Megabathynella totemensis Camacho & Abrams & Moulds 2024, gen. et sp. nov.
Creators: name: Camacho, Ana I.
name: Abrams, Kym M.
name: Moulds, Tim
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Bathynellacea
Parabathynellidae
Megabathynella
Megabathynella totemensis

description: Megabathynella totemensis Camacho & Abrams gen. et sp. nov.
urn:lsid:zoobank.org:act: F03F8CE0-8F61-4803-B5A9-0ADDBFEA599C
Figs 1–8, 9F
Diagnosis
AI multisegmented, 12–15 articles with terminal aesthetascs present on fifth to last segments. AII 7-segmented. Labrum flat, free margin with 17–21 teeth. Md pars molaris (molar process) protruding with many well-developed claws (18–23); with strong triangular proximal tooth; mandibular palp bisegmented with several setae (7–9). Proximal endite of MxI with four claws; 9–11 claws present on distal endite. Exopod of ThI to ThVII multisegmented (11–18 articles); epipod present from ThI to ThVII; first and second article of endopod of ThI to ThVII each with a plumose dorsal seta. Male ThVIII unusually large, twice as long as wide; basal region of penial complex supports three independent lobes: inner lobe, outer lobe and dentate lobe; dentate lobe as inner lobe, rounded and as long as the outer lobe; very long curved outer lobe, as a finger; large basipod with a seta and a pronounced crest on internal face; dentate small exopod; endopod large with two basal setae and with the distal end rounded with four teeth and two setae of different length, the longest barbed. Female ThVIII one-segmented, almost triangular with three long barbed terminal setae. Pleopods absent. Inhomonomous sympod of uropod, with many long spines (56–85), distalmost 25% longer than the rest; endopod with four to six spines, the two terminal spines stronger than the rest, and setae, two barbed apical ones, one subterminal and two basal plumose setae; exopod with 15 to 18 setae. Furca very enlarged with 37 to 46 spines, the two distal ones twice as long as the rest. Anal operculum not pronounced. Giant species, more than 4 mm long.
Etymology
The specific name ‘ totemensis ’ is dedicated to the Totem Pole Cave where the new species was found.
Material examined
Holotype AUSTRALIA • ♂ (all appendages dissected in glycerine and preserved as permanent slides, special metal slides, glycerine-gelatine stained and paraffin as mounting medium); Northern Territory, Pungalina Karst area, Totem Pole Cave; 16°48′ S, 137°27′ E; 24 Jul. 2006; T.A. Moulds leg.; NTM Cr19141.
Allotype AUSTRALIA • ♀; same collection data and storage as for holotype; NTM Cr19142.
Paratypes AUSTRALIA • 5 ♀♀, 3 ♂♂; same collection data and storage as for holotype; WAM C73466E (in toto, 5.6 mm, not in Table 1), WAM C73466F (in toto, 5.6 mm, not in Table 1), WAM C73466J, WAM C73466L (females), WAM C73466G, WAM C73466H (males) • 1 ♀, 1 ♂; same collection data and storage as for holotype; MNCN 20.04/20932 (female), MNCN 20.04/20931 (male).
Type locality
Ten specimens, six females and four males, were collected at the type locality by T.A. Moulds on 24 Jul. 2006.
Description
MEASUREMENTS AND APPEARANCE. Body total length of male holotype 5.9 mm, allotype 6.2 mm. Body elongated (Figs 1–2), segments widening towards posterior end ~8 × as long as wide. Head slightly longer than broad. All drawings are of the holotype, except ThVIII (Fig. 5C), labrum (Fig. 3D), mandibular palp (Fig. 3F) and ThI (Fig. 4B) which are of the allotype.
