Taxonomic diversity of marine planktonic ‘ y-larvae’ (Crustacea: Facetotecta) from a coral reef hotspot locality (Japan, Okinawa), with a key to y-nauplii
Author
Olesen, Jørgen
6B569425-6BE7-4A73-B165-87E0C097715A
Natural History Museum of Denmark, University of Copenhagen, Universitetsparken 15, DK- 2100 Copenhagen Ø, Denmark.
jolesen@snm.ku.dk&jolesen@snm.ku.dk&thecostracans@gmail.com
Author
Grygier, Mark J.
0A2FB16C-56B0-45E5-BB7B-61C3F0F7D46D
National Museum of Marine Biology & Aquarium, 2, Houwan Rd., Checheng, Pingtung 944401, Taiwan.
thecostracans@gmail.com&jolesen@snm.ku.dk&thecostracans@gmail.com
text
European Journal of Taxonomy
2024
2024-03-25
929
1
1
90
https://europeanjournaloftaxonomy.eu/index.php/ejt/article/download/2479/11077
journal article
10.5852/ejt.2024.929.2479
2118-9773
10876286
832192E7-A85A-4971-BA2F-D7420D299E8D
Y-nauplius
Type
W
Figs 2
,
11A–G
Material examined
JAPAN
–
Okinawa
,
Sesoko I.
, laboratory pier,
26°38ʹ09.4ʺ N
,
127°51ʹ55.2ʺ E
•
1 LSN
; 1991–2005
•
9 LSN
, 8 of which molted to cyprids; 2018–2019 (
Tables 1 and S1
).
Description
LAST-STAGE
NAUPLIUS (LSN)
. Lecithotrophic. Body spoon-shaped in dorso-ventral view; about 1.8 times as long as wide; cephalic shield circular/ellipsoidal, with discontinuity in body outline leading into trunk. In lateral view, body axis bent downwards 30° with respect to cephalic axis. Length ca 250 µm (without dorso-caudal spine), greatest width ca 130 µm, greatest dorso-ventral thickness ca 80 µm. Labrum balloon-shaped, with surface divided into facets by cuticular ridges, midline produced into keel-like elevation, and free posterior margin bearing small median spine; pores not examined. Caudal end attenuate, terminating in 75–80 µm long, slightly dorsally curved dorso-caudal spine bearing small spines; spine upturned ca 20° to trunk axis and accompanied ventrally at base by pair of ca 10 µm long triangular furcal spines.
CYPRID VIEWED THROUGH CUTICLE OF LSN. Body overall weakly brownish-pigmented. Cephalon most often with two to four lipid vesicles along anterior margin and one to three laterally. Telson slightly longer than wide and about half as long as thorax, often with pair of distinct lipid vesicles.
Identification and variation
Recognizable by the combination of its general body shape, the balloon-shaped, keeled labrum with a spine on the posterior margin and the large, rather straight dorso-caudal spine flanked by relatively robust furcal spines. Variation is seen among nauplii in the form of the dorso-caudal spine (either broad-based and more or less straight or more slender and curved); in the morphology of the posterior margin of the labrum (spine sometimes absent/diminutive, margin sometimes weakly serrate); and among unmolted cyprids in the number of lipid vesicles.
Distribution
Japan
(Sesoko Island,
Okinawa
).