Eocyzicus taiwanensis, Wang, 2017

Wang, Yung-Chuan, 2017, A new Eocyzicus (Branchiopoda: Spinicaudata) from Taiwan, with a review of the genus, Zootaxa 4318 (2), pp. 254-270 : 255-257

Eocyzicus taiwanensis n. sp.

( Figures 1 , 2 )

Type Material. Holotype (male) NMNS-7796-001, reared from sediment collected from type locality, and; Allotype (female) NMNS-7796-002, same data as holotype. Paratypes (one male and one female) NMNS-7796- 0 0 3, same data as holotype.

Material Examined. A total of 35 males and 15 females all from the type locality, cultured from eggs in dry sediment, which was originally collected 18 January 2016. Types were selected from animals seven days old. Specimens used for developmental series were collected on day 3, 4, 5, 6, and 7 from hatching.

Type Locality. ( Figure 2 F) Taiwan: Qigu District : 23°05'23.4"N, 120°06'21.9"E, Garlic fields on north side of highway 173 and east side of road 39, between Qigu and Annan.

Etymology. The specific epithet is in reference to this species being endemic to Taiwan, R.O.C. ( Republic of China).

Description. Male. ( Figure 1 C-G): head with blunt, conical occipital condyle ( Figure 1 C), slightly smaller than ocular tubercle, length subequal to basal width, occipital notch deep and broad. Head dorsal margin with shallow concavity between occipital condyle and ocular tubercle. Compound eyes large, fused, subcircular. Ocellus at rostral base, variable in shape. Rostrum broadly quadrate in lateral view, anterior margin length ~ 2x distance between ocular tubercle apex and occipital condyle apex. Fornix wide extending posteriorly to a point just posterior to ocular tubercle. Fornices joined at rostral apex. Rostrum without a spine.

First antennae ( Figure 1 F) length 1.5x head length, antennomeres with approximately 22 anterolateral major lobes, each directed anteriorly, and separated by minor lobes. Major lobes constricted basally, with a few scattered setae, distally with lobules, each lobule with an apical conical spine. Proximal most major lobe with two lobules, second major lobe with four lobules, subsequent lobes with four to seven lobules, with distal most major lobes with diminishing numbers of lobules. First antenna posterior and medial margins smooth.

Second antenna length ~ 2x head length. Second antennal peduncle one third head length, subcylindrical, bearing nine anterior transverse ridges and one distal oblique ridge, all margined with long simple setae. Second antennal anterior flagellum (exopod) with 16-20 (mean =17) flagellomeres, posterior flagellum (endopod) with 14- 21 (median = 17) flagellomeres. Flagellomeres each anteriorly with a transverse ridge, margined with three to twelve long spines and posteriorly with a longitudinal row of elongate natatory setae, increasing in length distally. Endopod flagellomeres may bear one or two anterior lobes, each with a transverse ridge.

Carapace ( Figure 1 G) elongate oval, with dense raised growth lines without spines, setae, or ornamentation. Dorsal margin rounded and with umbone prominent. Carapace average 9.9 (8.8-10.1) mm in length, by 6.0 (5.8- 6.3) mm in height (n= 10).

Trunk of 23 segments, each with pair of thoracopods, decreasing in size posteriorly from segments 3-14, with segments 15-23 thoracopods very reduced. First and second pairs modified as claspers.

Thoracopod I clasper ( Figure 1 D), with endopod (finger) basal 50% strongly arcuate, apically acute, with a single anterior, subapical spine, directed distally, overreaching apex. Endite V outgrowth (large palp) subclavate, slightly longer than endopod (finger), with apex (“gripping area”) broadly rounded and covered with fine denticles.

Endite IV (thumb) subcylindrical, pedunculate, with distal portion broad and apically flattened and covered in dense, stout spines, increasing in length posteriorly. Endite IV outgrowth (small palp) ovoid, directed distally, with anteriodistal surface covered in fine setae. Endite III angular, strongly projecting, and bearing a distomedial conical projection.

Thoracopod II clasper generally similar to thoracopod I clasper. Not appreciably varying.

Thoracopod III epipod smooth, subcylindrical. Exopod and flabellum narrowly triangular, margined with long plumose setae; lateral and medial setae plumose ventrally, distal setae plumose on both margins. Endopod subcylindrical, bearing dorso-distolaterally plumose setae. Endite V + outgrowth both cylindrical, elongate and lacking setae, apex rounded and bearing dense denticles. Endites IV, III, and II lamellar, rectangular, longitudinally arranged on limb medial surface, margined in dense plumose setae 3- 5x as long as the endite. Endite I falciform, strongly arcuate medially, dorsally with elongate plumose setae, ventrally with very dense, arcuate, pectinate setae.

Trunk segments ( Figure 1 E) 14 or 15 through 23 each bearing a dorsomedial projection. Segments 14-16 bear a single, elongate, narrow, straight medial spine. Segments 17-20 each bear a single, stout, posteriorly curving, spiniform projection. Segments 21-23 each bear a single, posterior lobiform projection, directed distally, and broadly oval or spiniform.

