Hydora laticeps (Carter & Zeck, 1932)

Barr, Cheryl B. & Shepard, William D., 2021, A review of the Larainae of Australia with description of seven new species and the new genus Australara (Coleoptera, Byrrhoidea, Elmidae), ZooKeys 1073, pp. 55-117 : 55

Hydora laticeps (Carter & Zeck, 1932)

Figs 2 , 15 , 16 , 17-19 , 20, 21 , 22

Type locality.

Upper Shoalhaven River, Tallong; 34.700°S, 150.083°E (approximate); New South Wales, Australia (lectotype deposited in the Australian Museum, Sydney). Note: The geographic coordinates given in the>AM database place the type locality north of Tallong, whereas the Shoalhaven River is to the south.

Type material examined

(2). Lectotype male (here designated). New South Wales. "Australian Museum / K 579881 // Tallong / N.S.W. / FHTaylor // Stetholus / Stetholus laticeps / Carter & Zeck / Id. by H. J. Carter // K67434 // HOLOTYPE / Stetholus / Stetholus laticeps / Carter & Zeck, / 1932 [red label] // Hydora / Hydora laticeps / (Carter & Zeck) / det. A.Calder 1999 // LECTOTYPE / Stetholus laticeps / Carter & Zeck, 1932" [red label, handwritten]. Deposited in the Australian Museum, Sydney. Paralectotype male (here designated). New South Wales. Australian Museum / K 579882 // Tallong / N.S.W. / FHTaylor // K69264 // Stetholus / Stetholus laticeps / Carter 1932 // PARATYPE / Stetholus laticeps / Carter & Zeck, / 1932 [blue label] // Hydora / Hydora laticeps / (Carter & Zeck) / det. A.Calder 1999 // PARALECTOTYPE / Stetholus laticeps / (Carter & Zeck, 1932) [yellow label, printed]. Deposited in the Australian Museum, Sydney.

Type material examined from photographs

(2). Paralectotype males (here designated). New South Wales. Tallong / N.S.W. / FHTaylor // Stetholus / Stetholus laticeps C & Z / Id. by H. J. Carter // Hydora / Hydora laticeps (C&Z) / det. A. Calder 1992 // Genitalia prep. / HH-224 ♂/ A. Calder 198792 // PARALECTOTYPE / Stetholus laticeps / (Carter & Zeck, 1932) [yellow label, printed] (1 ANIC); Tallong / N.S.W. / FHTaylor // Stetholus / Stetholus elongatus / C & Z / Id. by H. J. Carter // Paratype [blue label, printed] // PARATYPE [blue label, printed] // Genitalia prep. / HH-247 ♂/ A.Calder 1997 // ANIC / Image // PARALECTOTYPE / Stetholus laticeps / (Carter & Zeck, 1932) [yellow label, printed] (1 ANIC).

Other material examined

(4). Australian Capital Territory. AUSTRALIA: / Lyneham / at light / A.C. T. 22.xii.66 / B.P.Moore (1♂ 1♀ ANIC) . Victoria. Cann River , E. Vic. / 28.i.1967. / G. Monteith // EX UQIC / DONATED / 2011 (2♀♀ QM) .

Differential diagnosis

(n = 8). Hydora laticeps (Figs 15 - 22 ) is the only species of Hydora known to occur in Australia. It can be distinguished from other Australian laraines by a combination of the following characters: Eyes protuberant, hemispherical; maxillary palpi narrow at the apices; pronotum with strong basal, sublateral carinae and without a distinct transverse impression at anterior 1/3; and prosternum moderately long anterior to the coxae but not extending beneath head. Stetholus species (Figs 34 - 42 ) have ovoid eyes, not usually prominent; maxillary palpi each with palpomere 4 wide and oblique at the apex; pronotum with a distinct transverse impression; and prosternum very short and narrow anterior to the coxae.

Australara glaisteri (Fig. 13 ) most obviously differs by its lack of sublateral pronotal carinae and by the mesoventrite having an anterior projection containing a slit-like mesoventral cavity; the eyes are also not quite as protuberant.

