IULOPIDIDAE, Zeidler, 2004

Zeidler, Wolfgang, 2004, A review of the families and genera of the hyperiidean amphipod superfamily Phronimoidea Bowman & Gruner, 1973 (Crustacea: Amphipoda: Hyperiidea), Zootaxa 567, pp. 1-66 : 35-36

Family IULOPIDIDAE , new family

Diagnosis

Body length of 4–8 mm. Body and pereopods covered with fine setae. Head large, round. Eyes large, occupying most of the head surface. Pereon broad. Pereonites all separate. Pereonite 1 with lateral, anteriorly pointed projection, just above coxa. Pereonites 2–7 raised into transverse, rounded folds. Coxae separate from pereonites. Antennae 1, four­articulate in females; multi­articulate in males, with enlarged callynophore, with twofield brush of aesthestascs medially. Antennae 2, three­articulate, or absent, or reduced to small knob on cuticle in females; multi­articulate in males. Mandibles without palp in females, with or without palp in males; molar reduced to broad plate with two small tubercles and row of small robust setae. Maxillae 1 with broad palp and slightly less­developed outer lobe; inner lobe absent. Maxillae 2 bilobed with robust setae. Maxilliped with slender, rounded outer lobes; inner lobe rudimentary, or absent. Gnathopod 1 weakly subchelate. Gnathopod 2 chelate. Pereopods 3–7 usually simple, rarely P5–7 may be minutely subchelate. Pereopods 5–7 subequal in length. Uropods with articulated endopods and exopods. Telson triangular, about half­length peduncle of U3. Gills on pereonites 2–6. Oostegites on pereonites 2–5.

One genus: Iulopis .

Remarks

This family has been established to accommodate the genus Iulopis because it has characters that preclude it from the families Hyperiidae and Lestrigonidae , as defined here.

The availability of the vast collections of the ZMUC, especially from the Dana expeditions, enabled me to examine more material than had previously been available to other researchers, particularly of the rare species, I. mirabilis . An examination of this material, especially of the antennae and mouthparts, resulted in a couple of unexpected discoveries.

According to the literature (e.g. Bovallius 1889, Bowman & Gruner 1973, Vinogradov et al. 1982) males have a mandibular palp which is absent in females. However, it seemed likely that if the coxae are free from the pereonites, and all pereonites are separate, that Iulopis should belong with the family Hyperiidae , and that the females probably possessed a mandibular palp which had been overlooked. Thus, specimens of I. loveni Bovallius, 1887 (72 females, 41 males) and I. mirabilis Bovallius, 1887 (34 females, 22 males) in the ZMUC were examined to determine the presence or absence of a mandibular palp. Upon examining this material no mandibular palp could be found in either sex of I. loveni but was present in males of I. mirabilis ! The mouthparts of Iulopis are relatively large ( Fig. 3 ), so it is relatively easy to determine this character without dissection. Careful dissection of a mature male of I. loveni confirmed the absence of a mandibular palp in this species. This finding is very surprising as the presence/absence of mandibular palps is consistent in all other genera of Hyperiidea and can be one of the characters used to separate families. Bovallius (1889) clearly illustrates a mandibular palp for the male of I. loveni (pl. 7, fig. 5), and says of the female (p.123) “the mouth­organs are like those in the male”. One can only assume that Bovallius confused his preparations of mandibles and illustrated one from I. mirabilis .

In regard to the second antennae of females I found that in I. loveni they are absent, or at most represented by a small knob on the cuticle but in I. mirabilis they are three­articulate ( Fig. 4 )! Bovallius (1889) records females of I. loveni with second antennae with two small articles, but provides no illustrations. It seems unlikely that this character is variable, or that it is dependent on maturity, as several juveniles and ovigerous females were examined. It seems that Bovallius (1889) is incorrect in this regard, but his erroneous observation has unfortunately, been repeated in the literature. He did not have females of I. mirabilis .

Iulopis loveni is a most unusual species as the absence of a mandibular palp in both sexes is a rare condition amongst the Physocephalata and this character, combined with second antennae absent in females, is only found in the family Dairellidae . On the other hand I. mirabilis most closely resembles the family Lestrigonidae in the morphology of the antennae and the mandibular palp. If it were not for the similarity in morphology of the pereopods, mouthparts and the body in general, one might have placed these two species in different genera if not families.

dditional characters that distinguish Iulopis are the maxillipeds, which lack inner lobes, the mandibles, in which the molar is reduced to a broad plate and pereonites 2–7, which are raised into distinctive, transverse, rounded folds. The hirsute body is also unusual.

Figures

FIGURE 3. Iulopis loveni, male, 6.0 mm, Mediterranean (Thor stn. 698). Scale bar = 0.1 mm.

FIGURE 4. Iulopis mirabilis. A, lateral view of female, 5.3 mm, tropical NE Atlantic (Dana stn. 4001iii). B, lateral view of male, 5.2 mm, SW Indian Ocean (Dana stn. 3935ii). Scale bars = 0.5 mm (A, B), 0.2 mm (remainder).