THREE NEW SPECIES OF THE GENUS MEGOKRIS (DECAPODA,
PENAEIDAE) FROM HALL’S AND MOTOH’S COLLECTIONS
BY
S. SHINOMIYA1,2,3 ) and K. SAKAI1,4,5 )
1 ) Crustacean Laboratory, Shikoku University, Tokushima 771-1192, Japan
ABSTRACT
Three new species of the genus Megokris, M. manihine sp. n. and M. halli sp. n. from the
South China Sea and the East China Sea, and M. motohburiorum sp. nov. from the Philippines,
are described. In these three new species, the rostral teeth as well as the dorsal carinae on abdominal
somites 2-6 are very similar to the corresponding structures in Megokris granulosus (Haswell, 1879)
from Torres Strait, Queensland, and M. pescadoreensis (Schmitt, 1931) from Taiwan. However,
the thelycum and petasma are characteristically different: in M. halli sp. n., the anterior plate of
the thelycum bears a longitudinal middle protuberance, which is largely concave laterally in its
middle region, and elevated with a round projection in its posterior part; and the anterior plate of
the thelycum does not reach the posterior margin of the seminal receptacle. In M. manihine sp. n.,
the anterior plate of the thelycum bears a median longitudinal protuberance with a median ridge, the
posterior part of which is conspicuously elevated with a pair of lateral swellings; the anterior plate
of the thelycum does not reach the posterior edge of the seminal receptacle. In M. motohburiorum
sp. n., the prominent median protuberance of thelycum is narrow in its anterior half and broadened
with an elevation in its posterior half, while the posterior margin is rounded; the anterior plate of the
thelycum is connected with the posterior edge of the seminal receptacle.
RÉSUMÉ
Trois nouvelles espèces du genre Megokris, M. manihine sp. n. et M. halli sp. n., de la mer
de Chine méridionale et de la mer de Chine orientale, ainsi que M. motohburiorum sp. nov.,
des Philippines, sont décrites. Chez ces trois espèces nouvelles, les dents rostrales ainsi que
les carènes dorsales situées sur les somites abdominaux 2-6 sont très similaires aux structures
correspondantes présentes chez Megokris granulosus (Haswell, 1879) de Torres Strait, Queensland,
et chez M. pescadoreensis (Schmitt, 1931) de Taiwan. Cependant, le thelycum et le petasma sont
typiquement différents : chez M. halli sp. n., la plaque antérieure du thelycum porte une protubérance
longitudinale médiane, qui est très concave latéralement dans sa région médiane et présente une
2 ) Also: Laboratory of Marine Biology, Graduate School of Science, Kochi University, Kochi, Japan
3 ) e-mail: shinomiya-s@shikoku-u.ac.jp
4 ) Emeritus Professor of Shikoku University.
5 ) e-mail: ksakai@mb3.tcn.ne.jp
© Koninklijke Brill NV, Leiden, 2006
Also available online: www.brill.nl/cr
Crustaceana 79 (10): 1251-1268
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S. SHINOMIYA & K. SAKAI
projection arrondie dans sa partie postérieure ; la plaque antérieure du thelycum n’atteint pas le bord
postérieur du réceptacle séminal. Chez M. manihine sp. n., la plaque antérieure du thelycum porte
une protubérance longitudinale médiane, avec une ride médiane, dont la partie postérieure présente
une paire de proéminences latérales ; la plaque antérieure du thelycum n’atteint pas le bord postérieur
du réceptacle séminal. Chez M. motohburiorum sp. nov., la protubérance proéminente médiane du
thelycum est étroite dans sa moitié antérieure, puis plus large avec une proéminence dans sa moitié
postérieure tandis que le bord postérieur est arrondi ; la plaque antérieure du thelycum est reliée au
bord postérieur du réceptacle séminal.
INTRODUCTION
The former genus Trachypenaeus Alcock, 1901 was divided into four genera: by
Pérez Farfante & Kensley (1997: 70) Trachypenaeus Alcock, 1901, Trachysalambria Burkenroad, 1934, Megokris Pérez Farfante & Kensley, 1997, and Rimapenaeus Pérez Farfante & Kensley, 1997. In the genus Megokris, four species: were
listed by those authors M. gonospinifer (Racek & Dall, 1965), M. sedili (Hall,
1961), M. pescadoreensis (Schmitt, 1931), and M. granulosus (Haswell, 1879).