Redescription

(n = 2). Male lectotype and male paralectotype. Body: Size 4.2 mm long, 1.6 mm wide (lectotype); size 4.0 mm long, 1.5 mm wide (paralectotype); elongate, parallel-sided. Color light to dark brown; head and pronotum darkest; antennae, mouthparts, legs, venter lightest. Dorsum with fine, pale setae, short on elytra, longer on head and pronotum; venter with long, dense setae. Head: Eye large, protuberant, hemispherical. Antenna with antennomere 1 elongate, antennomere 2 ovoid, antennomeres 3-11 smaller, weakly clavate. Labrum emarginate anteriorly, lateral margins with long setae. Maxillary palpus long, robust, setose; palpomere 4 much enlarged, ovoid, apex blunt with small, oval sensory area. Labial palpus shorter, palpomere 4 conical, apex pointed with very small, circular sensory area. Pronotum: Shape generally trapezoidal, 0.9 mm long, 1.1 mm wide (at base); anterior angles obscure, lateral margins crenulate, posterior angles acute, depressed; disc weakly sculptured except for two distinct, basal, sublateral carinae, 1/2 the pronotal length; two shallow, obscure transverse impressions laterad of midline at anterior 1/5-1/4. Elytron: 3.2-3.3 mm long, 0.7-0.8 mm wide (at base); lateral margin narrowly marginate, apex narrowly rounded, acute; disc with ten rows of moderately striate punctures, accessory basal stria present between striae 1 and 2; disc in lateral view flattened at anterior 1/2. Prosternum: Moderately long anterior to coxae, not extending beneath head; prosternal process narrow, curved, posterior 1/3 semi-carinate with a short, faint row of granules at midline, tip narrowly rounded. Mesoventrite: Longer than prosternum; mesoventral cavity deep and moderately wide Metaventrite: Very convex, especially in lateral view. Legs: Long and slender. Tibia of all legs with a pair of stout spines at ventral apex; meso- and metatibia with posterior surfaces shallowly sulcate, glabrous, shiny. Tarsus with tarsomere 5 shorter than tarsomeres 1-4 combined; covered with short, dense setae; claws simple, slender, acute. Abdomen: Ventrite 1 triangular intercoxal projection moderately narrow; ventrite 5 nearly truncate at apex. Aedeagus: Phallobase longer than parameres and penis, penis slightly longer than parameres (Fig. 16 ). Phallobase open dorsally. In dorsal view (Fig. 16A ), parameres broad, with lateral margins gradually convergent, apices bluntly rounded; medial margins parallel-sided at basal 2/3 then gradually divergent, margins appearing more sclerotized than rest of parameres. Penis slightly longer than parameres, approximately as wide at base as paramere base; lateral margins widened and arcuate just distal to base, then evenly convergent to apex; apex narrow, nipple-like, laterally flattened, tip narrowly rounded; no corona visible; basal apophyses short, 1/4-1/3 as long as phallobase, straight, broad, blunt at tips. Fibula absent. In lateral view (Fig. 16B ), paramere nearly straight dorsally at apical 3/4, weakly arcuate ventrally, tip broadly rounded and slightly wider than paramere tip.

Variation.

