Branchinecta lateralis, Rogers, D. Christopher, 2006

Rogers, D. Christopher, 2006, Three new species of Branchinecta (Crustacea: Branchiopoda: Anostraca) from the Nearctic, Zootaxa 1126, pp. 35-51 : 36-41

Branchinecta lateralis n. sp.

Figures 1 , 3

Synonymy: Branchinecta campestris Lynch, 1960 ; Sublette and Sublette, 1967; Horne, 1974; Types: Holotype, male, data: USA: WYOMING; Sweetwater Co.: East Cyclone Rim, Big Bend Lost Creek Pond #1, 42º 12’ 41”N, 108º 07’ 01”W, 8 June 1987, G. D. Langstaff, deposited: National Museum of Natural History, Washington D.C. USNM 1014987. Paratypes: same data as holotype, 5 females, 5 males, National Museum of Natural History, Washington D.C. USNM 1014988.

Material examined: USA: COLORADO: Alamosa County: San Luis Lakes State Wildlife Area, site 115, 7 July 2003, Collector unknown, Det. D. C. Rogers. MONTANA: Teton Co.: Saline pools in the vicinity of Pishkun Reservoir, 4 July 1997, D. L. Gustafson, det. D. C. Rogers, DCR­ 552. WYOMING: Albany Co.: Laramie Basin, Pond XIV (Horne), 41º 07’32”N, 105º 43’15”W, 4 June 1988,G. D. Langstaff, (DB [Denton Belk’s collection number]­865). Carbon Co.: Long Pond, 3 June 1993, G. D. Langstaff, (DB­1237). Screeching Avocets Pond, 3 June 1993, G. D. Langstaff, (DB­1239). Yellow Pond, 3 June 1993, G. D. Langstaff, (DB­1240). Freemont Co.: Sweetwater Valley, Soda Lakes Far Eastern Pond, 13 km ENE of Jefferey City, 42º 32’ 25”N, 107º 40’ 21”W, 9 June 1989, G. D. Langstaff, (DB­950). Natrona Co.: Sweetwater Valley, Steamboat Lake Oxbow Pond, 2.7 km ESE of junction WY220 and Dry Creek Road, 42º 32’ 15”N, 107º 03’ 32”W, 7 June 1989, G. D. Langstaff, (DB­944). Sweetwater Valley, Steamboat Lake, 30 km W of Alcova and 1.2 km E of WY220 and Dry Creek Road junction, 42º 32’ 44”N, 107º 04’ 23”W, 7 June 1989, G. D. Langstaff, (DB­945). Sweetwater Co.: East Cyclone Rim, Big Bend Lost Creek Pond #1, 42º 12’ 41”N, 108º 07’ 01”W, 8 June 1987, G. D. Langstaff, (DB­810). East Cyclone Rim, Big Bend Lost Creek Pond #1, 42º 12’ 41”N, 108º 07’ 01”W, 5 June 1988, G. D. Langstaff, (DB­866).

Type Locality. Big Bend Lost Creek Pond #1, is on the south side of the East Cyclone Rim of Great Divide Basin in Sweetwater County, Wyoming, (42º 12’ 41”N, 108º 07’ 01”W). This basin literally is in the middle of the Continental Divide. The type locality pool is at an elevation of 2069 meters, and is a clay bottomed, desert playa pool. The pool is 300 meters across, and less than 5 meters deep, with whitish, turbid water.

Etymology. The specific epithet is from the Latin word for side “lateral”, and refers to the lateral projections of the female’s brood pouch, and the laterally directed apices of the distal segments of the male second antennae. The gender is feminine.

Description. Male. ( Figure 1 B) Average length of preserved material 22 mm. Head rounded, anteriolateral corners projecting slightly over compound eye peduncles. First antenna twice as long as stalked compound eye, with apex truncated, bearing four to six setae. Second antennae extending posteriorly to ninth thoracic segment.

Second antenna proximal antennomere subcylindrical, approximately five times as long as broad. Medial surface with small, scattered spines and fine chitinized papillae. Proximal antennomere with a posteriomedial proximal apophysis. Apophysis subcylindrical, tapering distally, with apex truncated. Pulvillus absent.

Second antennal distal antennomere subequal in length to proximal antennomere, laterally flattened, curving nearly 90° medially at the proximal fourth. Anterior and posterior margins expanded slightly in distal two­thirds, truncating towards apex. Posterior margin distal half, except apex, covered in chitinized papillae. Apex thickened, constricted, and abruptly bent 90° laterally, with tip curving slightly posteriad, tapering to a point ( Figure 3 ).

Labrum with chitinized papillae on ventral surface. Distal lobe smooth, rounded, and directed ventrally.

Mandibles and maxilla 2 typical for the genus. Maxilla 1 with an apical transverse row of hooked aciculate spines, palp with an apical transverse row of digitiform spines each with a hook shaped setaform distal portion.

