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A new fish, Peristedion nesium (Scorpaeniformes: Peristediidae) from Isla del Coco, Costa Rica.

The armored searobins (Peristediidae) are usually found in waters greater than 100m. Their body is encased in four rows of spinous scutes on each side of the body and the wide snout is extended by a pair of flattened bony extensions. The genus Peristedion, although speciose in the Western Atlantic, has only three previously known representatives along the Eastern Pacific coastline: P. crustosum Garman, P. barbiger Garman and P. paucibarbiger Castro-Aguirre & Garcia-Dominguez, 1984. Another species, P. ecuadorense Teague, 1961, was incorrectly recorded from the eastern Pacific, although Miller (1967) has indicated that the correct locality for the type series is off Charleston, South Carolina in the Western Atlantic.

MATERIALS AND METHODS

Specimens of the new species were collected by 30ft. trawl during the 1972 R/V Searcher Expedition. Counts and measurements follow Teague (1961) and especially the anatomical characters and terminology of Miller (1967). All body proportions are in percent of standard length (SL). vertebral numbers were determined from digital and photographic radiographs. Institutional acronyms follow Leviton et al. 1985.

RESULTS

Peristedion nesium, new species Figures 1-4, Tables 1, 2.

Holotype: LACM 32265.003, 117.9mm SL, collected 2.4km north of Isla Iglesias (05[degrees]34'38" N; 87[degrees]03'55" W) Isla del Coco, Costa Rica. Collected with 30' trawl, depth 183m, April 3, 1972 by R. Lavenberg and W. Bussing aboard the R/V Searcher (S-522).

Paratypes: Material collected off Isla del Coco by R. Lavenberg and W. Bussing aboard R/V Searcher: LACM 32269.007 and 32269.008 (S-526), 2.7km SSE off Cabo Dampier; collected with 30' trawl, depth 120m, April 3, 1972; 05[degrees]28'30" N; 87[degrees]04'00" W; 41 specimens (51.5-116mm SL). LACM 32281.001 (S-541), 1.9km N of Isla Iglesias; collected with 15' trawl, depth 128m, April 5, 1972; 05[degrees]34'21" N; 87[degrees]03'48" W; 1 specimen (72.5mm SL). UCR 720.007 (S-520), 1.3km NNW of Punta Gissler; collected with 30' trawl, depth 109m, April 3, 1972; 05[degrees]33'32" N; 87[degrees]04'44" W; 18 specimens (74.5-117.5mm SL). CAS 228407, same data as UCR 720.007, 6 specimens (83.5-98.2mm SL). UCR 721.008 (S-521), 2.6km WNW Punta Gissler; collected with 30' trawl, depth 137-146m, April 3, 1972; 11 specimens (77-107mm SL). Other material: UCR 2272.004, Isla del Coco; collected with tangle net, April 8, 1992; 2 specimens (86-108mm SL). UCR 2273.001, Isla del Coco; collected with tangle net, April 2, 1992; 1 specimen (112mm SL).

[FIGURE 1 OMITTED]

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[FIGURE 3 OMITTED]

[FIGURE 4 OMITTED]

Diagnosis: A species of Peristedion with very short (12.1-18.2% in head length) and widely spaced rostral exsertions; pericranial rim terminating in a right-angled flange; rostral and nasal spines present from juveniles to adults; gill rakers 5-9+27-31, total 33-40 and length of filamentous barbel 31.8-44.2% of head length.

Description: Tables 1 and 2 give morphometrics of the holotype, 20 adult paratypes and one specimen from the Galapagos of P. crustosum.

Holotype: Standard length 117.9mm. Dorsal fin rays VII, 17. Anal fin rays 16. Pectoral fin rays 9+2 free rays. Pelvic fin rays I-5. Lip barbels 5/2:5/2; chin barbels 12/5:11/5. Gill rakers on first branchial arch 6+27=33. Serrated ridge on mandible 1. Vertebrae 31. Scutes: dorsal series 25; superomedian series 30, last 7 with bicuspid spines; inferomedian series 24; ventral series 20; caudal series 2+1+2. Additional measurements (in percentage of head length): mandibular ridge length 6.9; mandibular ridge width 1.9; 1st ventral scute length 24.0; 1st ventral scute width 13.0; 2nd ventral scute length 21.2; 2nd ventral scute width 12.1.