There is some size variation among the known specimens, particularly between males and females. Specimens from the type series, all males (n = 4), measured 4.0-4.3 mm long, 1.4-1.6 mm wide. Carter and Zeck (1932) stated in the type description "Dimensions: 5 × 1.5 mm" but the length probably included the head. Among the specimens examined (including two from the type series), the females (n = 3), 4.5-5.2 mm long, 1.7-1.8 mm wide, are considerably larger than the males (n = 3), 4.0-4.5 mm long, 1.4-1.6 mm wide. In addition, the females (Figs 20B , 22B ) have prosternal processes broader than those of the males (Fig. 15C ), and noticeably narrower maxillary palpi. The prosternal processes of the two male specimens examined from the type series (Fig. 15C ) are slightly narrower than those of the non-type male. The surface of the prosternal process varies, and may be convex, depressed only between the procoxae, or entirely flat except posterior to coxae, but in all specimens the process is granulate, swollen, and an indistinct carina is usually visible. Non-sexual variation was also observed in the morphology of the elytral punctures (size and depth), pronotum (width, lateral margins, posterior angles, sculpturing); and prosternal process (width, surface features). On the pronotum, two shallow, anterior, transverse impressions are present laterad of the midline. In most specimens the impressions are weak or altogether obscure (Figs 17-19 ), but they are quite obvious in one of the two non-type specimens from Cann River (Fig. 22A ). In addition, the single male non-type specimen from Lyneham (Fig. 21A, C ) has a slightly broader aedeagus than the two specimens examined from the type series (Fig. 16A, C ). This variability in external morphology and male genitalia raises the possibility that more than one species is involved.

Lectotype designation.

It appears that none of the four known specimens from the type series of Stetholus laticeps was given a holotype or paratype label at the time of description, and those subsequently added to the specimens were not done so by the authors. In their description, Carter and Zeck (1932) stated that they had "five examples" and that the holotype was "in Coll. Carter," but did not mention designating paratypes. Two specimens were deposited at the Australian Museum 35 years apart: According to the original register of specimens, the first (Fig. 15 ) was presented by H. J. Carter in 1936, and bears an old, handwritten determination label saying " Stetholus laticeps Carter & Zeck Id. by H. J. Carter" (Fig. 15A ). The specimen was subsequently given a holotype label by an unknown person, i.e., it was not written in the same hand as the determination label by Carter and appears much newer. This specimen is here designated as the lectotype to fix the concept of Hydora laticeps (Carter & Zeck). The second specimen (Fig. 17 ) was obtained from the late E. H. Zeck in 1971, lacks an original determination label, and likewise bears a newer paratype label; it is designated a paralectotype.

There are also two specimens housed at Australian National Insect Collection. One of them bears the surprising, original determination label " Stetholus elongatus C & Z Id. by H. J. Carter" and two printed paratype labels, one older and one newer (Fig. 19 ). Probably the identification predated the description of S. laticeps by Carter and Zeck in 1932, however, Tallong was not among the localities cited in their 1929 description of S. elongatus ( Carter and Zeck 1929). The other specimen has an original determination label, " Stetholus laticeps C & Z Id. by H. J. Carter," but has no paratype label (Fig. 18 ). These two specimens are likewise designated as paralectotypes. We were unable to examine the ANIC specimens because they were on loan to another researcher, but we were provided with habitus images (Figs 18 , 19 ) and measurements of body length for this article.

The location of the fifth specimen from the type series is unknown. Lambert et al. (2014) cited the SAMA as a specimen depository for the species, but we have examined their material and found no specimens of H. laticeps , so this report was in error.

Distribution.

Hydora laticeps is known from only three localities in Australia: the Shoalhaven River near Tallong, New South Wales, the type locality; Lyneham, Australian Capital Territory; and Cann River, eastern Victoria (Fig. 2 ).

Associated byrrhoid taxa.

Elmidae : Larainae : Stetholus elongatus (>AM, ANIC, NMV, SAMA); Elminae : Notriolus sp. (>AM).

Comments.

Hydora laticeps was originally described in the genus Stetholus by Carter and Zeck (1932), and subsequently reassigned to Hydora by Hinton (1935). Hinton stated that he studied only the description and figures, not actual specimens, and gave no specific reasons for the new combination.

In the diagnosis following their description, Carter and Zeck (1932: 203) noted that the prosternal process of S. laticeps lacks a carina, in contrast to Stetholus elongatus Carter & Zeck (1929) which has a carina. The actual situation is less clear-cut. The surface of the apical 1/2-1/3 of the process is convex to varying degrees and may be somewhat granulate at the midline, resembling an indistinct carina. However, this is a poor diagnostic character because dense setation can make examination difficult.

