Arenopontia problematica Masry 1970
Creators: name: Sak, Serdar
name: Karaytuğ, Süphan
name: Huys, Rony
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Copepoda
Harpacticoida
Arenopontiidae
Arenopontia
Arenopontia problematica

description: Arenopontia problematica Masry, 1970
(Fig. 1)
Arenopontia (Arenopontia) problematica Masry, 1970: Bodin (1979: 124)
Original description. Masry (1970): 249–251; Fig. 12.
Type locality. Israel, Levantine coast. Masry (1970) did not explicitly designate a type locality but mentioned that he collected material in five different sites: Nitzanim, Mikhmoret, Palmahim, Yel Yavne and south of TelShiqmona. The latter site was labelled on the holotype slide and is consequently designated as the type locality (ICZN Art. 76.1).
Material examined. Hebrew University, Jerusalem: damaged holotype ♀ mounted in toto on slide.
Partial redescription of female. Total body length from tip of rostrum to posterior margin of caudal rami 277 μm [290–320 μm according to Masry (1970)]. Hyaline frills unconfirmed but probably like in other species of the genus (thoracic ones weakly developed and crenulated, abdominal ones consisting of rectangular digitate lappets).
Caudal ramus (Fig. 1F) short, 1.7 times longer than wide (measured in lateral view from anterior margin to apex of spinous process), tapering posteriorly; with a pore laterally; outer distal corner produced into posteriorly directed recurved spinous process, accompanied at base by outer spinular row; dorsal surface without spur-like process but with row of strong spinules near inner margin. Armature consisting of seven setae; seta I small; setae II and III long and naked; seta IV short, located between seta V and spinous process; seta V long and with fracture plane; seta VI small, naked and located at inner distal corner; seta VII distinctly foliaceous and tri-articulate at base.
Antennule (Fig. 1E) short, six-segmented. Segment 1 with a short seta near anterodistal margin. Segment 2 longest, about twice longer than maximum width. Segment 4 with long aesthetasc (L: 25 μm) fused at base with seta. Distal segment with seven naked setae (none of which clearly spatulate) and apical acrothek consisting of short aesthetasc (L: 15 μm) and two slender setae. Armature formula: 1-[1], 2-[7 + 1 plumose], 3-[4], 4-[(1 + ae)], 5-[1], 6-[7 + acrothek].
Antenna (Fig. 1G). Coxa (not figured) small, without ornamentation. Allobasis about 2.6 times as long as maximum width; original basis-endopod boundary marked by partial transverse spinule row; with fine spinules along exopodal margin as figured. Exopod one-segmented, elongate, with short naked apical seta (about 1.5 times longer than exopod). Free endopod with two spinular rows on anterior surface and finer spinules at outer distal corner; medial armature consisting of two short spines; apical armature consisting of two spines and three geniculate setae, strongest of which with spinules around geniculation and fused basally to tiny accessory seta.
The detailed morphology of the mouthparts and maxillipeds could not be discerned in the mounted specimen.
P1 (Fig. 1A). Basis with spinular row near bases of endopod and exopod; anterior surface with a small inner seta. Exopod three-segmented; exp-1 and -2 with spinules around outer margin; exp-1 longest, with long bare outer spine; exp-2 without outer element; exp-3 with short unipinnate outer spine, a long curved unipinnate spine and one geniculate seta distally, and one inner, apically penicillate seta subdistally. Endopod two-segmented, prehensile; enp-1 6.9 times longer than wide, and about 1.68 times longer than exopod; with a serrate inner seta in proximal third, and three pairs of spinules along outer margin; enp-2 slightly longer than wide, with a short unipinnate spine, a geniculate claw and a small inner spinule.
P2–P4 (Fig. 1B–D). Bases with a spinular row near base of endopod (P3–P4; not figured for P3) and outer distal corner (P2, P4); outer basal seta absent (P2), plumose (P3) or naked (P4). Exopods three-segmented; segments with spinular ornamentation as figured; inner distal seta of exp-3 sparsely bipinnate, all other elements unipinnate; hyaline frills of exp-1 and -2 well developed; exp-2 with lateral pore halfway down inner margin length; P3–P4 exp-3 with anterior surface pore. Endopods two-segmented; P2–P4 enp-1 about 1.7, 1.9 and 3.3 times longer than their respective distal endopodal segments, with few spinules as figured. P2 enp-2 with a long, apically serrate, posteriorly oriented seta near inner margin and a long, sparsely pinnate distal seta. P3 enp-2 with a long bipinnate seta distally. P4 enp-2 minute, with a basally fused, apically serrate seta, and long unipinnate seta at outer distal corner. Spine and seta formula as follows:
The structure of the P5 and genital field could not be observed in the badly preserved holotype.
Remarks. Our re-examination of the holotype showed that Masry’s (1970) illustrations and text contain several significant errors, invalidating most of his criteria proposed to separate A. problematica and A. subterranea: (1) the author claimed that the female antennule is only five-segmented with a single, very long aesthetasc arising from the annulated apical segment; in reality, the antennule in A. problematica displays the typical arenopontiid pattern, being six-segmented with aesthetacs on segments 4 and 6 and no subdivisions of the apical segment (Fig. 1E); (2) the antennary exopod, claimed to be absent, was overlooked (Fig. 1G); (3) the innermost seta on P1 exp-3 is distally penicillate and not pinnate (Fig. 1A); (4) the inner serrate seta on P1 enp-1 was overlooked (Fig. 1A); (5) contrary to Masry’s Figure 62, the P2 basis does not have an outer seta (Fig. 1B); (6) P2 enp-2 has one apical seta instead of two (the short outer one illustrated in his Figure 62 is a spinule (Fig. 1B)); (7) P3 enp-2 has one apical seta instead of two, the short outer one figured by Masry being a spinule (and in reality much shorter; Fig. 1C); (8) P4 exp-3 has only one outer spine instead of two (Fig. 1D); Masry (1970) lists two elements in the armature formula and illustrates two in his Figure 64; for this reason A. problematica keys out to the wrong codon in Wells’ (2007: 188) key; and (9) caudal seta VII is clearly foliaceous. In addition, his claim that the male P6 bears three spines is almost certainly wrong since the maximum number of armature elements observed in any arenopontiid is two. The female P5 displays a deep incision along its free distal margin; this unique morphology could not be confirmed due to the bad condition of the holotype. Masry (1970) also states that the posterior margins of all body somites are smooth but this is highly unlikely given that the hyaline frills of the abdominal somites have rectangular digitate or nondigitate lappets in all other members of the family.
Arenopontia problematica is extremely close to A. subterranea, differing only in body size (the former being smaller), the morphology of the female P5 (unknown in the male) and the relatively shorter P2–P4 enp-1 and caudal ramus. A proper redescription of the fifth legs and the male are required before potential conspecificity with A. subterranea can be ruled out. The species is known only from the Israeli coast and has not been recorded again since its original description. According to Masry (1970), females (95%) greatly outnumbered males.
description: Published as part of Sak, Serdar, Karaytuğ, Süphan & Huys, Rony, 2024, A revision of the genus Arenopontia Kunz, 1937 (Copepoda, Harpacticoida, Arenopontiidae), including the description of five new species, pp. 1-50 in Zootaxa 5433 (1) on pages 7-9, DOI: 10.11646/zootaxa.5433.1.1, http://zenodo.org/record/10953646