Gnathia brevicula, Botha & Smit & Erasmus & Hadfield, 2025

Gnathia brevicula sp. nov.

Figs 6 View Figure 6 , 7 View Figure 7 , 8 View Figure 8 , 9 View Figure 9

Gnathia spongicola var. minor — Barnard 1920: 334.

Gnathia barnardi — Smit 1997: 128–142 (nomen nudum).

Material examined.

Holotype. South Africa • 1 ♂ ( 2.9 mm); False Bay ; 34°19.002'S, 18°33'E; depth 55 m; 4 May 1898; SS Pieter Fauer; trawl; branching sponges ( SAMC A 099275 ) GoogleMaps .

Paratypes. South Africa • 162 ♂♂ (3.0– 3.1 mm); same data as holotype ( SAM A 4150 ) GoogleMaps • 135 ♂♂ ( 2.5–2.8 mm); False Bay ; no coordinates provided; depth 55 m; trawl ( SAM A 4151 ) .

Other material. South Africa • 1 ♂ ( 3.2 mm); Cape Point ; 34°31.3'S, 18°341'E; depth 71 m; 22 May 1961; RV Africana II; dredge ( SAM A 43146 ) • 1 ♂ (damaged); False Bay ; 34°19.002'S, 18°33'E; depth 77 m; 27 October 1961; RV Africana II; dredge ( SAM A 43147 ) GoogleMaps • 1 ♂ (3.0 mm); Cape Point ; 34°31.3'S, 18°31.1'E; depth 66 m; 22 May 1961; RV Africana II; dredge ( SAM A 43162 ) GoogleMaps .

Description of adult male.

Body (Fig. 6 A View Figure 6 ) 2.3 times as long as greatest width, widest at pereonite 3; dorsal surfaces anteriorly with tubercules and posterior smooth, sparsely setose. Cephalosome (Figs 6 B View Figure 6 , 9 A View Figure 9 ) 0.6 times as long as wide; lateral margins sub-parallel; posterior margin concave; dorsal surface with numerous granules; dorsal sulcus narrow, shallow, short; translucent region absent; para-ocular ornamentation strongly developed with several tubercles and setae; posterior median tubercle present. Frontolateral processes absent. Frontal margin slightly produced, median point excavate. External scissura present, narrow, deep. Mediofrontal process absent. Superior frontolateral process present, single, strong, rounded and extended, with 1 pair of long simple setae. Inferior frontolateral process absent. Mesioventral margin straight, setose, anterior tip not dorsally visible. Supraocular lobe not pronounced, wide and rounded, accessory supraocular lobe not pronounced. Eyes present, elongate, 0.5 times as long as cephalosome length, contiguous with head surface, ommatidia arranged in rows.

Pereon lateral margins narrowing posteriorly, without setae; anteriorly with large granules. Pereonite 1 not fused dorsally with cephalosome; dorsolateral margins fully obscured by cephalosome. Pereonite 2 wider than pereonite 1. Pereonite 4 without anterior constriction, median groove absent. Areae laterales present on pereonite 5; dorsal sulcus obscured by pereonite 6. Pereonite 6 with weak lobi laterales; lobuii weak, globular. Pereonite 7 not visible in dorsal view. Pleon epimera not dorsally visible on all pleonites.

Pleotelson (Fig. 6 F View Figure 6 ) 1.1 times as long as anterior width; lateral margins smooth; anterolateral margins weakly concave; posterolateral margin straight with 2 pairs of submarginal setae; apex with 2 setae.

Antennula (Fig. 6 C View Figure 6 ) shorter than antenna. Peduncle article 1 without tubercles; article 2 0.8 times as long as article 1; article 3 1.9 times as long as article 2, 1.9 times as long as wide. Flagellum as long as article 3, with 5 articles; article 3 with 1 aesthetasc and 1 simple seta; article 4 with 1 aesthetasc; article 5 terminating with 1 aesthetasc and 3 simple setae. Antenna (Fig. 6 D View Figure 6 ) peduncle with 4 articles; article 3 1.9 times as long as wide, 1.6 times as long as article 2, with 3 penicillate setae and 2 simple setae; article 4 as long as article 3, with 2 penicillate setae, twice as long as wide, with 6 simple setae. Flagellum with 7 articles; 1.5 times as long as article 4; terminating with 3 simple setae.

Mandibl e (Fig. 6 E View Figure 6 ) 1.3 times as long as width, 0.4 times as long as length of cephalosome, weakly curved distally; apex 35.4 % total length; mandibular seta present. Carina present, smooth along proximal half. Incisor elevated, standing clear of surface, distal denticulation present. Blade present, weakly convex, dentate along 64.6 % of margin. Internal lobe absent. Dorsal lobe absent. Basal neck short. Erisma and lamina dentata absent.

Pylopod (Fig. 7 A View Figure 7 ) article 1 1.4 times as long as wide; with 2 distinct areolae; without distolateral lobe; posterior and lateral margins forming rounded curve; lateral margin with 22 large plumose setae; mesial margin with continuous scale-setae; 3 simple setae present on the surface; distal margin with 5 simple setae; article 2 1.3 times as long as wide, with 6 simple setae; article 3 minute (Fig. 7 B View Figure 7 ), with 2 setae.

