Prohyperia shihi ( Gasca, 2005 )

Zeidler, Wolfgang, 2015, A review of the hyperiidean amphipod genus Hyperoche Bovallius, 1887 (Crustacea: Amphipoda: Hyperiidea: Hyperiidae), with the description of a new genus to accommodate H. shihi Gasca, 2005, Zootaxa 3905 (2), pp. 151-192 : 183-186

Prohyperia shihi ( Gasca, 2005)

( Figs. 16–17 )

Hyperoche shihi Gasca, 2005: 618 –621, figs. 1–4.— Garcia-Madrigal 2007: 147, 191 (list). Gasca 2009a: 88 (table). Gasca 2013: 1539 –1549, figs. 1–4

Hyperoche medusarum [mis-identification]— Gasca & Haddock 2004: 532 (table), 533, fig. 2B (type of H. shihi ).

Type material. The unique holotype female (ovigerous, 10.3 mm) of Hyperoche shihi is in the zooplankton collection of the El Colegio de la Frontera Sur (ECOSUR), Chetumal, Mexico (ECO-CHZ-02507), in spirit. The type locality is the Gulf of California, Carmen Basin, south of Guaymas Basin [26°11.04’N 110°36.07’W], ROV Dive 546, 1136 m, B. Robison ( MBARI) on R/V Western Flyer, 29 March 2003.

Diagnosis. Females: Sexually mature at about 10 mm. Antennae 1 relatively long, almost as long as head and first pereonite combined, about 1.5 x A2. Gland cone relatively large, about 0.2 x head height, slightly bent forwards. Head length equal to first 1.5 pereonites combined. Pereon globular, length almost 1.8 x pleon. Gnathopod 1; basis with slight bulge on anterior margin, slightly shorter than remaining articles combined; merus spoon-shaped, projecting only slightly under carpus, with fringe of setae on distal margin; carpus with very narrow process, slightly shorter than propodus (or as long as propodus for holotype), posterior margin, and margin of carpal process, with several strong setae; propodus with several very short, fine setae on posterior margin; dactylus slightly curved, length about 0.4 x propodus. Gnathopod 2 much stronger and longer than G1; basis and merus similar to G1; carpus very robust and broad, carpal process relatively narrow, extending into sharp tooth, reaching just beyond the distal margin of the propodus, proximal two-thirds of anterior margin with several strong setae; posterior margin of propodus with a row of fine setate; dactylus length slightly more than 0.3 x propodus. Pereopod 3 noticeably the longest pereopod, about 1.2 x P4; basis with straight posterior margin and slightly convex anterior margin, length about 3.2 x merus; posterior margin of merus, carpus and especially propodus armed with several strong setae; carpus with postero-distal corner slightly produced, with three strong setae, length about 1.3 x merus and 0.7 x propodus; propodus relatively slender; dactylus length about 0.3 x propodus. Pereopod 4 similar in structure to P3 except the basis is relatively more slender and longer. Pereopods 5–7 are similar in size and structure, with P7 marginally longer because the basis is relatively longer. Pereopod 5 slightly longer than 0.8 x P4; basis length about 3.0 x merus; carpus length about 1.3 x merus, about 0.8 x propodus; dactylus length 0.4 x propodus. Epimeral plates without distinct points; first one rounded; second and third more sub-rectangular. Uropod 1; peduncle reaching beyond limit of peduncle of U2 and to about 0.4 x peduncle of U3; inner ramus slightly longer than outer, about 0.8 x peduncle. Uropod 2; inner ramus slightly longer than outer, slightly more than 0.8 x peduncle. Uropod 3; peduncle relatively broader, inner ramus slightly shorter than outer, length about 0.7 x peduncle. Telson triangular, slightly wider than long, marginally shorter than half of peduncle of U3.

Colour in life: “body orange, eyes red” ( Gasca 2005).

Males: According to Gasca (2013). Sexually mature at about 12 mm. The eyes cover relatively less of the head surface than in females. Appendages generally more slender, otherwise very similar in structure and relative lengths of articles, except for the following minor variations. Gnathopod 1 slightly more massive, with merus projected slightly further under the carpus and with more elongate carpal process, as long as propodus, overlapping with propodus to form strong chela. Gnathopod 2 more similar to G1, with more elongate carpus overlapping propodus, similar to some species of Phronima . Pereopod 3 only slightly longer than P4. For all pereopods the carpus is relatively longer and the propodus is slightly shorter than the carpus (the reverse for females). Uropod 1; both rami with characteristic proximal excavation. Telson slightly longer than wide.

Material examined. Female (ECO-CHZ-07791), on scyphomedusa Nausithoe rubra, Gulf of California [24°20.47’N 109°14.5’W], ROV Dive 343, 970 m, S.H.D. Haddock ( MBARI) on R/V Western Flyer, 25 February 2012.

Remarks. It is of interest to note that the habitus of the female illustrated here ( Fig. 16 ) is just like that of the holotype, with pereopods 1–2 projected backwards between pereopods 5–7, which are in turn projected distinctly forward. The gnathopoda are, as usual, tucked under the head with the merus and carpus of the second gnathopoda twisted at right angles.

In this species the gnathopoda of females become more robust with age, judging by comparing the figures of the holotype (10.3 mm) ( Gasca 2005) and the specimen illustrated here (5.8 mm); and in the adult male (12 mm) the carpal process is very elongate, overlapping the propodus and dactylus ( Fig. 17 ). Also, the dactylus is not as sharp and appears worn in Gasca’s (2013) illustration. In addition, in the current specimen the left mandible has a palp of only two articles, but this seems to be an abnormality because Gasca (2005) illustrates it with three articles for the type and also for the only known male ( Gasca 2013), and this has been confirmed by the re-examination of specimens (Gasca pers. com. Feb. 2014).

This seems to be a deep-water species inhabiting depths of more than 500 m, yet the eyes are not reduced in any way, and are more typical of shallower water species. It is possible that it normally inhabits more shallow waters and was drawn deeper by its host but this is not supported by the limited information available.

The type was found on the hydromedusa Chromatonema erythrogonon (Bigelow, 1909) . More recently, additional specimens have been collected from the same general locality; an adult male and female on the scyphomedusa Nausithoe rubra ( Gasca 2013) . Additional information, and ecological observations, of this species and its hosts is provided by Gasca (2005, 2013).

Distribution. Known only from a few records from the Gulf of California, collected at depths of 554–1136 m.

Figures

FIGURE 16. Prohyperia shihi (Gasca, 2005). Female (5.8 mm), ECO-CHZ- 07791; Gulf of California [24 ° 20.47 ’ N 109 ° 14.5 ’ W], RV Western Flyer, Dive 343 (ROV), 970 m, SHD Haddock, 25 Feb. 2012. Scale bars = 0.5 mm.

FIGURE 17. Prohyperia shihi (Gasca, 2005). Mouthparts from female (5.8 mm); G 1, G 2 from male (12 mm) (redrawn from Gasca (2013 )); both ECO-CHZ- 07791; Gulf of California [24 ° 20.47 ’ N 109 ° 14.5 ’ W], RV Western Flyer, Dive 343 (ROV), 970 m, SHD Haddock, 25 Feb. 2012. Scale bars = 0.1 mm (mouthparts); 0.5 mm (G 1, G 2).