Two species, M. ghamrawyi Shinomiya & Sakai, 2005 and M. akademik Shinomiya & Sakai, 2005, both from the Arabian (=Persian) Gulf, have recently been
added (Shinomiya & Sakai, 2005: 1219-1232).
A re-examination of Hall’s material of M. pescadoreensis (Schmitt, 1931) from
numerous localities, deposited in the collections of the Natural History Museum,
London, showed that his specimens do not belong to M. pescadoreensis proper,
but rather to two new species, M. manihine sp. n., and M. halli sp. n., respectively.
Motoh & Buri (1984) reported M. pescadoreensis from the Philippines. However,
their specimens also belong to a new species, M. motohburiorum sp. n. As a result
of the re-examinations presented in this paper, the total number of species in the
genus Megokris now becomes nine.
MATERIAL AND METHODS
The following abbreviations are used throughout this paper: A1, antennule;
CL, carapace length, measuring the distance between the postorbital margin and
the median posterior border of the carapace, in millimeters; Mxp, maxilliped; P,
pereiopod; BM, The Natural History Museum, London; CBM, Natural History
Museum and Institute, Chiba; NSMT, National Science Museum, Tokyo; USNM,
United States National Museum, Washington, D.C.; SMF, Forschungsinstitut
Senckenberg, Frankfurt am Main; ZRC, Raffles Museum of Biodiversity Research,
Singapore; O.T., Otter trawl.
THREE NEW SPECIES OF MEGOKRIS
1253
TAXONOMIC ACCOUNT
Megokris Pérez Farfante & Kensley, 1997
Megokris Pérez Farfante & Kensley, 1997: 95; Sakaji & Hayashi, 2003: 141; Shinomiya & Sakai,
2005: 2.
Type species. — Penaeus granulosus Haswell, 1879, by original designation.
Species included. — Megokris gonospinifer (Racek & Dall, 1965), M. sedili
(Hall, 1961), M. pescadoreensis (Schmitt, 1931), M. granulosus (Haswell, 1879),
M. ghamrawyi Shinomiya & Sakai, 2005, M. akademik Shinomiya & Sakai, 2005,
M. manihine sp. n., M. halli sp. n., and M. motohburiorum sp. n.
K EY
TO THE
S PECIES
OF THE
G ENUS MEGOKRIS
1. Anterior plate of thelycum protruded on anterior margin, with a shortly pointed or large, sinuous
apex . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
– Anterior plate of thelycum convex on anterior margin, lacking anterior protrusion . . . . . . . . . . 3
2. Body slender; rostrum curving downwards; distolateral projections of petasma very wide,
laterally-directed wings occupying three-quarters of length of petasma; thelycum with large
spinous anterior process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. gonospinifer (Racek & Dall, 1965)
– Body broad; rostrum curving upwards or horizontally; distolateral projections of petasma
narrow, laterally-directed wings occupying one quarter of length of petasma; thelycum with short,
pointed anterior process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. sedili (Hall, 1961)
3. Anterior plate of thelycum connected with posterior plate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
– Anterior plate of thelycum separated from posterior plate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Distolateral projection of petasma bearing a wing-like flap on outer curve, and anteromesial
margin of petasma triangularly protruded; anterior plate of thelycum provided with a prominent
median protuberance, anterior half of which is narrow, and posterior half broadened and
elevated . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. motohburiorum sp. n.
– Distolateral projection of petasma not provided with wing-like flap on outer curve, and
anteromesial margin of petasma protruded with narrow triangular projection; anterior plate of
thelycum not provided with prominent median protuberance, broadened, and not elevated, in its
posterior half . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. granulosus (Haswell, 1879)
5. Anterior plate of thelycum without prominent median protuberance . . . . . . . . . . . . . . . . . . . . . . . . . 6
– Anterior plate of thelycum with prominent median protuberance . . . . . . . . . . . . . . . . . . . . . . . . . . 7
6. Thelycum bearing small, pointed mid-projection at posterior end of anterior plate . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. akademik Shinomiya & Sakai, 2005
– Thelycum bearing roundly swollen projection at posterior end of anterior plate . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. ghamrawyi Shinomiya & Sakai, 2005
7. Median longitudinal protuberance of anterior plate of thelycum truncate on posterior margin
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. manihine sp. n.
– Median longitudinal protuberance of anterior plate of thelycum rounded on posterior margin .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.
