Eulimnadia graniticola

Rogers, Christopher, Weeks, Stephen C. & Hoeh, Walter R., 2010, A new species of Eulimnadia (Crustacea; Branchiopoda; Diplostraca; Spinicaudata) from North America, Zootaxa 2413, pp. 61-68 : 63-66

Eulimnadia graniticola species novae

( Figure 1 )

Etymology: The name “ graniticola ” comes from the word “granite”, referring to the rock type that the type locality is situated in, and the Latin suffix “-cola”, which means “dweller”.

Types: Holotype: female/ hermaphrodite, data: USA: Georgia: Dekalb County: Stone Mountain: rock outcrop depressional temporary wetland, ~ 500m elevation, 29 August 2005, T. Sanderson, R. Posgai and S. Weeks, deposited Los Angeles County Museum, LACM type number CR 2005-038.1. Allotype: same data as holotype, deposited LACM CR 2005-038.2. Paratypes: same data as holotype, 9 female /hermaphrodites, 3 males, deposited LACM CR 2005-038.3. Paratypes: same data as holotype, 5 females / hermaphrodites, deposited D. C. Roger’s collections (DCR accession number 707).

Additional Material Examined: USA: Florida: Monroe County: Upper Matecumbe Key, rainwater pool, 11 female / hermaphrodites, 17 April 2007, L. Hribar. Lower Matecumbe Key, rainwater pool, 1 female / hermaphrodite, 17 April 2007, L. Hribar. Windley Key, rainwater pool, 14 female / hermaphrodites, 1 male, 17 April 2007, L. Hribar. Vaca Key rainwater pool, 2 female / hermaphrodite, 31 October 2007, L. Hribar. All additional material deposited at Virginia Museum of Natural History.

Description. Female: Head with ocular tubercle prominent, overreaching rostrum ( Figure 1 A). Head broader than ocular tubercle. Contiguous compound eyes large, subcircular to reniform, 0.75 times the width of the ocular tubercle. Ocular angle smoothly arcuate to rostrum. Naupliar ocellus subtriangular, lying just posterior to, or slightly above and posterior to rostrum. Rostrum pronounced, broadly rounded to truncated, 0.5 to 0.3 times the width of the ocular tubercle ( Figure 1 C, D). Ventral surface of rostrum even with ventral surface of head. Dorsal organ prominent, slightly pedunculate, directed anteriorly, hemispherical, with anterior face flat and circular.

First antennae well below and posterior to rostrum, pedunculate, and 0.5 times as long as second antennal peduncle ( Figure 1 A). Second antennae 2 to 2.5 times as long as head. Second antennal peduncle subequal in length to head, slightly geniculate, and bearing dorsal transverse rows of spiniform setae. Second antennal anterior flagellum (exopod) with six (right) or seven (left) annulations, each dorsally with a transverse row of spiniform setae. Posterior flagellum (endopod) with four (right) or five (left) such annulations, and about 0.17 times longer than anterior flagellum. Both flagellae with a ventral, longitudinal row of long plumose natatory setae, about 0.6 times the length of the peduncle.

Carapace broadly oval, with three or four well separated, shallowly impressed, obscure growth lines, with the subapical growth line most salient ( Figure 1 F). Adductor muscle scar broad, oblong, about twice as long as wide.

Fourteen to sixteen pairs of thoracopods, with tenth and eleventh pairs bearing dorsally elongated flabellae for carrying the eggs ( Figure 1 B).

Telson with ten to thirteen pairs of posterior spines borne on the posteriolateral ridges ( Figure 1 B). Caudal filaments originating on the posterior surface between the ridges at or about the fourth pair of spines. Telson posteriolateral ridges each terminating in an elongated spiniform projection, 2.5 to 3.0 times as long as the nearest spines. Cercopods projecting posteriorly from the ventral surface of the telson, each subtended by a anteriobasal spiniform projection, directed posteriolaterally over the base of the cercus. Cerci are subequal in length to the telson, and are margined medially with a longitudinal row of long plumose setae that extends from the base distally to the point where the cercus abruptly tapers to the apex.

Male: Head as in female, except rostrum pronounced, truncated, 0.3 to 0.2 times the width of the ocular tubercle ( Figure 1 E). Ventral surface of rostrum even with ventral surface of head. First antennae well below and posterior to rostrum, pedunculate, and subequal in length to second antennal peduncle. antennae approximately 2.5 times as long as head, and otherwise as in female. Carapace broadly oval (although maybe slightly acute anteriorly, Figure 1 G) and otherwise as in female.

