Triops maximus Korn

Korn, Michael & Hundsdoerfer, Anna K., 2016, Molecular phylogeny, morphology and taxonomy of Moroccan Triops granarius (Lucas, 1864) (Crustacea: Notostraca), with the description of two new species, Zootaxa 4178 (3), pp. 328-346 : 338-340

Triops maximus Korn sp. nov.

( Fig. 6 , 7 )

This species refers to the phylogenetic lineage ‘ Triops granarius 10’ (see Table 1 ).

Etymology. The name refers to the generally large size reached by adults. This name is formed as an adjective.

Type locality. Thiéry’s temporary pond no. 7 ( Thiéry 1991) or ‘C7’ ( Thiéry 1987), Chaouia plain, south of Casablanca, Morocco.

Type material. Holotype. Adult male, Museum of Zoology Dresden (MTD-Cru S 184, population no. 3, reared from sediments collected 11 April 2005).

Other material examined. Population no. 1, 1♂; population no. 2, 1♂; population no. 3, 12♂♂, 5♀♀; population no. 5, 1♂; population no. 6, 4♂♂; population no. 7, 1♂; population no. 18, 6♂♂, 8♀♀.

Diagnosis. Larva ( Fig. 6 A): exopodite of the second antenna with 10–12 setae. Distal masticatory spine short (see Fig. 6 A).

Description. Holotype. Adult male. Body rings 35; total number of trunk limbs 45. 1st trunk limb ( Fig. 7 C): distal portion of the limb corm (see Fig. S. 2 in Korn et al. 2013) strongly broadened, its maximum diameter 1.73 mm; exopodite large, 4.35 mm from anterior to posterior corner. 2nd trunk limb ( Fig. 6 E): length of endopodite (excluding distal claw) 3.02 mm; length of distal claw 0.13 mm; length of largest digging spine 0.14 mm; length of 5th endite 3.78 mm. 10th trunk limb: 8 anterior meshwork spines on 3rd endite; 11 sub-marginal spines on 4th endite. Carapace ( Fig. 7 A): length of carapace 17.74 mm (measured along its median line); no dorsal carina spines present; sulcus with 32 spines; no terminal carina spine expressed; length of nuchal organ 0.58 mm; mystax present. 2nd maxilla well developed, with long terminal setae ( Fig. 7 B). Telson ( Fig. 6 F): telson width 2.24 mm; length of largest furcal spines on each side of the telson 0.19 and 0.18 mm; 2 posterior marginal spines, i.e., no additional secondary posterior marginals developed; marginal spines of medium size, 7 median spines (1 of these very small). Apodous abdominal segments 10.4, with only few supernumerary spines expressed.

Adult (and sub-adult) male ( Fig. 6 B–G, 7). 2nd trunk limb. ‘Proportional endopodite length’ 65.1–83.8% (mean=75.0%; SD=4.7; n=27); digging spines on endopodite show a rather regular pattern of a few strongly enlarged heavily chitinised spines each separated by several considerably smaller spines ( Fig. 6 E), giving a ‘wide-spaced’ appearance of digging spines at lower magnification; ‘proportional length of digging spines’ on endopodite 5.35– 7.49% (standardised values; mean=6.08%; SD=0.51; n=27); absolute size of largest digging spines on endopodite 77– 235 µm (range of telson width in studied specimens 1.4–4.3 mm); distal claw of endopodite 1–8% the length of the endopodite (excluding the distal claw), slightly curved to almost straight.

2nd maxilla ( Fig. 7 B) well developed, with long terminal setae.

Carapace. Nuchal organ as shown in Fig. 6 C; dorsal carina smooth (no dorsal carina spines recorded, Fig. 7 A); terminal carina spine frequently lacking; sulcus spines usually large ( Fig. 7 A) but may be reduced to tiny bulges; mystax (as defined by Obregón-Barboza et al. 2007) present.

Telson ( Fig. 6 F, G). ‘Proportional length of furcal spines’ 5.4–14.3% (mean=8.6%; SD=2.0; n=27).

Body rings 34.0–39.0 (mean=35.8; SD=1.2; n=27).

Apodous abdominal segments 9.4–11.8 (mean=10.2; SD=0.6; n=27), supernumerary spines of highly variable number, from complete absence to high numbers (with up to 97 supernumerary spines / segment recorded).

Adult (and sub-adult) female. 2nd trunk limb. Digging spines on endopodite show a rather regular pattern of size distribution as in males.

2nd maxilla as in males.

Carapace. Shape of nuchal organ as shown in Fig. 6 C; dorsal carina smooth (no dorsal carina spines recorded); terminal carina spine expressed in most specimens; sulcus spines usually large.

Body rings 34.0–36.5 (mean=34.8; SD=0.9; n=13).

Apodous abdominal segments 8.1–8.9 (mean=8.4; SD=0.2; n=13); supernumerary spines of variable number, from complete absence to medium numbers.

Differential diagnosis. The species is morphologically well differentiated from remaining species of Triops by the increased number of setae (10–12 instead of the hitherto reported 5–7) on the exopodite of the second antenna in early larval stages and by the peculiar arrangement and size of digging spines on the margin of the endopodite of the second trunk limb (and of following trunk limbs) in sub-adult and adult stages (see Fig. 6 D, E; the unequal size of these spines was already reported by Pérès 1939 and shown in his Fig. P, plate I). The latter character also allows a clear separation from the type of Triops granarius (see fig. 2D in Gauthier 1934). In addition the endopodite of the mid-thoracic appendages is of a more rounded shape in Triops granarius s.s. (see discussion section).

Range. Chaouia plain and foothills of Anti-Atlas Mountains north-east of Guelmim.

Figures

FIGURE 6. Triops maximus sp. nov. A, second antenna of a second instar larva (from the type locality) as seen in a shed exuvium, ventral view. B, general aspect of adult male (showing a specimen of population 7). C, variation in the shape of the nuchal organ: examples from specimen of 3.0 (above, left: population 2) 2.3 (below, left: population 18) and 2.2 mm telson width (center, right: holotype). D, endopodite of 6 th trunk limb of a male of 2.3 mm telson width (from the type locality), anterior view. E, endopodite and 5 th endite of 2 nd trunk limb of the holotype (male), anterior view. F, telson of the holotype, dorsal view. G, telson of a male of 2.3 mm telson width (population 18), lateral view.

FIGURE 7. Triops maximus sp. nov. A, carapace of the holotype (male), right lateral view. B, second maxilla of the holotype, anterior view. C, detail of the 1 st trunk limb of the holotype, anterior view.