Hyperoche Bovallius, 1887

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 : 153-154

Genus Hyperoche Bovallius, 1887

Hyperoche Bovallius, 1887a: 18 .— Bovallius 1887b: 563. Bovallius 1889: 79 (key), 83. Stebbing 1888: 1399. Sars 1895: 8 –9. Chevreux & Fage 1925: 400 (key), 405. Schellenberg 1927: 625 (key), 630. Spandl 1927: 152 (key). Pirlot 1929: 118. Bowman 1973: 4 (key). Bowman & Gruner 1973: 28 (key), 32–33. Vinogradov et al. 1982: 261 (key), 282. Weigmann- Haass 1991: 170. Shih & Chen 1995: 64 (key), 84. Vinogradov 1999: 1181 (key), 1185.

Metoecus Kröyer, 1838: 63 (291).— Milne-Edwards 1840: 71 (key), 78. Dana 1852: 315. Dana 1853: 981. Boeck 1871: 86.

Type species. Metoecus medusarum Kröyer, 1838 . This species was originally identified with that of Cancer medusarum Müller, 1776 and Oniscus medusarum ( Fabricius 1780) , both of which are based on Strøm’s (1762) non-binomial species, “ Pulex cancriformis antennis brevissimus corpore latiore ”, now considered to be Hyperia medusarum ( Müller, 1776) , and the type species of Hyperia Latreille in Desmarest, 1823 (Bowman 1973). However, as noted by Bovallius (1885), the species described and figured by Krøyer (1838) is not the same as that of Müller (1776). Thus, Hyperia medusarum ( Krøyer, 1838) becomes a secondary homonym of H. medusarum ( Müller, 1776) and so Bovallius renamed it H. Kroeyeri . Later (1887a) he transfered it to his new genus, Hyperoche , along with Hyperia martinezi Müller, 1864 ; Hyperia prehensilis Bate & Westwood, 1868 ; Metoecus abyssorum Boeck, 1871 , and Hyperoche Luetkeni n. sp., with H. Kroeyeri becoming the type species, it being the oldest described species. However, in the genus Hyperoche , Krøyer’s (1838) species name is no longer a secondary homonym of Hyperia medusarum ( Müller, 1776) and is once more available, although Bovallius (1887b, 1889) and some later authors continued to use H. kroeyeri instead of H. medusarum for Krøyer’s species.

Diagnosis. Sexually mature specimens with body length 5–20 mm. Ovigerous females with numerous eggs or larvae. Habitus similar to Hyperia . Pereonites 1–2 partially fused, especially dorsally, but suture is present. Coxa 7 fused with pereonite, with barely discernable suture, remaining coxae free from pereonites. Epimeral plates with postero-distal corner produced into slight point, or distal margin rounded. Head large, semi-circular, slightly deeper than first pereonite and about as long as the first two pereonites. Eyes occupy entire lateral surface of head, barely contiguous dorsally. First antennae with three-articulate peduncle; callynophore much longer than peduncle. Second antennae of females four-articulate, usually much shorter than the first. Maxilliped with well-developed inner lobe, about half-length outer lobes. Mandibles with three-articulate palp in both sexes; molar laminate, without conspicuous dentate process; left mandible with well-developed lacina mobilis, slightly narrower than incisor. Maxillae 1 with broad, leaf-like palp; outer lobe with four large denticles terminally and bunches of very strong setae. Gnathopoda similar in structure, chelate, with knife-shaped carpus produced to limit of propodus, or slightly beyond (sometimes slightly shorter in G1), with denticulate anterior margin. Pereopoda all simple, sometimes with dactyls retracted. Pereopods 3 & 4 marginally shorter or longer than P5 & 6, but usually marginally longer than P7, with postero-distal corner of carpus slightly produced, especially for P3. Telson triangular, length about half, or less, of peduncle of U3.

Sexual dimorphism. Apart from the long filamentous antennae, males differ from females in the following characters: the habitus is more slender; the gnathopoda and pereopoda are also more slender; the head is relatively smaller; the gland cone at the base of the second antennae is slightly smaller; the epimeral plates are relatively larger, as is the urosome, and the rami of U3 have a proximal excavation on the inner margin, a male character found in other allied genera.

Remarks. During this study several unusual characters were discovered that, in combination, seem to be unique to the genus Hyperoche . Unlike other genera of Hyperiidea, the molar of the mandibles is laminate and lacks the characteristic broad dentate process; the first two pereonites are partially fused, especially dorsally, but with a suture present; the coxa of pereopod 7 is fused with the pereonite, and sometimes some (not all) of the gnathopoda and pereopoda have the dactylus retracted, sometimes only partially. The later character has not been noted previously, except for H. cryptodactylus , probably because it occurs sporadically, usually only on one or two appendages, not necessarily on both sides, and would easily be mistaken for being damaged. This discovery calls into question the validity of H. cryptodactylus , which, apart from the retractile dactyl of gnathopod 2, is almost indistinguishable from H. luetkenides . Consequently the two are here considered to be synonymous (see under H. luetkenides ).

Ovigerous females carry numerous eggs or larvae, indicative of species that deposit their larvae on the host at a much earlier stage as opposed to those, with fewer large eggs, that retain the larval stage until it is more fully developed.

The gelatinous plankton associates of Hyperoche are summarised by Laval (1980). Most are with ctenophores but H. medusarum ( Kröyer, 1838) is mostly found with medusae. Additional biological information is provided by Bowman et al. (1963), Brusca (1970), Evans and Sheader (1972), Flores and Brusca (1975), Westerhagen (1976), Westerhagen and Rosenthal (1976), Harbison et al. (1977) and Cahoon et al. (1986).

Species. Hyperoche medusarum ( Kröyer, 1838) ; H. martinezii ( Müller, 1864) ; H. picta Bovallius, 1889 : H. luetkenides Walker, 1906 ; H. mediterranea Senna, 1908 ; H. capucinus Barnard, 1930 ; H. macrocephalus sp. nov.