8. Median longitudinal protuberance of anterior plate of thelycum bearing no projection on posterior
part . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. pescadoreensis (Schmitt, 1931)
– Median longitudinal protuberance of anterior plate of thelycum with round projection on
posterior part. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .M. halli sp. n.
Fig. 1. Megokris halli sp. n., whole body, lateral view, BM 1961.7.1.2540, holotype, female (CL 16.2 mm).
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S. SHINOMIYA & K. SAKAI
THREE NEW SPECIES OF MEGOKRIS
1255
Fig. 2. Megokris halli sp. n., A, carapace, lateral view; B, first pereiopod; C, thelycum, ventral view;
D, thelycum, lateral view. A-D, BM 1961.7.1.2540, holotype, female (CL 16.2 mm).
Megokris halli sp. n. (figs. 1, 2)
Trachypenaeus pescadoreensis, Hall, 1962: 29 (in part), table 1 (in part), table 10 (in part).
Material examined. — Holotype, BM 1961.7.1.2540, female (CL 16.2 mm) Singapore Fisheries
Research stn. B 146, Permanent Buoy 10, Angler Buoy, 9 m, 31.viii.1956.
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S. SHINOMIYA & K. SAKAI
Diagnosis. — Rostrum straight, upcurved in distal fifth, and armed with 11
dorsal teeth (excluding epigastric spine); rostral tip reaching distal end of A1
penultimate segment.
Anterior plate of thelycum not reaching posterior margin of seminal receptacle;
longitudinal median protuberance largely concave on both sides in median region,
ending posteriorly in an elevated, rounded projection.
Description of female holotype (fig. 1). — Rostrum straight, and upcurved
in distal fifth, provided with 11 dorsal teeth, reaching distal end of antennular
penultimate segment (fig. 2A). Postrostral carina almost extending to posterior 1/9
of carapace. Pterygostomian angle blunt.
Prosartema failing to reach distal end of cornea. Antennal carina present.
Scaphocerite reaching distal end of A1 peduncle. A1 flagellum as long as peduncle.
Mxp3 reaching distal 1/3 of A1 penultimate segment. P1 reaching distal 1/3 of A1
proximal segment, ischium with a small spine, and basis with a spine (fig. 2B). P2
reaching distal 1/5 of A1 proximal segment, basis with a spine. P3 overreaching A1
peduncle by chela. P4 reaching distal 1/5 of A1 proximal segment. P5 overreaching
A1 peduncle by dactylus.
Abdominal somite 2 with short dorsal carina in middle part, somite 3 with
dorsal carina in anterior 1/4 to posterior end. Somites 4-6 with dorsal carina, and
simply pointed at posterior end, and somite 6 with a median spine at posterodorsal
end. Telson with a pair of conspicuous subapical spines and two pairs of minute
spines on lateral margin. Anterior plate of thelycum bearing longitudinal median
protuberance, largely concave on both sides in median region, ending posteriorly
in elevated rounded projection; anterior plate of thelycum not reaching posterior
margin of seminal receptacle (fig. 2C, D).
Remarks. — The present new species, Megokris halli sp. n. is selected from
Hall’s collection in the Natural History Museum, London, and was formerly indentified as Trachypenaeus pescadoreensis, and is closely similar to M. pescadoreensis as the median longitudinal protuberance of the anterior plate of the thelycum
is rounded on its posterior margin. However, in M. pescadoreensis the median
longitudinal protuberance of the anterior plate of the thelycum is unarmed on the
posterior part, not reaching to the posterior edge of the seminal receptacle, whereas
in M. halli the median longitudinal protuberance is largely concave on both sides
in the median region, and elevated with a rounded projection in the posterior part,
not reaching to the posterior margin of the seminal receptacle (fig. 2C, D).
Type locality. — Singapore Strait.
Etymology. — The species name is named in honor of Dr. D.N.F. Hall, who
described the holotype specimen for the first time.
Fig. 3. Megokris manihine sp. n., whole body, lateral view, BM 1961.7.1.2526, holotype, female (CL 22.2 mm).
THREE NEW SPECIES OF MEGOKRIS
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S. SHINOMIYA & K. SAKAI
Fig. 4. Megokris manihine sp. n., A, carapace, lateral view; B, first pereiopod; C, petasma, ventral
view; D, thelycum, ventral view; E, thelycum, lateral view. A, B, D, E, BM 1961.7.1.2526, holotype,
female (CL 22.2 mm); C, CBM ZC 4959, male (CL 16.2 mm).
