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| Hyastenus tabolongi Lee & Ng, 2019
RAFFLES BULLETIN OF ZOOLOGY. 67
Photographs: A.C. Podzorski.
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Abstract
The poorly known epialtid spider crab, Hyastenus inermis (Rathbun, 1911), from the Indian Ocean is re-described on the basis of the types. Specimens of a similar species from North Sulawesi, Indonesia, collected from among zoanthid polyps are here assigned to a new species, Hyastenus tabolongi. It differs from H. inermis by its more prominent gastric region, more slender and smooth chelipeds and structure of the male first gonopod. In life, the dorsal surfaces of the carapace and appendages of H. tabolongi, new species, are completely covered by zoanthid polyps.
Key words. spider crab, Epialtidae, Majoidea, taxonomy, new species, Indonesia, Philippines, associate of Epizoanthidae
Superfamily Majoidea Samouelle, 1819
Family Epialtidae MacLeay, 1838
Hyastenus White, 1847
Hyastenus inermis (Rathbun, 1911)
Distribution. Hyastenus inermis is known from its type locality, Amirante, Indian Ocean, and between Mauritius and Cape Guardafui (Rathbun, 1911; Griffin, 1974).
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| Fig. 4. Hyastenus tabolongi, new species, observed in situ from Bunaken, Lekuan on different dates. A, B, photographed in November 2011; C, D, photographed in July 2018.
Photographs by: A.C. Podzorski.
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Hyastenus tabolongi new species
Diagnosis. Carapace pyriform, regions defined. Pseudorostral spines straight, divergent. Supraorbital eave forming rectangular lobe; preorbital angle rounded, antorbital angle rounded, outer margin slightly constricted; orbital hiatus between supraorbital and postorbital lobes form narrow U-shape; postorbital lobe cup-like. Carapace lacking granules; gastric region prominently swollen; small tubercle on mesogastric region; epibranchial region swollen, slightly arched; cardiac region swollen; intestinal region swollen with 3 slightly swollen areas; 2 on metabranchial region and 1 medially on intestinal region (Fig. 3A, D). Antennal flagellum shorter than pseudorostral spine. Basal antennal article longer than broad, distolateral angle of article sharp, outer margin distinctly constricted medially. Pterygostomial region with single granule on outer margin (Fig. 3B, E). Cheliped slender; surface smooth (Fig. 3A, D). Ambulatory legs slender; P2 longest (Fig. 3A, D). Male thoracic sternum slightly concave anteriorly; sternites 3, 4 with lateral margin constricted. Male pleon slender, triangular, telson triangular (Fig. 3B). G1 slightly curved, distal tip sharp (Fig. 2G, H).
Etymology. This species is named after Maxi Tabolong, a senior dive guide who first showed the crab to Andrew Podzorski, who was then able to photograph it over the years.
Distribution. Currently only known from its type locality, north Sulawesi, and Pulau Molana, Ambon, Indonesia.
Bee Yan Lee and Peter K. L. Ng. 2019. On The Identity of Hyastenus inermis (Rathbun, 1911), and Description of A New Species from Sulawesi, Indonesia (Crustacea: Decapoda: Majoidea: Epialtidae). RAFFLES BULLETIN OF ZOOLOGY. 67: 490–497.