Sixteen pairs of thoracopods, with first and second pairs modified as claspers to amplex the female. First thoracopod (terminology follows McLaughlin, 1980) with endite I and II each bearing a longitudinal row of aciculate setae. Endite III without setae. All three endites slope out to the endite from the thoracopod, with an abrupt declivity distally. Endite IV broad, transverse, grasping surface with numerous flat topped denticles, and a distal fringe of spiniform setae. Endite IV with palp pedunculate, slightly longer than endite, and bearing a few short apical spiniform setae. Endite V broadly arcuate proximally, distal portion parallel to basal portion, grasping surface with numerous ventral flat topped denticles, and a subapical, suctorial organ on posterior side of endite apex. Endite VI elongate, slightly arcuate in proximal segment, and straight in distal segment. Proximal segment attaining the distal most portion of the arc of endite V, and bearing an anteriapical transverse row of spines. Endite VI distal segment apex broader than remainder of endite, and bearing several short aciculate setae apically, and three to five arcuate spines subapically posteriorly. Exopod filiform, not attaining endite IV. Epipod broadly ovate. Second thoracopod similar to first. Last seven to nine thoracic segments each with a dorsal transverse row of spines, directed posteriorly, and originating submarginaly.

Thoracic segments and telson as in female.

Egg: Subspherical, ~200 μm in diameter. Surface with numerous, narrow, rectilinear paired polygons, ~ 100 μm in length, ~10 μm wide, with truncated ends. Spaces between polygons produced as rounded ridges. Spines or other projections absent.

Differential Diagnosis: Eulimnadia graniticola n. sp. is a typical member of the genus Eulimnadia as defined by Rogers, et al. (in review). Specifically it is a typical limnadiid clam shrimp, with the occipital notch and condyle absent; frontal organ present and pedunculate; first antennae not segmented; carapace with dorsal margin smooth, lacking carinae, with an arcuate hinge line, rarely sinuate, umbone absent; male first two thoracopods with endite five bearing an apical suctorial organ; telson with a posteriorly directed spiniform projection present on the ventroposterior angle, anteriad of the cercopod base; caudal filament borne on a projecting mound; eggs spherical to subspherical or cylindrical to cylindrical with one end larger than the other, with large rectilinear polygonal depressions separated by ridges, occasionally with lamellar or setaform spines at polygon ridge line confluences (Belk, 1989; Martin, 1989; Martin and Belk, 1989; Rogers et al., in review; Rabet, in press).

Unfortunately due to the tremendous morphological plasticity in the genus Eulimnadia , an adequate differential diagnosis of the adults is not possible at this time. This inherit plasticity in the Spinicaudata has frustrated many workers ( Straškraba 1966; Sissom 1971; Belk 1989; Martin and Belk 1989; Martin 1989), however a certain amount of morphological stability in the eggs has been shown to be useful in defining Eulimnadia species (Belk 1989; Martin and Belk 1989), or at least species groups ( Brendonck et al. 1990). With this in mind, based on egg morphology, we can say that E. graniticola is most similar to E. follisimilis . Both species bear subspherical, spineless eggs, with linear, often paired, polygons, however the linear polygons in E. follisimilis are simple slits, whereas in E. graniticola the polygons are rectilinear, about one tenth as wide as long. All other American Eulimnadia species with subspherical eggs have subcircular, unpaired polygons (i.e.; E. brasiliensis , E. ovilunata , E. ovisimilis , E. diversa ), or if paired rectilinear polygonal depressions are present, the eggs are much more angular, with the angles produced as spiniform structures (i.e.; E. astrova ).

Eulimnadia graniticola is separated from all other Eulimnadia species by the basic subspherical form of the egg. All remaining Eulimnadia species have a strongly angular, cylindrical or subcylindrical egg form (Belk, 1989; Martin, 1989; Martin and Belk, 1989; Rogers et al., in review; Rabet, in press).

Reproduction: Among the 11 families that successfully hatched, both all “female” and mixed cohorts were noted ( Table 1 ). Because these families were produced by isolated “females,” there was no possibility of male parentage, and thus these isolated “females” were either parthenogenetic females or self-compatible hermaphrodites. To distinguish between these alternatives, we examined the sex ratios among the families with males: these families produced an average of 18% males and 82% “females.” The sex-determining mechanism found in Eulimnadia texana predicts that selfing hermaphrodites that are “amphigenic” will produce 75% hermaphrodites and 25% males ( Sassaman and Weeks 1993). The male-producing “females” in the current comparisons did not significantly deviate from this expectation (χ2 (2) = 2.45; 0.3 <P <0.2), and thus we inferred that E. graniticola is androdioecious, with mixtures of males, monogenic (M) hermaphrodites and amphigenic (A) hermaphrodites ( Table 1 ). Among the 11 isolated hermaphrodites, 4 (36%) were found to be monogenic and 7 (64%) were found to be amphigenic ( Table 1 ).

Figures

FIGURE 1. Eulimnadia graniticola n. sp. A) Holotype: head, right lateral view, scale bar = 2 mm. B) Holotype: posterior trunk and telson, right lateral view, scale bar = 2.9 mm. C & D) variation in female / hermaphrodite head morphology. E) Allotype: head, right lateral view. F) Holotype: carapace outline, right lateral view, scale bar = 5.8 mm. G) Allotype: carapace outline, right lateral view, scale bar = 5.8 mm. CF = caudal filament; T = telson; AI = first antenna; AII = second antenna; AF = anterior flagellum; PF = posterior flagellum; FG = frontal organ; OT = ocular tubercle; NE = naupliar eye; R = rostrum.