THREE NEW SPECIES OF MEGOKRIS
1259
Megokris manihine sp. n. (figs. 3, 4)
Trachypeneus pescadoreensis, Hall, 1962: 29 (in part), fig. 111-111b, table 1 (in part), table 10 (in
part), table 15 (in part).
Trachypenaeus pescadoreensis, Liu & Zhong, 1986: 191-193, fig. 118.
Megokris pescadoreensis, Sakaji & Hayashi, 2003: 143.
Material examined. — Holotype, BM 1961.7.1.2526, female (CL 22.2 mm), 5◦ 12 N 114◦ 59 E,
37 m, 2.xii.1955, Singapore Fisheries Research stn. c5/15, R/V “Manihine”. Paratypes, BM
1961.7.1.2529-2538, 10 females (CL 15.8-21.1 mm), 5◦ 12 N 114◦ 59 E, 37 m, 2.xii.1955, Singapore
Fisheries Research stn. c5/15, R/V “Manihine”; BM 1961.7.1.2539, paratype, female (CL 16.6 mm),
2◦ 06 N 109◦ 40 E, 33 m, 24.xi.1955, Singapore Fisheries Research stn. c 5/6, R/V “Manihine”; BM
1961.7.1.2527-2528, paratypes, 2 females (CL 21.3-21.6 mm), 0◦ 11 S 105◦ 30 E, 9 m, 27.i.1956,
Singapore Fisheries Research stn. c 6/33, leg. R/V “Manihine”; BM 1961.7.1.2486, 1 male (CL
10.7), 2 females (CL 10.4, 15.9 mm), 28.xi.1956, P. S. 5 Singapore Strait, 82 m, Singapore Fisheries
Research stn. B 158; BM 1961.7.1.2487, 1 female (CL 10.8 mm), 6.i.1955, Singapore Strait, 40 m,
Singapore Fisheries Research stn. B60. CBM ZC 4959, 6 males (CL 13.6-18.4 mm), 6 females (CL
15.2-24.0 mm), Singapore, Fishery Port, 10-30 m, 06.v.1997, commercial trawler, coll. T. Komai;
CBM ZC 2814, 1 female (CL 24.7 mm), Tong-Kong, Ping-Tong County, SW Taiwan, 30-50 m,
sand-mud bottom, 5.viii.1996, shrimp trawler, coll. T. Komai; ZRC 1979.8.10.7-8, 2 females (CL
18.1-20.2 mm), Singapore from west coast of Malaya, 11.v.1979, coll. Juan C. Miquel; SMF 30966,
1 female (CL 22.6 mm), Sanya Bay, south coast, Hainan, China, st. 9, coordinates square: 18◦ N
109◦ 15 E – 18◦ 10 N 109.25 E, Otter trawl, sandy mud, 16 m, 27.xi.1990, China-Germany Biological
Expedition to Hainan, 1990.
Diagnosis. — Rostrum straight, slightly curved upward near apex, downward
distally, and provided with 9-10 dorsal teeth, reaching about distal end of A1
penultimate segment. In males, distolateral petasmal projections broad, tips curving forward in broad sweep, ending in mucronate, inwardly directed tips, with
wing-like flaps on outer curve; anteromedian margins not forming a sharp triangular prominence. In females, anterior plate of thelycum provided with prominent
median protuberance, posterior part of which is conspicuously elevated, and slanting with a pair of prominences; anterior plate of thelycum not reaching posterior
edge of seminal receptacle.
Description of female holotype (fig. 3). — Rostrum straight, slightly curved upward near apex, downward distally, and provided with 10 dorsal teeth (figs. 3, 4A).
Postrostral carina flat, nearly reaching posterior end of carapace. Pterygostomian
angle quadrangular. Prosartema not reaching distal end of cornea.
Antennal carina well developed. Scaphocerite reaching distal end of A1 peduncle. A1 flagellum shorter than peduncle. Mxp3 reaching distal end of A1 peduncle.
P1 reaching distal end of A1 proximal segment; ischium with small spine, basis
with subdistal spine (fig. 4B). P2 reaching distal end of A1 penultimate segment,
basis with spine. P3 overreaching A1 peduncle by two times length of its propodus; epipod present. P4 reaching to midlength of A1 penultimate segment. P1-5
with exopod, exopod on P5 small.
