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

Y-nauplius Type L

Figs 2 , 15A–F

Type L – 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 • 8 LSN, 3 of which molted to cyprids; 2018–2019 ( Tables 1 and S1 ).

Description

LAST-STAGE NAUPLIUS (LSN) . Lecithotrophic. Body narrowly ovate, almost lanceolate in dorso-ventral view; about 1.8 times as long as wide; lateral margins without marked discontinuity in body outline between cephalic shield and trunk. In lateral view, trunk axis downturned 20° with respect to cephalic axis. Length 270–290 µm (of short form, see below) (without dorso-caudal spine), greatest width ca 150 µm, greatest dorso-ventral thickness ca 100 µm. Labrum produced as nearly equilateral sub-triangular elevation; divided into facets by cuticular ridges; pore pattern not examined in detail but three pores present in midline. Caudal end attenuate, terminating in ca 50–60 µm long, basally annulate but essentially smooth dorso-caudal spine, this being bent slightly upwards (5°) with respect to trunk axis and accompanied ventrally by pair of small, pointed furcal spines ca 6–7 µm long.

CYPRID VIEWED THROUGH CUTICLE OF LSN. Body overall with strong brown pigmentation. Telson portion of gut-like tube with orange yolk granules. Telson longer than wide and more than half as long as thorax.

Identification and variation

Recognizable by the combination of its general shape, small furcal spines and strong brown pigmentation. Four specimens are ca 270 µm long, but four others are 360–380 µm long with more robust dorso-caudal spines than the smaller ones, suggesting that this morphospecies may consist of two separate species.

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.