Glossocephalus aurantium, Zeidler & Browne, 2023

Zeidler, Wolfgang & Browne, William E., 2023, Another new species of Glossocephalus (Crustacea: Amphipoda: Hyperiidea Oxycephalidae) from the Monterey Bay region, California, USA, Zootaxa 5228 (4), pp. 448-454 : 449-453

Glossocephalus aurantium sp.nov.

( Figs 1–4 )

Material examined. Holotype: Female (10.0 mm), Monterey Bay Canyon, off California, eastern Pacific Ocean [centroid 36°36’13”N, 122°22’34”W], ROV Doc Ricketts, Dive D 777 (d7), launched from R / V Western Flyer , 2804 m, SHD Haddock cruise leader, 7 July 2015. USNM 1516629 . Associated with an undescribed lobate ctenophore.

Paratypes: Female (8.8 mm), also ovigerous, collected with holotype on same host ; USNM 1661950 . Juvenile, Monterey Bay , California [36.54°N 122.53°W], ROV Doc Ricketts, Dive D 1402 launched from R / V Western Flyer , 2939 m, 14 November 2021 ; USNM 1643184 ; associated with an undescribed lobate ctenophore. BH Robison cruise leader .

Other records: Because this species is easily recognisable, the following records from photos and video footage are regarded as reliable records. All additional records include an observed association of G. aurantium with an undescribed lobate ctenophore from near the type locality. All submersibles were launched from R / V Western Flyer.

Two individuals, ROV Tiburon, Dive T512 [36.34°N 122.90°W], 3164 m, 21 November 2002. BH Robison cruise leader .

At least 5 individuals (1- 2 adults and juveniles), ROV Doc Ricketts, Dive D908 [36.46°N 122,56°W], 2994 m, 30 November 2016. BH Robison cruise leader.

One individual, ROV Doc Ricketts, Dive D918 [36.59° 122.42°W], 2913 m, 17 December 2016. SHD Haddock cruise leader.

Description of holotype. Female 10.0 mm, ovigerous. Head as long as first five pereonites combined, with sharp rostrum occupying half of head, more or less triangular in shape with distinct neck posterior to eyes. Eyes distinctively bulbous, with large crescent-shaped, strongly pigmented photoreceptor fields orientated perpendicularly to the anteroom-posterior body axis, occupying almost half of head between rostrum and neck. Pereon cylindrical, length about 1.5 x pleon. Pleonites with rounded postero-distal corners. Gnathopods more or less sub-chelate; relatively small, with G1 marginally shorter than basis of P3. G1 basis length about 1.3 x remaining articles combined, relatively narrow; carpus quadrate, barely projecting under propodus, produced into strong postero-distal tooth medially, armed with three or four strong setae medially near outer postero-distal corner; propodus rectangular, as long as carpus, posterior margin with slight excavation for distal quarter, preceded by small tooth, forming weak sub-chela with carpal process; dactylus relatively short, stubby. G2 slightly longer than G1, similar in structure except carpus is relatively longer, rectangular and excavation on propodus is less prominent. P3 and P4 relatively slender, similar in structure. P3 slightly shorter than P4, about 0.8 x P5; basis length about 1.8 x merus; carpus length about 0.8 x merus; propodus slightly longer than carpus; dactylus length marginally less than 0.2 x propodus. P5 with normal articles (not particularly widened), all with smooth margins; length 1.3 x P6; basis slightly broadened with convex margins, length about 1.7 x merus; carpus length about 0.7 x merus; propodus similar in length to merus; dactylus length slightly more than 0.1 x propodus. P6 similar to P5 except anterior margin of merus, carpus and propodus with fine serrations; basis length about 1.7 x merus; carpus length almost 0.6 x merus; propodus length 1.5 x carpus; dactylus length 0.3 x propodus. P7 basis oval-shaped, length about 1.8 x width, slightly shorter than remaining articles combined; merus slightly longer than carpus; propodus marginally shorter than carpus; dactylus very small. U1 peduncle reaching beyond limit of peduncle of U2, to middle of U3; outer ramus slightly wider than inner, length about 2.2 x inner ramus, about 0.7 x peduncle. U2 peduncle reaches just short of base of peduncle of U3; inner ramus length about 0.8 x peduncle, about 1.3 x outer ramus. U3 peduncle very short, slightly longer than wide; inner ramus damaged but much longer and wider than outer ramus. Telson relatively broad, about as long as wide, not quite reaching limit of outer ramus of U3, with minor point terminally. Margins of rami and telson finely denticulate.

Colour of fixed specimens: Eyes orange. The remainder of the animal is relatively translucent. Fixation did not alter the distribution of the orange screening pigment associated with the eye field photoreceptors or the translucent opacity of the body.

Etymology. The species name, derived from Latin, refers to the distinctive, orange-coloured eyes that retain their colour even in fixed samples.

Remarks. Glossocephalus aurantium is most readily distinguished from its congeners by the bulbous shape of the eyes containing large fields of crescent shaped, orange pigmented, photoreptor fields ( Figs 2–4 ). In that the eyes are relatively large it resembles G. milneedwardsi , a species readily distinguished by the following characters: i) the head is relatively smaller and shorter, as long as the first 3.5 pereonites combined and the rostrum is relatively shorter and rounded; ii) the carpus of G1 and G2 is spoon-shaped; iii) P3 and P4 are relatively long, with thin articles; and iv) P5 and P6 are paddle-like with relatively broad articles. Except for the unique eye morphology, G. aurantium shares more morphological similarity with G. rebecae , particularly in the morphology of the pereopods. However, the gnathopods of G. aurantium are more blade-like than spoon-shaped, with a more elongate carpus having a less pronounced postero-distal tooth and retaining a few long setae on the medial face.

Glossocephalus aurantium is known only from the two type lots and the sightings as detailed above. This species has always been observed in close association with an undescribed lobate ctenophore host from the Monterey Bay Canyon.

Figures

FIGURE 1. A and appendages: Glossocephalus aurantium sp. nov. Holotype female 10.0 mm (USNM 1516629). B: dorsal view of head of G. milneedwardsi, female 10.2 mm (SAMA C5816), N.E. Pacific off California [33°27’N 110°23’W]. Scale bars = 1.0 mm (habitus, dorsal view of head of A and B), 0.5 mm (remainder).

FIGURE 2. Glossocephalus aurantium sp. nov. photograph of holotype female.

FIGURE 3. Glossocephalus aurantium sp. nov. photograph of holotype (bottom) and paratype (top) females.

FIGURE 4. Close up of head capsules for the three species of Glossocephalus to illustrate the morphology of the eyes. A. Holotype of G. aurantium. B. G. rebecae. Enlargement of in vivo photograph from Zeidler and Browne (2015) of male from Monterey Bay region, ROV Tiburon, from R/V Western Flyer, 541 m. C. G. milneedwardsi female from Pelican Cayes region, BZ (16.40ºN, 88.11ºW), 0-3 m.