Queenslandnella spinosa Perina & Camacho, 2024

Queenslandnella spinosa Perina & Camacho gen. et sp. nov.

( Figs 8–11 View Figure 8 View Figure 9 View Figure 10 View Figure 11 )

Zoobank registration: urn:lsid:zoobank.org:act:56A90520-8943-4B5D-953A-E95E6C3C099C

Material examined

Holotype: WAMC 59223 . GoogleMaps

Paratypes: WAMC 57521 , WAMC 57522 , WAMC 57526 , WAMC 57527 , WAMC 59222 , WAMC 59224 , WAMC 59225 , WAMC 59226 , WAMC 59227 , WAMC 59228 , WAMC 59229 , WAMC 59230 , WAMC 59231 , WAMC 59232 , WAMC 59233 , WAMC 5922234 .

Additional material (whole specimen used for DNA extractions, sequences available): WAMC 57523 , WAMC 57524 , WAMC 57525 , WAMC 59200 , WAMC 59201 , WAMC 59202 .

Details of the type series and additional material studied are listed in Table 2 View Table 2 .

The description is based on adult specimens of the type series. All drawings correspond to the holotype (male) and specimens of the type series. Unfortunately, many specimens were in poor condition, especially females; therefore, drawings of the female ThVIII are not available.

Type locality: Bore EEUN2 (23°53 ʹ 5.43″S 150°58 ʹ 19.49″E), 8 km South of Mount Larcom , QLD, Australia ( Fig. 2 View Figure 2 ) GoogleMaps .

Holotype male: WAMC 59223 .

Description

Body: Total length of male holotype 0.73 mm; length of females: 0.63–0.98 mm; length of males: 0.68–0.84 mm. Body elongated, segments slightly widening towards posterior end, approximately six times longer than wider. Head slightly longer than wider ( Fig. 8 View Figure 8 ).

Antennule ( Fig. 9A View Figure 9 ): Seven-segmented; first three articles almost as long as last two articles combined; first article nearly as long as sixth article; seventh article longest, fifth article shortest, third and fourth articles similar in length, inner flagellum almost square, reduced; setation as in Figure 9A View Figure 9 ; article three with two smooth setae; article six with two aesthetascs; article seven with three aesthetascs of unequal length. AI similar in length to antenna.

Antenna ( Fig. 9B View Figure 9 ): Eight-segmented; first five articles about as long as the last three; the second article is the shortest, followed by the first article; third, fourth, and fifth articles are similar in length and shorter than the sixth and seventh, which are similar in length; the last segment is the longest; exopod very small, about one and a half times longer than the second article, without medial seta; setal formula: 0+0/2+0/2+0/2+0/2+1/2+1/2+1/4.

Labrum ( Fig. 9C View Figure 9 ): Almost flat; free edge with two teeth. Paragnaths ( Fig. 9D View Figure 9 ): Almost trapezoidal, with a very strong tooth and setulation on distal part.

Mandible ( Fig. 9E–J View Figure 9 ): Palp with three articles ( Fig. 9E, F View Figure 9 ) and three long, strong barbed claws, one of them smaller than the other two. Masticatory part ( Fig. 9G–J View Figure 9 ): incisor process [pars incisiva] with two teeth; processus incisivus accesorius [accessory incisor process] with two teeth and one seta-like tooth; pars molaris [molar process] formed by two parts (toothed structures), well differentiated, parallel to the main axis of the teeth, each with five small denticles.

Maxillule ( Fig. 9K View Figure 9 ): Proximal endite with three very long setae; distal endite with five very thin seta-like claws, four of which have denticles; two smooth setae of similar length along outer margin.

Maxilla ( Fig. 9L View Figure 9 ): Three articles with long smooth setae; setal formula: 6, 4, 6.

Thoracopods I–VII ( Fig. 10A–G View Figure 10 ): Well developed; ThI-V ( Fig. 10A–E View Figure 10 ) of similar length, and ThVI and ThVII slightly longer. ThI and ThII without epipod. Epipod present on ThIII-VII, less than half length of basipod in ThIII and about same length as basipod in ThIV-VII. ThI very different from the rest: coxa with a long barbed seta that extends beyond the end of the basipod; basipod shaped as an inverted ‘L’, with three distal smooth setae and exopod inserted in the middle; exopod of ‘atrophied appearence’, exceeding the distal end of the first article of the endopod and with two distal setae and one medial seta, all barbed; endopod four-segmented, with rectangular first and fourth articles of equal length and slightly longer than the two almost square middle articles, with many smooth setae on the inner edge of all articles, and without plumose outer seta on the second article. ThII-VII: basipod almost square, with a distal inner seta; exopod one-segmented, shorter than endopod in all cases, similar in length to first two endopodal articles combined in ThII, ThVI, and ThVII, slightly longer than first two articles combined in ThIII-V, with four barbed setae (two terminal) with ctenidia at base; endopod four-segmented, first and second articles similar in length in ThII and III, while the second article is slightly longer in ThIV-VII, with an internal distal seta on each article, and an external plumose seta on second article, third article slightly longer than previous articles and bearing a subterminal external plumose seta in all thoracopods (except ThI), and it is about twice as long as the second article in ThVII; the fourth article is very small with three distal claws in ThII-IV and only two claws in ThV-VII, shorter distal claws in ThVI and ThVII; setal formula of endopods: ThI, 12+0/8+0/8+0/11; ThII-IV, 1+0/1+1/0+1/3; ThV-VII, 1+0/1+1/0+1/2.

