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 : 39-41

Y-nauplius Type AB

Figs 2 , 15G–M

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

Type AB – Dreyer et al. 2023a: figs 4, 5a, c, tables s1–s2. — Olesen et al. 2024: fig. 3b.

Material examined

JAPAN – Okinawa, Sesoko I. , laboratory pier, 26°38ʹ09.4ʺ N, 127°51ʹ55.2ʺ E • 3 LSN; 1991–2005 • 9 LSN, 7 of which molted to cyprids; 2018–2019 ( Tables 1 and S1 ).

Description

LAST-STAGE NAUPLIUS (LSN) . Lecithotrophic. Body dipper-shaped/ovate in dorso-ventral view, about 1.6 times as long as wide; cephalic shield widely ovate, with sharp discontinuity in body outline leading into trunk. In lateral view, trunk axis downturned ca 50° with respect to cephalic axis. Length 210–240 µm (ventral view in life, without dorso-caudal spine), greatest width ca 150 µm, greatest dorso-ventral thickness ca 90–100 µm. Labrum elevated, spatulate in outline; surface divided into facets by cuticular ridges; with free posterior margin; pore pattern not examined in detail but one in midline posteriorly and a pair in postero-lateral corners. Caudal end obtuse, terminating in small, robust broad-conical, ca 5–10 µm long dorso-caudal spine, its axis upturned 20–30° with respect to trunk axis, this spine being accompanied ventrally by pair of even smaller, broad-conical furcal spines approximately 2–3 µm long.

CYPRID VIEWED THROUGH CUTICLE OF LSN. Body overall weakly brownish, but telson with brown/black spots arranged in rows and circles and gut-like tube packed with yellowish and orange yolk granules. Cephalic shield with lipid vesicles along lateral margins (3–4 on each side) and frontal margin (about 4).

Identification and variation

Easily recognizable by the combination of its compact form, spatulate labrum, short dorso-caudal spine and the brown-spotted pigmentation of the developing cyprid’s telson. At least one specimen has a larger dorso-caudal spine than the others.

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. 15. Last-stage nauplii of two different morphospecies of y-larvae (Facetotecta) from Sesoko Island (Okinawa, Japan). A–F. Y-nauplius Type L. G–M. Y-nauplius Type AB. Shown either in life (A–C, G–J) or as slide-mounted exuviae (D–F, K–M). Abbreviations: A1 = first antenna; A2 = second antenna; Md = mandible.