Research Article |
Corresponding author: Tin-Yam Chan ( tychan@mail.ntou.edu.tw ) Academic editor: Ingo S. Wehrtmann
© 2021 Guo-Chen Jiang, Tin-Yam Chan.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Jiang G-C, Chan T-Y (2021) Morphology of the first three zoeal stages of the deep-sea caridean shrimp Heterocarpus fascirostratus Yang, Chan & Kumar, 2018 (Crustacea, Decapoda, Pandalidae). ZooKeys 1042: 23-34. https://doi.org/10.3897/zookeys.1042.64407
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The larvae of the deep-sea pandalid shrimp Heterocarpus fascirostratus Yang, Chan & Kumar, 2018 were successfully hatched and cultured to the third zoeal stage. The larvae reached the third zoeal stage nine days after hatching at a water temperature of 21 ± 1 °C. Although members of Heterocarpus A. Milne-Edwards, 1881 have rather diverse body forms and are often separated into many species groups, the early zoeal morphology of H. fascirostratus follows the general developmental pattern of the species in Heterocarpus. The main differences amongst these larvae are body size, spines on the anteroventral margin of the carapace, and the endopod setation of the third maxilliped.
Laboratory rearing, larval development, zoea
The deep-sea pandalid shrimp genus Heterocarpus A. Milne-Edwards, 1881 is often considered as having fishery potential (
Heterocarpus fascirostratus Yang, Chan & Kumar, 2018 is the last species described in the genus and belongs to a different species group from those species of the same genus with known larval morphology. Heterocarpus fascirostratus only has pleonite III bearing an overhanging spine. Heterocarpus ensifer, H. hayashii and H. sibogae have posterior spines on both pleonites III and IV. Heterocarpus abulbus completely lacks a spine on the pleon. In the present work, an ovigerous female of H. fascirostratus was collected off the South China Sea and its hatching larvae were cultured for the first time until the third zoeal stage.
An ovigerous female of H. fascirostratus was captured by the research vessel ‘Ocean Researcher I’ (station CP 4128) with a French beam trawl at depths of 420–444 m off Dongsha Island (Pratas, Taiwan, 20°44.857'N, 116°08.010'E) in the South China Sea. The ovigerous female was maintained in sea water (35 ± 1‰ salinity) at 14 ± 1 °C in the laboratory. After hatching, ~ 200 actively swimming larvae each were transferred to two beakers (5 L) with aerated seawater, temperature at 21 ± 1 °C and natural photoperiod. The larvae were fed daily with Artemia nauplii and rotifers from Zoea I to III and with water changed every day. Specimens of each zoeal stage were collected immediately after the larvae molted and subsequently preserved in a 70% ethylene glycol solution. About five larvae were sampled each day to check for moults. At least two larvae from each stage were dissected, mounted on glass slides and examined under a stereo microscope (OLYMPUS SZX12) using fine entomological needles. Appendages were drawn using a camera lucida installed on a compound microscope (Olympus BX50). About 80% of the larvae developed to Zoea II, but only two larvae moulted to Zoea III and the rearing terminated then.
The descriptions and figures were arranged according to the standards proposed by
Period from hatching to end of instar: 1–5 days.
Size (N = 5): CL, 0.44 mm (0.41–0.47 mm); BL, 2.24 mm (2.16–2.35 mm); TL, 2.63 mm (2.51–2.76 mm).
Carapace (Fig.
Antennule (Fig.
Antenna (Fig.
Mandible (Fig.
Maxillule (Fig.
Maxilla (Fig.
First maxilliped (Fig.
Second maxilliped (Fig.
Third maxilliped (Fig.
Pereiopods: Absent.
Pleon (Fig.
Pleopods: Absent.
Uropod: Absent.
Telson (Fig.
Period from hatching to end of instar: 6–8 days.
Size (N = 2): CL, 0.50 mm (0.48–0.51 mm); BL, 2.52 mm (2.37–2.66 mm); TL, 2.74 mm (2.62–2.86 mm).
Carapace (Fig.
Antennule (Fig.
Mandible (Fig.
Maxillule (Fig.
Maxilla (Fig.
First maxilliped (Fig.
Second maxilliped (Fig.
Third maxilliped (Fig.
Telson (Fig.
Period from hatching: 9 days.
Size (N = 2): CL, 0.62 mm (0.60–0.63 mm); BL, 2.77 mm (2.71–2.82 mm); TL, 2.93 mm (2.86–2.99 mm).
Carapace (Fig.
Antennule (Fig.
Antenna (Fig.
Maxillule (Fig.
Maxilla (Fig.
Third maxilliped (Fig.
Pereiopods (Fig.
Pleon (Fig.
Uropod (Fig.
Telson (Fig.
