Morphological features of larvae of the genus Argis (Decapoda, Crangonidae) from coastal Kamchatka and adjacent waters

2018·5.2 MB·

by  N. A. Sedova

ZOOSYSTEMATICA ROSSICA, 27(1): 11–33 25 JUNE 2018
Morphological features of larvae of the genus Argis (Decapoda,
Crangonidae) from coastal Kamchatka and adjacent waters
Морфология личинок креветок рода Argis (Decapoda, Crangonidae)
из прикамчатских вод
N.A. SEDOVA* & S.S. GRIGORIEV
Н.А. СЕДОВА, С.С. ГРИГОРЬЕВ
N.A. Sedova, Kamchatka Federal Technical University, Petropavlovsk-Kamchatsky 683003, Russia.
E-mail: [email protected]
S.S. Grigoriev, Kamchatka Division of Pacific Institute of Geography, Far East Branch, Russian Academy of Science,
Petropavlovsk-Kamchatsky 683000, Russia. E-mail: [email protected]
Larvae of five species of the family Crangonidae (Argis crassa, A. dentata, A. lar, A. ochotensis
and A. ovifer) from plankton of east part of Okhotsk Sea and from Avacha Gulf are described.
Morphological features of the larvae are compared for purpose of their identification in plank-
tonic samples. The main morphological features of larvae at corresponding stages are revealed.
Larvae of these species are similar in most features. Distinctions concern only several details
of their structure. Figures of early and late stages of zoea are presented. It is shown that larvae
of the genus Argis can have two or three zoeal stages. Generalized morphological characteristic
for the larvae of shrimps from the genus Argis is given.
Описаны личинки пяти видов семейства Crangonidae (Argis crassa, A. dentatа, A. lar,
A. ochotensis и A. ovifer) из планктона восточной части Охотского моря и Авачинского
залива. Сравниваются морфологические признаки личинок с целью их разделения в
планктонных пробах. Выявлены основные морфологические различия личинок соответ-
ствующих стадий. По большинству признаков личинки этих видов сходны. Различия ка-
саются лишь отдельных деталей строения. Приведены рисунки младших и старших зоэа.
Показано, что личинки из рода Argis имеют две или три стадии зоэа. Дана обобщенная
морфологическая характеристика для личинок креветок из рода Argis.
Key words: shrimps, larval morphology, shortened development, zoeal stages, decapodid,
Crustacea, Decapoda, Crangonidae, Argis
Ключевые слова: креветки, морфология личинок, укороченное развитие, стадии зоэа,
декаподит, Crustacea, Decapoda, Crangonidae, Argis
INTRODUCTION A. ovifer (Rathbun, 1902) and A. ochotensis
Komai, 1997 (Slizkin, 2006).
Currently, genus Argis Krøyer, 1842 in-
In northern part of Russian Far East ma-
cludes ten species (De Grave et al., 2009).
rine waters, eastern and northern parts of
Many of them are commercially important
Okhotsk Sea and deep-sea waters of Bering
(Marin, 2013). Five species of this genus oc-
Sea have been most actively studied. Con-
cur in marine waters near Kamchatka Pen-
cerning decapods, the main attention was
insula: Argis crassa (Rathbun, 1999), A. den-
paid to Kamchatka crab and shrimps from
tata (Rathbun, 1902), A. lar (Owen, 1839),
the family Pandalidae. Biology and distribu-
tion of other commercial decapods from this
* Corresponding author area are less studied. Species without com-
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12 N.A. SEDOVA & S.S. GRIGORIEV. MORPHOLOGY OF LARVAE OF ARGIS
mercial value remained practical-
ly unexplored. Biology of shrimps
from the genus Argis is studied
insufficiently. Only fractional
information on bottom depths
of dwelling and heating environ-
ments in Okhotsk and Japan seas
exist about species A. ochotensis
and A. ovifer, and some more data
exist about A. dentatа and A. lar
(Komai, 1997; Sokolov, 2001; Sl-
izkin, 2006).