Maxilliped (Fig. 7 C View Figure 7 ) 5 - articled; article 1 lateral margin with continuous marginal scale-setae; article 2 lateral margin with 4 plumose setae; article 3 lateral margin with 6 plumose setae; article 4 lateral margin with 5 plumose setae; article 5 with 7 plumose setae and 4 simple setae; endite extending to mid-margin of article 3.

Pereopods 2–6 (Fig. 8 A – E View Figure 8 ) with long, simple setae and randomly covered in pectinate scales; propodus distal robust seta slightly longer than proximal robust seta; inferior margins with prominent tubercles. Pereopod 2 (Fig. 8 A View Figure 8 ) with tubercles on basis to carpus; basis 1.8 times as long as greatest width, superior margin with 6 setae, inferior margin with 8 setae; ischium 0.5 times as long as basis, 1.6 times as long as wide, superior margin with 4 setae, inferior margin with 7 setae; merus 0.6 times as long as ischium, as long as wide, superior margin with 2 setae; superior margin with bulbous protrusion; inferior margin with 5 setae; carpus 0.6 times as long as ischium, twice as long as wide, superior margin with 1 seta, inferior margin with 3 setae; propodus 0.8 times as long as ischium, 2.8 times as long as wide, superior margin with 2 simple setae, superior margin with 2 penicillate setae, inferior margin with 1 simple seta, and 2 robust setae; dactylus (with unguis) 1.2 times as long as propodus. Pereopods 3 (Fig. 8 B View Figure 8 ) and 4 (Fig. 8 C View Figure 8 ) similar to pereopod 2. Pereopod 6 (Fig. 8 E View Figure 8 ) with tubercles on superior margin of basis and with tubercles on inferior margin of merus; basis 1.6 times as long as greatest width, superior margin with 5 simple setae, and 1 penicillate seta, inferior margin with 7 setae; ischium 0.8 times as long as basis, 2.1 times as long as greatest width, superior margin with 1 seta, inferior margin with 3 setae; merus 0.5 times as long as ischium, 1.2 times as long as wide, superior margin with 2 setae, without dense patch of scale-setae; carpus 0.4 times as long as ischium, 1.7 times as long as wide, superior margin with 2 setae; propodus 0.7 times as long as ischium, 3.4 times as long as wide, superior margin with 3 setae, and 2 robust setae; dactylus (with unguis) 0.7 times as long as propodus.

Penial process 0.6 times as long as basal width, slightly produced lobe.

Pleopod 2 (Fig. 6 G View Figure 6 ) exopod 2.1 as long as wide, distally broadly rounded, with 9 plumose setae; endopod twice as long as wide, distally broadly rounded, with 8 plumose setae; appendix masculina absent; peduncle 1.2 as wide as long, mesial margin with 2 coupling setae, lateral margin with 1 simple seta.

Uropod (Fig. 6 G View Figure 6 ) rami extending to pleotelson apex, apices broadly rounded. Peduncle with 1 dorsal seta. Endopod 2.6 as long as greatest width; lateral margin straight; distomesial margin sinuate, with 8 long plumose setae. Exopod extending to end of endopod, 3.8 as long as greatest width; lateral margin weakly sinuate, with 6 simple setae; distomesial margin sinuate, with 4 long, plumose setae.

Etymology.

The species name brevicula is derived from the Latin adjective brevis, meaning “ short ”, combined with the diminutive suffix - cula, which conveys smallness. The name thus translates as “ the little short one, ” in reference to the species’ smaller body size compared to G. spongicola . This etymology proves particularly fitting as Barnard originally regarded the specimens as a diminutive form of G. spongicola .

Remarks.

Gnathia brevicula sp. nov. can be distinguished by a slightly produced frontal margin; two strong frontolateral processes that are rounded and extended; wide and rounded supraocular lobes that are minimally developed; mandibles that are weakly curved distally; and a pereonite 5 divided into two by pereonite 6.

Barnard (1920) originally designated this taxon as Gnathia spongicola var. minor , considering the morphological differences too minor to justify recognition as a separate species. He attributed these variations to habitat differences, with G. brevicula sp. nov. inhabiting smaller, branching sponges, while G. spongicola was found in larger sponges. Morphological differences noted by Barnard (1920) included a smaller body size, more robust antennae, a greater number of tubercles on the cephalosome, and stouter pereopods.

Upon closer examination, however, these morphological distinctions support the recognition of G. brevicula sp. nov. as a separate species. In addition to Barnard’s observations, the shape of the frontal margin differs between G. brevicula sp. nov. and G. spongicola . Although both species have maxillipeds composed of five articles, the distal four articles of G. spongicola bear plumose setae in the sequence 5–6 – 5 – 8, while in G. brevicula sp. nov. the sequence is 4–6 – 5 – 7. Moreover, G. spongicola displays a greater number of simple setae on the pylopod than G. brevicula sp. nov.

The name G. spongicola var. minor was first proposed as a separate species in Smit’s (1997) dissertation under the provisional name Gnathia barnardi . Since then, G. barnardi has appeared in online sources, often cited as G. barnardi Smit & Basson, 2002 . However, this name was never formally described following International Commission on Zoological Nomenclature (ICZN) rules and is therefore not considered a validly established species name.