Microcerberidae Karaman, 1933

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Suggested Common Name: Cerberuses
Number of subordinate taxa: 48 species in at least 8 genera worldwide, at least 15 species in 5 genera.
Etymology: after Microcerberus Karaman, 1933. Common name refers to the commonly-used suffix in almost all genera (except Isoyvesia).
Taxonomic History: Microcerberidae Karaman, 1933. At times this family was considered a subfamily of Anthuridae, likely due to the similar body shape and general lifestyle, however it is now understood that the two taxa are almost as distantly related as they can be in Isopoda, with the similarities between them being a fairly extreme case  of convergent evolution due to their similar ecologies.
Size Range: most species reach around 1mm, although in our area Texicerberus can reach over 2mm.
Description: Body extremely elongate, usually 8-10x longer than wide, pigmentless. Antenna 1 peduncle poorly differentiated from flagellum. Mandible palp reduced, 1-segmented, with long apical seta, segment often fused to mandible body. Maxilliped coxa apparently absent or fused with basis; basis reduced, often resembling a palp segment, usually with a distomedial lobe (absent in Protocerberus); epipod absent. Oostegites absent. Pereopods 1-7 set dorsolaterally on pereonites. Pereopod 1 proposubchelate. Pleopod 1 absent (present in Mexicerberus and the extralimital Bulgarocerberus). ♂ pleopod 2 exopod 1-segmented. Pleopods 3-5 set laterally, appearing lateral to pleopod 2 in ♂'s and on either side of a trapezoidal sternite in ♀'s (also present in ♂'s but hidden by pleopod 2). Uropod prominent, biramous (sometimes uniramous); exopod smaller than endopod, often minute or absent. Anus (when known) terminal.
Type taxon: Microcerberus Karaman, 1933
Notes: All genera in this odd subcosmopolitan family are fairly range-restricted with the exception of Robustura, which is subcosmopilitan in tropical to temperate marine interstitial environments. Microcerberids can potentially be confused with Anthuroids (see Taxonomic History), however, the pleon, telson and their associated appendages are dramatically different between the two taxa. Microcerberidae has a somewhat typical asellote-type pleon and pleopods (with the exception of the absence of ♀ pleopod 2) and simple apical uropods on the telson, while the Anthroids have all 5 pleopods present on a 5-segmented pleon (1-segmented in Anthuridae) and a bizzare "flower-shaped" uropod and telson morphology. Also similar are the various intersitial members of Asellota (such as Microcharon, Angeliera and Caecianiropsis), however they can be seperated by the fusion of at least some of the coxae to their respective tergites (although this is absent in some extralimial genera) and details in the mouthparts and pleopods.

Subordinate taxa: Isoyvesia, Mexicerberus, Microcerberus, Robustura, Texicerberus

Key to genera
1 a. Head with a rostrum; pleonites fused with telson (segmentation still visible ventrally; pleopod 1 present; endemic to Tamaulipas --> Mexicerberus
b. Head lacking a rostrum; pleonites free; pleopod 1 absent; not as above --> 2

2 (1) a. Pereopods 2-4 with coxae fused to tergites as coxal plates (absent in R. mexicanus but then head fused to pereonites 1-2); ♂ pleopod 2 endopod distally bifid or trifid; marine coasts --> Robustura
b. Pereopods 2-4 with coxae free, ring-like; ♂ pleopod 2 endopod distally pointed, not bifid or trifid; freshwater environments (Isoyvesia is partially marine)  --> 3

3 (2) a. Pleopod 4 elongate, triramous with equally-sized rami, rami only basally being covered by pleopod 3 --> Microcerberus
b. Pleopod 4 short, biramous, rami mostly being covered by pleopod 3 --> 4

4 (3) a. Antennae 1 segment 3 not medialy produced into a spine; maxilliped segments 2-3 not greatly expanded; Texas and adjacent Mexico --> Texicerberus
b. Antennae 1 segment 3 medially produced into a spine; maxilliped segments 2-3 greatly expanded; Cuba --> Isoyvesia

Sources

Coineau, N. & Botosaneanu, L. (1973). Isopodes interstitiels de Cuba. Resultats des Expeditions Biospeologiques Cubano-Roumaines a Cuba. Academy of the Socialist Republic of Roumania, 191-222.

Hutchins, B. T., Schwartz, B. F. & Coleman, W. T. (2021). Three new microcerberids (Isopoda: Microcerberidae) from subterranean freshwater habitats in Texas, USA. Journal of Natural History, 55(35-36):2261-2278.

Schultz, G. A. (1974). Mexicerberus troglodytes n. gen., n. sp. from a cave in Mexico, with notes on isopod crustaceans of the Microcerberidea from the New World. Crustaceana, 26(3):308-312.

Wägele, J. W. (1982) Isopoda (Crustacea: Peracarida) ohne Oostegite: Über einen Microcerberus aus Florida. Mitt. Zool. Mus. Uni. Kiel, 1(9):19-23

Wägele, J. W., Voelz, N. J., & Vaun McArthur, J. (1995). Older than the Atlantic Ocean: discovery of a fresh water Microcerberus (Isopoda) in North America and erection of Coxicerberus, new genus. Journal of Crustacean Biology, 15(4):733-745.

Published: Feb 15, 2023