Praeepipodites and epipodites typical for genus. Thoracopod I with exopodite and endopodite triangular. Endopodite bearing stout, curved, pectinate setae. Endite 1 + 2 and endite 3 with numerous long plumose setae. Endite 4 with anterior plumose setae and stout posterior setae. Endite 5 with plumose anterior setae and posterior pectinate setae. Endite six with anterior proximal setae plumose, distal setae pectinate, and posterior setae plumose. The setae of endites 1 + 2, 3, and 4, and the non­pectinate setae of endites 5 and 6, with distal 60% filiform with paired lateral spinules along their lengths.

Thoracopod V with exopodite with lateral margin straight, curving apically towards the rounded apex. Endopodite triangular, bearing stout, curved, pectinate setae. Endite 1 + 2 and endite 3 as in thoracopod I. Endite 4 with anterior and posterior setae plumose. Endite 5 with anterior plumose setae and posterior pectinate setae. Endite 6 with pectinate setae, the proximal four being half the length of the remaining distal setae. All plumose setae as described for thoracopod I.

Thoracopod XI with exopodite oval. Endopodite subtriangular bearing stout, curved, pectinate setae. Endite 1 + 2 as in thoracopod I. Endite 3 with two short, digitiform anterior setae, the posterior setae plumose. Endites 4 and 5 with anterior and posterior setae plumose. Endite 6 with all setae plumose.

Genital segments smooth. Penes each with basal portion bearing a large ventral subconical, ventroposteriorly directed lobe, and a ventromedial digitiform spur. Everted penes short, just reaching the first abdominal segment. Apices of everted penes bearing one lateral and one medial “wart”­ like mounds. Medial mound round, bearing ten to fifteen recurved spinules about one fourth as long as “wart”­ like mound. Lateral mound in the form of a longitudinal ridge, directed anteriorly, with 35 to 40 recurved spinules.

Cercopods as typical for the genus.

Female. ( Figure 1A ) Average length of preserved material 17 mm. Head without dorsal protuberances. First antennae sub­equal to second antennae. Second antennae smooth, with or without a small lateral protrusion. Distal fourth before apex bearing scattered setae. Apex subcylindrical, curving anteromedially, and tapering to a point. Anterior surface of head and labrum with fine spinules. Labrum, mandibles and maxillae as in male.

Thorax with rounded, dorsolateral bosses on all segments. Genital segments and first two abdominal segments with paired, angular dorsolateral bosses. Third abdominal segment with unpaired, angular, dorsolateral bosses. Thoracic and abdominal bosses are transverse, nearly bilobed in more posterior thoracic pairs, and densely papillose.

Thoracopods similar to male, save that the endopodites and epipodites ovate. Setation is similar to the male.

Brood pouch fusiform with short, subconical, papillose lateral out­pocketings in 64% of females. Brood pouch extending to post­genital abdominal segment five or six. Ovaries extend anteriorly into thoracic segment 10 or 9, and posteriorly into abdominal segment 4 or 5.

Cercopods as typical for the genus.

Cyst. Approximately 300 µm in diameter, with dense, small, shallow depressions 10 µm in diameter or less.

Differential diagnosis. Male Branchinecta lateralis are separated from all other reported Branchinecta species by the distal antennomere of the second antennae, which has the apex bent laterally (90º) and tapers to a posteriorly directed point ( Figure 1 B and D, 3).

Male B. lateralis most closely resemble Branchinecta campestris Lynch, 1960 and Branchinecta potassa Belk, 1979 ; however, the distal antennomeres of the second antenna of B. campestris males curve medially 30º at the basal third, and have the apices truncated and bent laterally 60º ( Figure 1 E, also see Figure 2 D in Lynch 1960). In B. lateralis the distal antennomere curves nearly 90º in its proximal fourth, and the apex of the second antennomere is more produced, and arcs posteriorly in ventral view, which is never found in B. campestris .

B. potassa are separated from B. lateralis primarily by the lack apophyses, and have the distal antennomere of the second antenna with the apex bent laterally 60º, apically acute, and with a medial “swelling” at the base giving the apex a “foot­like” shape in anterior view ( Figure 1 C).

Branchinecta readingi Belk, 2001 , males have the apex of the distal antennomere of the second antennae bent laterally approximately 75º ( Figure 1 F) and Branchinecta mackini Dexter, 1956 have the second antennal apices rounded ( Figure 1 G).

Furthermore, the penes of B. lateralis have a lateral and a medial “wart”­ like mound, whereas in B. campestris the penes sport a lateral and a dorsolateral “wart”­ like mound.

Branchinecta lateralis and B. campestris females share the lateral out­pocketings of the brood pouch. However in B. lateralis the out­pocketings (when present) are much smaller, and are never armed with one or more subtending spines as in some B. campestris (see Figure 5 in Lynch 1960). Furthermore, the brood pouch in B. lateralis extends to the fifth or sixth abdominal segment, whereas in B. campestris , the brood pouch extends to the fourth or fifth abdominal segment.

