 ) Figure 1. Prionocrangon ommatosteres Wood-Mason and Alcock, 1891 . (A–H), (J–M), ovigerous female (CL 7.0 mm) from Indonesia, KARUBAR stn CC 57; (I) ovigerous female (CL 6.8 mm, same lot); (N) female (CL 7.5 mm, same lot); (O, P) male (CL 6.9 mm) from Indonesia, KARBUAR stn CP 91. (A) Carapace (tip of rostrum broken) with cephalic and thoracic appendages, lateral; (B) carapace (tip of rostrum broken) and anterior cephalic appendages, dorsal; (C) anterior part of carapace (tip of rostrum broken), eyes, basal parts of antennule and antenna, dorsal; (D) fifth abdominal somite, dorsal; (E) posterior part of abdomen and tailfan, lateral; (F) posterolateral process of sixth abdominal somite, lateral; (G) telson, dorsal; (H, I) posterior part of telson, dorsal; (J) chela of left first pereopod, ventral; (K) dactylus and propodus of left fourth pereopod, lateral; (L) left first pleopod, lateral; (M, O) left second pleopod, lateral; (N) endopod of left third pleopod, mesial; (P) appendix masculina of left second pleopod, ventral. Prionocrangon ommatosteres Wood-Mason and Alcock 1891 , p 362 [ type locality: south of Port Blair, Andaman Islands]; Alcock and Anderson 1894 , p 152; 1895, Plate 9 Figure 4 ; Alcock 1901 , p 123; Holthuis 1993 , p 300, Figure 297 (after Alcock and Anderson 1895 ). Prionocrangon curvicaulis : Chace 1984 , p 56 (key), 57, Figure 24 [ non Yaldwyn 1960 ].? Prionocrangon ommatosteres : Takeda and Hanamura 1994 , p 31 . Not Prionocrangon ommatosteres : de Man 1920 , p 308 , Plate 25 Figure 76, 76a–i; Chace 1984, p 56 (key), 58 [5 Prionocrangon demani sp. nov. ]. Not Prionocrangon ommatosteres : Ohta 1983 , p 230 (list) [5 Prionocrangon dofleini Balss, 1913]. Material examined Indonesia . KARUBAR: stn CC 57, 8 ° 199S, 131 ° 539E, 603–620 m , 31 October 1991 , 1 „ (CL 5.0 mm), 1♀ (CL 7.5 mm ), 5 ovig. ♀♀ (CL 6.8–7.1 mm ), MNHN-Na. 15068; stn CP 91, 8 ° 449S, 131 ° 059E , 884–891 m , 5 November 1991 , 1 „ (CL 6.9 mm ), MNHN-Na. 15069 . Philippines . Albatross stn 5445, 12 ° 449420N, 124 ° 599500E, 700 m , 3 June 1909 , Agassiz beam trawl, 1 „ (CL 6.4 mm ), USNM 205089 (id. by Chace, 1984 as P. curvicaulis ). MUSORSTOM 1, stn 47, 13 ° 40.79N , 120 ° 30.09E , 689–757 m , beam trawl, 25 March 1976 , 1 „ (CL 6.7 mm ), MNHN-Na. 6041. MUSORSTOM 2, stn 78, 13 ° 499N, 120 ° 289E, 441–550 m , beam trawl, 1 December 1980 , 1♀ (CL 8.0 mm), 1 ovig. ♀ (CL 7.0 mm), MNHN-Na. 6040 . Type material Holotype : Investigator stn 116, Andaman Sea, 11 ° 25950N, 92 ° 47960E, 741 m , 1 „ (CL including rostrum about 10 mm ), Indian Museum (No. 6744/9). Not examined. Description Rostrum slightly falling short of tip of branchiostegal spine, 0.13–0.16 times as long as carapace ( Figure 1A, B ). Mid-dorsal carina of carapace armed with six to nine spines ( Figure 1A ). Fourth abdominal somite without median carina; fifth somite with or without low median carina ( Figure 1D ); sixth somite 0.56–0.59 times as long as carapace, posterior margin of posterolateral process subtruncate, with slightly produced dorsal and ventral angles ( Figure 1F ). Telson ( Figure 1G ) slightly shorter than sixth abdominal somite ( Figure 1E ), 0.45–0.53 times as long as carapace, posterior half strongly convergent; posterior margin subtruncate, armed with two pairs of long spines, with or without minute median denticle ( Figure 1H, I ). Eyestalks drawn out to bluntly cylindrical or villiform extremities, slightly downcurved but not reaching in between antennules ( Figure 1C ). Antennular peduncle with proximal segment greatly elongate, 0.70–0.78 times as long as carapace ( Figure 1A, B ). Stylocerite with tip elongate and sharp ( Figure 1C ). Scaphocerite falling short of distal margin of proximal segment of antennular peduncle, 0.52–0.60 times as long as carapace ( Figure 1A, B ). Palm of first pereopod slender, 4.95–5.25 times as long as wide ( Figure 1J ). Dactyli of fourth and fifth pereopods short, 0.32–0.42 times as long as propodi ( Figure 1K ). Females with endopod of second pleopod short, about 0.20 times length of exopod ( Figure 1M ); second to fifth pleopods each with endopod bearing small proximolateral lobe and protopod having small distoventral projection ( Figure 1N ). Size Males CL 5.0– 6.9 mm , females CL 7.5–8.0 mm, ovigerous females CL 6.8–7.1 mm . Male holotype CL about 10 mm including rostrum ( Wood-Mason and Alcock 1891 ). Ovigerous female from Bay of Bengal CL 8.5 mm including rostrum ( Alcock 1901 ). Distribution Andaman Sea and Bay of Bengal off Sri Lanka , 366–741 m ( Alcock 1901 ); Indonesia and the Philippines , 441–891 m (present study). Colour in life Not known. Variations Of the 12 specimens examined, two specimens have six spines on the mid-dorsal carina of carapace, three specimens have seven spines, five specimens have eight spines and two specimens have nine spines. With respect to the median carina on the abdomen, eight specimens bear low median carina on the fifth abdominal somite ( Figure 1D ) while the other four lack this median carina. Of the nine specimens still with intact telsons, four specimens have a minute median denticle on the posterior margin of the telson ( Figure 1I ) but five others lack such a