Larvae of shrimps from the
genus Argis occur in plankton
rarely and during short time due
to shortened development of this
group. Larvae were described only
for three species from mentioned
above. Zoea I of A. crassa and A.
dentatа were described in detail
(Ivanov, 1968). There is also a
description of two zoeal stages
and one decapodid stage of larvae
from Atlantic waters considered
as A. dentatа (Squires, 1965). Be-
sides, Makarov (1966, 1967) gave
poor description of larvae A. lar
Fig. 1. Distribution of larvae samples, belonging to the ge-
from plankton samples collected nus Argis, in coastal Kamchatka and adjacent waters.
in eastern part of Okhotsk Sea.
During processing of plank-
of Okhotsk Sea (above western Kamchat-
tonic samples from Avacha Gulf and eastern
ka shelf) in summer 2013, 2015, and 2016,
part of Okhotsk Sea we found a number of
and in the Pacific waters along southeast-
larvae, which obviously belonged to the ge-
ern coast of Kamchatka Peninsula (Avacha
nus Argis. All of them had features of larvae
Gulf) in spring-summer 2009, 2014, 2016,
with shortened development. Some larvae
and 2017 (Fig. 1; Table 1), according to
were identified according to available de-
scriptions of corresponding stages by Ma- fisheries research program of the Pacific In-
karov (1966) and Ivanov (1968). More de- stitute of Fisheries and Oceanography.
veloped larvae correspond to description of Ichthyoplanktonic gear with mouth di-
larvae from waters of western Kamchatka, ameter 80 cm and mesh size 0.56 mm was
identified as A. lar by Makarov (1966). De- used. Vertical total haul from bottom to
scription of morphology of separate zoeal surface was carried out with bottom depth
stages that we found is presented below. 500 m and less, and from 500 m to surface
in smaller bottom depths. Minimal bottom
MATERIAL AND METHODS depth of larvae sampling was 9 m and maxi-
mal bottom depth was 1800 m. Planktonic
Samples collection
samples were fixed in 4% formaldehyde. Lar-
Plankton samples were collected during vae were examined with binocular micro-
research surveys, performed in eastern part scope at 32-fold and 56-fold magnification.
© 2018 Zoological Institute, Russian Academy of Scienсes, Zoosystematica Rossica 27(1): 11–33
N.A. SEDOVA & S.S. GRIGORIEV. MORPHOLOGY OF LARVAE OF ARGIS 13
Table 1. Data on collection of Argis larvae studied in present work, including locality, species, time
period, and developmental stage
Larval stages
Period
Regions A. ochotensis
of collection A. dentata A. lar A. crassa A. ovifer
Form 1 Form 2
Western August 2013 – II – – – –
Kamchatka June–July 2015 – II II II – –
shelf June–July 2016 I, II II, III I II – –
May 2009 – I – – I –
Avacha May–June 2014 I – – – I, II I
Gulf May 2016 – – I – – I
May 2017 – – – – – I
Classification and morphology of larval length (RL) from anterior tip of rostrum to
stages eye socket.
Classification was made following Za-
RESULTS
renkov (1965) and Komai (1997). Larval
description followed method proposed by
Almost all zoea found in eastern part of
Clark et al. (1998) and Garm (2004). Setal
Okhotsk Sea and identified as the genus
terminology is in accordance with Garm
Argis were very close in morphology to late
(2004). Long plumose setae on distal end of
zoeal stages of A. lar described by Makarov
exopods were drawn truncated.
(1967). Also one larva caught in Avacha
Abbreviations used in text and figures:
Gulf we identified as zoea I of the same spe-
A1, antennules (first pair of antennae); A2,
cies, since they obviously correspond by all
antenna (second pair of antennae); P1–P5,
features to the described zoea II and zoea
first to fifth pereiopods; Mp 1–3, first to
III. In particular, these larvae were of close
third maxilliped, respectively; Mx1, max-
sizes and had smooth posterior margin of
illule; Mx2, maxilla; GV, general view; T,
pleomeres and short spine of scaphocerite,
telson; pl, pleopods; Sg, scaphognathite;
which is characteristic to this species. Zoea
Cp, anterior ventral margin of carapace; Sc,
III, almost indistinguishable from zoea II of
scaphocerite; TL, total length; CL, carapace
length; RL, rostrum length. A. lar by its morphology, was also found.
Available descriptions used in present- Two larvae of zoea II from northern part
ing certain stages (Ivanov, 1968; Makarov, of western Kamchatka shelf strongly re-
1966, 1967; Squires, 1965). semble in their morphology to the previous
species, though having certain differences.
