Triops multifidus 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 : 340-343

Triops multifidus Korn sp. nov.

( Fig. 8 , 9 )

This species refers to the phylogenetic lineage ‘ Triops granarius 8’ (see Table 1 ).

Etymology. The name refers to the strongly increased number of swimming setae on the exopod of the 2nd antenna as seen in early instars. With a count of up to 15, the species shows a doubling or tripling of the usual set of 5–7 setae that has hitherto been reported for Notostraca . This name is formed as an adjective.

Type locality. Temporary pond located at the crossroads of road ‘N1’ and the road leading to Imjad , approx. halfway between Agadir and Tiznit, Morocco.

Type material. Holotype. Adult male, Museum of Zoology Dresden (MTD-Cru S 185, population no. 17, leg. Michael Korn 15 April 2005).

Other material examined. Population no. 8, 5ƋƋ, 1♀; population no. 9, 1♀; population no. 10, 6ƋƋ, 2♀♀; population no. 11, 2ƋƋ, 1♀; population no. 12, 5ƋƋ, 4♀♀; population no. 13, 5ƋƋ; population no. 14, 2ƋƋ, 1♀; population no. 16, 2ƋƋ, 2♀♀; population no. 17, 3ƋƋ, 3♀♀.

Diagnosis. Larva ( Fig. 8 E). Exopodite of the second antenna with 11–15 setae. Distal masticatory spine short (see Fig. 8 E).

Description. Holotype. Adult male. Body rings approx. 35.3 (i.e. 35 + 1 incomplete ring); total number of trunk limbs 44. 1st trunk limb ( Fig. 9 C): distal portion of the limb corm (see Fig. S. 2 in Korn et al. 2013) broadened, its maximum diameter 1.38 mm, length of exopodite 3.59 mm from anterior to posterior corner. 2nd trunk limb ( Fig.

8A): length of endopodite (excluding distal claw) 3.27 mm, length of distal claw 0.17 mm, length of largest digging spine 0.09 mm, length of 5th endite 3.76 mm. 10th trunk limb: 6 anterior meshwork spines on 3rd endite, 8 submarginal spines on 4th endite. Carapace ( Fig. 9 A): length of carapace 16.02 mm (measured along its median line), no dorsal carina spines, sulcus with 38 spines, length of nuchal organ 0.89 mm, mystax present. 2nd maxilla well developed ( Fig. 9 B). Telson ( Fig. 8 H): telson width 2.38 mm, length of largest furcal spines on each side of the telson 0.14 and 0.16 mm, 7 posterior marginal spines, i.e. 5 additional secondary posterior marginals developed, posterior marginal spines small, 4 median spines (1 of these very small), one additional spine approx. half-way between median and setal spines. Apodous abdominal segments approx. 10.4 (10.1 + 1 incomplete segment); numerous supernumerary spines, broad, scale-shaped.

Adult (and sub-adult) male ( Fig. 8 A, C, D, F–I, 9). 2nd trunk limb ( Fig. 8 A, D). ‘Proportional endopodite length’ 80.2–96.5% (mean=89.5%; SD=3.4; n=31); row of digging spines on endopodite of rather homogeneous appearance (see Fig. 8 A, D); ‘proportional length of digging spines’ on endopodite 3.52–4.76% (standardised values; mean=4.36%; SD=0.26; n=31); absolute size of largest digging spines on endopodite 54–115 µm (range of telson width in studied specimens 1.2–4.0 mm); distal claw of endopodite 2–6% the length of the endopodite (excluding the distal claw), stronger curved than is usual in the majority of specimens with its tip bent proximally giving a hook-shaped appearance (in 71% of the 31 specimens studied; this character expression was found in specimens of all 8 populations studied morphologically), distal claw thereby often reaching a position of approx. a right angle to the row of digging spines (see Fig. 8 D).

1st maxilla. The row of spines not confined to the centrally directed face but extending to a part of the ventral margin; spines on the ventral margin typically bent postero-ventrally.