Telson ( Figure 1 E) dorsal posterior margin bearing a pair of large, posteriorly directed spines. Posterolateral ridges with 12 to 15 pairs of large, conical spines, with smaller conical spines interspersed. Telson posterolateral ridges each terminating distally as a stout, elongated, spiniform projection, slightly curved dorsally. Caudal filaments between the second to fifth pair of spines.

Cercopods stout, straight, with apical fifth curving dorsally, and exceeding telson distal elongated projections. Dorsomedial margin proximal four fifths fringed with ~25 plumose setae. Setal fringe terminates distally with a spine. Cercopod apex inerm.

Female. ( Figure 1 A, B) Generally similar to in male. Rostrum triangular ( Figure 1 A), subacute, with fornices thickening posteriorly. Thoracopods I and II not modified as claspers. Thoracopods VIII and IX with exopodites filiform ( Figure 1 B), extending dorsally for carrying eggs. Thoracopod VIII exopod dorsal extension 5x longer than thoracopod VII exopod dorsal lobe ( Figure 1 B). Thoracopod IX epipod dorsal extension 2x longer than thoracopod VII epipod dorsal lobe. Remaining thoracopods and thoracic segments as in male.

Trunk segments ( Figure 1 B) 14 or 15 through 23 each bearing a dorsomedial projection. Segments 14-16 bear a single, elongate, narrow, straight medial spine. Segments 17-23 each bear a single, stout, posteriorly curving, spiniform projection.

Telson ( Figure 1 B) dorsal margin straight, projecting posteriorly. Posterolateral ridges have ~50 uneven spines, smaller than in male. Cercopods extending slightly beyond telson distal elongated projections. Cercopods straight, with apex bent abruptly dorsally. Setae and spine arrangement as in male.

Egg. Smooth, spherical. Diameter 130-140 µm.

Differential diagnosis. Eocyzicus taiwanensis n. sp. is separated from all other Eocyzicus species by the form of the male clasper which has a large, conical spur on endite III, projecting distally, proximal to endite IV. Eocyzicus taiwanensis n. sp. shares the rounded carapace hinge line with the African E. irritans and E. latirostris , and the Iraq endemic E. spinifer . All other described species have a straight carapace hinge line. These species also share the single dorsomedial spiniform process on the posterior abdominal segments and the quadrate male rostrum with E. taiwanesnis n. sp. However, both E. irritans and E. latirostris females have a rounded rostrum as opposed to a triangular rostrum in E. spinifer and E. taiwanesnis n. sp. Eocyzicus spinifer is separated from all other Eocyzicus by the telsonic spines (which are multifid as opposed to unifid) and the form of the cercopods (which each has a dorsomedial longitudinal spine row instead of a setal row).

In addition to the form of the clasper, Eocyzicus taiwanensis n. sp. is separated from all other east Asian Eocyzicus by the rounded (as opposed to straight) carapace hinge line.

Ecology. Eocyzicus taiwanensis n. sp. is known only from the type locality; a series of fields, currently used to cultivate garlic and onions. The site lies just north of Tzeng-Wen Creek, which shaped the landscape in this area. The fields are flood irrigated, and actively ploughed, planted and harvested. The site is probably also subject to the application of fertilisers and pesticides. The fields are inundated either by irrigation or monsoonal rains from May through September or October, when air temperatures are between 29 to 32˚C. Active clam shrimp are found throughout the inundation period, becoming scarcer later in the season.

Conservation status. Eocyzicus taiwanensis n. sp. is known only from artificial habitats, specifically flood irrigated garlic fields. This species is threatened by possible changes in local agricultural practices, as well as pesticide applications. Additional surveys need to be conducted to ascertain the actual status of this species. As it currently stands, this species meets the criteria under the IUCN Red List ( IUCN 2001) as Critically Endangered (CR), with the area of occupancy less than 10 km 2, known only to exist at a single site (B2), and projected decline in extent of occurrence, occupancy and quality of habitat (ab).

Figures

FIGURE 1. Eocyzicus taiwanensis n. sp.: A) female head, left lateral view; B) female abdomen, telson, cercopods and egg bearing epipodital extensions; C) male head, left lateral view; D) male left clasper, thoracopod I, medial view; E) male abdomen, telson, and cercopods; F) male first antenna, peduncle and proximal portion of flagellum; G) male carapace outline, left valve, left lateral view. Scale bar = 2 mm for A and C, 5 mm for B and E, 0.8 mm for D, 0.5 mm for F, and 6 mm for G.

FIGURE 2. Eocyzicus taiwanensis n. sp. A-E) male head, left view, developmental sequence, from youngest to oldest, ages as follows: A) Day 3, B) Day 4, C) Day 5, D) Day 6, E) Day 7; F) type locality during flood irrigation, when adults shrimp were active.