These larvae had longer rostrum, with den-
Measurements of larvae
ticles on carapace in other position, larger
Measurements of larvae were made quantity of setae on scaphognathite, en-
with an ocular micrometer with precision dopod of antenna better developed. It is
of 0.1 mm as follows: carapace length (CL) known that A. ovifer is the most closely re-
from anterior tip of rostrum to posterior lated species to A. lar (Sokolov, 2001; Ko-
carapace margin; total length (TL) from an- mai, 1997). Makarov (1941) even assumed
terior tip of rostrum to posterior margin of that A. ovifer is a subspecies of A. lar (Sliz-
telson, excluding telson processes; rostrum kin, 2006). Therefore we identified these
© 2018 Zoological Institute, Russian Academy of Scienсes, Zoosystematica Rossica 27(1): 11–33
14 N.A. SEDOVA & S.S. GRIGORIEV. MORPHOLOGY OF LARVAE OF ARGIS
larvae as A. ovifer. Similar larvae of zoea I Larvae of various species of Argis in cor-
were not caught. responding stages of development differ
Two larvae of zoea I, collected in Avacha only in structure of carapace, telson, pleon,
Gulf, completely corresponded to descrip- pleopods, maxillules and maxillas. Struc-
tion of A. dentata, given by Ivanov (1968). ture of antennules, maxillipeds, and pereio-
We found zoea II, morphologically corre- pods in most cases is the same, therefore, we
sponding to this species, in eastern part of describe legs in detail only for the first spe-
Okhotsk Sea. This larva had rather long cies. Descriptions of individual species in
spine on scaphocerite, serrate pleon and stages of development are presented below.
anterior ventral margin of carapace, large
number of setae in scaphognathite, and
Argis crassa
similar body length. Therefore, we believed
(Fig. 2)
that they were also A. dentata.
A few larvae of zoea I, identical to de-
Zoea I
scriptions of Ivanov (1968) and Makarov
(1967) for zoea I of A. crassa, were found Material examined. Avacha Gulf: 1 larva, 20
in Avacha Gulf. One larva, corresponding May 2016, over depth 157 m. Western Kam-
to morphology of zoea II, was found in the chatka shelf: 3 larvae, 6 June 2016, over depth
eastern part of Okhotsk Sea. This larva had 41–80 м. TL 6.7–7.8 mm. CL 1.6–2.0 mm. RL
very long spine on scaphocerite, serrate ple- 0.63–0.95 mm.
Description. Carapace (Fig. 2, Cp (I),
on, and anterior ventral margin of carapace,
GV (I)): rostrum straight, not very long;
a large number of setae on scaphongatite,
eyes sessile; supraorbital spines absent; 3
characteristic shape of telson, and corre-
or 4 small sharp spines located along ante-
sponding dimensions.
A few early larvae of zoea I, collected rior ventral margin; pterygostomian spine
in Avacha Gulf in summer, were most of all very small and short. Antennule (Fig. 2, A1
morphologically close to A. dentata, but dif- (I)): peduncle unsegmented; outer flagel-
fered from it by smaller number of cuspidate lum with three aesthetascs and one strong
setae in basial endite of maxillula and plu- seta terminally. Antenna (Fig. 2, A2 (I)):
mose setae in scaphognathite. These larvae protopod unsegmented, with one small
were the largest that we found, and did not distal spine; endopod of antenna slightly
correspond to any of available descriptions. longer than scaphocerite; scaphocerite un-
Only five species of genus Argis have been segmented, with 17 plumose setae on inner
known in Kamchatka marine waters (Sl- margin and one small seta on outer margin;
izkin, 2006), and by process of elimination spine of scaphocerite absent; base of endo-
it could only be A. ochotensis. Besides, it is pod separated. Maxillule: coxal endite with
most similar to A. dentata (Sokolov, 2001). seven papposerrate setae; basial endite with
Larva of zoea II, morphologically similar to nine cuspidate setae; endopod 2-segmented,
A. dentata but having some differences from with proximal segment having one short
this species and significant differences from simple and two strong papposerrate se-
other species of Argis, was found in Avacha tae, and with distal segment having three
Gulf. We also identified it as A. ochotensis, strong terminal papposerrate setae. Max-
as only species which remained. illa (Fig. 2, Sg (I), Sg (I)*): coxal endite bi-
All studied larvae have number of com- lobed, with 11+4 papposerrate setae; basial
mon structural features. Below we present endite trilobed, with 4+3+3 papposerrate
total characteristic of early and late larvae setae; endopod unsegmented, trilobed, with
of the genus Argis from marine waters near 2+1+1+1 papposerrate setae; scaphogna-
Kamchatka Peninsula, and also descrip- thite with 8–10 marginal plumose setae.