Abdominal somite 2 with short dorsal carina in middle part, somite 3 with the
dorsal carina prominent in posterior two-thirds; somites 4-6 with dorsomedian
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S. SHINOMIYA & K. SAKAI
carinae, carinae of somites 4 and 5 each with a simple small, pointed spine at
posterior end, and somite 6 with median small spine on its posterior margin.
Anterior plate of thelycum bearing longitudinal median protuberance with median
ridge, and conspicuously elevated with a pair of lateral swellings in posterior part;
anterior plate of thelycum not reaching posterior margin of seminal receptacle
(fig. 4D, E).
Description of paratype females (CL 15.2-24.7 mm). — Almost similar to
female holotype, but differing as follows: Rostrum provided with 9-10 or rarely
13 dorsal teeth, reaching to between distal end and distal 2/3 of length of A1
penultimate segment, or rarely overreaching it. Mxp3 reaching distal end of A1
proximal segment or only to that of penultimate segment, or rarely distal end of
A1 peduncle. P1 reaching from distal end to middle of A1 proximal segment.
P2 reaching middle of A1 penultimate segment or to distal end of A1 peduncle,
basis with spine. P3 overreaching A1 peduncle by three-fourths to twice of its
propodus length. P4 reaching to midway of A1 proximal or terminal segment. P5
overreaching A1 terminal segment by dactylus or propodus, or rarely reaching
distal end or proximal third of A1 terminal segment.
Abdominal somite 2 with short dorsal carina in its middle or slightly anterior
part.
Small females (CL 10.4, 10.8 mm). — Rostrum straight, slightly curved upward
near apex, provided with 9-10 dorsal teeth, reaching 1/2 of A1 penultimate
segment. A1 flagellum as long as or slightly shorter than peduncle. Mxp3 reaching
to distal end or proximal third of A1 penultimate segment. P1 reaching to midway
of A1 proximal segment. P2 reaching distal end of A1 proximal or penultimate
segment, basis with a spine. P3 overreaching A1 peduncle by propodus. P4
reaching to proximal three-fourths of A1 penultimate segment. P5 overreaching
A1 peduncle by 1/2 of propodus.
Anterior plate of thelycum armed posteriorly with a small projection, and in
small female (CL 10.4 mm), anterior median margin of anterior plate pointed with
weak longitudinal median ridge in posterior part, but in another small female (CL
10.8 mm), anterior median margin of anterior plate rounded.
Description of male (CL 13.6-18.4 mm). — Rostrum straight, provided with 910 dorsal teeth, reaching distal end of A1 penultimate segment. Postrostral carina
reaching posterior end of carapace.
Mxp3 slightly overreaching proximal margin of A1 penultimate segment or
reaching nearly to proximal three-fourths of its length. P1 reaching to middle of
A1 proximal segment or nearly to proximal 2/3 of it; ischium with small spine and
basis with spine. P2 reaching nearly to proximal 1/4 or distal end of A1 penultimate
segment, basis with spine. P3 overreaching A1 peduncle by dactylus length. P4
THREE NEW SPECIES OF MEGOKRIS
1261
reaching to proximal 2/3 or distal end of A1 proximal segment. P5 overreaching
A1 peduncle by more than dactylus length.
Distolateral petasmal projections broad, tips curving forward in broad sweep,
ending in inwardly directed mucronate tips, with wing-like flaps on outer curvature; anteromedian margins not forming sharp triangular prominences (fig. 4C).
Small male (CL 10.7 mm). — Rostrum straight, directed slightly upward at
tip, provided with 11 dorsal teeth, reaching to half of A1 penultimate segment.
Prosartema not reaching to distal end of cornea.
Scaphocerite reaching distal end of antennular peduncle. Mxp3 reaching to half
of A1 penultimate segment. P1 reaching to proximal 2/3 of A1 proximal segment;
ischium with a small spine, and basis with a spine. P2 reaching to distal end of
A1 penultimate segment, basis with a spine. P3 overreaching A1 peduncle by
dactylus. P4 reaching to proximal 2/3 of A1 penultimate segment. P5 overreaching
A1 peduncle by distal 1/3 of propodus.
