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 : 35-37

Y-nauplius Type K

Figs 2 , 5D–F , 13F–J

Type K – 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 • 5 LSN; 1991–2005 • 27 LSN, 6 of which molted to cyprids; 2018–2019 ( Tables 1 and S1 ).

Description

LAST-STAGE NAUPLIUS (LSN). Lecithotrophic. Body widely ovate in dorso-ventral view; about 1.3 times as long as wide; cephalic shield very wide-ovate, with some discontinuity in body outline leading into trunk. In lateral view, trunk axis downturned ca 55° with respect to cephalic axis. Length 190–220 µm (ventral view in life, without dorso-caudal spine), greatest width ca 140 µm, greatest dorso-ventral thickness ca 65 µm. Labrum produced as sub-trapezoidal elevation with surface divided into facets by cuticular ridges; bearing total of five pores: three near midline posteriorly and one postero-lateral pair along left and right labral margins. Caudal end truncate, terminating in simple, ca 5 µm long dorso-caudal spine, this upturned ca 10° relative to trunk axis and flanked ventrally by pair of triangular furcal spines ca 10 µm long.

CYPRID VIEWED THROUGH CUTICLE OF LSN. Body generally transparent or weakly brownish. Cephalic shield often with a few small, transparent lipid vesicles along anterior margin. Posterior part of gut-like tube containing small, orange yolk granules. Telson twice as long as wide and significantly shorter than thorax, often not clearly demarcated from latter.

Identification and variation

Recognizable by the combination of its short, compact body, truncate caudal end and very small dorso-caudal spine. No significant variation recognized among specimens. Type K is the smallest lecithotrophic morphospecies treated in this work.

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. 5. Scanning electron micrographs of three significantly different kinds of last-stage lecithotrophic (non-feeding) y-nauplii (Facetotecta) illustrating key characters (general body size and shape, and morphology of labrum and caudal spines) used herein to separate and describe 34 y-naupliar morphospecies, with various measurements explained directly on the figure. A–B. Hansenocaris demodex Olesenet al., 2022, ventral view with detail of labral area.C. Hansenocaris cristalabri Olesen & Grygier, 2022 (holotype, NHMD), lateral view. D–F. Type K, lateral view with details of labrum and caudal spines. A–B from Olesen et al. (2022); C from Olesen & Grygier (2022).

Fig. 13. Last-stage nauplii of two different morphospecies of y-larvae (Facetotecta) from Sesoko Island (Okinawa, Japan). A–E. Y-nauplius Type X. F–J. Y-nauplius Type K. Shown either in life (A–B, F–H) or as slide-mounted exuviae (C–E, I–J). Abbreviations: A1 = first antenna; A2 = second antenna; Md = mandible.