tions of species by stages of development. First maxilliped: coxa with five papposer-
© 2018 Zoological Institute, Russian Academy of Scienсes, Zoosystematica Rossica 27(1): 11–33
N.A. SEDOVA & S.S. GRIGORIEV. MORPHOLOGY OF LARVAE OF ARGIS 15
Fig. 2. Morphology of larvae of Argis crassa: (I) – zoea I; (II) – zoea II; GV – general view; Т – telson;
pl – pleopod; Sg – scaphognathite; A1 – antennule, А2 – antenna; Cp – anterior ventral margin of
carapace. Same structure of another specimen marked with asterisk. Scale bars 1 mm.
© 2018 Zoological Institute, Russian Academy of Scienсes, Zoosystematica Rossica 27(1): 11–33
16 N.A. SEDOVA & S.S. GRIGORIEV. MORPHOLOGY OF LARVAE OF ARGIS
rate setae; basis with 12 papposerrate setae; spines absent. Antennule: peduncle 3-seg-
endopod 4-segmented, with 3, 1, 2, 3 pap- mented, first segment with three small plu-
poserrate setae; exopod unsegmented, with mose setae on stylocerite, one strong spine
one long plumose seta on lateral margin and located at half of segment length, and six or
three long terminal plumose setae. Second seven small plumose setae located terminal-
maxilliped: coxa with one papposerrate ly; second segment with six small plumose
seta; basis with eight papposerrate setae ar- setae distally; third segment with one long
ranged as 1, 1, 3, 3; endopod 5-segmented and three or four short plumose setae ter-
with 3+1, 1, 1+1, 2+1 and five papposerrate minally; outer flagellum 2-segmented, with
terminal setae; exopod unsegmented, with four aesthetascs and one strong seta termi-
two subterminal and three long terminal nally. Antenna (Fig. 2, A2 (II)): protopod
plumose setae. Third maxilliped: coxa un- 2-segmented, with one short spines; endo-
armed; basis with two papposerrate setae; pod 18–19-segmented; scaphocerite with
endopod 5-segmented with 2, 1, 1+1; 2+2 22 plumose setae along inner and posterior
and five papposerrate terminal setae; exo- margin; outer setae on scaphocerite absent;
pod unsegmented, with two subterminal spine of scaphocerite very long. Maxillule:
and three terminal plumose setae. Pereio- endopod 2-segmented, with proximal seg-
pods uniramous, well developed, segment- ment having one short simple and two strong
ed; first pereiopod with epipod in basis; papposerrate setae, and with distal segment
subchela available; second pereiopod cheli- hgaving three strong terminal papposerrate
pedal; third, fourth and fifth pereiopods uni- setae; basial endite with nine cuspidate se-
ramous, 6-segmented, without setae. Pleon tae; coxal endite with five distal and two
(Fig. 2, GV (I)) with five smooth pleomeres; lateral papposerrate setae; scaphognathite
posterior margin of 2nd–5th pleomeres with 23 or 24 plumose setae. Maxilla: (Fig.
with spicules; fifth pleomere with a pair of 2, Sg (II)): coxal endite bilobed, with 10+4
dorsolateral spines; anal spine absent. Pleo- papposerrate setae; basial endite trilobed,
pods uniramous, without setae (Fig. 2, pl with 4+3+3 papposerrate setae; endopod
unsegmented, trilobed, bearing 2+1+1+1
(I)). Telson (Fig. 2, T (I), T (I)*) of peculiar
papposerrate setae; scaphognathite with 23
shape, with rounded corners; small notch
or 24 marginal plumose setae. First maxilli-
on posterior margin of telson of semicircu-
ped: coxa with epipod and six papposerrate
lar shape; telson not clearly separated from
setae; basis with 12 papposerrate setae; en-
pleon; two larvae with 8+8 plumose setae,
dopod 4-segmented, with 4, 1, 2+1, 3 pap-
but one larva with 9+9 plumose setae, and
poserrate setae; exopod unsegmented, with
one larva with 8+9 plumose setae; in larva
one long plumose seta on lateral margin and
with 9+9 plumose setae, next stage of zoea
four long terminal plumose setae. Second
also with 9+9 setae visible through cuticle.