Abdominal somite 2 with short dorsal carina in middle part, somite 3 with
dorsal carina in anterior 1/3 to posterior end, somites 4-6 with dorsomedian carina,
somites 4-5 quadrangular at posterior end, and somite 6 with a small median spine
at posterior end. Telson with a pair of conspicuous subapical spines on distal sixth
and two pairs of minute spines on lateral margin.
Remarks. — This type specimen of M. manihine sp. n. is also selected from
Hall’s specimens in The Natural History Museum, London, formerly identified
as Trachypenaeus pescadoreensis Schmitt, 1931. M. manihine sp. n. and M.
pescadoreensis are closely similar, but in M. pescadoreensis a prominent median
protuberance of the anterior plate of the thelycum is posteriorly terminated by
the rounded projection of the margin, not reaching the posterior edge of the
seminal receptacle, whereas in M. manihine a longitudinal median protuberance
of the anterior plate of the thelycum is posteriorly terminated by a strong truncate
projection, not reaching the posterior edge of the seminal receptacle.
Type locality. — 5◦ 12 N 114◦ 59 E, 37 m.
Distribution. — Malaysia, Indonesia, Singapore, Hainan (Sanya Bay), and
Taiwan.
Etymology. — The species name, manihine, is derived from R/V “Manihine”,
the research vessel of the Singapore Regional Fisheries Research Station, from
which the holotype of the present new species was collected.
Megokris motohburiorum sp. n. (fig. 5)
Trachypenaeus pescadoreensis, Motoh & Buri, 1984: 92, figs. 63, 64 [not Trachypeneus pescadoreensis Schmitt, 1931].
Material examined. — Holotype, BM 2006.548, female (CL 21.4 mm), Iloilo, Philippines,
vii.1980. Paratypes, BM 2006.546-551, 3 males (CL 12.7-14.2 mm), Iloilo, Philippines, vii.1980.
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S. SHINOMIYA & K. SAKAI
Fig. 5. Megokris motohburiorum sp. n., A, carapace, lateral view; B, first pereiopod; C, petasma,
ventral view; D, thelycum, ventral view; E, thelycum, lateral view. A, NSMT Cr-9183, paratype,
female (CL 22.2 mm); B, NSMT Cr-9183, female (CL 17.8 mm), C, BM 2006.549, paratype, male
(CL 14.2 mm); D, E, BM 2006.548, holotype, female (CL 21.4 mm).
THREE NEW SPECIES OF MEGOKRIS
1263
Paratype, BM 2006.553, female (CL 20.5 mm) (antennule peduncle, right eye and antenna absent,
left scaphocerite broken), Iloilo, Philippines, vii.1980; NSMT-Cr. 9183, 3 females (CL 17.8-22.2
mm), female (CL 18.6 mm) (anterior part from eye separated), male (CL 13.3 mm) (carapace
separated), Iloilo, Tigbauan, Panay I., Philippines, vii.1980, 1977.
Diagnosis. — Rostrum straight, directed upward in its anterior third; tip
slightly bent ventrally, armed with 9 dorsal teeth, reaching nearly distal end of
A1 penultimate segment. Distolateral projection of petasma bearing a wing-like
flap on outer curve, and anteromesial margin of petasma triangularly protruded.
Prominent median projection of thelycum narrow in its anterior half, broadened
with elevation in its posterior half. Abdominal somite 2 medially with short dorsal
carina; somites 3-6 dorsally carinate from anterior third of somite 3 to posterior
end of somite 6. P3 with epipod.
Description of female holotype (fig. 3). — Rostrum straight, slightly directed
upward in its anterior 1/3, and slightly curved ventrally at tip, not reaching distal
end of A1 penultimate segment; bearing 9 dorsal teeth.
A1 flagellum slightly shorter than A1 peduncle, though more or less damaged.
Postrostral carina reaching posterior end of carapace. Scaphocerite reaching distal
end of A1 peduncle. Mxp3 reaching distal end of A1 penultimate segment. P1
reaching distal end of A1 proximal segment; basis with spine on mesial margin,
ischium with small spine on mesial margin. P2 reaching distal end of A1 peduncle,
basis with spine on mesial margin. P4 reaching distal end of A1 penultimate
segment.
Abdominal somite 2 medially with short dorsal carina; somites 3-6 dorsally
carinate from anterior third of somite 3 to posterior end of somite 6, carina of
anterior 1/2 of somite 4 and anterior 1/3 of somite 5 somewhat reduced in height;
dorsal carinae of somites 4 and 5 unconspicuously pointed at posterior end, somite
6 with small spine at posterior end. Telson with two pairs of minute lateral spines
and a pair of distolateral spines. Prominent median protuberance of thelycum
narrow in anterior half, broadened and elevated in posterior half, and rounded on
posterior margin; anterior plate of thelycum connected with posterior margin of
seminal receptacle (fig. 5D, E).