Male thoracopod VIII ( Fig. 11A, B View Figure 11 ): Massive, highly elongated; penial region with three very well-developed lobes, trapezoidal inner lobe; elongated outer lobe, similar in length to inner lobe; outer protuberance as long as basipod, with four teeth; basipod large, integrated in penial region, vertical, with a pointed frontal crest provided with a strong distal tooth and one distal seta; exopod highly elongated, as long as the exopod of other thoracopods, but larger, with three setae; endopod two-segmented, with first article expanded and ornamented with an inner strong seta and one modified spine with spinulas as long as the second article, second article slightly longer than first article, with two distal teeth.

Pleopods ( Fig. 11C View Figure 11 ): Two-segmented; first article with one long smooth seta; second article longer than the first one,with seven setae (two subterminal, four terminal, and one medial): five barbed setae similar in length, two longer setae, one barbed and one plumose.

Uropods ( Fig. 11D View Figure 11 ): Sympod almost square, similar in length to endopod and exopod, with six spines located distally on a small protuberance, with the two distal ones slightly longer; endopod about twice as long as wide, with six strong spines, distal spine four times longer than the others, and eight barbed setae, five of them located dorsolaterally and the other three distally; exopod with six setae (two terminal, two medial on each side).

Pleotelson ( Fig. 11E View Figure 11 ): With a short dorsal plumose seta on each side near the base of furca.

Furcal rami ( Fig. 11E View Figure 11 ): Small almost square, with only three spines of different size: outer spine twice as long as inner spine, and dorsal spine very small, nearly five times shorter than inner spine. Denticles present on outer distal end of furca, possibly corresponding to the furcal organ.

Etymology

The subfamily name Queenslandbathynellinae and the generic name Queenslandnella come from the name of the Australian state Queensland, where the taxon was collected.

The species name spinosa (Latin adjective meaning ‘of many spines’) refers to the numerous spines on the endopod of the uropod.

Morphological remarks

Queenslandbathynellinae show unique characters compared with the other three described subfamilies ( Table 3 View Table 3 ), such as: AII eight-segmented ( Fig. 9B View Figure 9 ), with setae on the antepenultimate article, and short exopod (whereas in most species of Bathynellidae, AII has seven articles, except in some Gallobathynellinae that can have five or six); antepenultimate article of AII as long as the penultimate one, bearing three setae, whereas in all other Bathynellidae this article is shorter than the last two [very small in Austrobathynella patagonica ( Fig. 12E View Figure 12 ) and in the other four Australian genera] and lacks setae; free edge of labrum with two medium teeth and not completely smooth like in other bathynellids ( Fig. 9C View Figure 9 ); three setae on mandibular palp ( Fig. 9F View Figure 9 ) instead of two; two teeth and a spine on the processus incisivus accesorius [accessory incisor process], whereas other subfamilies have only a triangular tooth and sometimes a spine ( Fig. 13A–H View Figure 13 ); pars molaris [molar process] consists of two parts, as in other subfamilies, but very distinct and formed by small denticles; only two smooth lateral setae on the distal endite of MxI ( Fig. 9K View Figure 9 ) instead of three; only three very long setae on the first endite of MxI (instead of four); MxII three-segmented ( Fig. 9L View Figure 9 ) instead of four-segmented; ThI basipod trapezoidal with exopod medially inserted ( Fig. 10A View Figure 10 ), instead of apically or subapically inserted ( Fig. 14 View Figure 14 ); article 4 of ThI endopod long (instead of short), articles 2 and 3 shorter compared with other Bathynellidae species, and all endopodial articles of ThI with profuse setation; ThII-VII with one subdistal outer plumose seta on article three, whereas other bathynellids do not have any outer setae on this article (see ThIII examples in Figs 15 View Figure 15 , 16 View Figure 16 ); male ThVIII with basal region formed by one projection and two lobes, endopod with two articles similar in length to the exopod (for male ThVIII comparisons with other species, see Fig. 17 View Figure 17 ); sympod of the uropod with spines situated on a distal bulge (usually, they sit on the sympod); exopod very long, as long as endopod, whereas in other taxa it is much shorter; endopod and exopod with many setae (eight and six, respectively) ( Fig. 11D View Figure 11 ; Fig. 18 View Figure 18 for comparison of uropods); furcal rami with only three spines of different size ( Fig. 11E View Figure 11 ), whereas other bathynellids usually have five ( Fig. 19 View Figure 19 ).

