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 : 44

Y-nauplius Type N*

Figs 2 , 17F–I

Type N* – Dreyer et al. 2023a: figs 3, 5a, c, tables s1–s2.

Material examined

JAPAN – Okinawa, Sesoko I. , laboratory pier, 26°38ʹ09.4ʺ N, 127°51ʹ55.2ʺ E • 1 LSN; 1991–2005 • 19 LSN, 8 of which molted to cyprids; 2018–2019 ( Tables 1 and S1 ).

Description

LAST-STAGE NAUPLIUS (LSN). Lecithotrophic. Body ovate in dorso-ventral view; about 1.6 times as long as wide; lateral margins with only little discontinuity in body outline between cephalic shield and trunk. In lateral view, trunk axis downturned 45° with respect to cephalic axis. Length 220–240 µm (without dorso-caudal spine), greatest width ca 150 µm, greatest dorso-ventral thickness ca 70 µm. Labrum produced as sub-trapezoidal elevation; surface divided into facets by cuticular ridges; pores not examined in detail but at least with one pore in posterior half of midline and additional pair of pores in postero-lateral corners. Caudal end nearly acute, terminating in ca 20 µm long, robust, conical dorso-caudal spine, axis of which upturned 25° with respect to trunk axis, and pair of triangular furcal spines ca 5 µm long.

CYPRID VIEWED THROUGH CUTICLE OF LSN. Body generally transparent but many specimens with brown telson. Cephalic shield typically with 2–3 pairs of transparent lipid vesicles along lateral margins and 1–2 smaller pairs along frontal margin. Telson triangular, approximately as long as wide, about half as long as thorax.

Identification and variation

Recognizable by the combination of its ovate/triangular shape in ventral view, degree of bending between cephalon and trunk (bent more than Type O*) and robust, conical dorso-caudal spine. Variation was noted in developing cyprids; a few lack brown coloration of the telson or have fewer vesicles than usual along the cephalic margin.

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).