minute denticle ( Figure 1H ). Remarks Prionocrangon ommatosteres was originally described based on a somewhat mutilated male from the Andaman Sea collected at a depth of 405 fathoms ( 5741 m ). Subsequently, Alcock and Anderson (1894 , 1895 ) reported and illustrated an additional specimen (ovigerous female, 200–350 fathoms or 366–640 m deep) of this species from the Bay of Bengal off Sri Lanka . De Man (1920) reported one male and one female taken from Indonesia at depths of 1158–1301 m , which he referred to P. ommatosteres with some doubts. However, Chace (1984) suspected that de Man’s (1920) material might not be the true P. ommatosteres because of the different shape of the eyes and because of the rather different depth from which it was collected. An attempt to re-examine the type of P. ommatosteres from the Indian Museum was unsuccessful and no topotypic material of this species is available for the present study. Nevertheless, P. ommatosteres from the Indian Ocean appears to have the following characteristics: carapace bearing six to seven dorsal spines, telson slightly shorter than sixth abdominal somite, proximal antennular segment about 0.7 times as long as carapace, scaphocerite about 0.5 times as long as the carapace and falling short of the distal margin of the proximal antennular segment (see Wood-Mason and Acock 1891; Alcock and Anderson 1894 ; Alcock 1901 ). In these respects, the present specimens from Indonesia and the Philippines (six to nine dorsal carapace spines, APL/CL ratio 0.70–0.78, SL/CL ratio 0.55–0.60) agree well with P. ommatosteres and differ from those reported by de Man (1920) . The present specimens were collected from 441–891 m deep, similar to those obtained from the Indian Ocean ( 366–741 m deep). Nevertheless, some important characters such as the shapes of the eyestalks, pleopods, telson and the length of pereopod dactyli were not described for the Indian Ocean material. Direct comparisons with topotypic specimens will be necessary to conclude whether the present Indonesian and the Philippines specimens are truly P. ommatosteres . If the present identification is correct, P. ommatosteres is most similar to P. dofleini from Japan and Taiwan in having the eyestalk drawn out to a bluntly cylindrical or villiform extremity, the stylocerite with a long acute tip, the posterior half of the telson strongly convergent, and the dactyli of the fourth and fifth pereopods relatively shorter. Nevertheless, it can be distinguished from P. dofleini by the fourth abdominal somite lacking completely a median carina, the posterior margin of the telson truncate and armed with two pairs of long spines ( Figure 1H, I ), the posterior margin of the posterolateral process of the sixth abdominal somite produced at both the dorsal and ventral angles ( Figure 1F ), the palm of the first pereopod more slender ( Figure 1J , 4.95– 5.25 times as long as wide versus 3.70–4.55 times in P. dofleini , see Figure 5K ), and females with the endopods and protopods of the second to fifth pleopods bearing a small proximolateral lobe and distoventral projection, respectively ( Figure 1M, N ). The Albatross male from the Philippines identified as ‘‘ P. curvicaulis ’’ by Chace (1984) is essentially identical to the present KARUBAR and MUSORSTOM material, and therefore assigned here to P. ommatosteres . However, the other Albatross specimen, a damaged female from Indonesia , tentatively assigned to ‘‘ P. ommatosteres ’’ by Chace (1984) , actually represents an undescribed species (see under P. demani sp. nov. ). It should be pointed out that another damaged female ( Figure 2 ) from the Sulu Sea ( Philippines , RV Hakuho-Maru , KH-02-04 Cruise, stn 14, 10 ° 00.709N – 10 ° 01.629N , 120 ° 54.729E – 120 ° 55.279E , 1482–1488 m , 8 December 2002 , 1♀ CL 5.0 mm, CBM-ZC 7842) is generally similar to P. ommatosteres in form (e.g. carapace with eight dorsal spines, rostrum nearly reaching to tip of branchiostegal spine, eyestalk drawn out to bluntly cylindrical extremity, stylocerite with tip elongate and acute, scaphocerite 0.64 times as long as carapace, palm of first pereopod more than five times as long as wide, endopod of second pleopod 0.20 times as long as exopod, small proximolateral lobe present on endopods of second to fifth pleopods). However, it is unusual in that the proximal segment of the antennular peduncle is exceptionally long (APL/CL50.93, Figure 2A, B ). Moreover, this Sulu Sea female was collected from a much greater depth. As the telson, distal parts of the antennular peduncle and the last two pairs of pereopods are missing in this specimen, more material will be necessary to determine if it is really distinct from P. ommatosteres or not. The Flores Sea specimen reported by Takeda and Hanamura (1994) is also badly damaged. M. Osawa re-examined this specimen at the National Science Museum, Tokyo (NSMT-Cr 4242) and found that it has the eyestalks drawn out to villiform extremities but with slightly more stout subchela (palm 4.51–4.69 times as long as wide) and longer dactyli (0.48–0.51 times as long as propodi at fourth pereopods). This specimen is tentatively assigned to P. ommatosteres for the time being.