Eocyzicus Daday, 1915

Wang, Yung-Chuan, 2017, A new Eocyzicus (Branchiopoda: Spinicaudata) from Taiwan, with a review of the genus, Zootaxa 4318 (2), pp. 254-270 : 260-261

Eocyzicus Daday, 1915

= Caenestheria Daday, 1913 nomen nudum

= Eocyzicus Daday, 1913 nomen nudum

= Caenestheria Daday, 1915 (pro partim) fide Brtek et al., 1984, Rogers et al., this paper

Diagnosis. Populations composed of males and females; amplexus is transverse, and venter to venter.

Head with rostrum usually sexually dimorphic, and changing shape with age. Rostrum subtriangular (usually females) to subquadrate (usually males) or rounded. Rostrum without or with (usually females) an apical spine. Angle between rostrum and frons 170 to 180. Occipital notch very shallow and broad or obsolete. Occipital condyle low, rounded or obsolete, length half or less basal width.

Carapace valve length ~1.5 times valve height (hinge to ventral margin). Carapace growth line intervals smooth or ornamented (scarring from algae often mistaken for ornamentation). Carapace typically brown, occasionally black, sometimes with marginal setae.

Clasper endopod apically unarmed, or with a few setae or ventral scales. Endite IV broadly transverse to cylindrical, bearing a dense, apical field of short spiniform setae.

Thoracic segments smooth or with a central dorsoposterior projection and/or set of spines or setae. Eggs attaching to prolonged exopods of thoracopods VIII and IX, or IX and X.

Telson posterior margin posterolateral spine rows confluent dorsally, with confluence spines often larger than subsequent spines and not or slightly projecting. Spine rows have six to 30 spines depending on species, age, and gender. Females typically have more and smaller spines than males. Caudal filaments originating between spine rows at third, fourth, fifth, sixth, or seventh spine pairs from confluence. Caudal filament borne on projecting mound.

Cercopods arcuate or straight. Cercopod with a dorsomedial longitudinal row of setae or spines on proximal 40-80%. Setae plumose and either long or short. Row terminates distally with single short spine. Cercopod with subapical, dorsal cirrus, extending from 50-20% of cercopod length.

Egg surface smooth or with polygons or projections.

Comments. Eocyzicus is currently understood to comprise most species under Daday’s concepts of Eocyzicus and Caenestheria ( Brtek et al. 1984, following Straškraba 1966:584-585), with the exception of the Australian taxa that are now in the genus Ozestheria Schwentner et al. (2015a) and Caenestheria syriaca , which Brtek (1997) synonymised with Cyzicus grubei ( Simon, 1886) . Naganawa (2001a) treats Eocyzicus as a junior synonym of Cyzicus (possibly due to comments made by Brtek et al. 1984: 95), however this is not supported by molecular studies ( Schwentner et al. 2009), which demonstrate that Eocyzicus is a distinct genus, sister to Leptestheria .

Eocyzicus has its centre of diversity in Asia, with approximately ten taxa, all but four found in temperate regions. Africa has six (probably fewer) described species from the Saharan (four) and Southern (three) regions. Two described species occur in inland Australia and one is known in the North American deserts. None have been reported for South America or Antarctica. Brendonck (1999) provides the most recent keys for Southern Africa, Timms and Richter (2009) review the species of Australia (but see Schwentner et al. 2013 and discussion below), and Rogers & Padhye (2015) review the species of the Indian Subcontinent. Hu (1988, 1993a) provides problematic keys for the northern Chinese species. Eocyzicus digueti is commercially important in México ( Martínez-Pantoja et al. 2002). Naganawa (2001b) synonymized many of the East Asian Eocyzicus taxa, however no analyses or explanation was provided, nor is there any indication that any material was examined. The keys in Naganawa and Orgiljanova (2000) and subsequently republished by Naganawa (2001b), rely on equivocal characters.

There is little consensus on which characters are useful in delimiting species. Many characters used, such as growth lines, dorsal armature, number of antennomeres, number of thoracopods, setal arrangements on the thoracopods, have been demonstrated to be of little use in other spinicaudatan genera (e.g., Straškraba 1962, 1965a, b, 1966, Rogers et al. 2012). Durga Prasad et al. (1981) comparing the world Eocyzicus , and Simhachalam & Timms (2012) focusing just on the Indian species, each provide a table using these types of characters among others to distinguish species, many of which have been since synonymized (e.g., Rogers & Padhye 2015).

Daday (1915) defined and separated Caenestheria from Eocyzicus based on the form of the male rostrum, which is rounded or triangular in the former, and quadrate in the latter. However, developmental series from cultures of E. taiwanensis n. sp. demonstrate that the rostral form is a function of age ( Figure 2 A–E), with the male rostrum starting out rounded and gradually becoming quadrate as the animal matures. This supports the assertion of Brtek et al. (1984) that Caenestheria is a synonym of Eocyzicus .

Schwentner et al. (2013) using DNA barcoding identified eleven separate lineages as ten potential species (two described, eight undescribed) from across Australia. However, due to the great uncertainties involved with using DNA barcodes exclusively (e.g., Meyer & Paulay 2005, Meier et al. 2006, Song et al. 2008, Buhay 2009) and problems attempting to separate closely allied species (e.g., Meier et al. 2006, Song et al. 2008, Buhay 2009, Carew & Hoffman 2015), further genetical and morphological analyses are needed to verify these potential species.

It would seem that the fully adult rostrum shape, carapace hinge shape, arrangement and number of telsonic spines, and the form of the cercopods, provide some of the best characters, although others may also. Characters of the clasper seem useful. However, clasper characters must be robust and not simple differentiations between numbers of setae, or palp articles, which could readily be affected by regeneration or age ( Rogers et al. 2012). All morphological character states used to define adult spinicaudatan species need to be tested.

Daday (1915) presented 24 species (divided into two genera) in his monograph, Durga Prasad et al. (1981) recognized 19 (only those taxa Daday referred to Eocyzicus ), and Brtek (2002) listed 44 species. We tentatively recognize 19 Eocyzicus species, three nomina dubia and inquirendae, and 71 synonyms. We present eleven species from the Palaearctic, two from the Oriental Region, three from the Ethiopian Region, ~2 from Australia, and one from the Nearctic.

Attributed species. Eocyzicus argillaquus Timms & Richter, 2009

Comments. Endemic to Australia, occurring in highly turbid habitats from western Queensland, New South Wales, southern Northern Territory, and Western Australia.

Figures

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.