The new subfamily presents some similarities to other genera, such as paragnaths ( Fig. 9D View Figure 9 ), which are similar to those of some Bathynellinae genera (e.g. Pacificabathynella ; Fig. 13R View Figure 13 ) and Gallobathynellinae genera (e.g. Hobbsinella ; Fig. 13S View Figure 13 ); fourth article of ThII-VII (see ThIII example in Figs 15 View Figure 15 , 16 View Figure 16 ) much smaller than other articles, similar to those seen in the sister family Parabathynellidae .

Table 4 View Table 4 shows similarities and differences between Queenslandnella spinosa and the five described Australian genera. One of the main differences of the new species is the male ThVIII, which is much more developed than in all the other Australian species ( Fig. 17 View Figure 17 ). The male of Bathynella primaustraliensis is unknown, hence comparison is not possible. The new genus has two aestethascs on segment 6 of AI and three on segment 7, like Anguillanella callawaensis and Muccanella cundalinensis . Also, in the new genus AII is eight-segmented, with third article very long, and with setae on the antepenultimate article, whereas the other four species have AII seven-segmented, with third article very small (unknown in Bathynella primaustraliensis because there are no drawings of AI) and without setae. Other different characters are the mandibular palp, the exopod of ThI, the absence of epipod on ThII; the endopod and exopod of uropod; and the furca.

Six described genera of Bathynellidae [ Indobathynella , Agnatobathynella , Baicalobathynella , Nannobathynella , Serbanibathynella , and Tianschanobathynella ] are not assigned to a known subfamily and are classified as incerta sedis (Camacho 2018); however, they show very distinctive characters in comparison to the new subfamily here described.

Indobathynella presents characters very different from all other bathynellids ( Table 3 View Table 3 ), such as a great reduction of segmentation and ornamentation on AI (six-segmented), AII (four-segmented, with endopod two-segmented and exopod shorter than first endopodal article; Fig. 12G View Figure 12 ), Md with prehensile three-segmented palp and gnathobase fused with basal segment of palp and represented by five teeth ( Fig. 13G View Figure 13 ); paragnaths wedge-shaped and basally fused ( Fig. 13T View Figure 13 ); endopod of thoracopods two-segmented (except in ThI, which is three-segmented; Fig. 14D View Figure 14 ), and exopods two-segmented ( Fig. 15G View Figure 15 ); a one-segmented first pleopod with sexual dimorphism, whereas in all genera of Bathynellidae View in CoL , including the new one, it is two-segmented and without sexual dimorphism; male ThVIII ( Fig. 17K View Figure 17 ) greatly reduced; uropod very simplified ( Fig. 18H View Figure 18 ). Indobathynella currently comprises two species ( Ranga Reddy and Totakura 2012, Shaik 2019), and it is provisionally placed in the Bathynellidae View in CoL family; however, according to Ranga Reddy and Totakura (2012), it could belong to a new family currently undescribed. Baicalobathynella contains very large species (> 2 mm) that show some unique characters important at the subfamily level, such as AII nine-segmented without exopod ( Fig. 12A View Figure 12 ); MxI with five claws on the proximal endite and four barbed setae on the distal outer corner of the distal endite; profuse setation on thoracopods ( Figs 14L View Figure 14 , 15H View Figure 15 ); two pairs of pleopods, and furca with three thin spines and two long setae ( Fig. 19H View Figure 19 ) ( Drewes and Schminke 2011).

Agnatobathynella presents some unique characters, such as elongated and distally tapered paragnaths; mandible with no masticatory part, and palp with terminal claws not pointed; endopod of thoracopods with very little setation; and extremely simplified male ThVIII that resembles the pleopod ( Schminke 1980).

Nannobathynella exhibits peculiar characters, such as reduced mandible; partly ciliated labrum; two setae on distal segment of MxI; male ThVIII simplified, with exopod like the exopod of other thoracopods and with no endopod (Noodt 1969, Schminke and Wells 1974, Schminke 1979).

Serbanibathynella displays unique characters, such as AII held at a right angle to the long axis; mandible highly transformed (with no gnathobase); setation of thoracopod endopods reduced; male ThVIII similar to Nannobathynella ( Ranga Reddy and Schminke 2005, Totakura and Ranga Reddy 2014).

Tianschanobathynella has a mandibular palp with sexual dimorphism, a modified mandible with pars molaris [molar process] formed by a denticulate lobe and AII endopod six-segmented (like the new subfamily); however, the first two articles of AII are partly fused ( Jankowskaya 1964, Serban 1993).