Previous studies together with the present work have shown the five species of Heterocarpus with known larval morphologies to belong to three different species groups: H. abulbus lacking spines on the pleon, H. ensifer / H. hayashii / H. sibogae bearing posterior spines on the pleonites III and IV, and H. fascirostratus only has pleonite III bearing an overhanging spine. Nevertheless, the general appearances of the early zoeal stages are rather similar amongst these five species. Thus, the early zoeal morphology of H. fascirostratus also has the common characters of pandalid larvae, such as the eye peduncle narrowed at the base, carapace with two dorsal protuberances and the anteroventral margin bearing spines, antennule with the peduncle strongly concave and exopod bearing spatulate seta, the antenna with a segmented exopod, and the rostrum elongated in earlier stages (see
Characters | H. abulbus | H. ensifer | H. fascirostratus | H. hayashii | H. sibogae |
---|---|---|---|---|---|
(see |
(see |
(present study) | (see |
(see |
|
Carapace length (mm) | 0.53–0.58 | ~ 0.42 | 0.41–0.47 | 0.38–0.45 | 0.38–0.43 |
Anterolateral spines | 2 | 2 | 0 | 2 | 1 |
Antennule | |||||
Peduncle tubercle | 1 small tubercle | 2 small tubercles | 1 small tubercle | 1 small tubercle | 1 small tubercle |
Maxillule | |||||
Endopod setation | 5 | 6 | 6 | 5 | 5 |
Maxilla | |||||
Coxal endite setation | 9+4 | 9+4 | 9+4 | 8+3 | 9+4 |
Basial endite setation | 4+4 | 5+5 | 4+4 | 4+4 | 3+4 |
First maxilliped | |||||
Coxal setation | 5 | 7 | 5 | 4 | 4 |
Basial setation | 11 | 12 | 11 | 10 | 9 |
Second maxilliped | |||||
Coxal setation | 2 | 1 | 1 | 1 | 1 |
Basial setation | 8 | 9 | 9 | 9 | 6 |
Endopod setation | 3,1,2,5 | 3,1,2,4 | 3,1,2,5 | 3,1,2,5 | 2,1,2,4 |
Third maxilliped | |||||
Endopod setation | 2,1,2,4 | 2,1,2,4 | 2,1,2,3 | 2,1,2,4 | 2,1,2,4 |
Although
Table
Characteristics of the first three zoeal stages of Heterocarpus fascirostratus. Abbreviations: a, aesthetascs; b, basal spine; c, cuspidate seta; p, plumose seta; pa, pappose seta; pe, papposerrate seta; s, spatulate seta; sh, sparsely hardy plumodenticulate; sp, sparsely plumose seta; lob, lobed; t, stout seta; seg, segment/segmented; v, slender spine; x, simple seta.
Appendage | Stages | ||
---|---|---|---|
Zoea I | Zoea II | Zoea III | |
Carapace length (mm) | 0.41–0.47 | 0.48–0.51 | 0.60–0.63 |
Antennule | |||
Peduncle | 1 small tubercle+1p | 3p | 6p, 2x+7p |
Primary flagellum setation | 3a+1p+1s | 5a+1x | 1a+2p+1x |
Antenna | |||
Peduncle | 1b | 1b | 1b |
Endopod | 1p+1v | 1p+1v | 0 |
Exopod | 6-seg,11p+1x | 6-seg, 11p+1x | 4-seg, 14p |
Maxillule | |||
Coxal endite setation | 5p | 7(1x+1pa+5p) | 7(1x+1pa+5p) |
Basial endite setation | 2t+2x | 4c+3x | 5c+3x |
Endopod setation | 1x+1sp+1sh+3(1sh+2sp) | 1x+1sp+1sh+3(1sh+2sp) | 1x+1sp+1sh+3(1sh+2sp) |
Maxilla | |||
Coxal endite setation | 9p+4p (2pe+11p) | 11p+4p | 11p+4p |
Basial endite setation | 4p+4p | 4p+5p | 4p+5p |
Endopod setation | 5-lob, 3,2,1,1,2 | 5-lob, 3,2,1,1,2 | 5-lob, 3,2,1,1,2 |
Exopod setation | 5p | 5p | 7p |
First maxilliped | |||
Coxal setation | 2pe+3p | 7p | 7p |
Basial setation | 11p | 14p | 14p |
Endopod setation | 4-seg, 3,1,2,4 | 4-seg, 3,1,2,4 | 4-seg, 3,1,2,4 |
Exopod setation | 4p | 5p | 5p |
Second maxilliped | |||
Coxal setation | 1p | 1p | 1p |
Basial setation | 1pe+8p | 1pe+8p | 1pe+8p |
Endopod setation | 4-seg, 3,1,2,5 | 5-seg, 3,1,0,2,5 | 5-seg, 3,1,0,2,5 |
Exopod setation | 5p | 6p | 6p |
Third maxilliped | |||
Basial setation | 4p | 4p | 4p |
Endopod setation | 4-seg, 2,1,2,3 | 5-seg, 2,1,0,3,4 | 5-seg, 2,1,2,4,5 |
Exopod setation | 5p | 6p | 6p |
First pereiopod | Absent | Absent | Biramous bud |
Uropod | |||
Protopod | – | – | 0 |
Endopod | – | – | 2p |
Exopod | – | – | 6p |
Telson | 7p+7p | 8p+8p | (1x+7p)+(1x+7p) |
This work was supported by research grants from the Ministry of Science and Technology, Taiwan, and the Center of Excellence for the Oceans (National Taiwan Ocean University), which is financially supported by the Featured Areas Research Center Program within the framework of the Higher Education Sprout Project by the Ministry of Education (MOE) in Taiwan.