maxilliped: coxa with one papposerrate seta;
Uropods absent.
basis with eigth papposerrate setae arranged
as 2, 3, 3; endopod 5-segmented with 3+1,
Zoea II
1, 1+1, 2+1, 5 papposerrate terminal setae;
Material examined. Western Kamchatka exopod unsegmented, with two subterminal
shelf: 1 larva, 9 June 2015, over depth 30 m. TL and four long terminal plumose setae. Third
8.4 mm. CL 2.02 mm. RL 0.82 mm. maxilliped: coxa unarmed; basis with two
Description. Carapace (Fig. 2, Cp (II)): papposerrate setae; endopod 5-segmented
eyes stalked; rostrum long, straight, fac- with 2, 1, 1+1; 2+2, 5 papposerrate termi-
ing forward, reaching front of ocular pe- nal setae; exopod unsegmented, with two
duncle; pterigostomial spine present; three subterminal and four terminal plumose se-
small spines along anterior ventral margin; tae. Pereiopods uniramous, well developed,
pterygostomian spine present; supraorbital segmented; first pereiopod with epipod on
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N.A. SEDOVA & S.S. GRIGORIEV. MORPHOLOGY OF LARVAE OF ARGIS 17
basis, terminal segment having well devel- ite rather long; spine on right limb slightly
oped subchela, and propodus and dactylus shorter than on left one; base of endopodite
distinct; second pereiopod with well devel- separated. Maxillule: coxal endite with
oped chela; third, fourth and fifth pereiopod seven papposerrate setae; basial endite with
uniramous, 7-segmented, without setae. nine cuspidate setae; endopod 2-segmented
Pleon with six pleomeres; posterior margin (proximal segment with one short simple
of 5th–6th pleomeres with spicules; fifth and two strong papposerrate setae, distal
pleomere with a pair of long and sharp dor- segment with three strong terminal pap-
solateral spines; small anal spine present. poserrate setae). Maxilla (Fig. 3, Mx (I), Sg
Pleopods (Fig. 2, pl (II)): protopod naked, (I)): coxal endite bilobed, with 11+4 pap-
bearing endopod in form of small tubercle poserrate setae; basial endite trilobed, with
and exopod without setae. Uropods absent. 4+3+3 papposerrate setae; endopod unseg-
Telson (Fig. 2, T (II)) separated from pleon, mented, trilobed, with 2+1+1+1 papposer-
with rounded corners, small semicircular rate setae; in first specimen, one scaphogna-
notch as in zoea I, and 8+8 setae (inner six thite of maxilla armed with seven marginal
and outer two plumose only on proximal plumose setae, but its other scaphognatite,
axis); small anal spine present; next decapo- with 8 setae. First maxilliped: coxa with
did stage seen through telson (five pairs of five papposerrate setae; basis with 12 pap-
setae and well developed uropods visible poserrate setae; endopod 4-segmented, with
through cuticle). 3, 1, 2, 3 papposerrate setae; exopod un-
segmented, with one long plumose seta on
lateral margin and three long terminal plu-
Argis dentata
mose setae. Second maxilliped: coxa with
(Fig. 3)
one papposerrate seta; basis with eight pap-
poserrate setae arranged as 1, 1, 3, 3; endo-
Zoea I
pod 5-segmented, with 3+1, 1, 1+1, 2+1 and
Material examined. Avacha Gulf: 1 larva, 5 five papposerrate terminal setae; exopod