Paratypes: Dorsal fins VI-VIII, 16-18 (modally VIII, 17); anal 16-18 (modally 17); pectoral 2+9-11, (modally 11); pelvic I-5. Gillrakers on first branchial arch 5-9+27-31, total 33-40 (modally 8+29, total 36). Vertebrae 31-33. Lip barbels 4-6/2 (modally 5/2). Chin barbels 10-15/5 (modally 12/5). Filamentous barbel short, rarely extending beyond middle of eye; filaments along barbel variable in length, occasionally longer than 50% length of entire filamentous barbel. Sensory pores on underside of rostral exsertions four: anterior three rounded, fourth pore elongated and considerably posterior to others.

Head spines and serrations: Spination is stronger in larger specimens; description of adult specimens of approximately 100mm SL follow. Lateral ethmoid and mesethmoid spines are absent. Both rostral and nasal spines are well-developed, retrorse and elevated. Four or 5 spines and smaller serrations on the 2nd infraorbital of the perifacial rim, anteriormost spine largest and elevated or lateral. Three or 4 preocular spines strongly retrorse; supraocular and postocular spines rounded, less developed. Frontal I spine undeveloped, a tubercle or low spine. Frontal II spine very small. Parietal spine a low, rounded tubercle. Opercular spine well developed, pungent. Fourth infraorbital ridge finely serrate. Two or 3 nuchal spines, sharp, retrorse, elevated. Two or 3 spines on adjacent 1st dorsal scute.

Scutes: Dorsal series 25-26 scutes (modally 25), with robust spines preceded by minute serrations; size of spines decreasing posteriorly and more depressed. Superomedian total series 28-32 scutes (modally 30), first 4 scutes in arch with minute serrations only, succeeding scutes with large spines with anterior serrations; last 6 to 10 spines (modally 7 or 8) bicuspid, the last sometimes unicuspid. Inferomedian series 22-24 scutes (modally 23); all spines well developed, with anterior serrations, decreasing in size and flattening posteriorly. Ventral series 20 or 21 scutes (modally 20) all with minute spines, 1st two very depressed or slightly raised tubercles; last scute at posterior anal-fin ray with flat spine or serrated tubercle. Caudal series consisting of two ventral, two dorsal and one lateral scute all with well-developed spines; lateral spine especially long and slender.

A key to Eastern Pacific Peristedion

1a. Head narrow; perifacial rim narrow and terminating in a retrorse spine; rostral and nasal spines absent (Fig. 5) ... P. paucibarbiger

1b. Head and perifacial rim broad; rostral spines present ... 2

2a. Perifacial rim terminating in acute-angled spine; rostral exsertions wider than interspace, often convergent; nasal spines weak or absent; chin and lip barbels prominent; filamentous barbel short, rarely reaching to eye (Fig. 4) ... P. barbiger

2b. Perifacial rim terminating in a right-angled or rounded flange; rostral exsertions narrow, widely spaced; nasal spines present; chin and lip barbels less bushy; filamentous barbel long, reaching to or beyond eye ... 3

3a. Rostral exsertions longer than pupil diameter (21.1-25.8% of head length); total gill rakers on first arch 27-29; length of filamentous barbel 61.5-69.4% of head length (Fig. 4) ... P. crustosum

3b. Rostral exsertions very short, less than pupil diameter (12.1-18.2% of head length); total gill rakers on first arch 33-40; length of filamentous barbel 31.8-44.2% of head length (Fig. 4) ... P. nesium

[FIGURE 5 OMITTED]

