Chirocephalus cf. bobrinskii ( Alcock, 1898 )

Dadykin, Ivan A., Karimov, Gafur N., Sinev, Artem Y., Volkova, Polina A. & Kotov, Alexey A., 2024, Branchiopoda (Crustacea: Anostraca and Diplostraca) diversity in Tajik Pamir and plain West and South Tajikistan, Zootaxa 5497 (1), pp. 1-32 : 16-19

Chirocephalus cf. bobrinskii ( Alcock, 1898)

( Fig. 3 ; Figs. 4C–F )

Description. Male. Body length 9.0–12.0 mm. First antenna long, unisegmented. Proximal segment of second antenna as long as first antenna, bearing two appendages ( Figs. 3A–C ). Frontal appendage bilobed; anterior lobe fan-shaped; posterior lobe elongate, subtriangular; both lobes with serrate outer margins ( Figs. 3B, C ). Terminal appendage palm-shaped, with 8–12 spine-like lobes ( Figs. 3A, B ). Inner surface of second antennal proximal antennomere with two outgrowths; basal outgrowth acute, as long as the distal segment of antenna; distal outgrowth short, blunt ( Fig. 3B ). Distal antennomere of antenna slightly to strongly arcuate ( Figs. 3D, E ), in adult males bearing several spines basally ( Fig. 3D ).

Eleven thoracic appendages of similar structure ( Figs. 3F, J ): two pre-epipodites; a smooth epipodite; exopodite and endopodite armed with a row of feathered setae; endites 3–5 subconical, bearing several anterior setae and a group of feathered posterior setae; endites 1 and 2 spatulate, bearing two anterior setae and a row of feathered posterior setae. Thoracic limb I with serrate pre-epipodites; endopodite subtriangular, its inner margin bears 6–11 blunt spines, each with a short seta at its base; exopodite two times shorter than the endopodite. Distal endites of thoracic limb I with a highly variable armature: endite 5 bears 2–5 anterior setae and two posterior setae; endite 4 bears 2–4 anterior setae and two posterior setae; endite 3 bears 2–4 anterior setae and three posterior setae. Endite 2 with two relatively long anterior setae; short seta is 0.6–0.7 times as long as the larger one; both setae feathered ( Fig. 3H ). Endite 1 with two short setae, the shorter one 2.5 times shorter than the longer one; the longer seta armed with unilateral setulae ( Fig. 3I ). Thoracic limb V similar to that in limb I but somewhat larger; endopodite of limb V ovoid.Thoracic limb XI with very short pre-epipodites, distal one tear-shaped, with an acute apex ( Fig. 3J ). Epipodite narrow, elongate, with an acute apex; exopodite and endopodite subequal in length; endopodite rounded.

Gonopods short, their basal portions closely spaced ( Fig. 3L ). Basal portion bears proximally a long slightly curved process; inner margin of process armed with 3–4 rows of short dense spines. A small finger-shaped process distally. Eversible portion bilobed, smooth.

Nine abdominal segments. Cercopods elongate (cercopod 1.5–3.0 times as long as the last abdominal segment), both outer and inner margins armed with feathered setae progressively elongating distally ( Fig. 3K ).

Female. Body length 8.9–11.5 mm. Thoracic limb armature similar to that of male. Nine abdominal segments, bearing a spine on lateral surface ( Figs. 3M, N ). Genital segment not doubled. Egg pouch short (as long as the abdominal segments I–IV), pear-shaped in ventral view with a maximum length in the anterior half ( Fig. 3M ). Two small lobes in the posterior end of the egg pouch ( Fig. 3N ). Cyst diameter 0.250 –0.335 mm, the surface with a sculpture of wrinkles and protuberances ( Fig. 3M ; Figs. 4C–F ).

Remarks. This is a new record for Tajikistan, their populations were found in several temporary water bodies in Pamir (loc. 30, 31, 36–38, 40–42, 51). Chirocephalus bobrinskii s. str. was previously reported from Afghanistan, Kyrgyzstan and Kazakhstan ( Alcock 1898; Rogers et al. 2019). A sibling species described from Kopetdag, Kazakhstan, C. turkestanicus Daday, 1910 , differs from C. bobrinskii in a shape of second antennomere ( Daday 1910; Rogers et al. 2019). The morphology of studied individuals corresponded to that in figures of C. bobrinskii in Alcock (1898), despite the author provided only a differential diagnosis. Several young males’ distal antennomere shape is similar to that of C. turkestanicus ( Fig. 3E ). However, all the observed males possessed a terminal appendage absent in the latter species ( Daday 1910; Alekseev & Tsalolikhin 2010). Also, a high number of individuals with asymmetrical cercopods and deformed endopodites was observed in the studied populations. Nevertheless, both С. bobrinskii and C. turkestanicus require a taxonomic revision, thus we propose C. cf. bobrinskii as a preliminary identification for the studied populations.

Figures

FIGURE 3. Chirocephalus cf. bobrinskii (Alcock, 1898) from the small lake in Alichur River valley, Tajik Pamir (loc. 41). A–L, male.A, head, anterior view (frontal appendage not shown). B, second antenna, inner view. C, frontal appendage, anterior view. D, E, terminal segment of second antenna, anterior view. F, thoracic limb I, anterior view. G, endopodite of thoracic limb I. H, I, anterior setae of thoracic limb V. J, thoracic limb XI, anterior view. K, cercopod, dorsal view. L, gonopods, ventral view. M, N, female, egg pouch. M, ventral view. N, right lateral view.Abbreviations: bp, basal portion of gonopod; c, cyst; e1–5, endites; en, endopodite; ep, eversible portion of gonopod; epp, epipodite; ex, exopodite; fa, frontal appendage; pep, pre-epipodite; sg, shell gland; ta, terminal appendage.

FIGURE 4. Cysts of Anostraca from Tajik Pamir (SEM). A, B, Artemia cf. sinica Cai, 1989 from Lake Chukurkul (loc. 34). C–F, Chirocephalus cf. bobrinskii (Alcock, 1898). C, puddle in Alichur River valley (loc. 30). D, puddle in Lake Zorkul Valley (loc. 36). E, F, puddle in South Toguzbulak River valley (loc. 51).