Mature female B. lateralis are separated from B. campestris and B. potassa by the dorsolateral, transverse, angular bosses on the thoracic (including genital) and first few abdominal segments. Female B. campestris and B. potassa have oval dorsolateral lobes on the pre­genital thoracic segments only. These structures are present only in mature animals. The first antennae of female B. potassa and B. mackini Dexter, 1956 are longer than the second antennae, whereas in B. lateralis and B. campestris the first and second antennae are sub­equal or shorter. Female B. lateralis are separated from all other reported Branchinecta species by the presence of lateral out­pocketings of the brood pouch.

Distribution and Habitat. B. lateralis has been collected from Colorado, Montana, Wyoming and Texas. Collection sites tend to be saline or clay playa type desert and grassland pools with clear to highly turbid water. B. lateralis often co­occurrs with the brine shrimp Artemia franciscana Kellogg, 1906 in similar situations as B. campestris ( Lynch 1960; Sublette & Sublette 1967; Horne 1974). Collections made by Sublette and Sublette (1967) and Horne (1974) of B. campestris from saline pools in Lynn County, Texas on the Llano Estacado were probably B. lateralis ( Lynch, 1960) , as were Broch’s (1969) and Hartland­Rowe’s (1966) Canadian collections. Unfortunately their material is not available for comparison. This species could potentially occur in eastern New Mexico and Colorado.

Comments. Lynch (1960) first commented on B. lateralis as a ëformí of B. campestris in the original description, but did not investigate the differences between the eastern and western forms further. Lynch mentions the defining characters for B. lateralis in material from Wyoming and Texas, however his material was limited and that which I examined at the Smithsonian and appears to have been not fully mature.

Branchinecta mackini , B. readingi , B. campestris , B. lateralis , and B. potassa are all closely related to each other based upon molecular analysis ( Fugate 1992), bear strong morphological similarity ( Belk 1979, 2000; this work), and all occur in temporary waters high in dissolved sodium salts ( Belk 1979; Broch 1969, 1989; Daborn 1977; Hartland­ Rowe 1966; Lynch 1960; McCarraher 1970). The species pairs with the greatest morphological similarity are B. mackini and B. readingi ( Belk 2000) , and B. campestris and B. lateralis (this work) with each species in each of the pairs separated geographically; B. mackini and B. readingi are separated by the continental divide ( Belk & Fugate 2000). B. campestris occurs west of the continental divide in Washington and Oregon, and west of the Sierra Nevada Mountains in California, whereas B. lateralis ranges east of the continental divide in Canada, Montana, Wyoming and Texas, and east of the Great Basin Desert in Utah and Colorado. B. potassa also occurs east of the continental divide in Nebraska, shares affinities with both species pairs ( Belk 1979; Fugate 1992).

The discovery of this new species represents another instance where more than one species of North American Branchinecta was being treated under a single name. In 1993, Fugate recognized that well­known Branchinecta populations in southern California, USA and Baja California, Mexico were not B. lindahli Packard, 1883 but a new species, B. sandiegonensis Fugate, 1993 .

Belk recognized B. readingi Belk, 2000 , as a distinct species, separate from B. mackini Dexter, 1956 . B. readingi had been studied intensively for years under the name of B. mackini ( Belk 2000) . Belk and Rogers (2002) found that a form of B. coloradensis Packard, 1874 with small apophyses, and the then undescribed B. oriena Rogers and Belk, 2002 , had been reported as B. dissimilis Lynch, 1972 .

IUCN Red List Status. This species is widespread, and does not appear to be in any immediate danger, and therefore is categorized as “Least Concern” (IUCN 2000). However, B. campestris is more restricted. Originally reported from several localities in Washington State, most of these populations, including the type locality are now under Grand Coulee Reservoir. Outside of Washington, this taxon is only reported from Lake Abert, Oregon ( Fugate 1992) and from Soda Lake, California ( Belk & Serpa 1992). Therefore B. campestris meets the International Union for the Conservation of Nature and Natural Resources (IUCN) red list criteria for designation as a VU D2 species (IUCN 2000). That is to say, B. campestris is vulnerable due to the population being very small and restricted, that may be prone to the effects of human activities or stochastic events within a short period of time.

Figures

FIGURE 2. Branchinecta constricta n. sp.; A – C) male left second antennal distal segment: A) lateral view; B) posterior view; C) medial view. D) Male, anterior view of left side of head; E) female, anterioventral view of left side of head; F) outline of exopodite and endopodite of female fifth thoracopod; G) outline of exopodite and endopodite of male fifth thoracopod; H) female, lateral view. Scale bar for: A – E = 0.3 mm, F and G = 1.0 mm, H = 5 mm.

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 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.

FIGURE 1. A) Branchinecta lateralis n. sp. female, anterior view of left side of head; B) Branchinecta lateralis n. sp. male, anterior view of left side of head. C – G) Branchinecta male left second antennal apices: C) B. potassa; D) B. lateralis n. sp.; E) B. campestris; F) B. readingi; G) B. mackini. Scale bar for: A and B = 1.0 mm, C – G = 2.4 mm.