DISCUSSION

Peristedion nesium n. sp. is apparently an island derivative of P. crustosum. Trenchant differences between the two species are shown in the key to species. Differences in coloration and head serration also exist between these two species. Adult P. crustosum, as well as P. barbiger from Costa Rica, have a jet black blotch on the upper half of the first five dorsalfin spines; juvenile crustosum (70mm SL) also have a black dorsal-fin blotch as well as a black upper half of the pectoral fin. The upper half of the spinous dorsal of nesium is dusky or unmarked; a 112mm SL specimen has a pale dusky first dorsal fin and a black pectoral fin. Garman (1899) described crustosum and barbiger from off the mainland of Panama/Colombia as red in life with a black upper spinous dorsal fin, although the young specimen of crustosum figured has only a dusky dorsal fin. The Garman figure of P. crustosum is very similar to a remarkable photograph of a living specimen of Peristedion taken from the submersible Johnson Sea-link on a seamount off the Galapagos (Richards & McCosker 1998). The head is red, the upper body has four broad vertical red bars; the pectoral fins are bright red and the spinous dorsal fin is red with a white margin, and without a black blotch. A photograph of P. nesium taken by Avi Klapfer at Isla del Coco (Fig. 1) is very similar, with irregular red bars crossing the body, an anterior wide bar below the dorsal fin followed by five narrower irregular bars; dorsal and pectoral fins bright red with white margins; the head is red with a paler nape.

Differences in head spination between these similar species are most evident in large specimens. Frontal I and II spines and parietal spines in crustosum are sharp and elevated whereas these spines are small or reduced to tubercles in nesium. Contrarily nesium has three sharp elevated retrose nuchal spines compared to small single spines or tubercles in crustosum.

Some island species are shared between Isla del Coco and the Galapagos (eg. Elacatinus nesiotes Bussing, 1990; Dialommus fuscus Gilbert, 1891; Labrisomus dendriticus (Reid,1935); Odontoscion eurymesops (Heller & Snodgrass, 1903); Mycteroperca olfax (Jeynyns, 1842) and thus it was of interest to compare the new species with another deep-water Peristedion from the Galapagos archipelago. Grove and Lavenberg (1997) described a Galapagos specimen (LACM 20838) of Peristedion crustosum (Fig. 3) and obtained data on two CAS (56256, 54561) specimens. These three specimens look like typical mainland specimens, but differ in their short filamentous barbels (38.2-40.2% of head length) a characteristic which they share with P. nesium.

Also Figure 3 shows the very spinous 2nd infraorbital rim on the LACM specimen that is different from any of the mainland specimens of P. crustosum that I have examined. Richards & McCosker (ibid.) identified four additional specimens of Peristedion from the Galapagos during the Johnson Sea-Link cruise. On the basis of comparison with type material of the other two Eastern Pacific mainland species, they concluded the species to be P. crustosum. Clearly the Galapagos population of Peristedion retains the very characteristic long, slender rostral extensions of mainland P. crustosum, although through isolation has developed minor differences and in spite of their pelagic larvae, have maintained a separate population from the Isla del Coco P. nesium.

The species P. paucibarbiger was based on a single juvenile (70mm SL) specimen taken at a depth of 60m en Bahia de La Paz, Baja California (Castro-Aguirre & Garcia-Dominguez 1984). The authors compared this unique specimen with specimens of P. gracile Goode & Bean (1895) (and P. taeniopterum Fowler 1952 which=gracile) a Western Atlantic Peristedion that shares the characteristics of a retrorse spine on a very narrow perifacial rim and the lack of rostral and nasal spines. Miller & Richards (2002) included two other species in their narrow-headed "Peristedion gracile species group" from the Western Atlantic: P. imberbe Poey, 1861 and P. n. sp. "t". In its original description, P. paucibarbiger was not compared with the two other Peristedion species from the Eastern Pacific mainland, P. barbiger and P. crustosum. Both juvenile P. crustosum and P. barbiger differ markedly from P. paucibarbiger in their much wider head due to the wide perifacial rim. Juvenile P. barbiger have no labial barbels and fewer chin barbels than adult specimens, so perhaps the few barbels in P. paucibarbiger may only be a characteristic of immature specimens of the species. No additional specimens with narrow head and perifacial rim have been reported in the eastern Pacific to date.

Etymology: From the Greek nesos meaning islander; to be treated as an adjective.

