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 : 30-32

Y-nauplius Type AD

Figs 2 , 11H–M

Type AD – 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 • 10 LSN, 3 of which molted to cyprids; 2018–2019 ( Tables 1 and S1 ).

Description

LAST-STAGE NAUPLIUS (LSN). Lecithotrophic. Body short-handled spoon-shaped in dorso-ventral view; about 1.6 times as long as wide; cephalic shield ovate, with some discontinuity in body outline leading into trunk. In lateral view, trunk axis bent downwards ca 15–20° with respect to cephalic axis. Length 300–340 µm (ventral view in life, without dorso-caudal spine), greatest width 190–200 µm, greatest dorso-ventral thickness ca 100 µm. Labrum hoe-shaped in ventral view with free posterior margin; surface divided into facets by cuticular ridges; posterior half of labral midline with keel-like elevation extending into postero-median spine; pores not examined in detail, but one pair certainly present in left and right postero-lateral corners. Caudal end attenuate, terminating in ca 35 µm long, dorsally inclined dorso-caudal spine upturned ca 35° relative to trunk axis and accompanied ventrally at base by pair of broad-triangular furcal spines ca 10 µm long.

CYPRID VIEWED THROUGH CUTICLE OF LSN. Body overall weakly brownish-pigmented with more distinct brown/black pigmentation in labral region, lateral margins of thorax, and telson. Cephalon with about five lipid vesicles along anterior margin, about three along each lateral margin.

Identification and variation

Easily recognizable by the combination of its general body shape, the large number of lipid vesicles along the cephalic shield’s margin, the hoe-shaped labrum and the relatively short and broad dorso-caudal spine.

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