When Carter and Zeck (1932) described S. laticeps they made no mention that S. elongatus , described by them in 1929, was present in the Upper Shoalhaven River as well. That S. elongatus was collected with H. laticeps at the type locality is evidenced by museum specimens with locality labels identical to those of H. laticeps : "Tallong N.S.W. FH Taylor." This raised the question as to whether the missing specimen of H. laticeps might bear a S. elongatus label, as does one of the ANIC specimens, and thus has been overlooked. Unfortunately, examination of all known S. elongatus specimens with collection labels as above (>AM, 3 specimens; ANIC, 3; NMV, 2; SAMA, 4) revealed no misidentifications.

Until now, Hydora laticeps has been known only from its type locality, the Upper Shoalhaven River near Tallong, New South Wales, Australia. In the 90+ years since the type series was collected, deliberate attempts to re-collect it have been unsuccessful. Examination of unidentified museum specimens for this project resulted in the discovery of four additional specimens from two new localities, all of which were collected at light. The four type specimens available are all males, the Lyneham specimens are male and female, and the Cann River specimens are both female. In the absence of males, the latter two specimens are assumed to be H. laticeps due to external morphological similarities. The larva of the species is unknown.

As mentioned in the Variation section, is possible that not all of the specimens are conspecific because of mophological variation which is apparent even among those from the type series. However, there is not enough evidence at present to assign any to a species other than H. laticeps . DNA analysis would be helpful in this regard if fresh material could be obtained. A recent attempt to obtain DNA from a specimen in the type series failed due to its age (V. Sýkora, in litt.), and even the youngest of the specimens is at least 54 years old.

Figures

Figure 15. Hydora laticeps, lectotype male A specimen labels B dorsal habitus C ventral head and prosternum D lateral head and pronotum (photographs courtesy of the Australian Museum, Natalie Tees).

Figure 16. Hydora laticeps, lectotype; male genitalia A dorsal view B lateral view C ventral view.

Figure 22. Hydora laticeps, non-type female from Cann River, VIC A dorsal habitus B ventral habitus C lateral habitus (photographs courtesy of the Queensland Museum, Geoff Thompson).

Figures 1 - 12. Geographical distribution of species records 1 Australara glaisteri gen. nov., sp. nov. 2 Hydora laticeps 3 Ovolara australis 4 Ovolara lawrencei sp. nov. 5 Ovolara leai 6 Ovolara monteithi sp. nov. 7 Potamophilinus papuanus 8 Stetholus carinatus sp. nov. 9 Stetholus elongatus 10 Stetholus longipennis sp. nov. 11 Stetholus metatibialis sp. nov. 12 Stetholus woronora sp. nov.

Figures 17 - 19. Hydora laticeps, paralectotype males; dorsal habitus with specimen labels 17> AM specimen (photograph courtesy of the Australian Museum, Natalie Tees) 18 ANIC specimen (photograph courtesy of Vit Sykora, Charles University, Prague, Czech Republic) 19 ANIC specimen (photograph courtesy of the Australian National Insect Collection, CSIRO).

Figures 20, 21. Hydora laticeps, non-types from Lyneham, ACT 20 female habitus, 4.5 mm long A dorsal B ventral 21 male genitalia A dorsal view B lateral view C ventral view.

Figures 34, 35. Stetholus carinatus sp. nov., holotype male 34 habitus, 3.7 mm long A dorsal B ventral 35 male genitalia A dorsal view B lateral view C ventral view.

Figures 41, 42. Stetholus woronora sp. nov., holotype male 41 habitus, 5.2 mm long A dorsal B ventral 42 male genitalia A dorsal view B lateral view C ventral view.

Figures 13, 14. Australara glaisteri gen. nov., sp. nov., male 13 habitus A dorsal B ventral (photographs courtesy of the Australian National Insect Collection, CSIRO, Zhenhua Liu) 14 male genitalia A dorsal view B lateral view C ventral view.