Hansenocaris undetermined

Olesen, Jørgen & Grygier, Mark J., 2024, Taxonomic diversity of marine planktonic ‘ y-larvae’ (Crustacea: Facetotecta) from a coral reef hotspot locality (Japan, Okinawa), with a key to y-nauplii, European Journal of Taxonomy 929 (1), pp. 1-90 : 26-27

Y-nauplius Type AC

Figs 2 , 9F–H

Type AC – Dreyer et al. 2023a: figs 4, 5a, c, tables s1–s2.

Material examined

JAPAN – Okinawa, Sesoko I. , laboratory pier, 26°38ʹ09.4ʺ N, 127°51ʹ55.2ʺ E • 1 LSN; 2018–2019 ( Tables 1 and S1 ).

Description

LAST-STAGE NAUPLIUS (LSN) . Lecithotrophic. Body spoon-shaped in dorso-ventral view; 1.8 times as long as wide; cephalic shield elliptical, with sharp discontinuity in body outline leading into trunk. In lateral view, trunk axis downturned ca 35° with respect to cephalic axis. Length ca 270 µm (ventral view in life, without dorso-caudal spine), greatest width 160 µm, greatest dorso-ventral thickness ca 115 µm. Labrum with goblet-shaped outline; in ventral view with free posterior margin extended into large medial spine, preceded by ca six large, equal-sized posteriorly directed spines on labral midline; pore pattern not examined. Caudal end attenuate, terminating in robust, 67 µm-long dorso-caudal spine set with smaller spines and accompanied ventrally at base by pair of triangular furcal spines ca 12 µm long; long axis of dorso-caudal spine upturned 25° with respect to trunk axis.

CYPRID VIEWED THROUGH CUTICLE OF LSN. Body weakly brownish, with thick strand of orange yolk granules in gut-like central tube. Other details not discernable in the single specimen examined.

Identification and variation

Recognizable by the combination of its general shape, size and spiny-keeled labrum.

Distribution

Japan (Sesoko Island, Okinawa).

Figures

Fig. 2. Y-naupliar (Facetotecta) diversity at Sesoko Island (Okinawa, Japan). A. Schematic life cycle of y-larvae (modified from Itô 1991; Glenner et al. 2008). B. Overview of 34 morphospecies of lecithotrophic last-stage y-nauplii obtained by laboratory rearing of earlier-stage nauplii collected in the plankton; three of them represent formally described species while 31 remain undescribed. C. Nine types of planktotrophic y-larvae, of which only Type A* is treated in detail in this paper. All photos in B and C are to the same scale. Figure also used in Olesen (2004). Examples of live video of most of the y-naupliar morphospecies can be seen at https://youtu.be/er0mYLswV-c and are also deposited at Figshare.com: https://doi.org/10.6084/m9.figshare.24953568.v1.

Fig. 9. Last-stage nauplii of four different morphospecies of y-larvae (Facetotecta) from Sesoko Island (Okinawa, Japan). A–C. Hansenocaris cristalabri Olesen & Grygier, 2022. D–E. Hansenocaris aquila Olesen & Grygier, 2022. F–H. Y-nauplius Type AC. I–N. Y-nauplius Type AH*. Shown either in life (A–B, F–H, I–J), as slide-mounted exuviae (D–E, K–N) or in SEM (C). Abbreviations: A1 = first antenna; A2 = second antenna; Md = mandible. A–E from Olesen & Grygier (2022).