June 2014, over depth 115 m; 1 larva, May 2016. unsegmented, with two subterminal and
Western part of Okhotsk Sea: 1 larva, 6 June three long terminal plumose setae. Third
2016, over depth 157 m. TL 7.4 and 8.1 mm. CL maxilliped: coxa unarmed; basis with two
1.8 and 2.1 mm. RL 0.9 mm. papposerrate setae; endopod 5-segmented,
Description. Carapace (Fig. 3, GV (I)): with 2, 1, 1+1; 2+2 and five papposerrate
rostrum straight, slightly flattened, pointed, terminal setae; exopod unsegmented, with
not so long; eyes sessile; supraorbital spines two subterminal and three terminal plu-
absent; three small spine available along mose setae. Pereiopods uniramous, well
anterior ventral margin, well noticeable; developed, segmented; first pereiopod with
pterygostomian spine present. Antennule: epipod in basis and with terminal segment
peduncle unsegmented; outer flagellum of subchela developed; second pereiopod
with three aesthetascs and one strong seta cheliped; third, fourth and fifth pereiopod
terminally; distal part of terminal setae of uniramous, 6-segmented, without setae;
antennule covered with short spicules. An- small gills available at base of pereiopods
tenna (Fig. 3, Sc (I)): protopod unsegment- under carapace. Pleon (Fig. 3, GV (I)) with
ed, with one small distal spine; scaphocerite five smooth pleomeres; posterior margin
unsegmented, with 19–22 plumose setae on of 1st–5th pleomeres with small spicules;
inner margin and one small seta on outer fifth pleomere with one pair of long and
margin; apparent ugliness noticeable at one sharp dorsolateral spines; sixth pleomere
larvae (right A2 with two absolutely identi- not clearly separated from telson; anal spine
cal spines instead of one, and left A2 with absent. Pleopods (Fig. 3, pl (I)) uniramous,
only one similar spine); spine of scaphocer- without setae.
© 2018 Zoological Institute, Russian Academy of Scienсes, Zoosystematica Rossica 27(1): 11–33
18 N.A. SEDOVA & S.S. GRIGORIEV. MORPHOLOGY OF LARVAE OF ARGIS
Fig. 3. Morphology of larvae of Argis dentata: (I) – zoea I; (II) – zoea II; GV, A1, A2, Cp, pl, Sg, T – as
in Fig. 2; Sc – scaphocerite; Mx2 – maxilla; Р1–5 – pereiopods. Scale bars 1 mm.
© 2018 Zoological Institute, Russian Academy of Scienсes, Zoosystematica Rossica 27(1): 11–33
N.A. SEDOVA & S.S. GRIGORIEV. MORPHOLOGY OF LARVAE OF ARGIS 19
Telson (Fig. 3, T (I)) not clearly sepa- nal plumose setae. Second maxilliped: coxa
rated from pleon, with small notch of tri- with one papposerrate seta; basis with eight
angular shape and with 8+8 setae. Uropods papposerrate setae arranged as 2, 3, 3; endo-
absent. pod 5-segmented, with 3+1, 1, 1+1, 2+1 and
5 papposerrate terminal setae; exopod un-
Zoea II segmented, with two subterminal and four
long terminal plumose setae. Third maxil-
Material examined. Western part of Okhotsk liped: coxa unarmed; basis with two pap-
Sea: 1 larva, 18 June 2016, over depth 25 m. TL poserrate setae; endopod 5-segmented, with
7.3 mm. CL 2.0 mm. RL 0.9 mm. 2, 1, 1+1; 2+2 and 5 papposerrate terminal
Description. Carapace (Fig. 3, Cp (II)):
setae; exopod unsegmented, with two sub-
eyes stalked; rostrum rather long, straight,
terminal and four terminal plumose setae.