ANTENNULES (Figs 3A, 6A) (AI). Almost 35% longer than AII. 13-segmented; first three articles as long as the next six and slightly longer than the last four articles combined; first article longest, similar to third, second slightly shorter, but just as thick; the fourth article is the shortest; the fifth to eighth articles are similar in length, short and thick, and the last five are longer and narrower than all the previous ones. First article with three smooth dorsal setae and three plumose ones (Fig. 3A, I). Second article with four plumose setae and eight smooth setae on inner margin. Inner flagellum on third article, small and almost square with three smooth setae. Third article (Fig. 3J) with two smooth and one plumose outer lateral setae and eight smooth setae of different sizes on inner margin. Fourth article with two plumose setae on outer distal apophysis, one more dorsal plumose seta and one small, plumose stub on dorsal margin. Fifth to ninth articles (Fig. 3A, K) with three smooth setae, one strong and short curved seta with long setules and two aesthetascs, of similar size, on inner margin, and one smooth dorsal seta. Articles 10 to 12 with similar setation as previous ones but with three terminal aesthetascs instead of two. Last article with three subterminal aesthetascs and four terminal smooth setae.
ANTENNAE (Figs 3B, 6B) (AII). Seven-segmented, the fifth article longest, 20% longer than first three together and fourth, sixth and seventh similar in length. Thickness gradually decreases from fourth to seventh. All setae smooth. Setal formula: 0+0/0+0/3+0/4+1/4+1/2+1/8.
LABRUM (Figs 3C, 6C). Almost flat, with 12 main teeth, and two smaller teeth at each angle; ventral surface with several rows of strong spinules.
MANDIBLES (Figs 3E, 6D–F) (MD). Pars distalis with six well-developed teeth and six small and one triangular strong proximal tooth as in figures 3E and 6D; pars molaris (molar process) very big, with row of 18 claws, all strong and denticulate, with two more distal setulose ones, joined basally (Figs 3E, 6E); exceptional two-segmented mandibular palp with seven setae (Figs 3E, 6D, F) not exceeding distal part of Md.
MAXILLULES (Figs 3G, 6G–H) (MXI). Proximal endite with four unequal strong claws with strong setation; distal endite with ten claws (as spines), along inner edge, one apical smooth and very large and strong, remaining claws denticulate with strong row of denticles and setae, basal claw smallest, half length of others; three smooth setae subdistally on outer margin of endite as figured.
MAXILLAE (Figs 3H, 6I). Four-segmented, setal formula: 8, 16, 31, 8.
THORACOPODS (Figs 4A–B, 7A–D) (THI TO VII). Well developed; length gradually increasing from ThI to ThIV (Figs 1–2), ThV to VII similar in length; small epipod on ThI (Figs 4A, 7A) to VII, each about ⅓ of length of corresponding basipod. Basipod of all Ths with several (three to five) distolateral, barbed setae. Exopods multi-segmented, 14 to 17 articles; number of exopodal articles of thoracopods I to VII: 14-16-16-17-17-17-16; basal article very long and wide with several barbed setae plumose at base on each side; following eight articles almost square and last ones elongated, all with barbed seta (plumose at base) on each side and one strong spine at base of inner seta. Endopod 4-segmented; first article short, second and third long and similar in length and fourth article reduced with two smooth strong spinulose claws and two simple setae; first article with distal plumose inner seta as second article; second article with inner and outer barbed setae, and cluster of pairs of strong spinules along inner margin from base to first seta; third article with barbed setae on inner margin and one barbed distoventral seta. All thoracopods similar to ThI, but varying in number of articles of exopod, number of setae in basal article, number of setae on basipod and on first three articles of endopod. Size ratios between articles, of exopod and endopod, similar to those of ThI (Fig. 4A).
SETAL FORMULA OF ENDOPOD.
ThI (4 basipod setae): 2+1/3+4/3+1/4(2)
ThII (4 basipod setae): 2+1/3+4/5+1/4(2)
ThIII (4–5 basipod setae): 2+1/3+4/4+1/4(2)
ThIV (4–5 basipod setae): 1+1/4+2/5+1/4(2)
ThV (4-5 basipod setae): 1+1/2+1/3+1/4(2)
ThVI (4 basipod setae): 2+1/3+4/4+1/4(2)
THVII (4 basipod setae): 1+1/3+4/3+1/4(2)
MALE THORACOPOD VIII (Figs 5A–B, 8A–J, 9F). Unusually large, twice as long as wide; basal region of penial complex supports three independent lobes: inner lobe, outer lobe and dentate lobe; inclined dentate lobe, as long as outer lobe, with rounded distal end and big teeth (Fig. 5A–B); inner lobe rounded and longer than outer lobe; very long (6 × as long as wide) and curved outer lobe (as a finger) (Fig. 5A, 8B) that covers end of dentate lobe and not extending beyond basipod; large basipod with seta and pronounced crest-like protuberance (Fig. 5A–B, 8C) on internal face, and small almost triangular exopod with several denticles; endopod large with two basal setae and with distal end rounded, like skullcap or “helmet” (Figs 5A–B, 8F–G, J) with four teeth and two setae of different length, longest one barbed.