Habitat and associates: The new species was collected at Isla del Coco with otter trawls at depths between 110 and 180m. The species was not present in hauls made along the same transects at lesser depths. The sandy substratum is shown clearly in Figure 1. Typical demersal fishes found in the same hauls include Paralichthyidae, Triglidae, Anthiinae, Ophichthidae, Aulopidae, Ogcocephalidae and Malacanthidae.

ACKNOWLEDGMENTS

I am grateful to R. J. Lavenberg for organizing and taking part in the 1972 Janss Foundation cruises on the R/V Searcher to Costa Rica and Isla del Coco. Lavenberg recognized P. nesium as possibly new and obtained additional data for Peristedion from the Galapagos at CAS as well as the lectotypes of P. crustosum and barbiger. J. McCosker offered useful comments on an early version of the manuscript. Avi Klapfer kindly provided the photograph taken from a submersible. V. Garrison helped clarify several aspects of the manuscript.

Comparative material: Peristedion crustosum: MCZ 28704 (now USNM 153603) Lectotype designated by G. Miller. 111.5mm SL, collected off Panama. LACM 20838, 1 (127.8mm), collected at Daphne Minor, Galapagos. UCR 492.014, 1 (110.0mm); UCR 501.001, 2 (109.7-119.5mm); UCR 1501.001, 13 (72.2-101.3mm); UCR 1717.005, 7 (60.0-74.8mm); UCR 491.015, 7 (94-107mm) collected off Pacific coast of Costa Rica. R. Feeney provided radiographs and Figures 2 and 3.

Peristedion barbiger: MCZ 28708, 106mm SL; USNM 15360, 143mm. One chosen as lectotype by G. Miller. collected off Panama and Colombia. UCR 489.001, 7 (88.0-116.5mm); UCR 422.012, 4 (89.5-119.4mm); UCR 1730.003, 2 (88.5-90.0mm); UCR 1888.001, 4 (97.5-137.1mm) collected off Pacific coast of Costa Rica.

REFERENCES

Bussing, W.A. 1983. A new tropical eastern Pacific labrid fish, Halichoeres discolor, endemic to Isla del Coco, Costa Rica. Rev. Biol. Trop. 31: 19-23.

Bussing, W.A. 1990. New species of gobiid fishes of the genera Lythrypnus, Elacatinus and Chriolepis from the eastern tropical Pacific. Rev. Biol. Trop. 38: 99-118.

Bussing, W.A. 1991a. A new genus and two new species of tripterygiid fishes from Costa Rica. Rev. Biol. Trop. 39: 77-85.

Bussing, W.A. 1991b. A new species of eastern Pacific moray eel (Pisces: Muraenidae). Rev. Biol. Trop. 39: 97-102.

Bussing, W.A. 1997. Chriolepis atrimelum (Gobiidae) a new species of gobiid fish from Isla del Coco, Costa Rica. Rev. Biol. Trop. 45: 1547-1552.

Castro-Aguirre, J.L. & F. Garcia-Dominguez. 1984. Una nueva especie de Peristedion (Osteichthyes: Scorpaeniformes: Peristediidae) de la bahia de La Paz, Baja California Sur, Mexico. An. Esc. Nac. Cienc. Biol. Mex. 28: 29-38.

Garman, S. 1899. The fishes. In Reports on an exploration off the west coasts of Mexico, Central and South America, and off the Galapagos Islands, in charge of Alexander Agassiz, by the U.S. Fish Commission steamer "Albatross," during 1891, Lieut.... No. XXVI. Mem. Mus. Comp. Zool. Harvard Coll., 24: 1-431, Atlas: Pls. 1-85 + A-M.

Grove, S.G. & R.J. Lavenberg. 1997. The fishes of the Galapagos Islands. Stanford University, Stanford, California, USA,

Miller, G.C. 1967. A new species of western Atlantic armored searobin, Peristedion greyae (Pisces: Peristediidae). Bull. Mar. Sci. 17: 16-41.

