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 : 44-46

Y-nauplius Type AP

Figs 2 , 17L

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

Material examined

JAPAN – Okinawa, Sesoko I. , laboratory pier, 26°38ʹ09.4ʺ N, 127°51ʹ55.2ʺ E • 1 LSN; 1991–2005 ( Tables 1 and S1 ).

Description

LAST-STAGE NAUPLIUS (LSN) . Lecithotrophic. Body shape not examined in dorso-ventral view, but cephalic shield apparently ovate with sharp discontinuity leading into trunk. In lateral view, trunk axis downturned 40° with respect to cephalic axis. Length 300 µm (lateral view of mounted exuvia) (without dorso-caudal spine), greatest width unknown, greatest dorso-ventral thickness ca 110 µm. Labrum strongly produced and divided into facets by cuticular ridges, with row of three successively longer spines on distal midline. Caudal end truncate, terminating in robust, conical, ca 30 µm long dorso-caudal spine, its axis upturned 35° relative to trunk axis. Thick, triangular furcal spines situated ventrally far from dorso-caudal spine, ca 5–10 µm long.

CYPRID VIEWED THROUGH CUTICLE OF LSN. No live specimen examined.

Identification and variation

Recognizable by its protruding labrum with three spines. This morphospecies resembles Type AF but is larger, slightly less stout and has a differently armed labrum (three spines instead of a single needle-like extension).

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).