PLEOTELSON. Small ventral plumose seta. Anal operculum not pronounced, almost flat.
FIRST PLEOPODS. Absent.
UROPODS (Figs 5D–E, 7F–G). Sympod 6.5 times as long as wide, 15% longer than exopod and almost three times as long as endopod, with 59 barbed spines subequal, except distalmost spine, slightly longer than rest. Endopod 2.5 times as long as exopod, with three spines along distal half of inner margin and two stronger and enlarged distal ones; distolateral angle of ramous with one subterminal plumose and two terminal barbed setae; basal part of ramous with two plumose setae of different length. Exopod with 18 barbed setae, 14 lateral and four terminal.
FURCAL RAMI (Figs 5F, 7F). Each ramus almost triangular, very enlarged, with 37 barbed spines, six distal ones of different sizes, four slightly longer than first 31 and two terminal ones two times as long as others; two plumose setae of different lengths oriented dorsally, shorter one without reaching tip of terminal spines.
Female (allotype)
The female allotype is similar to the holotype, except for the ThVIII (Fig. 5C), the number of articles of AI and exopod of Ths; teeth of labrum; claws on Md and MxI; setae on Md palp, and spines on sympod of the uropod and furcal rami. See Table 1.
ANTENNULES. Similar to male but with more segments, 15.
LABRUM (Fig. 3D). With 14 main teeth and several lateral denticles on each side.
MANDIBLES. Pars molaris with 23 teeth and mandibular palp with nine setae (Fig. 3F).
MAXILLULES. Distal endite with 11 claws.
THORACOPODS. Number of exopodal articles of thoracopods I to VII: 12-17-18-18-18-17-18.
SETAL FORMULA OF ENDOPOD.
ThI (3 basipod setae) (Fig. 5B): 8+2/8+3/8+1/4(2) ThII (5 basipod setae): 2+1/3+5/4+1/4(2)
ThIII (5 basipod setae): 2+1/4+4/5+1/4(2)
ThIV (4 basipod setae): 2+1/3+5/3+1/4(2)
ThV (4 basipod setae): 1+1/2+1/3+1/4(2)
ThVI (5 basipod setae): 2+1/3+5/4+1/4(2)
ThVII (3 basipod setae): 1+1/3+5/4+1/4(2)
THORACOPOD VIII (Fig. 5C). One-segmented; almost triangular with three long barbed terminal setae.
UROPOD. Sympod with 78 spines
FURCAL RAMI. With 43 spines.
Variability
The size varies among the studied paratypes: females 5.4–6.1 (n = 5) and males 4.3–5.9 (n = 2). There is variation in the number of: articles of AI (13–15); claws on pars molaris (18–23), teeth on pars distalis (8–12) and setae on mandibular palp (7–9) of Md; claws on distal endite of MxI (10–11); spines on the furcal rami (37–46), spines on sympod of uropod (56–78); articles of exopod of Ths (11–18) and setation of three first articles of endopod, first article of exopod and basipod on all Ths. See Table 1 for details of the six studied paratypes and holotype and allotype also, of Megabathynella totemensis gen. et sp. nov.
description: Published as part of Camacho, Ana I., Abrams, Kym M. & Moulds, Tim, 2024, New giant genus of Parabathynellidae (Crustacea: Bathynellacea): first record of Bathynellacea in an Australian cave, pp. 54-80 in European Journal of Taxonomy 935 on pages 59-71, DOI: 10.5852/ejt.2024.935.2545, http://zenodo.org/record/11244606