Miller, G.C. & W.J. Richards. 2002. Peristediidae. Armoured searobins (armoured gurnards), 1278-1285 p. In K.E. Carpenter (ed.). The living marine resources of the Western Central Atlantic. FAO, Rome.

Richards, W.J. & J.E. McCosker. 1998. A new species of the genus Bellator (Pisces: Triglidae), with comments on the trigloids of the Galapagos Islands. Proc. Riol. Soc. Wash. 11: 936-941.

Teague, G.W. 1961. The armored sea-robins of America. A revision of the American species of the family Peristediidae. An. Mus. Hist. Nat. Montevideo Ser. 7: 1-27.

William A. Bussing

Escuela de Biologia & Centro de Investigaciones en Ciencias del Mar y Limnologia (CIMAR), Universidad de Costa Rica, San Jose, Costa Rica; william.bussing@ucr.ac.cr

Received 21-IX-2009.

Corrected 03-V-2010.

Accepted 04-VI-2010.
TABLE 1
Proportional measurements in percent of standard length for holotype
and paratypes of Peristedion nesium, n. sp. and one specimen of P.
crustosum

Body measurements                         20 paratypes *   Holotype

Standard length (mm)                        95.1-117.6      117.9
Head length                                 35.6-40.3        46.3
Body depth at first dorsal spine            18.1-22.6        21.5
Body depth at anal-fin origin                9.5-11.9        10.1
Body width at pectoral-fin origin           16.7-23.8        23.7
Greatest head width                         29.0-36.5        32.5
Length of joined pectoral-fin rays          17.0-22.3        16.8
Length of first free pectoral-fin ray       17.2-26.1        26.1
Length of second free pectoral-fin ray      15.8-26.7        17.6
Length of pelvic fin                        17.6-22.0        20.6

Body measurements                         Galapagos crustosum

Standard length (mm)                             127.8
Head length                                      36.7
Body depth at first dorsal spine                 20.9
Body depth at anal-fin origin                    11.7
Body width at pectoral-fin origin                23.4
Greatest head width                              40.5
Length of joined pectoral-fin rays               13.2
Length of first free pectoral-fin ray            18.6
Length of second free pectoral-fin ray           22.1
Length of pelvic fin                             18.5

TABLE 2
Proportional measurements in percent of head length for holotype and
paratypes of Peristedion nesium, n. sp. and one specimen of P.
crustosum

Body measurements                           20 Paratypes *   Holotype

Filamentous barbel length                     31.8-44.2        37.6
Lip barbel length                              7.9-13.7        11.9
Chin barbel length                            13.3-22.7        19.0
Snout length                                  41.5-45.7        44.9
Snout width                                   33.4-40.1        39.3
Orbital length                                23.8-29.8        25.5
Orbital depth                                 21.4-26.4        21.8
Interorbital width                            13.7-18.8        15.3
Rostral exsertion length                      12.1-19.0        10.6
Width between rostral exsertions               7.8-15.2        10.2
Greatest width of rostral exsertion base      10.5-14.1        10.4
Width of rostral exsertion at middle           6.1-7.9         8.0
Width between tips of rostral exsertions      20.0-27.5        21.4
Distance between parietal spines              17.6-22.3        20.1
Nape length                                   15.7-20.2        17.5

Body measurements                           Galapagos crustosum

Filamentous barbel length                          40.1
Lip barbel length                                  14.0
Chin barbel length                                 12.4
Snout length                                       47.1
Snout width                                        38.6
Orbital length                                     24.7
Orbital depth                                      23.9
Interorbital width                                 18.3
Rostral exsertion length                           19.2
Width between rostral exsertions                   13.0
Greatest width of rostral exsertion base           12.8
Width of rostral exsertion at middle                6.6
Width between tips of rostral exsertions           27.3
Distance between parietal spines                   21.1
Nape length                                        18.1

* UCR 720.007 (10 I. del Coco paratypes); LACM 32269.008 (10 I. del
Coco paratypes); LACM 20838 (I. Galapagos).
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Author:Bussing, William A.
Publication:Revista de Biologia Tropical
Article Type:Report
Date:Dec 1, 2010
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