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 : 23-24

Y-nauplius Type H

Figs 2 , 8H–J

Type H – Dreyer et al. 2023a: figs 3, 5a, c, tables s1–s2. — Olesen et al. 2024: fig. 3a.

Material examined

JAPAN – Okinawa, Sesoko I. , laboratory pier, 26°38ʹ09.4ʺ N, 127°51ʹ55.2ʺ E • 5 LSN, 2 of which molted to cyprids; 2018–2019 ( Tables 1 and S1 ).

Description

LAST-STAGE NAUPLIUS (LSN) . Lecithotrophic. Body widely ovate in postero-dorsal view; about 1.2 times as long as wide; lateral margins tapering gradually towards caudal end with some discontinuity at posterior end of cephalic shield. In lateral view, trunk axis downturned a full 90° relative to cephalic axis. Length ca 350 µm (in lateral view following body bend, without dorso-caudal spine), greatest width 210 µm, greatest dorso-ventral thickness ca 100 µm. Labrum not examined. Body terminating in very short (8 µm), conical dorso-caudal spine and very long (85 µm), curved, ventrally directed (thus parallel to cephalic axis) furcal spines with small spine at base of each.

CYPRID VIEWED THROUGH CUTICLE OF LSN. Body weakly brown-pigmented. Many lipid vesicles present in dorsal part of cephalon, and dense concentration of yolk granules along entire length of central gut-like tube. Red pigmentation associated with yolk granules in gut-like tube. Lateral margins of cephalon with large, rectangular areas of black pigmentation. Telson short, less than half as long as thorax, with black pigmentation (possibly remnant from the LSN).

Identification and variation

Easily recognizable by the combination of its right-angle bend of the body, the very large, talon-like furcal spines (‘large talon’ in comparison to the most similar morphospecies, Types F and G), accompanied by small basal spines, red pigmentation associated with the yolk granules in the gut-like tube and the large areas of black pigmentation laterally on the margins of the cephalic shield.

Distribution

Japan (Sesoko Island, Okinawa), Taiwan (Green Island).

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