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 : 43-44

Y-nauplius Type AF

Figs 2 , 17A–E

Undescribed form-taxa of lecithotrophic y-larvae – Grygier et al. 2019 pars: 1228, fig. 3f.

Type AF – Dreyer et al. 2023a: figs 4, 5a, c, tables s1–s2. — Olesen et al. 2024: fig. 2c.

Material examined

JAPAN – Okinawa, Sesoko I. , laboratory pier, 26°38ʹ09.4ʺ N, 127°51ʹ55.2ʺ E • 2 LSN; 1991–2005 • 12 LSN, 8 of which molted to cyprids; 2018–2019 ( Tables 1 and S1 ).

Description

LAST-STAGE NAUPLIUS (LSN) . Lecithotrophic. Body short, with unusually bloated trunk region; widely ovate in dorso-ventral view; about 1.35 times as long as wide; cephalic shield very widely ovate, with sharp discontinuity in body outline leading into trunk. In lateral view, trunk axis downturned ca 60° with respect to cephalic axis. Length 210–240 µm (ventral view in life, without dorso-caudal spine), greatest width ca 170 µm, greatest dorso-ventral thickness ca 130 µm. Labrum conical in lateral view and drawn into hypodermic-needle like distal extension; other features of labrum not examined. Caudal end truncate, terminating in broad, conical, ca 40 µm long dorso-caudal spine directed postero-dorsally, with its axis upturned ca 50° from trunk axis, and ventral pair of triangular furcal spines ca 5 µm long, these being widely separated both from each other and from dorso-caudal spine, sitting on distinct, conical bases.

CYPRID VIEWED THROUGH CUTICLE OF LSN. Overall weakly brownish, but more distinctly brown in telson region. Gut-like tube filled with yolk granules; some of these partly brown or black but those in telson often colored orange; some specimens with additional lipid vesicles spread out within cephalon and smaller vesicles behind compound eyes. Telson small.

Identification and variation

Easily recognizable by its bloated or blimp-like form, conical labrum with hypodermic-needle-like extension and extremely robust, conical dorso-caudal spine. Some variation exists in the size of the dorso-caudal spine and its angle of orientation with respect to the trunk axis.

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. 17. Last-stage nauplii of three different morphospecies of y-larvae (Facetotecta) from Sesoko Island (Okinawa, Japan). A–E. Y-nauplius Type AF. F–K. Y-nauplius Type N*. L. Y-nauplius Type AP. Shown either in life (A–C, F–G) or as slide-mounted exuviae (D–E, H–L). Abbreviations: A1 = first antenna; A2 = second antenna; Md = mandible. L from Grygier et al. (2019).