Branchinecta serrata, Rogers, D. Christopher, 2006

Rogers, D. Christopher, 2006, Three new species of Branchinecta (Crustacea: Branchiopoda: Anostraca) from the Nearctic, Zootaxa 1126, pp. 35-51 : 46-49

Branchinecta serrata n. sp.

Figure 4

Types. Holotype, male, data: USA:WYOMING: Fremont County: Bull Canyon Pond, 42º 26’24”N, 108º 11’25”W, 15 May 1987, G. D. Langstaff, deposited: National Museum of Natural History, Washington D.C. USNM 1014989. Paratypes: same data as holotype, 4 females, 4 males, deposited: National Museum of Natural History, Washington D.C. USNM 1014990.

Material Examined. USA:WYOMING: Fremont County: Bull Canyon Pond, West Crooks Mountain Range, 15 May 1987, G. D. Langstaff. Bull Canyon Pond, West Crooks Mountain Range, 6 June 1987, G. D. Langstaff. Bull Canyon Pond, West Crooks Mountain Range, 25 June 1995, G. D. Langstaff.

Type Locality. The type locality is Bull Canyon Pond (42º 26’24”N, 108º 11’25”W), in the West Crooks Mountain Range, at 2192m elevation. The pool is in sagebrush uplands, on lands currently owned by the Bureau of Land Management. The land is used for livestock grazing and recreation.

Etymology. The specific epithet is from the Latin word “serra”, literally “a saw”. The gender is feminine.

Description. Male. ( Figure 4 B) Average length of preserved material 22mm. Head smooth, anterior­lateral corners not or slightly projecting over eyestalks. First antenna twice as long as eye plus stalk. First antenna 0.5–0.6 times the length of the second antenna proximal antennomere. Second antennae extending posteriorly to thoracic segment five or six.

Second antenna proximal antennomere sub­cylindrical, smooth, 2.5–3 times as long as broad. Lateral surface may bear a few small setae. Second antenna medial surface with distal half with a longitudinal ridge bearing a longitudinal row of flat, “saw­tooth” like spines; each spine is apically curved dorsally. Second antenna proximal antennomere lateral surface with small tubercle bearing two or less small spines. Second antenna distal antennomere 0.7–0.9 times the length of the proximal antennomere; distal antennomere flattened laterally, slightly arcuate medially, bearing a slight twist with the distal­medial surface directed anteriorly; distal antennomere tapering to a narrowly truncate apex.

Labrum smooth, truncated. Distal lobe smooth. Mandibles and maxilla 2 typical as for the genus. Maxilla 1 with endite bearing a transverse row of 25 to 30 long setae each with fine lateral setules all intermeshed. Setal apices curving anteriorly.

Thorax smooth. Praepipodites and exopodites typical for the genus. Thoracopod I with exopodite suboval, margined with fine setae. Endopodite broad, arcuate medially, with spines on anterior surface of apex ( Figure 3 C, D). Endites 1+2 and 3 with numerous long plumose setae, bearing numerous fine setules. Endite 4 and 5 with anterior and posterior setae stout. Endite 6 with stout setae.

Thoracopod V with Exopodite oval, margined with long fine setae with fine setules all along lateral margins. Endopodite elongated, slightly arcuate, curving toward the ventral surface of the animal. Lateral margin with stout, straight setae, medial margin with short medially curved setae. Endopodite apex with stout submarginal setae on anterior surface. Endites 1+2 and 3 with numerous long filiform setae, bearing numerous fine setules. Endite 4 with anterior long filiform setae, and posterior long filiform setae. Endite 5 with anterior and posterior long filiform setae. Endite 6 with long filiform setae.

Thoracopod XI with exopodite and endopodite oval, subequal in size and shape, margined in filiform setae. Endites 1+2 and 3 with spaced filiform setae. Endite 4, 5, and 6 with three long filiform setae each.

Genital segments slightly expanded; everted penes extending to middle of first abdominal segment; medial spurs truncated, blunt, curving posteriorly ( Figure 3 E); penile apices each with two “wart­like” mounds, one medial and one lateral; medial mound with 4–7 spines, lateral mound with 10–17 spines ( Figure 4 F).

Cercopods as typical for the genus.

Female. ( Figure 4 A) Average length of preserved material 20mm. Head smooth without projections. First antenna1.5 times as long as eye plus stalk. First antenna 0.5–0.6 times as long as second antenna. Second antenna 2.5 times as long as broad, subcylindrical, with apex produced acutely. Second antenna with a lateral tubercle bearing short hair­like spines, and a sub­apical anterior­medial tubercle bearing short hair­like spines.

Labrum, mandibles, and maxillae as in male.

Thoracic segments III–VII with dorsolateral sub­conical bosses ( Figure 4 G). Thoracopods as in male, except that the endopodites are blunt and triangular.

Brood pouch fusiform, extending up to telson ( Figure 4 G). Ovaries extending anteriorly to thoracic segment IX, posteriorly to abdominal segment IV or V.

Cercopods typical for the genus.

Comparisons. B. serrata most closely resembles B. paludosa (Müller, 1788) , and B. kaibabensis Belk and Fugate, 2000 . Male B. serrata are separated from B. paludosa by the slight laterally directed twist of the distal antennomere of the second antennae, versus a straight distal second antennal antennomere in B. paludosa ( Figure 5 A, B). B. serrata is readily separated from B. kaibabensis by the serrate ridge on the male second antennal medial surface (versus a row of spines in B. kaibabensis ), and the lack of a conical process topped by a pulvillus on the basomedial surface of the proximal antennomere of the second antenna. The everted penes of B. serrata have denticulate “wart­like” mounds on opposite sides of the penis, whereas in B. paludosa the “wart­like” mounds are both on the penal lateral surface ( Figure 5 C). Female B. serrata are separated from the other two species by the dorsal­lateral ornamentation of the female ( B. paludosa and B. kaibabensis females are smooth dorsally).

Distribution and Habitat. B. serrata is known only from the type locality in the Crookís Mountains, on the north side of the Great Divide Basin. The type locality is a high altitude, alpine pool.

Comments. Co­occurs with B. coloradensis . Branchinecta paludosa collections from Wyoming and adjacent Utah, Colorado and Montana ( Linder 1941; Horne 1967; Saunders et al. 1993; Stern and Belk 1999) in the collections of D. Belk and the USNM were examined and were verified to be B. paludosa .

IUCN Red List Status. B. serrata is so far only known to occur at the type locality. This species meets the IUCN red list criteria for designation as a CR B2ab species (IUCN 2000). That is to say, this taxon is critically endangered due to the population being limited to a single population that may be prone to the effects of human activities or stochastic events within a short period of time.

Figures

FIGURE 3. Apex of male right second antennae, distal antennomere, ventral view: left Branchinecta lateralis; right, Branchinecta constricta. The anterior side of the antennomeres is to the right.

FIGURE 4. Branchinecta serrata n. sp.; A) female, anterior view of left side of head; B) male, anterior view of left side of head; C) outline of exopodite and endopodite of male fifth thoracopod; D) detail of spines on anterior surface of endopodite of male fifth thoracopod; E) male genitalia ventral view; F) left pene, ventral view; G) female, lateral view. Scale bar for: A – D and F = 1.0 mm; E = 0.5 mm; G = 2.0 mm.

FIGURE 5. Branchinecta paludosa male. A) anterior view of left side of head; B) anteriomedial view of left second antenna; C) lateral view of everted pene. Scale bars for: A = 0.8 mm; B = 3.2 mm; C = 0.1 mm.