Omangidiella, Iannilli, Valentina, Holsinger, John R., Ruffo, Sandro & Ronald, 2006

Iannilli, Valentina, Holsinger, John R., Ruffo, Sandro & Ronald, 2006, Two new genera and two new species of the subterranean family Bogidiellidae (Crustacea, Amphipoda) from groundwaters in northern Oman, with notes on the geographic distribution of the family, Zootaxa 1208, pp. 37-56 : 43-45

Omangidiella new genus

Diagnosis

A highly aberrant stygomorphic bogidiellid distinguished from almost all other members of the family by the following combination of characters: mandibles with triturative molars; maxilliped with coxal endite partially fused with inner (basal) plate; accessory flagellum of antenna 1 uniarticulate; carpus of gnathopod 2 elongate and subequal in length to propodus; propodus of gnathopod 2 subrectangular and reduced in length, with very short dactylus and palm; large lenticular organs marginally present on bases of gnathopod 2 and pereopods 3–6; pleopods without inner rami; uropod 1 with 3 basofacial spines; telson with both lateral and distal spines; very long, narrow, linguiform oostegites on pereopods 2–5; and coxal gills on pereopods 4–6.

Type species

Omangidiella parvidactyla new species, by monotypy. Gender is feminine.

Remarks

The genus Omangidiella is clearly distinguished from all other genera of bogidiellids by the remarkably different structure of gnathopod 2 and development of prominent oostegites, which suggest existence of a strong marsupium to hold and protect developing eggs. It should be noted that female bogidiellids have never been observed to brood eggs, although a number of them possess very small oostegites, which probably allow eggs to be given out freely in the environment. The exceptional development of oostegites in Omangidiella parvidactyla described below suggests that it has a different behavior than most other bogidiellids. However, this must be confirmed by future studies. The oostegites development could also be linked to tegumental respiration, because the gills are very small. The lenticular organs, which are very wide in Omangidiella , are in a marginal position on gnathopod 2 and pereopods 3–6, which is an unusual position for these organs in the bogidiellids. There is no existing hypothesis about the exact function of these “organs,” except that they could play a role in tegumental respiration. The fact that they are not always present in the bogidiellids, argues against a phylogenetic significance, and instead suggests only a functional importance. In support of this suggestion is the presence of analogous structures in several other subterranean amphipod families, such as the ingolfiellids and paracrangonyctids.

Perhaps of greater phylogenetic importance is the highly unusual presence of a third coxal lobe on the maxilliped, which is in addition to the basal and ischial endites and appears to be similar to that observed in Nubigidiella and discussed in a recent paper by Iannilli et al. (2005). This unusual structure is present in addition to these two endites, which are typically present in amphipods and often called, respectively, inner and outer plates or lobes. In Omangidiella the coxal lobe is partially fused with the basal lobe. A third coxal lobe or endite is also present in other African bogidiellids besides Nubigidiella , including Maghrebidiella and Afridiella . In Maghrebidiella the coxal endite is totally fused with the basal endite, whereas in Afridiella , a recent re­examination revealed a slender structure, largely fused with the basal endite. This unique structure appears to characterize a group of genera from Africa and Arabia. The presence of the coxal endite is clear in Nubigidiella , partially fused with the basal endite in Omangidiella , largely fused in Afridiella and completely fused in Maghrebidiella . The degree of fusion of the coxal endite appears to follow a graduated trend or pattern, leading us to regard the presence of this structure in the Afro­Arabian group as a plesiomorphic character state, with the more fused condition representing increasing reduction phases that tend toward an apomorphic state. Whether or not this actually represents a trend from primitive to advanced for this character is questionable for the moment and will remain unclear until the maxillipeds of specimens in the other bogidiellid genera are carefully re­examined.