Description of the males. — Rostrum straight, reaching to 1/2 of A1 penultimate
segment, with 9 teeth on entire dorsal margin (excluding epigastric spine). Postrostral carina slightly flat, and almost reaching posterior end of carapace. Mxp3 reaching to distal end of A1 proximal segment or 1/2 of A1 penultimate segment. P1
reaching to distal end or 1/2 of A1 proximal segment, basis with a spine on mesial
margin and ischium with a small spine on mesial margin. P2 reaching to distal end
or 1/2 of A1 penultimate segment, basis with a spine on mesial margin. P3 overreaching A1 peduncle by dactylus or anterior 1/5 of carpus. Epipod on P3 only. P4
reaching to distal end or 1/2 of A1 penultimate segment. Prosartema not reaching
distal end of cornea.
Fig. 6. Megokris pescadoreensis (Schmitt, 1931), whole body, lateral view, USNM 55587, holotype, female (CL 21.2 mm).
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THREE NEW SPECIES OF MEGOKRIS
1265
A1 flagellum shorter than A1 peduncle (but distal part broken) or slightly longer
than it.
Abdominal somite 2 medially with short dorsal carina; somites 3-6 dorsally
carinate, from anterior third of somite 3 to posterior end of somite 6; carinae of
anterior third of abdominal somite 4 and 5 slightly lower; dorsal carina of somite 3
terminating in quadrangular posterior end; those of somites 4 and 5 rather pointed
at posterior end; and the one of somite 6 pointed at posterior end. Telson with
two pairs of minute lateral spines and a pair of distolateral spines. Distolateral
projections of petasma forming ox-horn shape and directed forward; anteromesial
margin of petasma protruded, semitriangular in shape (fig. 5C).
Description of other females. — Rostrum straight and directed upward in
anterior 1/3, slightly curved ventrally at its tip, reaching to distal end or 1/2 of
A1 penultimate segment, with 9 teeth on entire dorsal margin (fig. 5A). Postrostral
carina rather flat, reaching nearly to posterior end. Pterygostomian angle blunt.
Prosartema not reaching distal end of cornea.
Scaphocerite reaching distal end of A1 peduncle. Mxp3 reaching to proximal
2/3 of A1 penultimate segment. P1 reaching distal end of A1 proximal segment;
basis with a spine and ischium with a small spine (fig. 5B). P2 reaching distal end
of A1 peduncle, basis with a spine. P3 overreaching A1 peduncle by dactylus or
distal 1/7 of carpus. Only P3 with epipod. P4 reaching distal end of A1 penultimate
segment. P5 overreaching A1 peduncle by distal 1/3 of propodus.
Abdomen medially armed with short carina on somite 2; dorsally carinate from
anterior 1/3 of somite 3 to posterior end of somite 6. Those carinae rather low
on anterior 1/2 of somite 4 and on anterior 1/3 of somite 5, slightly pointed at
posterior end on both somite 4 and 5, and armed with small spine at posterior end
of somite 6. Telson with two pairs of minute lateral spines and a pair of distolateral
spines. Anterior plate of thelycum with prominent median protuberance, greatly
protruded in its posterior half, and posteriorly fused with posterior margin of
seminal receptacle.
Remarks. — Megokris motohburiorum sp. n., resembles M. granulosus in the
form of the female genital organs. In M. motohburiorum and in M. granulosus the
anterior plate of the thelycum is elongated on its posterior margin, but the two
species differ as follows. In males of M. motohburiorum the distolateral projection
of the petasma bears wing-like flaps on the outer curve, and the anteromesial
margin of the petasma is triangularly protruded, whereas in M. granulosus the
distolateral projections of the petasma are not provided with wing-like flaps on
the outer curve, and the anteromesial margin of the petasma is protruded as a
narrow triangular process. In females of M. motohburiorum the anterior plate of
the thelycum bears a longitudinal median protuberance, which is largely broadened
and elevated in its posterior half, whereas in M. granulosus the anterior plate of
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S. SHINOMIYA & K. SAKAI
Fig. 7. Megokris pescadoreensis (Schmitt, 1931), A, thelycum, ventral view; B, thelycum, lateral
view. A, B, USNM 55587, holotype, female (CL 21.2 mm).
the thelycum is not produced to form a longitudinal median protuberance that is
posteriorly declined to a large rounded, rather low part in the posterior half of the
organ.