facing forward, reaching far beyond front of
Pereiopods (Fig. 3, P 1–5 (II)) uniramous,
ocular peduncle basis; pterigostomial spine well developed, segmented; first pereiopod
present; three or four very thin spines lo- with epipod on basis, terminal segment of
cated along anterior ventral margin; supra- subchela well developed, and propodus and
orbital spines absent. Antennule (Fig. 3, A1 dactylus distinct; second pereiopod with
(II)): peduncle 3-segmented; first segment well developed chela; third, fourth and fifth
with three small plumose setae on stylo- pereiopods uniramous, 7-segmented, with-
cerite, one strong spine at half of segment out setae. Pleon with six pleomeres; several
length, and six or seven small plumose se- very fine spicules available at posterior mar-
tae terminally; second segment bearing six gin of 2nd–4th pleomeres; fifth pleomere
small plumose setae distally; third segment with a pair of long and sharp dorsolateral
with one long plus three or four short plu- spines; anal spine small. Pleopods (Fig. 3,
mose setae terminally; outer flagellum 2.5 pl 1–5 (II)): protopod naked, bearing en-
times shorter then inner flagellum; 2-seg- dopod in form of small tubercle and exopod
mented, with four aesthetascs and one without setae. Pleopods of various length,
strong setae terminally, and with one aes- gradually decreased from first to fifth (fifth
thetasc on proximal segment. Antenna (Fig. pair shortest). Uropods absent. Telson (Fig.
3, A2 (II)): protopod 2-segmented, with one 3, T (II)) relatively narrow and separated
short spine; endopod two times as long as from pleon; its corners rounded; its poste-
antennal scale, 17-segmented; scaphocerite rior margin slightly convex, almost without
with 22 plumose setae along inner and pos- notch; all setae broken. Next stage of zoea
terior margin; outer setae on scaphocerite with 8+8 setae visible through cuticle.
absent; spine of scaphocerite longer than
carapace. Maxillule: endopod 2-segmented, Argis lar
with proximal segment having one short (Figs 4, 5)
simple and two strong papposerrate setae,
Zoea I
and with distal segment having three strong
terminal papposerrate setae; basial endite
Material examined. Avacha Gulf: 1 larva, ear-
with ten cuspidate setae; coxal endite with
ly May 2009, over depth 53 m. TL 6.7 mm. CL
five distal and two lateral papposerrate se- 2.01 mm. RL 0.80 mm.
tae. Maxilla: scaphognathite with 18 plu- Description. Carapace: rostrum thin,
mose setae. First maxilliped: coxa with epi- not so long; eyes sessile; anterior margin
pod and six papposerrate setae; basis with smooth in front of one of its side; rather thin
12 papposerrate setae; endopod 4-segment- spine along anterior ventral margin visible
ed, with 4, 1, 2+1, 3 papposerrate setae; exo- on other side if carefully inspected; ptery-
pod unsegmented, with one long plumose gostomian spine present. Antennule: pe-
seta on lateral margin and four long termi- duncle unsegmented; outer flagellum with
© 2018 Zoological Institute, Russian Academy of Scienсes, Zoosystematica Rossica 27(1): 11–33
20 N.A. SEDOVA & S.S. GRIGORIEV. MORPHOLOGY OF LARVAE OF ARGIS
Fig. 4. Morphology of larvae of Argis lar at I and III zoeal stages: (I) – zoea I; (III) – zoea III; Т, pl,
Sg, А2, Cp – as in Figs. 2–3; Mx1 – maxillule. Scale bars 1 mm.
three aesthetascs and one strong seta ter- with five plumose setae. Maxilla (Fig. 4,
minally. Antenna (Fig. 4, A2 (I)): protopod Sg (I)): coxal endite bilobed, with 11+4
unsegmented, with one small distal spine; papposerrate setae; basial endite trilobed,
endopod slightly longer than scaphocerite; with 4+3+3 papposerrate setae; endopod
scaphocerite unsegmented, with 18 plu- unsegmented, trilobed, bearing 2+1+1+1
mose setae on inner margin and one small papposerrate setae; scaphognathite with
seta on outer margin; spine of scaphocerite five marginal plumose setae. First maxilli-
short. Maxillule (Fig. 4, Mx1 (I)): coxal en- ped: coxa with five papposerrate setae; basis
dite with seven papposerrate setae; basial with twelve papposerrate setae; endopod
endite with eigth cuspidate setae; endopod 4-segmented, with 3, 1, 2, 3 papposerrate
2-segmented (proximal segment with one setae; exopod unsegmented, with one long
short simple and two strong papposerrate plumose seta on lateral margin and three
setae, distal segment with three strong ter- long terminal plumose setae. Second maxil-
minal papposerrate setae); scaphognathite liped: coxa with one papposerrate seta; basis
© 2018 Zoological Institute, Russian Academy of Scienсes, Zoosystematica Rossica 27(1): 11–33