2nd maxilla ( Fig. 9 B) well developed.

Carapace. Shape of nuchal organ as shown in Fig. 8 G; dorsal carina usually smooth ( Fig. 9 A), but a few dorsal carina spines may be present (1 to 2 recorded); terminal carina spine small, sometimes completely reduced; sulcus spines highly variable in size, from very prominent strongly chitinised structures to tiny, almost reduced bulges; mystax present.

Telson ( Fig. 8 H, I). ‘Proportional length of furcal spines’ 2.0–6.3% (mean=3.7%; SD=0.9; n=31).

Body rings. 33.0–37.0 (mean=34.9; SD=0.9; n=31).

Apodous abdominal segments 9.9–12.5 (mean=10.8; SD=0.6; n=31), with medium to high numbers of supernumerary spines.

Adult (and sub-adult) female: 2nd trunk limb ( Fig. 8 B). Digging spines on endopodite show a more regular pattern of size distribution than in preceding species, with large sturdy spines being separated by only few smaller spines, density of spines usually higher towards the distal claw.

1st maxilla as in males.

2nd maxilla well developed.

Carapace. Nuchal organ as shown in Fig. 8 G; dorsal carina smooth or with few dorsal carina spines (up to 3 recorded).

Body rings. 33.9–35.6 (mean=34.6; SD=0.5; n=15).

Apodous abdominal segments 7.2–9.1 (mean=8.3; SD=0.6; n=15) with medium to high numbers of supernumerary spines.

Differential diagnosis. The species is morphologically well differentiated from remaining species of Triops (except Triops maximus sp. nov.) by a strongly increased number of setae (11–15 instead of the hitherto reported 5– 7) on the exopodite of the second antenna in early larval stages. In adult females the largest digging spines in the 2nd trunk limb (usually located in the proximal half of the row of digging spines) are larger and/or broader than in females of other species (except Triops maximus sp. nov.) and digging spines show a lower density within the proximal half of the row of spines ( Fig. 8 B). In adult males, the 2nd trunk limbs show comparatively high values of ‘proportional endopodite length’ and, in the majority of specimens, a hook-shaped distal claw in the endopodite (though it should be noted that a similar morphology was also observed in ' T. granarius 1 and 5’, M.K. pers. obs.). The largest digging spines on the margin of the endopodite are relatively smaller than in Triops maximus sp. nov. (see Fig. 4C, D; Fig. 8 A, D). The species can be distinguished from Triops granarius s.s. by the slender elongated shape of the endopodites (with pointed tips) in mid-thoracic appendages (see Fig. 8 C), these are indicated to be more rounded in Triops granarius s.s. (see discussion section).

Range. Lowlands west of the High Atlas Mountains between Casablanca and Anti-Atlas Mountains, except for the area of the Chaouia plain inhabited by the preceding species.

Figures

FIGURE 8. Triops multifidus sp. nov. A, endopodite and 5 th endite of 2 nd trunk limb of the holotype (male), anterior view. B, endopodite of 2 nd trunk limb of a female of 2.3 mm telson width (from the type locality), anterior view. C, endopodite of 6 th trunk limb of a male of 2.3 mm telson width (from the type locality), anterior view. D, endopodite and 5 th endite of 2 nd trunk limb of a male of 2.2 mm telson width (from population 10), anterior view. E, second antenna of a second instar larva (from the type locality) as seen in a shed exuvium, ventral view. F, general aspect of adult male (showing a specimen of population 13). G, variation in the shape of the nuchal organ: examples (from left to right) from specimen of 2.2 (population 10) 1.8 (population 12, female) 2.4 (holotype) and 2.2 mm telson width (population 8). H, telson of the holotype, dorsal view. I, telson of a male of 2.3 mm telson width (from the type locality), lateral view.

FIGURE 9. Triops multifidus 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 (note that the epipodite is missing in this sample, possibly due to injury).