Type locality. — Iloilo, Philippines.
Etymology. — The species name, motohburiorum is dedicated to Dr. H. Motoh
and Dr. P. Buri, in honour of their past joint contributions towards the present
species. The name is a noun in the genitive plural.
Megokris pescadoreensis (Schmitt, 1931) (figs. 6, 7)
Trachypeneus pescadoreensis Schmitt, 1931: 265-267, pl. 32 figs. 2-4.
Not Trachypenaeus pescadoreensis, Motoh & Buri, 1984: 92, figs. 63, 64 [= Megokris motohburiorum sp. n.].
Not Trachypeneus pescadoreensis, Hall, 1962: 29 [in part = Megokris manihine and M. halli spp.
nov.]; fig. 111, 111b [= Megokris manihine sp. n.].
Not Trachypenaeus pescadoreensis, Liu & Zhong, 1986: 191-193, fig. 118 [= Megokris manihine
sp. n.].
Not Megokris pescadoreensis, Sakaji & Hayashi, 2003: 143 [= Megokris manihine sp. n.].
Material examined. — USNM 55587, holotype, female (CL 21.2 mm, carapace separated from
abdomen), Pescadores Islands, Formosa [= Taiwan], collected by M. Ohshima, 5.vii.1920.
Diagnosis of female holotype. — Rostrum uptilted, failing to reach A1 penultimate segment, altogether with 9 dorsal teeth. Postrostral carina flat, almost reaching posterior end of carapace.
THREE NEW SPECIES OF MEGOKRIS
1267
A1 flagellum shorter than A1 peduncle. Scaphocerite reaching distal end of A1
peduncle. Mxp3 reaching to proximal 2/3 of A1 penultimate segment. P1 reaching
to middle of A1 proximal segment. P2 reaching to proximal 2/3 of A1 terminal
segment. P3 overreaching A1 peduncle by chela. P4 failing to reach distal end of
A1 proximal segment. Anterior plate of thelycum not forming prominent median
projection continuing posteriorly to posterior plate without median intermediate
swelling.
Abdominal somite 2 with short and low dorsal carina in its middle part, somite 3
with dorsal carina in posterior 2/3; somites 4-6 with dorsal carina, somite 4 simply
pointed at posterior end, and posterodorsal margin of somite 6 triangularly pointed
at posterior end.
Remarks. — The name Megokris pescadoreensis (Schmitt, 1931) from Taiwan
has widely been applied for material collected from the Indo-West Pacific region,
but most of the specimens under this name were erroneously included in the present
species. The examination of the female holotype revealed that the anterior plate of
the thelycum is armed with a simple, prominent median protruberance (fig. 7A, B),
which is characteristic in shape as mentioned above.
ACKNOWLEDGEMENTS
We are most grateful to Dr. P. Clark and Ms. M. Lowe, The Natural History
Museum, London, who sent us Hall’s specimens for our review, and to Dr. H.
Motoh, director of the Japanese Carcinological Society for the Japan Sea in
Kanazawa and Dr. K. Nagasawa, Hiroshima University, Hiroshima, who also sent
us their material for the present review. Thanks extend to Dr. J. C. von Vaupel
Klein, University of Leiden, Prof. Dr. L. B. Holthuis of the Leiden Museum, and
to Dr. Michael Türkay of Frankfurt am Main, who reviewed this manuscript with
critical comments. We acknowledge also the sincere help to Dr. Michael Türkay
and Ms. K. Pietratus Forschungsinstitut Senckenberg, Frankfurt am Main; Dr. R.
Lemaitre, National Museum of Natural History, Washington, D.C.; Dr. P. K. L. Ng,
Raffles Museum of Biodiversity Research, National University of Singapore; Dr.
M. Takeda, Teikyo Heisei University, Tokyo, and Dr. T. Komai, Natural History
Museum and Institute, Chiba, who gave us an opportunity to examine material
under their care. This study is supported by Drs. Y. Machida and N. Iwasaki,
Graduate School of Science, Kochi University.
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First received 15 May 2006.
Final version accepted 17 May 2006.